Engine Controls - Basic Testing - Efi: Other Isuzu Rodeo I

TERMINOLOGY

Due to Federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The following table will help eliminate confusion when dealing with these components and systems.

SAE TERMINOLOGY

Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.

Exhaust System Backpressure

The exhaust system can be checked with a vacuum or pressure gauge. If using a pressure gauge, remove O2 sensor or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4 - 2 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restriction.

FUEL SYSTEM

FUEL SYSTEM PRESSURE RELEASE

Note. Fuel pump relay is located in engine compartment fuse/relay box.

Pickup 3.1L

1. Disconnect negative battery cable. Loosen fuel tank filler cap to relieve air pressure. Cover fuel inlet line fitting at throttle body with shop towel. Loosen fitting slowly to catch excess fuel.
2. The internal constant bleed feature of throttle body relieves fuel system pressure when engine is turned off. When fuel stops leaking, tighten fitting. Reconnect negative battery cable.

Except Pickup 3.1L

1. Loosen fuel tank filler cap to relieve tank pressure. Remove fuel pump relay from underhood fuse/relay box. Start and operate engine until it stalls. Crank engine an additional 30 seconds.
2. Loosen hose clamp of fuel line on side of pressure regulator, coming from fuel line inlet distributor pipe. Cover fuel hose with a shop towel, and slowly pull hose from pressure regulator to relieve fuel pressure. When fuel stops leaking, reinstall hose and clamp.

Fuel Pump Relay (2.6L Amigo, Pickup & Rodeo)

1. Power from charging circuit relay runs through fuse/relay box fuse No. 5 and diode box "A" to energize fuel pump relay. Relay is also energized from diode box "A" through oil pressure switch circuit in case of charging system failure.
2. When energized, fuel pump relay closes power circuit from main fuse No. 1, through fuse No. 2, through fuel pump relay to fuel pump. See appropriate wiring diagram in WIRING DIAGRAMS article.
3. To test relay, remove fuel pump relay from fuse/relay box on right fender panel. Using jumper wires, ground terminal No. 4 (Black wire) and apply battery voltage to terminal No. 5 (White wire). see scheme 4 There should be continuity between terminals No. 1 and 3 with relay energized. If continuity is not present, replace relay.

Fuel Pressure (Rodeo 3.2L & Trooper)

1. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE. Attach Fuel Pressure Gauge Set (J-34730-1) and Adapter (J-35957-1) to outlet side of fuel filter. Disconnect pressure regulator vacuum hose. Turn ignition on. Allow fuel pump to run for about 2 seconds.
2. Fuel system pressure should be about 41-46 psi (2.8-3.2 kg/cm 2 ) for Rodeo 3.2L and Trooper. Start engine and check for leaks. Connect pressure regulator vacuum hose. If engine will not start, fuel pump relay can be by-passed. Also see appropriate CHART A-3, ENGINE CRANKS BUT WILL NOT RUN under TROUBLE SHOOTING CHARTS. With engine idling, fuel pressure should be 25-30 psi (1.8-2.1 kg/cm 2 ).

Note. To test fuel pump relay circuit, proceed to appropriate CHART A-5, FUEL PUMP RELAY CIRCUIT under TROUBLE SHOOTING CHARTS.

Fuel Pump Relay (Rodeo 3.2L & Trooper)

1. ECM supplies power to relay as long as ECM receives ignition reference signals or starter crank signal. To run fuel pump without starting engine, remove relay and jumper terminals No. 2 and 4. (Scheme 21)and (Scheme 22).
2. To test relay, use jumper wires to ground terminal No. 4 of relay and apply battery voltage to terminal No. 2 of relay. Using ohmmeter, check for continuity between relay terminals No. 1 and 3. If continuity is not present, replace relay.

FUEL PUMP PERFORMANCE

Fuel Pressure (Pickup 3.1L)

1. Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE. Install fuel pressure gauge between steel line and flexible hose at throttle body. Start engine. Check for leaks and allow engine to idle. Fuel pressure should be 9-13 psi (.62-.91 kg/cm 2 ).
2. If engine will not start, apply battery voltage to fuel pump test terminal connector (Black/Red wire). Test terminal connector is a single wire with a clear-colored connector, located in wiring harness on left fender, under fuse/relay box. If engine still will not start, see appropriate CHART A-3, ENGINE CRANKS BUT WILL NOT RUN under TROUBLE SHOOTING CHARTS. NOTE: Ensure Code 54 is not set by ECM before going to next step. See appropriate SELF-DIAGNOSTICS article.
3. If Code 54 is not set and fuel pressure is not within specification, see appropriate CHART A-7, FUEL SYSTEM PRESSURE TEST under TROUBLE SHOOTING CHARTS.

