XJ only starts if I heat up the ECU?

[Thatsmydawg]

I've been having this problem for a few weeks where my xj doesn't have spark or fuel. Here an there I wiggle wires or move the computer an It would start. When I go to work on it it's usually dark so I put my shop light which gets hot over the computer. Not realizing the computer is cold. So to double check it I leave it cold an it won't start ever. I heat it up an it starts right up. Any idea why this would do this?

[4.3LXJ]

If wiggling wires helps, then I would suggest there is a bad connection there someplace and the heat is expanding metal enough to make the contact.

[JENSSEN]

Possibly a bad or cold solder joint in the ECM,. I have never opened one yet but I have seen some that cannot be repaired as they are coated on a goop so they can't be tampered with (easily)

[Mudderoy]

I've been having this problem for a few weeks where my xj doesn't have spark or fuel. Here an there I wiggle wires or move the computer an It would start. When I go to work on it it's usually dark so I put my shop light which gets hot over the computer. Not realizing the computer is cold. So to double check it I leave it cold an it won't start ever. I heat it up an it starts right up. Any idea why this would do this?

Remember when you heat or cool metal it expands or contracts.

One of the tricks old TV repairmen used to use was to spray freon(?) on the various components. The bad component would be very sensitive to the cold and malfunction noticeably. Then they would swap out that part.

They usually had an idea where to start looking based on the symptom they were told.

You may have a bad component in the ECU, or perhaps you just have bad contact between the connector and the ECU. You could even have a broken wire that is making contact when it is warm and shrinking and losing contact when cold.

Actually I bet if you get a can of spray, something really cold. You could do the same thing the TV repairmen used to do. Have the engine running and hit the various wires (start with where you were wiggling) with that cold spray. When the engine stops you know you have pinpointed the problem area.

[Thatsmydawg]

But the thing is its fine after I head the ecu up. All day it's fine when I drive it. Just when it sits for a long period of time i don't have spark or fuel pump. I don't have to wiggle any wires I just heat the computer where it is. It's kne of the ecu's that has the goop on it. An not sure how easy it would be to rip that stuff out an see what's under it. An once I rip the goop out what do I replace it with?

[4.3LXJ]

If that is the case, replace the whole thing

[Thatsmydawg]

Cash talks buddy. I have none. An a new one is $180. A used one is over $100

[bluedragon436]

Have you checked out local PNP's?? I would say check out your local JY's and PNP's, and see if you can't source another one to throw in there... should def be cheaper than $180 to pick on up from there..

[4.3LXJ]

Check Ebay. I think you can do better than that.