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View Full Version : non-starting 4.0 (TEAMFX3's)



MaineZJ
10-26-2004, 08:36 PM
95 4.0

OK some know my ZJ's recent saga, some don't....for those who don't here's the dilly:

My truck started out having some hard starting issues awhile back, ie: you could crank it over until the cows came home, but it would do nothing. Then I discovered the relays under the hood would chatter for a few seconds, then once they stopped the truck would start right up and run perfect until you shut it off and let it sit for awhile. There seemed to be no rhyme or reason to this chattering, you basically just had to wait a few minutes with the key in the run position and it would happen when it felt like it. This little scenario played out just fine until my run at TDR when seconds after blowing a hub the truck died and has only fired up once since(*more on that in a second) SO here is what I've replaced to date:

1) Crank position sensor
2) coil pick up assembly
3) relays under hood

I've determined the fuel pump and the ignition coil to be in working order. ** So the one other time I've managed to make the truck run was the other day after replacing the CPS and CPA I cranked it over with no improvement, then while cranking I put my test light on the power side of the coil feed and the truck started up, I removed the tester and it stalled. Repeated proceedure with identical results. SO, I figured well, for whatever reason that hot side wants to be grounded, so I took a small piece of wire and made a jumper, tried it again the jumper sparked and now the jeep refuses to run again. I dunno wtf is going on... all I know is I hate troubleshooting and am too poor to pay someone else to do it for me. Anyone have any productive thoughts????

LouisianaZJ
10-26-2004, 09:26 PM
new coil... and make sure the connections are good and the ground is grounded

MaineZJ
10-26-2004, 09:29 PM
I've been whitness to his relay clattering. really odd, really want to know what would cause it.

TEAMFX3
10-26-2004, 10:03 PM
new coil... and make sure the connections are good and the ground is grounded


Mmmm, I love broad based fix all replies, but thanks, it's not the freakin coil.

JeepinHank
10-27-2004, 10:05 AM
So, you can hear the fuel pump right? Said you know its working, but did you confirm that through a bench test or you can just tell when you turn the key to run? Are all of the underhood fuses good?

Have you actually confirmed if you're getting spark at the cylinders?

Which relays are chattering?

Even with all of the hi-tech stuff on engines these days, it really boils down to three basic things - air + fuel + spark

Which part of the equation are you missing?

MaineZJ
10-27-2004, 10:27 AM
the relays mounted behind the battery (the ABS, starter, etc) not sure which ones actually chatter, but it's in that set

when people were trying to figure this out a few weeks ago, it was determined the fuel pump was operating fine (rigged to be on a manual switch if needed), but there wasn't any spark at all. the coil was never getting power

JeepinHank
10-27-2004, 12:02 PM
My bet would be that there is a bad connection or short somewhere in those relays you're hearing. Break out your FSM and check out what goes in and out of the Fuel pump relay. I believe there's another one there, in the PDC, that is related to ignition (not sure and no manual right beside me). Check the wires going to / from that one as well. Its probably something like a loose connection or a short in one of the components attached to those two relays.

I had a problem where my Jeep would just die on me. After looking under the hood for a bit, I found a blown fuse. I'd replace the fuse and roll for a while then it would just suddenly die on me again (same fuse blown). Then I broke out my manual and stared at the wiring diagrams for a while. I checked out what sent a signal to that relay, and noticed that it got a signal from the downstream O2 sensor. It wound up being a wire on my O2 sensor that had been rubbed bare, and was shorting out on the driveshaft and causing the fuse to blow.

The story isn't really an explanation of your issue, but it does point out that sometimes your symptoms will have some kind of wierd ass cause that you wouldn't normally think of. Look at what connects to those relays, and see if that might help you to narrow it down, or cause you to look at something you wouldn't normally look at.

HTH

TEAMFX3
10-29-2004, 07:57 PM
Thanks fellas, I have a buddy in my club who is a ASE master tech who works at a Jeep dealership coming up tomorrow. He's bringing the FSM and a scan tool and other related tools with him, so hopefully we can get this biatch running again soon. I've found a ZJ on 38's to show up in a couple weeks, so it HAS to be running for that! :twisted:

MaineZJ
10-29-2004, 08:11 PM
Hope ya get that fixed. Not enough Grands out this way to lose a good one
just make sure that beast of your's gets out here to maine for that trip...

TEAMFX3
10-30-2004, 03:51 PM
It's Alive!!

There was a broken wire from the harness to the ignition coil. Runs as good as a truck with 200k ought to :wink:

OverkillZJ
10-30-2004, 04:43 PM
It's Alive!!

There was a broken wire from the harness to the ignition coil. Runs as good as a truck with 200k ought to :wink:

I thought about that, should've mentioned it. I always wondered why those 2 wires are so damn frail when the whole jeep depends on them working properly :roll:

Glad you got the beast running :twisted:

JeepinHank
11-01-2004, 11:34 AM
8)

Glad to hear it!!