lilredtruck

Everything was changed over to the '90 XJ. I took the fuel pump out of an old Explorer and hooked it directly to the fuel pump relay. It's a good strong puller pump and takes the pump out of the gas tank (which I prefer anyway). I also tried to check the timing using the timing mark on the harmonic balancer, but I had a weird thing happen: the timing light was blinking all over the place - not rhythmically like it should. I had the pickup on the #1 spark plug wire, but it was blinking haphazardly. Any ideas about that one?

Well, I tried a new computer thinking that maybe that was the problem, but it still runs bad (now I have 3 of the damn things). I also tried checking the timing marks at the timing chains, and everything seems to be okay there. Even the distributor seems to be in the correct position. There is a problem which I haven't mentioned to you fellas, and I'm hoping that one of you may know. I've got a dead short in the computer harness; I've not been able to find it in the wiring, but my test light shows a dead short at the battery. I know it's not in the rest of the harness, because we've already disconnected the bulkhead connector and it's still there. Anybody got an idea about this one? Is it supposed to have constant power to the computer which would read through to something?

The guy that I bought it from is a good friend of the guy who's helping me with the install. He installed this engine in the Cherokee about a year before it got wrecked. They started it before it was taken out of the XJ.

To preface the thread: here is what needs to happen and has happened. I got an '86 MJ for $30 with a bad V6 - tossed it. Bought a wrecked '90 XJ with a good 4.0L MFI and installed it in the MJ. Started it up yesterday and it runs, but it runs like crap! I tried replacing the map sensor, but no luck. Tried to diagnose the problem with a computer reader, but they weren't talking. Tried to replace the computer, but no luck. Made sure all of the vacuum hoses were plugged, but still no glory. Checked to make sure all of the sensors were plugged in and they were. It runs very rough and is backfiring through the air intake which sounds to me like a timing issue, but there is no adjustment on the distributor. I was told by my friend that the timing is controlled by two pieces of equipment: there's a piece in the distributor another at the back of the engine and these two communicate with each other to keep it running smoothly, but my friend says that it is unlikely that they are bad (need and opinion here from another source - what do you think?). The other part of this story is that I'm trying to get from Montana to Michigan by Christmas and need to resolve this rapidly. It's a three day trip (+/-), so I need to leave by this weekend. HEEEEEEELLLLP!

Hey Taz, You're everywhere... Now you have an MJ!!!? You may know me as BuddyOvrlnd elsewhere... Now I'm working on the lilred(pickup)truck. How've you been?

You're pretty close I'd guess. I've been given responses on other boards from 25psi to 39 psi and another again at 50psi. I'm going to go with the middle one of 39 psi - I know for a fact that my elec fuel pump that I was using on my LT-1 put out at least 45psi to run it, so it should handle up to fifty if necessary. Thanks for your input... Still could use the breakdown on the Firewall connector if anyone has that. Thanks, Ron

I got a 1990 fuel injected 4.0L and I need to know what the fuel pressure is at the fuel rail. does anyone know where I can get a wiring description of the firewall (bulkhead) connector for an '86 Comanche? I need to know where all the wires go in the engine compartment. It's nice to be a member of the club - now I just have to get the little guy running, with your help. Ron