Hey all,
Looking for some help. 95 ZJ 4.0L inline 6cyl. Replaced fuel pump and filter a week ago. Ran great for over 500 miles. On the way home today it just completely cut out on me. Luckily coasted next door to an autozone. It would start and run for a second then die, tried multiple times.
I borrowed a fuel pressure tester, 0psi at the rail. After releasing pressure from the system it wouldn't even start. Fuses were all good. That's about it any help would be appreciated.
UPDATE: After it sat overnight I checked and it has power at the pump.
Turned it over and it started right up. Now the question of why it happened in the first place. I work in the woods far from anywhere so really don't want to get stranded if it happens again. Any leads as to what would cause it to just die like that?
Did you listen to hear if the pump was running when you had 0psi? I could hear mine run but still had 0psi. Very odd indeed. If you don't hear it run, could be a lot of things like wiring, relay, regulator.
I didn't hear the pump making any noise so it wasn't getting power for some reason. Also forgot to say. After I checked for power to the pump I pulled the fuel pump relay and the auto shutdown relay switches to look at them. It started after that but it sat all night so not sure if it was the relays? Another thing the voltage was at 15+ so on the high side. After replacing the fuel pump relay today it is back at the normal 14. Any thoughts?
Thanks for the help
When you were getting the 15v reading was that at your dash voltage gauge instead of checking it with a meter? A bad crank sensor can cause wonky readings on the voltage gauge and gas gauge sometimes. And if the PCM doesn't receive a crank sensor signal sometimes it will cut the fuel off through the fuel pump relay.
I've had bad OE crank sensors where they would fail at normal operating temps then the engine would die. But it would start back up the next morning on first startup when cool. Since the crank sensor controls spark next time it dies check to see if you have spark at the distributor cap middle port/wire or check one of the plug wires for spark. If no spark there's a crank sensor resistance test in my signature you should try.
Also wouldn't be a bad idea to check your cam sensor connector which is right next to the distributor. The cam sensor, also called the coil-pickup, is in the bottom of the distributor and you'll see the wire coming out from under the cap with connector connected to the harness.
The cam sensor controls fuel and in unison with the crank sensor injector pulse/width and ignition timing is set through the PCM.
Both of the above may be long-shots but worth checking. May not explain why the fuel pump doesn't want to run for even a couple secs. Good luck.
Hey uni thanks for the response. The 15v was on the gauge. The only other time it hasn't started I traced it to the Crank pos sensor. Replaced it and started right up. I will look into the cam sensor.
Thanks again for ideas. Really not wanting her to die again on me. Did I mention she has 268,000k on her and going strong ?
You're welcome PickinPox. Hopefully when you installed a new crank sensor you went with Mopar. Know they're real pricey but I installed 2 brand new BWD crank sensors on my 96 4.0. While it would start/run it would all of the sudden die which drove me nuts since both aftermarket crank sensors were faulty. A new Mopar crank sensor fixed my problems. It may not be a bad idea to test the one you bought if not Mopar.
Yes, as mentioned before look at the crank sensor resistance test in my signature and it will tell you exactly how to test it. There should be no resistance, same as meter probes not touching anything, between the ground cavity (B) and the power cavity (C) or the crank sensor is bad.
Just had a similar problem on my 96 ZJ with the 4l. Thought it was the pump, but it tested fine. After some digging in the forums, I thought it might be the ECC connectors. Got it running and jiggled the three connectors to the computer and it failed. Replaced the ECC and all is good. Big issues with these and with the miles you have, the solder joints may have failed. Good luck!
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