Did a search, need more. Not a newbie :flipoff2:

A buddy just swapped his 4.2 in a '79 CJ for a 4.0 from a '94 GC. Computer is wired in, O2 sensor, CPS on new damper. Fuel pressure is correct. Engine starts, runs for 2 seconds, then shuts down. Adding fuel to the throttle body will keep it running. It seems that the injectors are shutting down from the ASD relay.
The VSS is not hooked up, we think it should stay running without the VSS.
The other thing is that when he heard this engine run at the boneyard, it did the same thing while still in the GC. The guy said it was the Sentry Key, he had to lock then unlock the door with the key, then the engine ran fine.
So, if it's not the VSS, is it this sentry key crap? Any ideas on how to get around that?
Thanks,

It definitely sounds like the sentry key thing... Do those employ a resistor in the key? If they do, you may have to wire in a resistor of the correct value before it will work. If you can check the key from the donor vehicle or just try resistors of different values and hope you get lucky... Knowing the possible range would help... Do you have the FSM for a '94 Grand?

Of course it could also be something else altogether... :flipoff2:

HTH,
Jake

use a computer from an XJ or YJ. the pre-obd-II computers should be all the same, except fpr that theft prevention crap.

Call 1-440-572-0725

order part numbers:
81-669-94021 JGC diagnostic manual ($7)
81--699-94027 Anti Theft System diagnostic manual ($11)
81--699-94010 2.5/4.0 EFI diagnostic manual ($11)

please worship me later as I am currently busy

:D

Thanks for the replies, guys.
He swapped out the ZJ computer, installed the one out of his daily driver '92 XJ. It started, ran, and didn't shut off. Apparently something to do with the ZJ security module.
He took off work today to head for the boneyard and scrounge up an XJ computer.

Again, thanks for the help.

Let me know if you don't find one, I gots a spare...

my 4.0 is froma GC and i am afriad it may have the key sentry crap. does anybody know the range of resistance for the key sentry thing? it is gonna be a BITCH if my computer was equiped with that.

I am having the same issue. Does anyone know how to disarm this sentry system. I swapped out a 2.5 for a 4.0 and don't have the donor 1998 JGC. I know I need the proper ecm do to the tranny controls.

Specifically the pin number that the purple with yellow stripe wire that is for the sentry. I don't have the donor vehicles cab harness (C3) so I need to know the pin number. Thanks in advance.