Fuel Pump Relay (Pickup 3.1L)

1. Fuel pump relay is powered through the ECM. During cranking, ECM will power fuel pump for 2 seconds or until ECM receives ignition reference signals. If engine does not start within 2 seconds after ignition is turned on, ECM cuts off power to fuel pump. NOTE: To test fuel pump relay circuit, see appropriate CHART A-7, FUEL SYSTEM PRESSURE TEST under TROUBLE SHOOTING CHARTS.
2. If fuel pump relay fails (setting Code 54), oil pressure switch provides back-up circuit to run fuel pump. Oil pressure switch circuit closes when oil pressure is greater than 4 psi (.28 kg/cm 2 ), operating fuel pump back-up relay.
3. Fuel pump relay and back-up relay are located in fuse/relay box, in engine compartment. see scheme 18- see scheme 20. Also see CODE 54 chart in appropriate SELF-DIAGNOSTICS article.

Ignition System Check

See appropriate CHART C-4, IGNITION SYSTEM CHECK under TROUBLE SHOOTING CHARTS.

Ignition Coil

Information is not available from manufacturer.

Crankshaft Position Sensor

Information is not available from manufacturer.

See appropriate CHART C-4, IGNITION SYSTEM CHECK under TROUBLE SHOOTING CHARTS.

Ensure ignition is off. Disconnect ignition coil connectors. Connect ohmmeter as shown in illustration. (Scheme 16) Replace coil if faulty.

Pick-Up Coil

Ensure ignition is off. Remove distributor cap. Connect ohmmeter as shown in illustration. (Scheme 17) Replace pick-up coil if faulty.

Scheme 16

Scheme 17

Information is not available from manufacturer.

1. Ensure ignition is off. Disconnect ignition coil wiring. Measure primary resistance between terminals "C" and "E". (Scheme 18) Measure secondary resistance between terminals "C" and "D". Measure insulation resistance between terminals "C" and body ground.
2. Ensure resistance is within specification. See IGNITION COIL RESISTANCE (NON-HEI SYSTEMS) table. Replace coil if resistance is not within specification.

IGNITION COIL RESISTANCE (NON-HEI SYSTEMS)

Scheme 18

Testing information is not available from manufacturer. However, faults in crankshaft position sensor will set Code 41. See appropriate SELF-DIAGNOSTICS article.

Note. A faulty power transistor or circuit will set Code 23, 35 or See appropriate SELF-DIAGNOSTICS article.

Power Transistor

1. Ensure ignition is off. Remove coil wire from distributor cap. Attach Spark Tester (J-26792), or, using insulated pliers, hold distributor terminal end of coil wire about 1/4" (5 mm) from metal surface.
2. Disconnect and remove power transistor from under intake manifold. This involves removing right front wheel and rubber inner fender panel cover to access power transistor.
3. Connect jumper wire between harness connector and power transistor connector Blue wire terminal. Connect negative end of 1.5-volt "D" battery to power transistor Green wire terminal. (Scheme 19) Connect positive end of 1.5-volt "D" battery to harness connector Yellow wire terminal. Ground power transistor.
4. Turn ignition on with engine off. Disconnect and connect jumper lead at power transistor connector several times. Verify spark is jumping across air gap at spark tester. If spark does not occur, check wiring for continuity or shorts. If wiring is okay, replace power transistor.

Scheme 19

IDLE SPEED & IGNITION TIMING

For adjustment procedures, see ADJUSTMENTS - EFI article.

IDLE SPEED SPECIFICATIONS

BASE IGNITION TIMING

CHART A-3 - ENGINE CRANKS BUT WILL NOT RUN (PICKUP 3.1L)

Note. Before performing this test, check battery condition, engine cranking speed and tank for adequate fuel. Test numbers refer to test numbers on diagnostic chart.

