volkswagen12

Hey Everyone,

I'm new here and new to Jeeps. Let me start off by saying sorry for the essay below. Also, I've been doing searches on here for this for about a week and came up with nothing really.

I picked up an '87 Cherokee 2.5 injected 5 speed. I got is super cheap because it wouldn't start. Looked like there was some sort of electrical short and a lot of the wires under the hood by the fuel pump relays were melted. I've cleaned that up and ran new vacuum lines. The weird thing is, if you have the fuel pump relay plugged in, the pump won't turn on (bought a new relay and same thing). I've jumped the relay socket and I'm able to get the pump to turn on with the ignition without the relay in (probably part of the problem). It has full power when you check the socket so it's not the wiring.

It will run for a few minutes then die. It seems to depend on how cold it is outside so my guess would be something failing when it decides that it's warm enough to drop the idle. When it was 18° here last week it would run for about 10 minutes, just now at 40° it ran for about 2 minutes and died.

I've also replaced the fuel filter, the fuel pump is working fine. I replaced the crankshaft position sensor and the map sensor.

I'm sort of at a loss here and was hoping maybe someone could point me in a direction other than a 4 liter swap haha.

Thanks in advance for any help.

volkswagen12

bump

volkswagen12

Well, found out it's losing injector pulse randomly. Any thoughts? Anyone here? Bueller?

freegdr

injector puse on 4.os are controlled by the pick up coil in the dist maybe check into that on yours

freegdr

the fuel prob could be the crank position sensor

volkswagen12

Very cool. I'll look into that. I replaced the crank position sensor already and that didn't make a difference. At least it's new so I won't have to worry about it in the future.

Thanks for the tip.

volkswagen12

Looks like it was the computer. Crossing fingers this thing stays working now.

volkswagen12

Well, new computer fried.