Fuel Injection System - Diesel Volkswagen Golf Mk1

DESCRIPTION

Diesel fuel injection systems consist of fuel tank, fuel filter, distributor-type injection pump, glow plugs, throttling pintle injection nozzles, and centrifugal governor. (Scheme 34)

Vane-type fuel pump, built into injection pump, supplies fuel from tank to fuel filter and then to injection pump. Injection pump supplies fuel to nozzles under high pressure, according to firing order (1-3-4-2). Excess fuel is returned to fuel tank by return lines.

FUEL INJECTION PUMP

Bosch single plunger mechanical pump consists of low- pressure, vane-type fuel pump, high-pressure distributor plunger injection pump, centrifugal governor, injection timing mechanism, electrical fuel shut-off solenoid, and manual injection pump shut-off valve. (Scheme 34)

Bosch Diesel Fuel Supply System Illustration applies to all models except Turbo. Scheme 34

As vane pump rotor turns, centrifugal force holds vanes against walls of pump's pressure chamber. Off-center design of rotor and pressure chamber squeezes trapped fuel between vanes and forces it out delivery port. Vane pressure is 42.7-99.6 psi (3-7 kg/cm 2 ). Main pump increases this pressure to approximately 1800-2400 psi (126-168 kg/cm 2 ). Pressures vary with model application.

Injection pump on Turbo models is also equipped with boost pressure enrichment device. (Scheme 35) Since turbocharger supplies more air to engine, boost pressure enrichment device is needed to increase amount of fuel delivered to engine.

At full throttle, when turbocharger boost pressure is low, no enrichment is needed. As turbocharger boost pressure increases, pressure begins to work on enrichment device diaphragm, forcing it down. This moves bell crank which in turn moves control ring further to right. Effective stroke of distributor plunger is lengthened and increases amount of fuel delivered to injectors.

Bosch Diesel Fuel Injection Pump Illustration applies to Turbo models only. Scheme 35

INJECTION NOZZLES

Bosch injection nozzles are used for all models. All nozzles are similar in appearance. Verify part numbers and injection pressures for each application before servicing.

Pressurized mist of fuel is injected into swirl chamber. Fuel swirls around chamber, mixing with hot air that is compressed to ratio of 23:1. Heat shields protect each injector.

Combustion begins in swirl chamber, continues on through small passageway, and then into leaner main chamber. As peak cylinder pressures build in swirl chamber, rather than main chamber, loads on connecting rods and crankshaft are reduced.

GLOW PLUGS

During cold starts, glow plugs are used to preheat swirl chambers. When current is applied, glow plugs become red hot. Coolant temperature sensor connected to time circuit in glow plug relay controls pre-heating time.

To start cold engine, pull out cold start knob which is on dash by steering column. Turn ignition switch to "ON" and make sure glow plug light comes on. When glow plug indicator light goes out, crank engine. Do not operate starter longer than 10 seconds. If engine does not start, wait 30 seconds. Rerun glow plug cycle and try to start engine again.

At temperatures above freezing, do not depress accelerator pedal. At temperatures below freezing, depress accelerator pedal while cranking and slowly release pedal as engine starts. About 2 minutes after engine starts, push cold start knob in fully.

FUEL FILTER

Fuel filter allows unrestricted flow of fuel from tank to injection pump, but stops any dirt or water. Replaceable element, similar to oil filter cartridge, threads onto removable flange. (Scheme 36)

Components of Fuel Filter. Scheme 36

To drain water from filter, open vent screw on top of filter flange. If there is no vent screw, disconnect fuel return line at injection pump. Remove flange mounting nuts and lift filter. Open water drain on bottom of filter.

Drain until clean fuel runs out. Close water drain and vent screw (or reconnect return line). Reattach flange and start vehicle. Make sure there are no fuel leaks. Bleeding is not necessary.

CENTRIFUGAL GOVERNOR

Amount of fuel injected is controlled by changing injection cut-off point according to engine speed and load conditions. Cut-off point is controlled by position of metering sleeve around distributor plunger.

Sleeve normally covers relief port in plunger. Uncovering port stops injection. Sleeve position is determined by centrifugal governor and accelerator linkage. Large quantity of fuel is supplied during starting, less at idle. Once engine obtains predetermined maximum RPM, fuel flow can no longer be increased.

INJECTION PUMP TIMING

Note. Before starting timing procedure, check valve timing and drive belt tension. Be sure cold start lever is against stop (toward drive gear on pump).

