1990 Isuzu Trooper

  • 4 CYL
  • 4WD
  • 80,000 MILES
2.6-4 cyl. I can get this car running for a while and then it dies and won't restart. I have replaced plugs, distributor cap, rotor, temp, throttle position and O2 sensors. Engine is running rich and idle is poor. Check engine light is on. EGR system has been crippled/removed by native mechanics. This car is in Haiti and parts are scarce. I will be going back down there in about a month to try and fix this car one more time. This trooper is used for medical missions (www. Angelmissionshaiti. Org) and needs to be reliable. Is it possible to put a carburetor on it and make it run that way or is the ignition tied into the fuel injection?
Do you
have the same problem?
Wednesday, August 5th, 2009 AT 8:41 PM

1 Reply

Hello .. thanks for the donation .. much appreciated

Basically the fuel systems on this vehicle are computer controlled and cannot be replaced with a carburettor ... hope this description helps .. let me know if you have anymore questions ?

Fuel pump is located inside fuel tank. Pump is integral in design and must be replaced as an assembly. See
When ignition is turned on, ECM energizes fuel pump relay. Relay will operate fuel pump for 4 seconds to pressurize fuel system. After engine start, relay contacts are held closed by ECM. If engine running signals to ECM are interrupted, ECM will de-energize relay.
When ignition switch is turned on, ECM will activate fuel pump relay to run fuel pump. Fuel pump will operate as long as engine is cranking or running and ECM is receiving ignition reference pulses. If there are no reference pulses, ECM will shut off fuel pump within 2 seconds after ignition is turned on. Should fuel pump relay, or 12-volt relay from ECM fail, fuel pump will run through oil pressure switch, which will activate backup relay circuit. Oil pressure must reach 4 psi (0.28 kg/cm2 ) before backup relay is activated.
Fuel pressure regulator governs flow of fuel to injectors. Pressure varies depending on different vehicle speed and load conditions. To improve hot restartability, ECM controls vacuum switching valve to change vacuum supplied to pressure regulator. Fuel pressure regulator consists of a fuel chamber and a vacuum chamber separated by a diaphragm. Fuel chamber has a fuel inlet pipe and a fuel outlet pipe. Fuel inlet pipe delivers fuel from fuel distributor pipe. Appropriate amount of fuel is then delivered to fuel injector.
Excess fuel is returned to fuel tank by fuel outlet pipe. Vacuum chamber is connected to intake manifold by a hose. Any change in fuel pump delivery pressure or intake manifold pressure will cause diaphragm to move. This movement will maintain pressure balance between intake manifold and fuel chamber to ensure a steady supply of fuel to fuel injectors.
Dropping Resistor (Impulse & Trooper 2.6L)
Dropping resistor is connected in series between power source and fuel injector. The dropping resistor reduces applied voltage to stabilize injection starting condition during initial stage.
Fuel Injectors
Fuel is metered into cylinders by electrically controlled solenoid valves in injectors. ECM controls on/off time (duty cycle) of fuel injectors to regulate air/fuel ratio. Fuel-Cut System (Except Trooper 2.8L)
Controlled by throttle position sensor, this system shuts off fuel flow during vehicle deceleration to reduce exhaust emissions. With engine at operating temperature, vehicle at cruising speed, and throttle position sensor returned to idle position, ECM reduces impulses to fuel injectors.
Fuel Pressure-Up System (Except Trooper 2.8L)
Fuel pressure-up system slightly increases fuel pressure on hot restarts for improved starting and idle stability. Pressure rise is accomplished by cutting off vacuum signal to fuel pressure regulator. ECU controls vacuum signal through Vacuum Switching Valve (VSV).
Injector Blower (Impulse)
Injector blower is located in engine compartment. Blower is used to cool fuel injectors. When ignition key is turned off, thermostatic switch will activate blower motor for about 15 minutes.

Oxygen (O2) Sensor
O2 sensor is located in exhaust manifold and informs ECM of amount of oxygen in exhaust gases.
Air regulator operates as an air by-pass during cold fast idle conditions. When engine is cold, air regulator allows additional flow of air to enter intake manifold.
Temperature sensitive electric element closes regulator as engine temperature increases. Air regulator is independent from I-TEC system and is operated by ignition switch through fuel pump relay.
When A/C is turned on, solenoid increases engine idle speed to prevent engine stalling.
IAC system is used to control idle speed. IAC system consists of an air control valve, ECM and sensors. ECM controls idle speed by opening and closing IAC valve to allow air to by-pass throttle body. It does this by sending voltage pulses to proper motor winding in IAC motor. This will cause motor shaft and valve to move in and out of motor a given distance for each pulse received. ECM pulses are referred to as counts.
Each time ignition is turned off, ECM will reset IAC valve. is done by sending enough counts to seat valve. Fully seated valve is ECM reference point. A given number of counts are then issued to open valve and normal ECM control of IAC valve will begin from this point. To increase idle speed, ECM will send enough counts to retract IAC valve to allow more airflow through idle air passage and by-pass throttle plate until idle speed reaches proper RPM. This will increase ECM counts. To decrease idle speed, ECM will send enough counts to extend IAC valve to reduce air flow through idle passage around throttle plate. This will reduce ECM counts.

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Thursday, August 6th, 2009 AT 4:41 AM

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