Fuel Injection System - Bosch Cis-E Volkswagen Jetta II

DESCRIPTION

Bosch CIS-E fuel injection system uses Continuous Injection System (CIS) for fuel delivery and electronic controls for mixture adjustment.

Mechanical portion of CIS-E system consists of Mixture Control Unit (MCU) which is also known as the fuel distributor, airflow sensor plate, diaphragm pressure regulator, auxiliary air regulator, cold start valve, fuel injectors, fuel pump and filter.

Electronic controls consist of airflow sensor position indicator (potentiometer), differential pressure regulator, thermo time switch, coolant temperature sensor, Electronic Control Unit (ECU), Lambda control and oxygen sensor. Some models also incorporate a heated oxygen sensor, knock sensor, knock sensor control unit, throttle valve microswitch(s) and/or an altitude (barometric) sensor.

Scheme 10

Fuel Pump & Relay

The fuel pump assembly, is equipped with a pressure damper at the suction end. Fuel pump is activated during start-up and when engine is running. Fuel pump relay switches off fuel pump in absence of signal from ignition control unit and provides voltage for oxygen sensor heating element (if equipped).

FUEL PUMP LOCATIONS

Mixture Control Unit (MCU)

Fuel is constantly sprayed to individual fuel injectors dependent on amount of air intake metered by airflow sensor plate.

Fuel Distributor

The fuel distributor controls the flow of fuel to the injectors. A control plunger, operated by the airflow sensor regulates the control pressure differential between the injector supply (upper chamber) and the lower chamber (fuel return). This differential in pressure controls the amount of fuel flow to the injectors.

Airflow Sensor Potentiometer

Airflow sensor potentiometer is attached to the side of the MCU and connected to the air sensor plate actuating lever. It generates a voltage signal based on the position of the airflow sensor plate. The ECU uses this signal to adjust cold acceleration enrichment.

Differential Pressure Regulator

Differential Pressure Regulator (DPR) is mounted on side of fuel distributor. An electrically operated plate valve combined with fixed outlet orifice, governs pressure in lower chamber. (Scheme 11) Pressure change in lower chamber causes movement of diaphragm and controls fuel volume flow to injectors.

Actuating signal comes from ECU and can range from -60 to +120 mA, depending upon engine operating conditions.

Scheme 11

Electronic Control Unit (ECU)

ECU is found behind plenum panel on driver's side of vehicle. ECU must not be exposed to temperatures above 180°F (85°C). ECU unit utilizes various input signals to control fuel delivery and hot idle speed.

Additional Enrichment

Some models use a standard thermo time switch and cold start valve to provide cold start enrichment. Other models use a combination of the following devices or systems to enrich the mixture.

During cold engine cranking, a signal from the starter relay is sent to the ECU to enrich the fuel mixture. A thermo timer controls enrichment cycle time after starting.

Fuel enrichment during warm-up is controlled by the DPR. When cold, the signal from the coolant temperature sensor allows more current to be supplied to the pressure regulator. This will provide greater fuel enrichment.

Altitude Sensor (Quantum & Quantum Syncro Only)

Injection control is influenced by altitude. As altitude increases (air pressure decreases), the altitude sensor sends a signal to ECU to reduce current to the differential pressure regulator. This causes a leaner fuel mixture.

Deceleration Fuel Shut-Off

During deceleration, circuit to ECU is closed by the throttle microswitch. Deceleration input signals received by ECU result in change of current direction to DPR coils. Plate valve opens and causes pressure in lower chamber to increase. Increased fuel pressure, combined with spring tension, forces diaphragm to cover injector ports in fuel distributor. This interrupts fuel supply to injectors.

Time period of deceleration fuel shut-off depends upon engine coolant temperature. Injection of fuel will restart at 900 RPM if engine is at operating temperature. If coolant temperature is lower than operating temperature, injection of fuel will begin at higher speed than 900 RPM.

If throttle is opened during deceleration, microswitch opens before throttle valve. This allows deceleration shut-off to be interrupted before throttle valve opens, preventing cut-in hesitation.

Knock Sensor Control

The knock sensor control unit receives signals from the knock sensor and vacuum signal from intake manifold. It transmits signals to the ignition timing unit to adjust timing.

Electronic Idle Speed Control

Idle speed air control valve or idle speed boost valve, located in throttle valve by-pass hose, receives signals from ECU. The ECU uses input from engine speed, the position of the airflow sensor potentiometer and the coolant temperature, to control idle speed.

A/C operation will also send a signal to the ECU which will modify the signal to the air control valve(s). Idle speed boost valves are used on 4-cylinder models. Vehicles without A/C use only one valve, called Idle Speed Boost Valve No. I. Vehicles with A/C also use second valve, called Idle Speed Boost Valve No. II.

With ignition on, constant voltage is supplied to idle speed boost valve No. I. If engine speed drops below 700 RPM, idle speed boost control (on relay board) completes ground circuit for boost valve No. I. Above 1050 RPM, control unit shuts off ground circuit to boost valve No. I.

