Noah911

This is a good call and a great suggestion.

You could also choose to use the windshield wiper relay as sort of a 'control' type relay. Swap this one out instead.. into and out of both the ASD and the fuel pump relays locations seperately, to verify for both of those to try and be sure.

You definitely do not need the windshield wipers to function while looking for the problem. Just make sure you try the wipers first to be sure this relay is in fact working as it should beforehand...

Jswfla

Thank you all for your replies. I have brought the vehicle to my house and now I’m all in on this.
I spent a little time today trying to find the ground for the fuel pump and had no luck. I went over and removed the rear quarter panel inside and no luck there. Any suggestions.

Note: fuel gauge wont read until fuel pump stop priming. At the same time I also hear a short buzzing noise coming from the engine bay close to the firewall driver side; is this related or just coincidence?

Does anyone knows where I can get the wiring diagram of the ground cable for the fuel pump?
Thank you in advance for your replies.

Jswfla

Does the cover for the fuse box tell me which relay is the windshield wipers?

Jswfla

All the fuel pump since my Dad acquired the vehicle have never stop priming. He told me that by moving the ignition switch from the OFF to the RUN position, the fuel pump will stop priming, and the car will occasionally start.

Jswfla

Today I also got the voltmeter ad tested the MAP, TPS, CKS, and CPS and all of then have power. Don't know what should read, but I got between 8-9V.
The green and orange cable at the ignition coil harness was not reading any volt or showing continuity with the ignition switch on RUN. Don't know either if it should read anything, the green or orange cable goes to a splice that continues to the injectors, crankshaft sensor (I think) and back to the fuse box to the ADS relay (I think not sure at all.) I also notice today that the ignition coil was crack so I replaced it.
Try to start the vehicle and just like my Dad told me I had to move the ignition switch from OFF to RUN several times to make the fuel pump stop priming; I was not letting the fuel pump go more than a few second. After the fuel pump stop priming, I got the fuel gauge to work, and the vehicle started.
Let it run for a couple minutes, shut it off, and it starts right up every time. I let it seat for a few minutes with staring, and had to do the all back and forth with the switch to get it to start again.
CRAZY!!! My head is spinning, so I will like to see if there is a short in the ground cable of the fuel pump and check the ignition switch tomorrow but I don't have any schematic, and I don’t trust myself with the voltmeter or Ohmmeter, since I have never used but today.
Any ideas or suggestion will be deeply appreciated.
Thank you

Jswfla

OK so I have study a bit the electrical diagram of the fuel pump, and my understanding is that if the motor in the sending unit is working, it should not be any issues with the ground. Now the fuel pump relay closes the circuit given power to the motor; therefore, ground cable should be OK as well as the relay right!?

boxburn

I'm coming back out from under my rock. I can only go off the 95 diagram but I would imagine this side of things to be the same on both years.

Does the fuel gauge work correctly when you are able to get it running or does it only work when the pump is off? I would certainly say that symptom (I can't see how it would relate to the long priming) is caused by a bad ground. A ground may work but still be bad and from my diagram, the fuel sender grounds with the fuel pump. If a bad ground is creating a 1V point instead of a 0V point, the gauge has no chance of displaying properly.

The fuel pump relay and ADS relay are both grounded together by the PCM and will not function if the ground is too bad however, unlike the above situation, if they are clicking over and working, then they are able to ground out.

Part of me is thinking PCM as it controls the operation of the fuel pump relay.

One thing you could try is use a multimeter and measure the voltage on one of the injector plugs which my diagram says should be dark green/orange. See if it stays powered and then shuts off when the fuel pump finally shuts off. This is to test that the ASD and fuel pump relay are indeed being controlled together. I cannot see anything else that links into circuit K51 so if there are any differences, you may need to do more digging and find out why.

boxburn

Oh and to add to your comment about a multimeter, as long as you don't do a resistance check on a live circuit or have the leads set to Amp measuring then try to measure voltage, you'll be fine. I totally haven't accidently gave the meter a zap on a circuit or blown it's internal fuse leaving the leads on wrong.

PatHenry

Does the Grand Cherokee have a ground point in the cargo area driver's side like the XJ does? If so, that may be where your bad ground is. On the XJ that ground is tied into the fuel system.

I was initially going to point out that maybe the improvised check valve might be the problem, but reading through the thread you definitely need to sort out the priming issue. Likely the excessive priming burned out the old pump.

So I'll X2 the check the relays and ground point. Maybe the folks at the Grand Cherokee side of the forum might have some more detailed or specific answers.

boxburn

I forgot it was a Grand, I may need to go back under my rock unless they are still similar.

PatHenry

It's still a ZJ (93-98), so it's as similar to an XJ as any GC can possibly be. 96 was just such an odd year... it was the only year in my lifetime that there was no Wrangler model of any kind produced. Compare that to the last model switch (JK -> JL) where you can get a 2018 JK OR a 2018 JL Wrangler....

Jswfla

Thank you for the reply
First time I check for fuel pump ground was on driver side rear cargo area and nothing. Followed the cable it look that is going to the rear of the driver seat floor pan. I will get to tomorrow and check, but I have a felling it will be fine.

Jswfla

Hello and thank you from coming out from under your rock to help out. Fuel gauge only works when fuel pump stop priming. It is hard to tell how accurate is measuring the level, but I will take an educated guest and said it is OK. Fuel pump and ADS relays seem to be working OK; I switch the wiper replay for those two and still having the same problem.
Now this morning didn't start regardless wether the fuel gauge was working or not; waited to late afternoon and it did start after fuel gauge work. Don't know what ta think about that!!!!
I could possible be the PCM.
Someone local told us that it could be a fuel injector that wont stop.
What about circuit K4 coming of the fuel pump after S102 and S135?

Jswfla

Try that today and no luck... Any other suggestion.

Jswfla

@awg Someone else mentioned today about a bad fuel injector. How I can test for that?