Scheme 37

1. Set crankshaft to TDC on No. 1 cylinder and align marks on flywheel and clutch housing. Check marks on injection pump sprocket and mounting plate. If timing adjustment is necessary, remove center plug from injection pump cover.
2. Install adapter (2066) and dial indicator (0-3 mm range) in place of plug. (Scheme 37) Preload dial indicator to.097" (2.5 mm). Slowly turn engine counterclockwise until dial indicator needle stops moving. Zero indicator. (Scheme 37): Adjusting Injection Pump Timing
3. Turn engine clockwise until TDC mark on flywheel lines up with reference mark. Check and compare dial indicator reading with specified lift. See Injection Pump Timing Specifications table. If necessary, loosen bolts on mounting plate and support. Turn pump to adjust timing and tighten bolts. Recheck dial indicator readings.

Note. It is not necessary to perform spray pattern test on injectors. Tests indicate that neither engine performance nor burnt glow plugs are related to spray pattern.

Preliminary Testing

Injection nozzle problems are usually accompanied by knocking in one or more cylinders, engine overheating, loss of power, smoky black exhaust, engine misfire, excessive blue smoke during cold start and increased fuel consumption. To locate and correct faulty injectors, use following procedure.

Scheme 38

1. With engine running at fast idle, loosen line unions on each injection nozzle one at time. If engine speed remains constant with line loosened, that nozzle is defective.
2. To remove nozzle, detach injector lines as group. Use special extra-deep socket (US 2775) to remove injection nozzles. To remove or install injector nozzles on Turbo models, remachine 1/2" (13 mm) socket wrench extension to dimensions shown. (Scheme 38)
3. To disassemble, place upper part of nozzle in vise and loosen lower part. Then reverse position of nozzle in vise, lightly clamp lower part of nozzle, and carefully remove internal parts from lower part of nozzle. Do not interchange parts from one nozzle to another.
4. Use fresh diesel fuel to clean injector parts. Check for carbonized or rough needle seat, worn injection needle and/or nozzle, or needle binding in nozzle. Reassemble injector and tighten halves to 51 ft. lbs. (69 N.m).
5. When one injector is replaced, all other injectors must be tested and adjusted if necessary. Adjust injectors to 2176 psi (150 kg/cm 2 ) for Turbo models and 1885 psi (132.5 kg/cm 2 ) for all others. NOTE: New and rebuilt injectors have settling effect of approximately 72.5 psi (5.1 kg/cm 2 ). When installing new/rebuilt injectors in conjunction with used injectors, new/rebuilt injectors must have 72.5 psi (5.1 kg/cm 2 ) higher opening pressure than that of used injectors. (Scheme 38): Fuel Injector Socket Wrench Extension Illustration applies to Turbo models only.

Installation

When installing injectors, new heat shields must be used. Insert heat shield with larger diameter sealing surface facing injector. (Scheme 39) Tighten injectors to 51 ft. lbs. (69 N.m). Bleeding is not necessary.

Exploded View of Injection Nozzle Heat shield must be installed as shown. Scheme 39

Noise Test

Listen to nozzle while it is being tested on special testing gauge (US 1111). Use long, slow strokes of testing pump lever (1-2 strokes per second). If nozzle is working properly, it will "ping" as fuel emerges.

Injection Nozzle Mounted on Tester. Scheme 40

Opening Pressure Test

With testing gauge (US 1111) still connected to injector, move pump lever down slowly. Note pressure at which injection nozzle releases fuel. Nozzle working pressure must be within specifications. Adjust, if necessary, by changing shims. Thicker shims increase pressure, thinner shims decrease pressure.

INJECTOR NOZZLE OPENING PRESSURE

Note. Shim thickness increase of .0019" (0.05 mm) increases pressure by 71 psi (5.0 kg/cm 2 ). Shims are available in thicknesses of .039-.070" (1.00-1.95 mm) in .0019" (0.05 mm) increments.

Leakage Test

With nozzle connected to gauge, press pump lever down slowly and hold pressure at about 1595 psi (112 kg/cm 2 ) for 10 seconds. No fuel should leak from nozzle tip.

1. Battery voltage must be higher than 11.5 volts. Connect test light between No. 4 cylinder glow plug and ground. Turn ignition to "ON" position for no more than 15 seconds. Test light should come on. If not, check glow plug relay, ignition switch, or fuse box relay plate.
2. If test light glows, turn ignition "OFF". Connect ammeter between No. 4 cylinder glow plug and battery positive lead. Turn ignition switch "ON" for several seconds. Initial current draw can be as high as 140 amps but should stabilize at 36 amps within seconds.
3. Total current draw of less than 36 amps indicates one or more defective glow plugs. Current draw of 27 amps indicates 1 bad glow plug, 18 amps indicates 2 bad glow plugs, and 9 amps indicates 3 bad glow plugs.
4. If total current draw exceeded 36 amps in step 2), check current to each individual glow plug. Replace any glow plug drawing more than 9 amps. To determine inoperative glow plug, disconnect wiring and bus bar from plugs. Connect test light to positive battery terminal.
5. Touch test light probe to each glow plug in turn. If light glows, glow plug is good. If light does not glow, glow plug is defective and should be replaced. If glow plugs check OK but engine is hard to start, remove glow plugs and clean any carbon off heating element. Reinstall plugs and check engine starting.