Idle speed boost valve No. II is always grounded. When A/C is turned on, voltage is supplied to boost valve No. II.

Sensor Plate Rest Position

Upper edge of sensor plate must be below lower edge of sensor cone.070-.080" (1.80-2.10 mm). (Scheme 12) If rest position is incorrect, raise sensor plate. Open or close wire clip to change position of sensor plate. DO NOT bend leaf spring.

Scheme 12

Centering Sensor Plate & Lever

1. Check sensor plate for centered position in airflow sensor housing. (Scheme 14)If plate binds on housing or is off-center, remove 6 mm bolt holding plate to lever. Coat bolt with locking compound and install finger tight.
2. Use Centering Gauge (US 1109) or.004" (.10 mm) feeler gauges to set plate equidistant from sensor housing. If plate cannot be centered, remove airflow sensor housing.
3. Turn housing upside-down and remove bolt clamping counterweight to sensor lever. Coat bolt with locking compound and install finger tight. Center sensor plate lever in housing and tighten clamping bolt. Complete centering of plate.

Scheme 13

1. Free play is measured between control piston and adjusting lever. To ensure Differential Pressure Regulator (DPR) current is 4-16 mA, position of sensor plate lever must be correct. Measure free play on side of sensor cone closest to fuel distributor. (Scheme 13)
2. Crank starter motor for 10 seconds to develop fuel pressure. Lift sensor plate slightly until resistance is felt. Minimum clearance is any noticeable free play. Maximum clearance is.078" (1.99 mm) up to sensor cone.
3. If free play clearance is incorrect, remove fuel distributor. Check basic adjustment of sensor plate lever. Install fuel distributor and repeat free play clearance check. If still incorrect, adjust sensor plate clearance with control piston stop screw.

Sensor Plate Clearance Adjustment

1. Remove fuel distributor from airflow sensor housing. Turn distributor upside-down to access stop screw for control piston. Basic clearance between screw head and flange of hex nut should be .023" (.6 mm).
2. Turning screw clockwise will increase clearance by keeping control piston higher in fuel distributor during operation. Turning screw counterclockwise will decrease clearance by allowing control piston to extend further out of fuel distributor during operation.
3. Adjusting stop screw 1/4 turn will make .05" (1.3 mm) difference at sensor plate. Idle speed and CO (current reading) must be checked.

Sensor Plate Lever Adjustment

1. Check basic adjustment of sensor plate lever. With fuel distributor removed from airflow sensor housing, measure distance between roller on sensor plate lever and contact points of fuel distributor on top of airflow sensor housing. NOTE: Always check sensor plate lever adjustment if fuel distributor or airflow sensor has been replaced.
2. Use a depth gauge or vernier caliper for measuring distance. (Scheme 14) Distance should be.74-.75" (18.9-19.1 mm). If distance is out of specified range, correct it with adjustment of mixture screw.

Scheme 14

Checking

1. Check sensor plate rest position and adjust if necessary. Edge of plate closest to fuel distributor must be .069-.079" (1.75-2.05 mm) below lower edge of sensor housing venturi cone. Disconnect wiring from potentiometer. Connect Test Harness (VW 1501) to potentiometer, leaving vehicle harness plug disconnected.
2. Using Digital Multimeter (US 1119), measure resistance of potentiometer at terminals of test harness. Harness terminal No. 1 corresponds to potentiometer terminal No. 18; terminal No. 2 corresponds to potentiometer terminal No. 17; terminal No. 3 corresponds to potentiometer terminal No. 14.
3. Reading should be greater than 4000 ohms with meter between harness terminals No. 1 and 2. Reading should be less than 1000 ohms with meter between terminals No. 2 and 3. Reading should increase evenly up to 4000 ohms as sensor plate is lifted smoothly. If readings are not correct, replace potentiometer.

Adjustment

1. Using Sensor Plate Adjustable Holder (VW 1348/1), lift sensor plate to lower edge (fuel distributor side) of airflow sensor housing. (Scheme 20) Install potentiometer. Partially tighten screws so that adjustment is possible. Connect multimeter between test harness terminal No. 2 and ground.
2. Reconnect vehicle harness to Test Harness (VW 1501). Set multimeter on 20 DCV scale and turn ignition on. Reading should be.2-.5 volt on Quantum models,.02-.2 volt on Cabriolet and Scirocco models or.2-.3 volt on all other models. If not, move potentiometer until reading is correct. Tighten mounting screws. To check adjustment, lift sensor plate to stop. Reading should be 7 volts. If correct, secure mounting screws with Loctite.

THROTTLE SWITCHES

Note. Stop screw is set by manufacturer and should not be moved.

Throttle Plate Stop Screw

If basic factory setting has been changed, turn throttle stop screw counterclockwise until there is a gap between stop and screw. Turn screw in until it just touches stop. Turn screw 1/2 turn (180 degrees) further. Check and adjust idle speed and CO.

