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1990 YJ 2.5 L No Fuel Wont Start

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fatfender

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Discussion starter · #1 ·
My 1990 Wrangler 2.5 L is not getting any fuel to the TBI ! I have replaced the fuel pump relay....no results. I unpluged the 3 wire weather pack plug at the fuel tank to see if I got any volts to it, with a test light and the key on there was to voltage on any of the wire to the fuel pump.


Any ideas ECU ? ICM ? Anyone had this problem? Does anyone know were the ECU is located?
 
#5 ·
fatfender said:
I can hear a relay clicking when I turn the key OFF ! I hear nothing when I turn it ON !
Click to expand...
so no priming of fuel pump? There no "whirrrrrr" or "bzzzzzz" when the key get clicked to on?

I'm going with faulty fuel pump if that is the case. You can check it be connecting the positive and negative prongs directly to a 12v power source. Kinda like a power probe.
 
Discussion starter · #8 ·
Today I ran a 12 volt lead off my battery to the fuel pump wiring harness and the pump immediately began running, turned the key and it started and ran fine.
So I am thinking its the ECU that's under the glove box.


I also spent time cleaning the fuel pump relay contacts but this did nothing, back to no start, no fuel.


Is it the ECU?
 
#9 ·
fatfender said:
Today I ran a 12 volt lead off my battery to the fuel pump wiring harness and the pump immediately began running, turned the key and it started and ran fine. So I am thinking its the ECU that's under the glove box. I also spent time cleaning the fuel pump relay contacts but this did nothing, back to no start, no fuel. Is it the ECU?
Click to expand...
you'll want to see if there's signal coming from the ecu by checking if there's signal in the harness
 
#10 ·
Easy issue. Fuel pump relay is on the side of the fender by the diagnostic connector. The first thing to do is to swap it with one of the other relays and see if it primes. You cannot check power to the pump unless you are cranking it, the ecu cuts power to the relay after the system primes until you are trying to start it. The relay has 5 pins on it. the middle is not used so you are dealing with 4 wires. On the side of the relay is a little diagram. 2 are control wires that the ecu use to operate it and 2 are the actual feed to the pump.


85 is ground
86 is switched ignition
30 is battery feed
87 is the output to the pump


If swapping the relay doesn't do anything do the following: Use your meter and with the key on check power from the battery negative to pin 86 and to pin 30 and verify the 12 volts for the battery and ignition feed are there. If they are take a little jumper wire with about a 1/4" on both ends exposed. Remove the relay and jumper between pins 30/87. This will force the pump on if the wiring is intact.


Post back what you find.
 
#13 ·
According to the diagram I had them backwards.
30 is output to fuel pump
87 is power




85/86 are both hot? Did you measure it with the relay in? Are you checking with a test light?
 
#16 ·
#18 ·
fatfender said:
After giving a second thought and listening better I do hear the fuel pump priming for a 3 seconds when I turn the key on. At this point I am wondering if its the TBI injector?
Click to expand...
have a friend crank her and see if fuel is coming out of the injector while it cranks. Or you can get a power source, unplug it, then feed a ground and power signal to it and listen for a click. The cranking method is easier though.

If you are getting fuel at the tbi then you're having trouble with spark.
 
#19 ·
fatfender said:
After giving a second thought and listening better I do hear the fuel pump priming for a 3 seconds when I turn the key on.
At this point I am wondering if its the TBI injector?
Click to expand...
You need a noid light on the injector. Should be able to get one from the local parts store. It flashes to let you know the injector is being triggered.
 
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