Scheme 41

1. Loosen and remove alternator belt. Remove crankshaft pulley bolts and pulley. Detach hoses from drive belt cover, then remove cover bolts and cover. NOTE: It is not necessary to remove timing belt sprockets when removing injection pump belt from engine.
2. Remove air cleaner, duct, and valve cover. Remove timing mark plug from top of bellhousing. Use bolt in center of crankshaft sprocket to rotate engine. Align TDC mark on flywheel with pointer. Check that both cam lobes on No. 1 cylinder are pointing up. (Scheme 41): Installing Camshaft Locking Tool
3. Install special setting bar (2065) in slot in end of camshaft. Rotate camshaft by hand until one end of bar touches cylinder head. Measure gap at other end of bar with feeler gauge and divide this number by 2. Use 2 feeler gauges of this size to lock camshaft on center.
4. Lock camshaft on center by inserting one feeler gauge at either end of bar between bar and cylinder head. Loosen camshaft drive belt tensioner lock nut and turn tensioner counterclockwise to remove tension from belt. Remove belt by working it off sprockets.

1. Ensure marks on pump sprocket, pump bracket, and pump housing are aligned. Install pump sprocket locking pin (2064). TDC mark on flywheel should still aligned with pointer.
2. Loosen camshaft sprocket bolt one turn, then loosen sprocket by tapping with rubber hammer. Do not remove sprocket from camshaft. Hand tighten bolt until end play is eliminated but sprocket still spins freely.
3. Install drive belt so there is no slack between camshaft and pump sprockets or between pump and crankshaft sprockets. Tighten tensioner to keep belt firmly in place. Remove pin (2064) from pump sprocket.
4. Install belt tension tester (VW 210). Adjust belt tensioner until tension tester reads 12-13. Tighten tensioner lock nut and camshaft sprocket bolt to 33 ft. lbs. (45 N.m). Remove locking tool from camshaft.
5. Turn crankshaft 2 complete revolutions. Strike belt with rubber hammer between cam and pump sprockets and recheck belt tension. Readjust if necessary. Check and adjust injection pump timing.

INJECTION PUMP

Note. Always check runout of pump gear with dial indicator when removing or installing pump. Maximum runout should be .008" (.20 mm). If runout is excessive, replace gear.

Removal

1. Remove injection pump belt. Remove injection pipes and cover fuel outlets to prevent contamination. Remove solenoid wire, hoses and control cables from pump.
2. Insert pump sprocket locking tool (2064) and remove sprocket bolt. Use puller (3032 or US 4494) to remove pump sprocket. Place puller so jaws are at right angle to bar and pointing in direction of spindle rotation.
3. Apply light tension to puller. Strike puller spindle head lightly to loosen sprocket from shaft. Do not pry on sprocket with bar or lever. Remove pump mounting bolts and remove pump from engine.

Removing Fuel Injection Pump Driven Gear Do not use pry bar on sprocket. Scheme 42

1. Install pump on mounting plate. Leave bolts loose until timing marks are aligned. After aligning marks, tighten mounting bolts to 18 ft. lbs. (25 N.m). Reconnect fuel pipes, hoses, solenoid wire and control cables.
2. Note that fuel return pipe union screw is marked "OUT" to avoid incorrect hookups. Align fuel pipe connections with fuel delivery valves. Tighten connections to 18 ft. lbs. (25 N.m). Install sprocket on pump shaft but do not tighten nut yet.
3. Turn pump sprocket by hand to align mark on sprocket with mark on mounting plate. Insert holding pin (2064) in pump sprocket. Tighten nut to 33 ft. lbs. (45 N.m). Make sure that crankshaft is at TDC and reinstall timing belt. Adjust belt tension and pump timing. Bleeding is not required.

Aligning Injection Pump Reference Marks. Scheme 43

Replace filter at maximum 30,000 mile intervals or more often if necessary due to fuel quality. On Turbo models, drain water from filter every 5000 miles. On all other models, drain water from filter every 7500 miles. Bleeding is not required.