Note. Fox does not use idle or full throttle switches.

Scheme 15

1. Connect Test Harness (VW 1501) between vehicle harness and throttle switch lead. Turn ignition on. Connect voltmeter between terminal No. 1 of test harness and ground. If battery voltage is NOT present, check voltage supply between terminal No. 2 of test harness and ground.
2. If battery voltage is NOT present, check and repair wiring. See WIRING DIAGRAMS at end of this article for wiring color and terminal numbers. If battery voltage is present, open and slowly close throttle valve.
3. Check switch-on point of idle switch, using feeler gauge between throttle lever and idle stop. Switch-on point gap should be.006-.002" (.15-.05 mm) before idle stop. (Scheme 15) If switch-on point is incorrect, loosen and adjust idle switch position. Idle switch is located on underside of throttle valve housing, opposite idle stop.

Scheme 16

1. To check and adjust idle switch, loosen upper left bolt on throttle valve housing. Attach Protractor Pointer (3084) under bolt. Attach Protractor (3084) on primary throttle valve shaft, removing shaft nut if necessary. (Scheme 16)
2. Disconnect wiring to switch. Connect ohmmeter between terminals of switch. Set protractor so pointer is on "0" degrees. Open throttle to 20 degrees and close it slowly. Switch must have continuity from one degree to 2.5 degrees when opening.
3. If reading is incorrect, remove throttle valve housing. Loosen idle switch mounting screws and adjust switch position. (Scheme 17) Switch must close (continuity) before throttle control reaches idle stop position.

Scheme 17

Full Throttle Switch (Except Fox)

1. Attach protractor pointer to upper left bolt on throttle valve housing. Attach protractor to secondary throttle valve shaft. Remove shaft nut if necessary. Disconnect throttle switch wiring. Connect ohmmeter between switch terminals. (Scheme 18)or (Scheme 19).
2. Set secondary throttle plate in full open position and move protractor until pointer is on "0" degrees. Allow secondary throttle valve to close about 30 degrees and reopen to full throttle position.
3. Ohmmeter must read zero ohms at 8-12 degrees before full throttle. Loosen mounting screws and adjust switch. Reading must be zero ohms (continuity) at full throttle position.

Scheme 18

Scheme 19

System Pressure (Quantum & Quantum Syncro Only)

1. Check and note existing pressure. Remove pressure regulating valve from fuel distributor.
2. Adjust pressure by changing shims in shim stack. Add shims to raise system pressure. Remove shims to lower system pressure.
3. A shim change of .020" (.5 mm) will change system pressure approximately 4.2 psi. (.3 kg/cm 2 ). Ensure any replacement shims are identical in diameter to existing shims.

Thermo Time Switch

1. Check thermo time switch at connector on cold start valve when engine coolant temperature is less than 86°F (30°C). Disconnect and ground high tension lead at distributor cap end.
2. Disconnect connector from cold start valve. Connect test light across 2 terminals of cold start connector. Crank starter motor for 10 seconds. Test light must light up for 1-8 seconds, depending upon temperature. Thermo time switch cut-off temperature rating is stamped on switch.

THERMO TIME SWITCH - OPERATIONAL TIME

Cold Start Valve

1. Check cold start valve with engine coolant temperature below 86°F (30°C). Disconnect and ground high tension lead at distributor cap end. Remove cold start valve from intake manifold with wiring and fuel line connected. Point tip into safe container.
2. Crank starter for 10 seconds. Valve should emit cone-shaped spray for time allowed by thermo time switch. Dry off tip and check for leaks. Acceptable leakage rate of cold start valve is one drip per minute or less.

Auxiliary Air Valve (Fox Only)

1. Engine coolant must be below 86°F (30°C) for cold condition testing. Ensure ignition has been off, so element in regulator is not warmed up. Disconnect wiring connector from air regulator. Start cold engine and let idle. Measure voltage across connector terminals. Voltage must be 11.5 volts.
2. Pinch either regulator hose. If idle does not decrease, replace auxiliary regulator. Attach wiring to regulator. Allow engine to idle for a minimum of 5 minutes. Pinch either regulator hose. If idle speed changes replace auxiliary air valve.

COLD START ENRICHMENT (CABRIOLET & SCIROCCO)

To ensure smooth running, the system supplies additional fuel to a cold engine by increasing differential pressure regulator current for a short period after starting and during warm up. A coolant temperature sensor provides control unit with temperature information. The starter provides an additional signal for after-start enrichment. After-start enrichment lasts approximately 40 seconds. Cold running enrichment decreases gradually as the engine warms up, finally reaching the normal warm running value.

To test either function, remove the harness connector from the coolant temperature sensor to simulate a cold engine. To check cold running enrichment, turn ignition on. Differential pressure regulator current should be 80 to 100 mA.

