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Not starting

2K views 42 replies 7 participants last post by  Uniblurb 
#1 ·
Hey guys so this has been happening alot latley especially in the morning my gas gauge wont register and I have to constantly turn the key on and off for it to finally work and when it's not working I can hear the fuel pump whining and it won't start at all now as soon as the gas gauge starts working it will start but now it's been getting harder harder to start just keeps cranking over and I have to step on the gas to make it start now I am assuming this is a fuel pump issue but just wanted to be sure
 

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#2 ·
The gas gauge and the FP motor are two separate circuits in the same harness and both are controlled by the pcm. Since both are malfunctioning, my first stop would be the connector at the FP. You may find some corrosion there that is causing voltage feedback into the PCM fuel control circuits.

The whining of the pump means that ground to the FP relay is constant from the PCM. This should be the case only when it is running or cranking. This tells me the PCM is malfunctioning for some reason.

You cant be sure it's the FP until you check the voltage to the pump and then check the fuel pressure at the rail.

Here is the obligatory FP troubleshooting drawing with standard cautions:
#2 is with key on
Socket 20 is the low voltage potential from the PCM that triggers the relay. Reverse bias that circuit and it may blow the PCM.

 
#14 ·
Yea I have 12 volts but my pump runs all the time regardless if the gauges aren't working I can hear it just whining then once the gauges start working again after i cycle the ignition on off a few times it stops whining and either will start or just crank and crank until it finally starts then sometimes when it does finally start it won't stay running
 
#15 ·
That's exactly what my 97 zj is doing..worse in the colder weather. In the warm weather I would cycle my key 3 times and the fuel gauge would come on and they would start. In the Colder Weather the fuel gauge and the battery gauge read 0 and the gas light stays on. The engine turns over but will not catch. I've checked my PDC and my PCM. No wires corroded. I even switched out my fuel pump relay and checked all my fuses and can find the problem. Today I stopped at a Jeep dealer and spoke to their most knowledgeable mechanic that's been there the longest. He is saying that it is possible it is the PCM as it controls the fuel pump. Please let me know if you find a solution or fix.
 
#19 ·
I hope it works out! Please post as soon as you have any results. Today I was able to narrow the issue down to the PCM. I'm going to be removing it tomorrow. I will also be ordering a remanufactured PCM first thing in the morning. I was able to determine that the PCM is causing issues with the charging system and causing the fuel pump to continuously run.
 
#25 ·
I have to do that anyways just to get the gauges to register before it will even start now today it wouldn't start at all this morning finally came home after work and it took me 20 min just tp get it started and when I did it wouldn't idle until it got warmed up and had to hold my foot on the gas to keep it running now that it's been running for a while it starts up no problem I just don't get it lol
 
#27 ·
Ok so after replacing several parts now including fuel filter, iacv, cap and rotor, coil, my jeep still would not start properly I read about the symptoms of a crank position sensor going out and in that diagnosis the fuel and volt gauge will sometimes not register which is what has been happening so I just replaced the crank position sensor today and it started up twice then would not start at all after that.. I reset the pcm by disconnecting the battery and now it has been starting so now the real test is to let it sit overnight and try in the morning now if I'm still having the same no start issue what else could this possibly be?? I have checked spark and fuel pressure which at first I wasn't getting very much spark which led me to the crank position sensor any one else have any ideas what else this could be ?? I have heard of the piece under the rotor in the distributor causing this issue but I'm not sure
 
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