TIMING SPECIFICATIONS

INJECTION PUMP TIMING SPECIFICATIONS

IDLE SPEED

1. Warm engine to normal operating temperature (oil temperature of 122-158°F or 50-70°C). Place engine RPM sensor (VWAG 1324) on valve cover. Connect sensor cables to battery. Attach positive lead of tachometer to sensor and negative lead to ground.
2. Check idle speed and adjust if necessary. To adjust, loosen lock nut and turn screw in to raise idle speed, or out to lower idle speed. Retighten lock nut and seal with paint.

IDLE SPEED SPECIFICATION

MAXIMUM SPEED

After idle speed is set, briefly accelerate engine to "full throttle" position. To adjust, loosen lock nut and turn screw out to raise maximum speed, or in to lower it. Tighten lock nut when adjustment is complete. Seal lock nut and screw with paint.

MAXIMUM SPEED SPECIFICATION

COLD STARTING CABLE

1. Insert washer onto cable and install cable into bracket with rubber bushing. Insert cable into pin. Install locking clip to hold cable housing in bracket.
2. Make sure cold start knob is completely pushed in against dash. Move pin end of lever as far as possible toward drive sprocket. Pull cable taut and tighten pin with clamping screw. (Scheme 44)

Adjusting Cold Starting Cable. Scheme 44

Quantum Models

1. Place accelerator pedal in full throttle position. On vehicles with manual transmissions, adjust accelerator cable by inserting locking clip in correct slot of cable housing. Lever on pump should just touch stop screw. No tension should be placed on lever or cable to set position.
2. On vehicles with automatic transmissions, put gear selector in "P" position and apply parking brake. Remove plastic cover from injection pump. Turn off engine. Loosen pedal cable adjuster at bracket on left side of transmission. Unhook pedal cable from transmission operating lever.
3. Remove clip and ball socket of accelerator cable at pump lever. Ball stud of pump lever must travel 1.219-1.299" (31-33 mm) between position at idle stop to position at full throttle stop. Travel is adjusted by changing ball stud position in elongated hole of pump lever.
4. Place ball socket and clip back on pump lever. Slip rubber boot off kickdown engagement spring housing. (Scheme 45) Loosen both accelerator cable adjusting nuts. Push transmission operating lever to closed throttle position and hold or lock it there. Pull accelerator cable housing away from pump lever.
5. Make sure kickdown engagement spring has not been compressed by pulling on cable housing. While holding housing in position, tighten accelerator cable adjusting nuts. Reconnect pedal cable to operating lever on transmission. Press accelerator pedal into kickdown position, making sure that kickdown engagement spring is compressed.
6. With accelerator pedal held in kickdown position, turn pedal cable adjuster until transmission operating lever touches stop. Lock pedal cable adjuster in position. Be certain that pedal is at stop and that cable is free of tension.
7. To recheck accelerator cable adjustment, push pump lever against idle stop. Make sure kickdown engagement spring is NOT compressed. Move transmission operating lever to closed throttle position. Press accelerator pedal to full throttle position.
8. Push pump lever against full throttle stop. Check kickdown engagement spring to make sure that it is NOT compressed (no kickdown). Press accelerator pedal past full throttle point to stop. Make sure that transmission lever is against stop.
9. Kickdown engagement spring must be compressed at this time if adjustment has been done correctly. Reattach rubber boot to spring housing. Reinstall plastic cover on injection pump.

Rabbit and Jetta Models (Manual Transmission Only)

Make sure ball pin on pump lever is pointing upward and is centered in elongated hole of lever. Adjust cable with adjusting nuts until pump lever just contacts stop without strain on cable.

Accelerator Cable Adjusting Points Auto. Trans. model shown; Man. Trans. model has 1 cable. Scheme 45

Scheme 46

1. If fuel cut-off solenoid fails in open position, engine will not shut off with key. If solenoid fails in closed position, engine will not start due to lack of fuel. Before replacing fuel cut-off solenoid, remove it from injection pump and clean it. (Scheme 46) (Scheme 46): Injection Pump Fuel Cut-Off Solenoid Always use new gasket.
2. When solenoid and plunger are clean, plunger must be checked for free movement in solenoid. Install solenoid in pump with new seal. Test for proper solenoid operation by connecting battery voltage. Good solenoid will click when 12 volts are applied or removed.
3. Manual fuel cut-off has been added to injection pump on models with automatic transmissions. If engine continues to run after key is turned off, move lever away from drive sprocket. (Scheme 47)

Injection Pump Manual Cut-Off Valve Move lever in direction of arrow. Scheme 47

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS