hshift

Got a problem that I cannot figure out, hoping to get ideas as to what to do next. I'm the original owner of a 2000 4.7 V8 GC Limited. 230K, garage kept, and well-maintained. About 6 weeks ago it started randomly stalling, by random I mean maybe once every two to three days, and could happen at highway speeds or at idle. Usually it would start back up, sometimes take awhile longer, like 30 minutes. It feels like its starving for fuel, and when it wont start it cranks fine and turns over but won't run but for a second or so. I changed out the crank sensor, camshaft sensor, and swapped out some relays, no change. Finally one day about a month ago it died and would not start after two hours, so I had it towed to the local Jeep dealer. They told me it was the fuel pump and $550 later it had a new fuel pump. It was OK for a week then it died again, so back to the dealer it went, but of course it was OK when they got to it and they drove it 40 miles without a problem so I took it back without them doing anything. Once home I changed out the fuel filter /regulator, the gas cap and the PCV valve, and also cleaned every ground wire under the hood. That did nothing and when my wife got stranded i had it towed to a local mechanic a friend recommended. He had it a week, and changed the IAC motor and the air temp sensor. He told me he idled it for two hours without an issue, then tried driving it the next day. He got only six miles and then it died again. Luckily he got it going again and after some experimenting he came to the conclusion that the fuel pump is shorted / being disabled, most likely by an after market alarm that was installed when i bought the car back in 2000. He told me he had never seen an aftermarket alarm like mine and was hesitant to unhook it for fear of disabling the car permanently. I have no documentation on the after market alarm, and the dealer I bought if from back in the day only keeps records for the past 15 years, so I don't know what I have in there. I talked to a local stereo/security shop and they will remove it for me for $50, but they told me at least to their knowledge no one installs car security systems that would affect the fuel pump. Before I spend that money, I tried disabling the factory alarm after reading about the SKIM module being able to disable the fuel pump, doing the grounding of the violet/yellow wire which goes thru the driver's door from the lock cylinder. That looked promising as I made it 3 days and 120 miles without a problem, however just today it died again and would not start. I was able to jumper the fuel pump relay to get it to run and it ran Ok so at least I wont be stranded anymore and can confirm the fuel pump is the issue.

I would love to hear if any of you guys have any ideas. The only other symptom I can report on this is it never refuses to run after sitting for awhile, once it cools down its fine, so seems like heat plays a factor, which is why I don't think its a bad or frayed wire somewhere. I am going to have the after market alarm removed this week and if that doesn't do anything then I'm thinking the PCM might be next. Thanks in advance and sorry for the length of this post.

dave1123

Don't be sorry. Most times we get very minimal info and have to use a crystal ball!

Just for jollies, check the harness connector to the CPS and the harness itself. If I remember correctly, on the 4.7 it's behind the exhaust pipe above the starter, correct? The wiring could be heat damaged. Also, you should replace the fuel pump relay just on the chance it's the problem.

The CPS is critical to the function of the entire system. Even a tiny blip in the signal will cause the PCM to drop out the fuel pump and ASD relays, killing the engine. Also if you didn't use a Mopar CPS, that could be a problem. They use a magnetic field to sense the windows in the flexplate to time everything. Mopar CPSs use a neodymium magnet whereas aftermarket ones don't. That's why they cost more.

One more thing. Check the plug on the fuel pump. It could have a broken wire inside it making intermittent contact. I had that happen on my neutral safety switch. The harness wasn't held by it's clamp and was constantly flexing as the transmission torqued, resulting in a broken wire. You may have a broken fuel tank strap doing the same thing. There are support straps under the shield. They may have been replaced when the pump was done, but the wire could have been the original problem.

That's about all I can think of. I hope it helps. Now I have to wait for the brain smoke to clear! LOL!

BTW, my WJ had a remote start unit installed when I bought it and the first thing I did was pull the 2 10amp fuses that power it and took the batteries out of the remotes. I crawled under the dash and there are no tags or names on the unit and about 30 or so wires running everywhere so I left it alone.

hshift

I replaced the Rock Auto CPS with the official Mopar one. The wiring seemed fine, no visible heat damage that i could see. Also getting the after market alarm removed tomorrow. I'll let you know.

97grand4.0

This would have Click and Clack pulling out their chin hairs.

hshift

I took it to an auto security and stereo place. On the way there the car died again so I had to jumper up the fuel pump relay to get her going. That turned out to be key because after the stereo guys removed the alarm, it still wouldn't run. The alarm guy then spent about a half hour rooting around the ignition wiring and relay box. He found the ground wire for the fuel pump relay must have had a break, and he ran a new wire from the relay box to ground and bingo! She started right up. Been three days now, no problems, and the stereo shop (American Radio here in Knoxville TN) only charged me $40 for everything. Awesome.

So to conclude, I spent $550 at the stealership for a fuel pump install I didn't need, and $360 for a local mechanic who installed a new ISC motor and a fuel/air temp sensor, and spent a ton of time trying to diagnose my problem, which he couldn't. At least he pointed me to the stereo guys though!

dave1123

HA! Broken wire, other end of the system!