90 XJ spark problems...

Ok, hers the JEEP again...

Thats just to refresh which jeep we are talking bout...

Here's my idea... I have tested the ECU and came back working. AM Radio test... I at this point do not accept that to be true. I wanna think one module or component in the ECU is failing to work. I want to go to a pull-a-part yard and purchase a new ECU. For a 1990 XJ Sport 4x4 4.oL 2DR Auto, what years and types of Jeeps should I be looking to take an ECU out from? How much should I offer as a low but reasonable price? I have a strong feeling that with a new ECU, I should solve my problem. My buddy has a 88 XJ with a '95 XJ 4.0L engine in it. Could I pull his ECU out and use it to test my theory? Lemme know what ur ideas on this approach is... -MOOSE

Did he swap electronics with his motor swap? If he did it won't wok. If he just used the old motor as a longblock and kept his ECU then it would work. Is that thing still in the pond and you're trying to work on it?

Heck naw, That was back in august, thats jus to show what happened... I got it home that night ab 2AM... Iight, so what yr n model Jeep am I lookin to yank the ECU from?

if I'm correct you should have a renix motor, as the HO came out in 91. Someone correct me if I'm wrong. If it's a renix then you should have three bolts holding the throtle body on. Renix years are 87-90.

If it was me, I'd do an ohm test from the small yellow wire at the ignition control module (under the coil) to the D-13 pin at the ECU connector (Renix). Then check for power (battery voltage with key in run position) at the large yellow wire at the ignition control module. Then check the large yellow wire again for voltage, with the key in the start position. Back pinning the wire and testing with it connected, might also be helpful.
Then I'd do an ohm test from the CPS connector to the ECU, C1 and D1 (I think).
Somebody in another post mentioned, that having the engine temp sensor disconnected or an open circuit, caused his not to start. I'm gonna check mine out tomorrow and find out if it causes no fuel or no spark.