93 wrangler keeps stalling

[Dave Watson]

Ok I need help and at my wits end.
My jeep just started stalling out this past week. I have replaced the fuel filter and pump and pump relay. Have cleaned every connector I can find related to the electrical wiring to the pump.
I did this because 9x out of 10 when it dies I can unplug the connector behind the rear tire that runs to the fuel pump and it will start running again.
Ammco says replace the wiring harness.
What else can it be?

 

[greg92jeepxj]

Welcome to jeepz.com . Hoping that the fuel pressure readings are good now that the pump has been changed. Pressure checked with pressure regulator vacuum line plugged in and unplugged ? There is an increase of about 8 psi with regulator unplugged which means it's working when plugged back in. To prove that bad wiring plays a part in this problem , you would literally have to check wiring with ignition on after stall with a voltmeter and harness connected using back probes and then crank starter to see if voltage still present. When trying to restart , do you recycle the ignition key or just crank from ignition position after stall ? Dosen't sound like PCM is at fault since the engine is starting after PCM primes fuel pump for cold start when CPS and CMS are feeding back to PCM for first start. Sounds like your experiencing this problem after initial start ? At what point does the stall occur ? How does engine run after first start ? Respect that you believe it's wiring since you disconnect harness but all your doing is restarting fuel pump like turning on key to ignition position and priming pump . Even though the test I previously mentioned would have to be applied to find out if power is still going to pump after stall , your still getting power to pump are you disconnecting and reconnecting with key off ? Look for the fuel pump ballast resistor and ballast resistor relay . Check ohm value of resistor and check of fuel pump ballast resistor relay are energized when running and when there is a stall . You'll have to probe wires since relay must be in place unless you have a test relay that terminals are acessable . If no trouble codes and engine runs well otherwise , I agree to make certain if any power is lost to fuel pump .

 

[Gennybro]

When you replaced the pump relay, did you disconnect the battery prior to installing the relay. If you did not , it could have damaged the relay. That happened to me once on an old ford car. You may have had a bad relay to begin with, and damaged the new one when you installed it without the battery diconnected.

 

[Dave Watson]

Yes all work had been done with battery undone.
There is not rhyme or reason when it dies. When it dies I turn the key off unplug that connector then just start it like normal. And runs fine till it dies again. Whenever that may be.
When it dies I have no fuel on the rail.
I don't know what a pressure regulator is.

 

[greg92jeepxj]

The fuel pressure regulator is on the fuel rail up front by #1 injector for #1 cylinder on the 2.5 and 4.0 liter . It will have a vacuum line plugged onto it. It's small and round and held on by one small screw and a bracket. The problem sounds like it may possibly be as simple as the ballast resistor for the fuel pump or the ballast resistor relay that energizes the resistor that is in line with the power to the pump through the harness to the connector your unplugging and re-plugging in. I know this sounds too easy of a fix and less likely but always worth a shot since problems do occur to the resistor or its relay. Heat , whether from under hood temperatures or electrical draw causes resistors to burn up.

 

[Dave Watson]

Where do I find these resisters?

 

[greg92jeepxj]

Where do I find these resisters?

I tried looking at my 1992 FSM for XJ MJ YJ but I only see the resistor and ballast resistor bypass relay for the XJ . I can only assume the YJ dosen't have one . This seems strange but not showing on this diagram for YJ . If there were a resistor , it would be a long white square box like device about four inches long and half inch square with two terminals and two twelve gauge wires plugged in . One would go to fuel pump and the other would go to the relay. This is a separate relay from the fuel pump relay . If you do not see this resistor under the hood anywhere , there wouldn't be one as per the manual.

 

[Dave Watson]

Thank all for the help. I think I found the issue. I bypassed that plug. Seems to be working. Only time will tell

 

[greg92jeepxj]

So , by bypassing it , you mean you've jumped the connector ? I guess the connector pins wer making poor contact ?