1. When ignition is turned on, the CHECK ENGINE light should come on, indicating battery voltage and ignition voltage are being supplied to ECM. If NO ALDL data (trouble codes) are displayed on scan tester, this may be due to ECM problem. See appropriate SELF-DIAGNOSTICS article to diagnose CHECK ENGINE light. If TPS voltage is more than 2.5 volts, engine may be in "clear flood" mode, which will cause starting problems. Engine will not start without ignition reference signals. Scan tester should indicate engine speed (RPM) during cranking.
2. No spark may be caused by one of several components related to ignition system. See IGNITION CHECKS to diagnose ignition problems related to a no-spark condition.
3. Fuel spray from injectors indicates fuel is available. However, engine could be severely flooded because of too much fuel.
4. While cranking engine, there should be no fuel spray with injector disconnected. Replace injector if it sprays or drips fuel while disconnected.
5. Fuel pressure will drop after fuel pump stops due to a controlled bleed in fuel system. Use of fuel pressure gauge determines if fuel system pressure is enough for engine to start and run.
6. No fuel spray from injector indicates a faulty fuel system, or no ECM control of injector.
7. This test checks ignition module reference pulse, wiring and ECM. Using a test light connected to 12-volt source, momentarily touch circuit No. B5 (Pink/Black wire). A reference pulse should be generated. If injector test light blinks, ECM and wiring are okay.
8. No fuel spray from one injector indicates a faulty fuel injector or no ECM control of injector. If test light blinks while cranking, ECM control should be considered okay. Ensure test light makes good contact between connector terminals during test. Light may be a little dim when it is blinking because of test light current draw. Brightness of test light is not important.
9. Circuit No. A6 (Light Green/Red wire) supplies ignition voltage to injectors. Using test light, probe each connector terminal to ground. There should be a light on at one terminal. If test light confirms ignition voltage at connector, ECM injector control circuits No. D16 or D14 may be open. Reconnect injector. Using a test light connected to ground, check at ECM connector terminal D16 or D14. A light at this point indicates injector is shorted. Replace injector and ECM.

CHART A-3 - ENGINE CRANKS BUT WILL NOT RUN (RODEO 3.2L & TROOPER)

Note. Before performing this test, check battery condition, engine cranking speed and tank for adequate fuel. Test numbers refer to numbers on diagnostic chart.

1. When ignition is turned on, the CHECK ENGINE light should come on, indicating battery voltage and ignition voltage are being supplied to ECM. If NO ALDL data (trouble codes) are displayed on scan tester, this may be due to ECM problem. See appropriate SELF-DIAGNOSTICS article to diagnose CHECK ENGINE light. If TPS voltage is more than 2.5 volts, engine may be in "clear flood" mode, which will cause starting problems. Engine will not start without ignition reference signals. Scan tester should indicate engine speed (RPM) during cranking.
2. Because electronic ignition system uses 2 plugs and wires to complete circuit of each coil, opposite spark should be left connected. If RPM is indicated during cranking, ignition control module is receiving crank signal. If no spark is present, ignition control module is not triggering coils. See IGNITION CHECKS to diagnose ignition problems related to no-spark condition.
3. Test light should blink, indicating ECM is in control of injectors. Brightness of light is not important.
4. This test checks ignition control module reference pulses, wiring and ECM. Connect test light connected to 12-volt source, and momentarily touch Yellow/Red wire. A reference pulse should be generated. If RPM is indicated, ECM and wiring are okay.
5. High resistance in spark plug wire could cause a no-start condition. If a spark plug wire is faulty, replace wire and retest system.
6. This test will check injector harness for an open or shorted circuit after engine harness connector.
7. A shorted or open injector could be cause of engine cranks but will not run symptom.
8. Test for short to ground in injector driver circuits.
9. Check for voltage at injector. An open in Red/Green wire at splice from main relay would result in engine cranks but will not run symptom.
10. Test engine control module for injector pulse.
11. A faulty resistor module could be cause of no-start condition. If module is faulty, recheck engine control module after replacing resistor module.
12. This test will determine if 12-volt supply and good ground are available at ignition control module.
13. This test checks for battery voltage in ignition feed circuit to ignition control module.
14. This test checks for continuity of crankshaft position sensor and connections.
15. Voltage will vary depending on engine cranking speed.