After-start enrichment is checked after operating the starter. To prevent engine from starting during test, disconnect ignition coil wire from center of the distributor cap and use a jumper wire to connect it to ground. Actuate starter 2 to 3 seconds, then leave the ignition on. The differential pressure regulator current should increase to more than 120 mA for 30 to 60 seconds and then return to the cold running value given above. When the test is incomplete, turn the ignition off. Reconnect coil wire and the coolant temperature sensor harness connector.

Test coolant temperature sensor by detaching its harness connector and checking resistance across the sensor's terminals. The correct resistance varies with engine coolant temperature. When replacing sensor, drain and refill coolant.

System Pressure

1. Connect Pressure Gauge (VW 1318) between line from fuel distributor to cold start valve and test port connection on lower chamber of fuel distributor, using Adapter Fittings (VW 1318/5). Test port is sealed by a threaded plug. Bridge fuel pump relay with Jumper Switch (US 4480/3).
2. Disconnect wiring from Differential Pressure Regulator (DPR). Open valve on pressure gauge (points at cold start valve line when open) and activate fuel pump. System pressure must be 75-82 psi (5.3-5.8 kg/cm 2 ). If pressure reading is low and fuel pump delivery quantity is good, replace pressure regulator.
3. If pressure reading is high, disconnect fuel tank return line from DPR. Repeat test. If reading is correct, check for plugged return line. If reading is incorrect with line open, replace DPR.

Differential Control Pressure

1. Close valve on pressure gauge. Activate fuel pump with jumper switch. Leave DPR disconnected. DPR reading should be 2.9-7.0 psi (.2-.5 kg/cm 2 ) less than system pressure. If pressure is incorrect, disconnect lower chamber return line and measure volume.
2. Close open port to diaphragm pressure regulator. Activate fuel pump with jumper switch. Fuel volume should be .14-.16 qts. (.13-.15L) for period of one minute. If volume is correct, replace DPR. If volume is incorrect, replace fuel distributor.
3. Close valve on pressure gauge. Install Test Harness (1315A/1) between DPR and vehicle harness. Set multimeter to DCA 200 mA scale. Connect multimeter to test harness. Disconnect wiring to coolant temperature sensor. Connect 15 k/ohm side of Test Resistor (VW 1490) to sensor wiring.
4. Turn on ignition and fuel pump. Differential pressure should be 10-17.5 psi (.7-1.2 kg/cm 2 ) less than system pressure. DPR current should be 50-80 mA. If pressure is incorrect and current is correct, replace DPR.
5. If both pressure and current readings are incorrect, remove test harness from DPR. Ensure resistance of DPR is 17.5-21.5 ohms. If reading is incorrect, replace DPR.
6. If reading is correct, check ground from temperature sensor to cold start valve. If ground is good, check power supply fuse. If fuse is okay, check terminals on ECU connector. If connector is okay, replace ECU.

Residual Pressure & Internal Leak Testing

1. Open valve on pressure gauge. Operate fuel pump for 30 seconds. Pressure can drop to a minimum of 38 psi (2.7 kg/cm 2 ) after 10 minutes. If pressure drops below specification, inspect fuel pump check valve and all fuel fittings for leakage. NOTE: Pressure and leak testing does not include checking cold start valve.
2. If there are no leaks, check airflow sensor plate clearance. If plate clearance is correct, replace diaphragm pressure regulator and repeat leak test. If pressure drop is not within specification, replace fuel distributor "O" rings.

Transfer Pump Delivery Volume

1. Check voltage supply to pumps. Connect Jumper Switch (US 4480/3) in place of fuel pump relay, on relay panel. Remove fuel filler cap. Disconnect and plug off Black fuel line from sending unit.
2. Connect hose to sender port and place in measuring container. Turn on fuel pumps. Minimum transfer pump delivery volume should be .42 qts. (.4L) in 10 seconds. Reconnect fuel line to sender.

Main Pump Delivery Volume

1. Check transfer pump (if equipped) and fuel filter. Disconnect fuel return line and place in measuring container. Switch on fuel pump with jumper switch. Check fuel pump delivery volume for 30 second period. Delivery rates are given with voltage reading at pump as volume will change with different voltages.
2. Minimum delivery volume for Fox, Quantum and Quantum Syncro models is .71 qts. (.68L) for 30 seconds with reading of 11.4 volts at fuel pump. Minimum delivery volume for other models is .62 qts. (.59L) with 11.4 volts at fuel pump.

1. Check sensor plate adjusting lever and fuel distributor control piston for smooth operation. Disconnect fuel injector lines at fuel injectors.
2. Remove fuel pump relay and bridge fuel pump circuit. Use Jumper Switch (US 4480/3) in place of fuel pump relay. When pressure has built up, turn off fuel pump. Move sensor plate from rest position to end of travel.
3. Uniform resistance should be felt during entire movement. No resistance should be felt on quick return to rest position. Connect injector lines. Install fuel pump relay.

Scheme 20

1. Remove fuel pump relay, from relay panel, and install Jumper Switch (US 4480/3) in off position in place of relay. Attach Fuel Quantity Analyzer (US 4480) to bumper and secure in place. Remove injectors from cylinder head with fuel lines attached. Check and replace fuel injector "O" rings as necessary.
2. Check tightness of injector insert (2-piece inserts). If inserts are loose, remove and clean threads. Use sealing compound when installing upper insert. Replace sealing washer that goes against cylinder head below lower portion of insert. Lubricate injector "O" rings with gasoline and install injectors, with fuel lines connected, into fuel quantity analyzer tubes.
3. Ensure lines are not kinked or bent. Loosen fittings to align fuel lines and retighten. Remove rubber boot from airflow sensor housing above sensor plate. Turn and lift setting screw and adjusting slide of Sensor Plate Adjustable Holder (VW 1348/1) into upper position. This simulates full throttle operation. (Scheme 20)
4. Place sensor plate adjustable holder on airflow sensor housing with holder centered over plate. Pointer on edge of holder base must point toward center of fuel distributor. Push adjusting slide of holder down onto stop.
5. Turn adjusting screw clockwise until magnetic end touches sensor plate retaining bolt. Activate fuel pump with jumper switch. Turn adjusting screw of holder counterclockwise until any one injector starts to deliver fuel. Turn off jumper switch and empty fuel quantity analyzer after taking sample.
6. Idle injection quantity is measured first. Lifting adjusting slide of holder to first stop simulates idle position of sensor plate. Activate fuel pump until fuel level reaches 20 ml on scale of any tube.
7. Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise sensor plate up quickly to full lift position and release. Repeat idle quantity test. Compare amounts of fuel delivered by all injectors with analyzer held level. Maximum difference in delivery quantity between injectors is 3.0 ml of fuel.
8. If fuel delivery quantity differs between high and low levels by more than 3.0 ml, interchange injectors and repeat test. If difference of delivery quantity changes with injectors, replace injectors. If difference of delivery quantity does not change with movement of injectors, either fuel lines are pinched or fuel distributor is defective.
9. Measure full throttle injection quantity. Empty analyzer into fuel tank and reinstall injectors in analyzer. Lift adjusting slide of holder to last stop to simulate full throttle position of sensor plate. Activate fuel pump with jumper switch until fuel level reaches 80 ml on scale of any tube of analyzer.
10. Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise sensor plate up quickly to full lift position and release. Repeat full throttle quantity test. Compare amounts of fuel delivered by all injectors with analyzer held level. Maximum difference in delivery quantity between injectors is 8.0 ml of fuel.
11. If fuel delivery quantity differs between high and low levels by more than 8.0 ml, interchange injectors and repeat test. If difference of delivery quantity changes with injectors, replace injectors. If difference of delivery quantity does not change with movement of injectors, either fuel lines are pinched or fuel distributor is defective.
12. Check fuel injectors for leakage immediately after delivery quantity test is complete. Set sensor plate in rest position. Activate fuel pump with jumper switch for 2 minutes. Injectors should not drip. Replace injectors that drip.

Fuel Pump Relay

1. Remove fuel pump relay from relay board. Turn ignition on. Using multimeter, measure voltage at following relay board sockets: between terminal No. 2 and ground, between terminals No. 2 and 1 and between terminals No. 4 and 1. Reading should be battery voltage or slightly less. NOTE: No testing procedure was available for Quantum or Quantum Syncro.
2. If reading is low or zero, check wiring. Refer to appropriate WIRING DIAGRAM in this article to check circuits. Measure voltage between relay board sockets No. 5 and 1. Battery voltage should be present. If reading is correct, ground middle wire of ignition distributor connector.
3. Voltage reading should drop for short time. If reading does drop, replace fuel pump relay and check Hall sender. If reading does not drop, check Hall ignition ECU.

Cold Start (Warm-Up) Enrichment (Fox Only)

Connect test harness and multimeter to Differential Pressure Regulator (DPR) and vehicle harness. (Scheme 21) Disconnect wiring from coolant temperature sensor. Turn ignition on. DPR current should be 80-110 mA. If not, replace ECU.

Scheme 21

Cold Acceleration Enrichment

1. Connect test harness and multimeter to DPR and vehicle harness. (Scheme 21) Disconnect wiring from coolant temperature sensor. Turn throttle valve halfway open on all except Fox. Remove intake air boot.
2. Turn ignition on and lift sensor plate quickly to full open position on Fox and Quantum or 1/3 open on all other models. DPR current should increase to more than 110 mA, and drop back to 80-110 mA range. If not, check potentiometer and wiring to ECU. If potentiometer and wiring are good, replace ECU.

After Start Enrichment

1. Connect test harness and multimeter to DPR and vehicle harness. (Scheme 21) Connect multimeter to test harness. Disconnect wiring from coolant temperature sensor. Ground high tension lead (terminal No. 4) from ignition distributor.
2. Crank starter for 3 seconds. Return key to "ON" position. DPR current reading should increase to more than 120 mA for 20-50 seconds, and return to 80-110 mA range.
3. If not, check starter signal to terminal No. 24 of ECU connector. Check signal from relay board to starter motor (terminal No. 15a on starter). On Quantum and Quantum Syncro, check voltage between ECU terminals No. 2 and 21. See VOLTAGE CHECKS and RESISTANCE CHECKS CHARTS in this article for appropriate testing procedure. If all wiring is okay, replace ECU.

Starting Enrichment (Quantum Only)

1. Connect test harness to DPR and vehicle harness. (Scheme 21) Disconnect wiring from coolant temperature sensor. Plug "jumper end" of Test Resistor (VW 1490) into harness connector of temperature sensor. Activate starter for 3 seconds.
2. Current reading should be more than 70 mA for first 1.5 seconds of starter operation. If not, check for open circuit between terminal No. 24 on ECU connector and terminal No. 15a on starter. If starter circuit is okay, check between terminals No. 2 and 21 on ECU connector. If wiring is okay, replace ECU.

Full Throttle Enrichment

1. Connect test harness to DPR and vehicle harness. (Scheme 21) Disconnect wiring from coolant temperature sensor. Plug "jumper end" of Test Resistor (VW 1490) into harness connector of temperature sensor. Unplug oxygen sensor. Turn ignition on. On Golf GTI and Jetta GLI start engine and increase speed to 3000 RPM.
2. Activate full throttle switch. Current reading should increase 16 mA on Golf GTI and Jetta GLI models (3 mA on all other models) when switch is activated. If not, check full throttle switch. See «ADJUSTMENTS»(/volkswagen/jetta/ii-1984-1992/remont/testing-diagnostics/#fuel-injection-system-bosch-cis-e).
3. If switch is functioning and adjusted correctly, check for open circuit between terminals No. 5 and 2 on ECU connector and terminals on full throttle switch. If wiring is good, replace ECU.

Deceleration Fuel Shut-Off Check

1. Engine oil temperature must be at minimum of 120°F (50°C). Reconnect wiring to temperature sensor. Start engine and run it at 2000 RPM briefly. Release throttle.
2. DPR current reading should briefly be negative (-30 to -60 mA) and return to positive when engine reaches approximately 1300 RPM. If not, check for open idle switch signal at ECU connector terminals No. 2 and 13. If switch is good, replace ECU.

1. Disconnect distributor high tension lead from distributor and connect to ground. Remove glove compartment and disconnect main connector from MCU. Disconnect connector terminal from potentiometer.
2. Measure resistance between connector pins No. 14 and 18 of the main connector. Resistance should be 2100-2600 ohms.
3. Measure resistance between connector pins No. 11 and 14. Resistance should be 200-3600 ohms.
4. If resistance is not to specification check wiring continuity. If wires have continuity replace altitude sensor.

Oxygen Sensor Heating Element (Quantum Syncro Only)

1. With engine cold, disconnect oxygen sensor heater connection. Connect ohmmeter between male terminals of sensor connector. Start and idle engine. Resistance should be 2-4 ohms. If resistance is incorrect replace oxygen sensor.
2. Connect voltmeter between terminals of oxygen sensor female connector. Battery voltage should be present. If not, check continuity of wiring using wiring diagram as a reference.

Oxygen Sensor (Fox Only)

1. Before testing oxygen sensor, ensure the following conditions are met: engine oil temperature is at 176°F (80°C) minimum, radiator fan must cycle at least once, pressure gauges NOT connected, exhaust system free of leaks, oxygen sensor control working correctly, oxygen sensor heating element functional, all electrical units turned off (radiator fan and A/C must be off during test), and engine speed at 3000 RPM for 2 minutes.
2. Connect test harness and multimeter between DPR and vehicle harness. Remove coolant temperature sensor. Insert a 15 k/ohm resistor in connector. Disconnect oxygen sensor.
3. DPR current must read 9-11 mA. Ground oxygen sensor wire. After 20 seconds DPR current must be 19-22 mA. If not, check wiring. If wiring okay, replace CIS-E computer.

Oxygen Sensor (All Other Models)

1. Before testing oxygen sensor, ensure the following conditions are met: engine oil temperature is at 176°F (80°C) minimum, radiator fan must cycle at least once, pressure gauges NOT connected, exhaust system free of leaks, oxygen sensor control working correctly, oxygen sensor heating element functional, all electrical units turned off (radiator fan and A/C must be off during test), and engine speed at 3000 RPM for 2 minutes.
2. Connect test harness and multimeter between DPR and vehicle harness. Run engine at idle. After 2 minutes running time, oxygen sensor will be operational.
3. Check current reading at 3000 RPM. If reading fluctuates, oxygen sensor is good. If reading does not fluctuate at 3000 RPM, replace oxygen sensor.

Idle Speed Boost Valves

1. To test boost valve No. I, engine oil temperature must be at 176°F (80°C) minimum. If equipped, A/C system must be off. Run engine at idle speed. Turn on all electrical units except A/C system. Turn in idle speed adjusting screw to lower idle. At 750 RPM, boost valve No. I should open and idle speed will increase.
2. Pinch shut outlet air hose after "T" connector. Engine speed should drop. Leaving air hose pinched shut, raise engine idle speed to 870-930 RPM. Open air hose. Idle speed should increase. When 1050 RPM is reached, boost valve No. I should close and engine speed should drop to 870-930 RPM.
3. To check boost valve No. II (A/C equipped only), ensure A/C is off. Run engine at idle speed and pinch outlet air hose shut. Engine speed should not change. When A/C is switched on with air hose pinched shut, idle speed should drop.

Idle Speed Stabilizer Valve

1. Connect Tester (VW 1367) using Cable Adapter (US 1112). Connect ohmmeter between terminal No. 1 of test connector and terminal No. 15 of main ECU connector. With stabilizer valve disconnected there should be continuity between these terminals.
2. Connect ohmmeter to terminal No. 2 of the test connection and terminal No. 3 of the central connector. With stabilizer valve disconnected there should be continuity between these terminals. Check and repair any open circuits using wiring diagrams for reference.
3. With stabilizer valve disconnected, connect voltmeter between terminal No. 2 of the idle stabilizer valve connector and ground. With ignition on, battery voltage should be present. (Scheme 22)
4. With ignition off, check for continuity between terminal No. 3 of the idle stabilizer valve connector and terminal No. 3 of the main ECU connector. Check for continuity between stabilizer connector terminal No. 1 and ECU connector No. 4.
5. Correct any open circuits and reconnect idle stabilizer valve connector. Connect ohmmeter between terminals No. 3 and 4 of the main ECU connector. Resistance specification is 24-30 ohms. Replace idle stabilizer valve if not within specification.

Scheme 22

Idle Speed Stabilization System

1. Engine oil temperature must be at 176°F (80°C) minimum. Ignition timing point is 4-8 degrees BTDC. A/C must be off. Connect Dwell Meter (VW 1367) using Adapter Cable (US 1112). Set "%" button on dwell meter and check duty cycle.
2. Reading should be 26-30% with oxygen sensor connected. Idle speed should be 800-900 RPM. If not, adjust duty cycle.
3. If reading shows 33% or 40%, ensure A/C is switched off. If A/C is off, check idle throttle switch function. Check for open circuit between idle switch and ECU connector.
4. If reading is fluctuating between 20-25%, check for open circuit in RPM signal from ignition ECU. If reading is a steady 25%, and idle speed is high. Check for air leaks in throttle body. If no leaks are found, check for open circuit between ECU and idle stabilizer control valve. If circuit is correct, replace idle stabilization valve.
5. Turn A/C on. Idle speed should increase by 100 RPM. If not, check for open circuit between A/C switch on dash and terminals No. 6 and 16 on ECU connector. Check for RPM increase of 100 RPM when A/C compressor cycles off.
6. If idle speed goes over 1000 RPM when A/C compressor switches off, check compressor signal wire to ECU. Wire should go to ECU connector terminal No. 19. Ensure it is connected to the correct terminal and not terminal No. 16. Check wiring diagram and correct.

Knock Sensor (16-Valve Engines Only)

1. With ignition off, disconnect knock sensor from control unit. Measure resistance between terminals No. 13 and 14. Type I sensor should have 300 k/ohms. A Type II sensor should measure infinity (4). Reconnect sensor to control unit.
2. Connect LED Test Light (US 1115) to single lead (Brown) connector and to battery (+) voltage. LED must light. CAUTION: Do not use a standard test light to test knock sensor. Higher voltage type light may damage control unit.
3. With engine running, LED should go out (may glow slightly). Increase engine RPM one time to 3000 RPM. If LED lights again connect a jumper wire between outside terminals of knock sensor connector and momentarily (3 seconds) ground (-) center terminal.
4. The LED light will blink on and off in a pattern. Blinking 2 times at intervals indicates a fault in the knock sensor (sensor defective, wiring, mounting torque) or defective control unit.
5. If the LED light blinks 3 times in intervals it indicates a break in the vacuum hose to the control unit or the control unit vacuum sensor is defective.

Knock Sensor Control Unit (16-Valve Engines Only)

1. Ensure ignition coil and Hall Effect control module are okay. Remove connector from knock sensor and turn ignition on. Check for battery voltage between connector pins No. 3 and 5.
2. Measure battery voltage between terminals No. 6 and 3. Open throttle valve, voltage should drop to zero volts. If voltage does not drop to zero check throttle idle switch.
3. Measure voltage between terminals No. 8 and 3 while opening throttle. Battery voltage should be present at full throttle. If battery voltage is not present check full throttle switch.
4. Remove harness connector from Hall Effect sender at distributor. Turn ignition on and measure voltage between outer terminals of connector. Voltage should be 5 volts minimum. Turn ignition off.
5. With ignition on, check voltage between terminals No. 1 (-) and 15 (+) of ignition coil. Touch center terminal of connector from Hall Effect control module to ground. Voltage should increase briefly to 2 volts minimum. If it does not, replace knock sensor control unit.

Throttle Valve Switch

See ADJUSTMENTS for checking and adjusting procedure for idle and full throttle valve switches.

Note. CIS-E fuel injection maintains constant fuel pressure throughout system. Relieve pressure before opening system. DO NOT allow fuel to leak on engine or electrical parts. DO NOT allow any open flame near fuel system being serviced.

SYSTEM TESTING

Following VOLTAGE CHECKS and RESISTANCE CHECKS charts show procedure for checking CIS-E system components from ECU connector. ECU connector terminal numbers are called out in testing procedures. Ignition MUST be off whenever ECU connector is disconnected or reconnected. Use care to avoid any terminal damage when testing, removing or attaching connectors.

Always check all connections used in test procedure. If readings are incorrect, disconnect terminals and determine if wiring or components are at fault. High tension lead (from coil) at distributor cap should be removed and grounded. Use Digital Multimeter (US 1119).

Scheme 23

16 VALVE CIS-E INJECTION - VOLTAGE CHECKS

Scheme 24

16 VALVE CIS-E INJECTION - RESISTANCE CHECKS

FOX CIS-E INJECTION - VOLTAGE CHECKS

FOX CIS-E INJECTION - RESISTANCE CHECKS

QUANTUM & QUANTUM SYNCRO VOLTAGE CHECKS

QUANTUM & QUANTUM SYNCRO RESISTANCE CHECKS

Removal

1. Disconnect battery and remove air cleaner. Disconnect all fuel and injector lines from fuel distributor. Plug fuel supply and return lines. Catch any spilled fuel.
2. Disconnect wiring from DPR. Remove screws holding fuel distributor to airflow sensor housing. Remove fuel distributor by turning back and forth while lifting up.

Installation

1. Lightly lubricate new sealing "O" ring and mount on fuel distributor. Install fuel distributor. Connect all fuel lines except those to fuel injectors. Check sensor plate adjusting lever and fuel distributor control piston for smooth operation.
2. Remove fuel pump relay and bridge fuel pump circuit. Use Jumper Switch (US 4480/3) in place of fuel pump relay. When pressure has built up, turn off fuel pump. Move sensor plate from rest position to end of travel.
3. Uniform resistance should be felt during entire movement. No resistance should be felt on quick return to rest position. Connect injector lines. Install fuel pump relay. Start engine and check for leaks.

Remove injectors from inserts in head with fuel lines attached. Using 13 mm hex head socket, remove inserts from head. Use 2 wrenches to remove injectors from lines.

To install, reverse removal procedures. Use 2 wrenches when tightening injector lines to injectors. Use new "O" rings. On models with 2-piece inserts, replace insert sealing washer (against head) and use sealing compound on upper insert threaded portion.

1. Disconnect accelerator cable from linkage. Disconnect return spring on TVH. Remove cruise control connecting rod on TVH (if equipped). Pull off vacuum hoses. Remove TVH mounting nuts.
2. Disconnect throttle valve switch. Remove 2 nuts holding TVH to metallic front vibration mounts. Disconnect fuel return hose from pressure regulator. Lift sensor housing upward and remove TVH. Remove gasket.

To install, reverse removal procedure. Use new gasket. Adjust accelerator linkage and idle speed.

Remove air filter and unscrew stop bracket. Using heat gun, heat locking compound on fastening bolt. Remove bolt slowly. Do not damage threads. Clean locking compound from bolt hole threads.

Insert airflow sensor plate. Ensure 5 punch marks are up. Lightly tighten self-locking screw. Ensure sensor plate is centered and rest position is correct. See ADJUSTMENTS . To complete installation, reverse removal procedure.

Removal & Installation

Remove DPR. Remove insulating compound covering mounting screws. Remove potentiometer. Do not touch or damage slide contact and conductor. To install, reverse removal procedure. Adjust potentiometer. See ADJUSTMENTS .

1. The knock sensor is attached at the front of the engine block. There are 2 types of sensors. The Type I sensor has its cable connection molded off center from the side of the sensor. No washers are used on fastening bolt. Tighten to 84-108 INCH lbs. (10-12 N.m).
2. The Type II sensor has its connector cable molding centered on the side of the connector. Tighten to 11-18 ft. lbs. (15-25 N.m) without washers.

CIS-E Wiring Diagram (Cabriolet). Scheme 25

CIS-E Wiring Diagram (Fox). Scheme 26

CIS-E Wiring Diagram (Golf GTI - 16-Valve). Scheme 27

CIS-E Wiring Diagram (Jetta GLI - 16-Valve). Scheme 28

CIS-E Wiring Diagram (Scirocco - (16-Valve). Scheme 29

CIS-E Wiring Diagram (Quantum & Quantum Syncro). Scheme 30

See also:
• ADJUSTMENTS