Question about 1990 Jeep Wrangler

1 Answer

No injector pulse, no current to the injector

I tested it with a noid light, it dosent light up while cranking. it has fire, fuel pump is working, fuel filter is new and in the right flow direction. is there a relay or fuse for the fuel injection?


1990 jeep wrangler yj 2.5l 4cyl throttle body injection

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  • erickirkland Mar 13, 2009

    thanks, its wet dark and cold out, but ill give it a shot in the morning. i appreciate your help

  • perrykinney Mar 28, 2009

    I have the same problem did this fix your touble

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  • Master
  • 1,392 Answers

Check the pickup in the distributor as this is the cam sensor. The injectors run of the pulses created while the rotor is turning around. It should be a plastic disk located under the rotor button.

Posted on Mar 13, 2009

  • Eldric Venne
    Eldric Venne Mar 13, 2009

    Check your cap and rotor button while you are in there if they are fairly old. Anything more than 60k old, change them.

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1 Answer

How do i ck if fuel pump defective or no pulse at injector no power.


If you have fuel coming out of the lines when you are cranking the engine then your fuel pump is working. You should only get a small burst of fuel when you first turn the key on and then nothing while the key is on, the ECU only tells the fuel pump to turn on when cranking and when it can see cam and crank sensor signals while the engine is running. The small burst of fuel you may or may not have experienced is only to prime the fuel rails. To test your injectors, you can buy what is called a "noid" light. They have them at most stores that have a good tool/automotive section, such as sears. You unplug one injector with the engine off, plug the noid light into the injector connector (harness side going to injector). Then start or crank the engine over and see if you can see the light pulse on and of very fast. You may need two people due to limited visibility while cranking the engine. Repeat this for the rest of the injectors. If you have an "ohm" meter, you can ohm check the injectors by disconnecting each one and touching the pins inside the connector cavity on each injector. The ohm reading should read between 5-20 ohms. I hope this info helps!

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1 Answer

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Check for spark on the side not firing. If there is spark, the injectors on the right side may have a problem in the wiring to them. Older multi port injection systems used a "bank fired" approach: all the injector grounds on one bank splice together before they go into the computer to be pulsed.
All of the injectors have a steady voltage applied to them when the key is on. The same color wire to all injectors is the power wire, it is a fused circuit, the fuse is in the power distribution box, and is hot in run or start. When the computer internally grounds the injectors, pulse occurs and fuel is sprayed out. Check if the right side has power to the injectors with key on, use a voltmeter or test light. To test an injector circuit, purchase a cheap "noid light" from a parts store. You plug it into an injector connector, then crank the engine over. If the noid light is blinking, the power and ground circuit is good for that injector.

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1 Answer

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Are you certain that the pump is on when the no start occurs? Do you hear it turn on with key on, not start, when the engine won't fire? It should turn on for 2 seconds to pressurize the line to the injectors. If you could, check fuel pressure when the no start occurs.

If it is the injectors, buy a cheap "noid light" to check the injector circuit. Buy the one that fits your injector harness connectors. You pull off a connector to one injector and put the noid light in the connector. When cranking the engine over the noid light should be blinking-that is the pulse that fires the injectors. The injectors have battery voltage to them any time the key is on. When the ecm momentarily grounds the injector circuit (internally in the ecm), the injector is pulsed. If the noid light does not blink or even light up when cranking, the injector circuit has a problem in the power side or the ground side.

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What test told you it is not firing?

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1 Answer

Fuel system


CHECK FOR INJECTOR PULSE IF YOU GO TO YOUR LOCAL AUTO ZONE OR ADVANCED AUTO PARTS ASK THEM FOR THE INJECTOR NOID LIGHT KIT GO HOME AND FIGURE OUT WICH NOID LIGHT FITS YOU PLUG IT INTO THE HARNESS SIDE WHEN YOU UNPLUG 1 OF THE FUEL INJECTORS THEN CRANK ENGINE IF LIGHT FLASHES THEN THE INJECTOR SHOULD BE OPENING IF ITS NOT INJECTOR IS BAD IF ITS NOT FLASHING THEN IT COULD BE A FUSE OR CAM OR CRANK SENSOR OR A BAD PCM OR FAULTY WIRING

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1 Answer

What causes injector not firing gas?


FUEL INJECTOR NOT FIRING COULD BE FAULTY FUEL INJECTOR.HOOK A NOID TEST LIGHT TO FUEL INJECTOR ELECTRICAL CONNECTOR. CRANK THE ENGINE WATCH THE NOID TEST LIGHT SHOULD BE BLINKING WHILE ENGINE TURN OVER.IF TEST NOID LIGHT STEADY PCM FAULTY NOT FIRING THE FUEL INJECTOR.IF FUEL INJECTOR DONT BLINK OR LIGHT UP.YOU HAVE OPEN WIRING CIRCUIT TO THE FUEL INJECTOR CONNECTOR.

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Turns over but wont start i got fire and fuel to the fuel rail but the injecters are not delivering fuel any ideas whats wronge


sounds like u got no injector pulse comin from ecm.we need to pull ecm codes an review them ,possible camshaft sensors faulty they usually provide reference pulses to ecm for injector firing or pulse.without this pulse ur injectors will never open up to let fuel enter combustion chamber. one way of checking pulse is to connect a noid light(small light bulb that plugs in injector pigtail to chek for power to injector and ur pulsing ground coming from ecm to injector) an test for a blinking light while cranking engine.

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1 Answer

My injector dont work and i need to know why


CHECK FUEL PUMP AND FUEL INJECTOR FUSE.IF FUSE IS GOOD.YOU NEED A NOID LIGHT TO CHECK TO SEE IF INJECTORS FIRING.YOU CAN BUY A NOID LIGHT AT ANY AUTO PARTS PLACES.WHAT YOU DO DISCONNECT FUEL INJECTOR CONNECTOR.HOOK NOID LIGHT TO CONNECTOR.CRANK ENGINE TO SEE IF NOID LIGHT BLINKS.IF YES INJECTORS FIRING.IF YOU GET STEADY LIGHT.PCM NOT WORKING NOT FIRING INJECTORS.IF YOU GET NO POWER OR LIGHT DONT WORK.YOU HAVE A WIRING PROBLEM.YOU NEED A HAYNES REPAIR MANUAL LOOK AT THE ELECTRICAL WIRE DIAGRAM.TO TRACE FAULTY WIRE.

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1 Answer

Have 99 sierra has spark and fuel to intake but wont start sometimes sputters but no go please help


You need to find out if you have enough fuel pressure, and if you have injector pulse. A noid light is a simple kind of test light that you can get at a parts house to test injector pulse. Unplug an injector and plug the noid light into the harness. Have someone crank the engine, if it flashes then your injectors are firing. Check all the fuses under the hood. You should have 55 to 60 psi fuel pressure.

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I have a 92 jaguar xj6 we have replaced the fuel pump and filter and ecu we have fuel up to the injectors but they are not firing what could be the problem?


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