Scheme 20

Scheme 21

Scheme 22

Scheme 23

CHART A-5 - FUEL PUMP RELAY CIRCUIT (RODEO 3.2L & TROOPER)

When ignition switch is turned to ON position, ECM activates fuel pump relay to run fuel pump. ECM activates relay as long as it receives ignition reference signals or starter crank signal. If no reference signals are received by ECM within 2 seconds after ignition is turned on, ECM cuts off power to relay.

Note. Test numbers refer to numbers on diagnostic chart.

1. This test checks for battery voltage at switching portion of fuel pump relay.
2. This determines if circuit between fuel pump relay (including fuel pump) and ground are okay.
3. This test will check relay circuit for availability of voltage to relay coil.

CHART C-4B - IGNITION SYSTEM CHECK (PICKUP 3.1L)

Note. Test numbers refer to numbers on diagnostic chart.

1. Two wires are checked to ensure an open is not present in a spark plug wire. If spark occurs with EST connector disconnected, pick-up coil output is too low for EST operation.
2. A spark indicates distributor cap or rotor problem.
3. With ignition on and engine off, there should be battery voltage at module terminals "C" and "+". Low voltage indicates an open or a high resistance circuit from distributor to coil or ignition switch. If terminal "C" voltage is low, but terminal "+" voltage is 10 volts or more, circuit from terminal "C" to ignition coil or ignition coil primary winding is open.
4. Checks for a shorted module or grounded circuit from ignition coil to module. Distributor module should be turned off, so voltage will be low, but greater than one volt. This could cause ignition coil to fail from excessive heat. With an open ignition coil primary winding, a small amount of voltage leaks through module (from battery to tachometer terminal).
5. Applying 1.5-8 volts to module terminal "P" should turn on module. Tachometer terminal voltage should drop to approximately 7-9 volts. This test determines whether module or coil is faulty, or if pick-up coil is not generating proper signal to turn on module. This test can be performed by using a DC battery with a rating of 1.5-8 volts. Using a test light is mainly to allow terminal "P" to be probed more easily. Some digital multimeters can also be used to trigger module. Voltage in ohm position can be checked by using a second meter or by checking manufacturer's specification of scan tester being used.
6. This should turn off module and cause a spark. If no spark occurs, fault is most likely in ignition coil because most module problems would have been found before this point in procedure. A module tester could determine what is at fault.

Scheme 24

CHART C-4D-1 - IGNITION SYSTEM CHECK (RODEO 3.2L & TROOPER)

Note. Test numbers refer to numbers on diagnostic chart.

1. If engine misfire occurs under load only, see CHART C-4D-2. Engine speed should drop equally on all plug leads.
2. A spark tester must be used to verify adequate available secondary voltage at spark plug.
3. If spark jumps test gap after grounding opposite plug wire, excessive resistance exists in plug that was by-passed. A faulty or poor connection at plug may also result in miss condition. Check for carbon deposits inside spark plug boot.
4. If carbon tracking is evident, replace coil and ensure plug wires relating to that coil are clean and tight. Excessive wire resistance or faulty connections may have damaged coil.
5. If no-spark condition follows suspected coil, that coil is faulty. Otherwise, ignition control module is cause of no spark. This test may also be performed by substituting a known-good coil for one causing no-spark condition.

Scheme 25

Scheme 26

CHART C-4D-2 - IGNITION SYSTEM CHECK (RODEO 3.2L & TROOPER)

Note. Test numbers refer to numbers on diagnostic chart.

1. If engine misfire occurs at idle, see CHART C-4D-1. A spark tester must be used to verify adequate available secondary voltage at spark plug. Spark should jump test gap on all 4 leads. This simulates a load condition.
2. If spark jumps test gap after grounding opposite plug wire, excessive resistance exists in plug that was by-passed. A faulty or poor connection at plug may also result in miss condition. Check for carbon deposits inside spark plug boot.
3. If carbon tracking is evident, replace coil and ensure plug wires relating to that coil are clean and tight. Excessive wire resistance or faulty connections may have damaged coil.
4. If no-spark condition follows suspected coil, that coil is faulty. Otherwise, ignition control module is cause of no spark. This test may also be performed by substituting a known-good coil for one causing no-spark condition.

Scheme 27

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to appropriate SELF-DIAGNOSTICS article. If no hard codes are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES - FUEL INJECTION article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.