Let me give you some background on my vehicle in question. I recently put an 5.7L/L98, out of an '88 GTA, into my 1976 Jeep CJ-7. I used a painless wairing harness for the speed density motor along with changing out the knock sensor to the correct one for the speed density system. It has the MAP sensor, correct computer and EPROM w/o VATS (both from Howell efi).

Wired up the motor in accordance with Painlesses manual.

OK, I had the motor running and it sounded GREAT! That was on a Friday.

The follow Monday, I was back at the shop and tried starting it again... nothing! It's been almost two weeks and I don't know what else is left to look at besides the computer.

Checked fuel pressure, 43psi
Checked spark, it's there.
Checked injector signal (using the required test light) - nothing

I was able to get the motor to run by spraying starting fluid into the intake so, I'm sure the problem is with the fuel injectors not being fired. I've also check the ECM fuse and it's fine.

Am I looking at a bad ECM? Is there anything else I could look at or that could cause this problem?

Thanks in advance.

 

Do you have the FSM for a TPI car? There's troubleshooting procedures in there that are very good.

Start with checking fuses for the injectors, then hook up a scan tool to see if you're getting reference pulses. If you get pulses, then look at the drivers or FI wiring. If no pulses, examine the distributor module or wiring from it to the ECM. IIRC (it's been awhile) the reference pulse wire is purple?

 

One way of checking to see if your injectors are firing, I believe, is to take a screwdrive and place it on the inectors wiring connector and put your ear up to the end of the screwdriver, then have someone try to crank it. Do that to all 8 cylinders... that should tell you if your injectors are firing or not.
---Justin Myers
Houston. tx.
'83 280zx n.a. <fs>
'86.5 Toyota Supra <just bought>
'86 TA <project car, working on it with my friend Brett>

 

Thanks for your help guys.

My buddy has the test light made to see if the injectors were firing. They weren't.

I did some further troubleshooting yesterday and determined it was the ECM. After replacing it, my Jeep fired right up.

Thanks again everyone!