BlueRidgeMark

IIRC, you need 39 psi, so I think you are good there. Got spark? If no, you might have also fried your crank position sensor. They aren't cheap, so test it, don't just buy a new one. Only Mopar - aftermarket units are notoriously horrible.

Noah911

And, to make sure the fuel injectors are all receiving the normal 12 VOLTS too...

rkt68411

The test light confirmed voltage to the injectors. It stayed on, did not flash, during cranking. I put the test light between the supply and ground terminals of the injectors and it flashed during cranking. This leads me to believe the injectors themselves are bad. Upgrading them was going to happen anyway. Is there a way to test an injector once it is removed?

dave1123

Yes. Even before removal you can disconnect the plug and supply 12v and a ground to the pins and they should click every time you add either. The computer cycles them at millisecond intervals when the engine is running and controls mixture by adjusting "on" time. They are either open or closed, not "throttled."

They are supplied with 12v constantly and the computer grounds them to spray fuel when needed.

Noah911

You can check the fuel injectors for their resistance values too. Off hand, I believe they should be at approximately 12 ohms between the terminals at ~68* farenheit (ambient). The higher the temperature is when testing (ie: hot engine compartment/operating temperature) will increase the resistance.

A very low resistance will kill the driver in the PCM to the injectors!!

BlueRidgeMark

Which is why you really can't tell anything with an ordinary test light, except that you have the correct voltage present. You need a noid light.

rkt68411

The lessons keep comin'! Incidentally, I did not hear or feel a click when I put 12v to each injector individually. I really appreciate all the knowledge ya'll have freely given.

rkt68411

They showed 14.6 - 14.9 ohms resistance. Outside temp was about 95 degrees.

BlueRidgeMark

Sounds good.

rkt68411

The noid light flashes during cranking. Just out of curiosity I attached a 9v battery to the injectors via test probes and they sound like they're working. A solid sounding 'click'. I don't know why I couldn't hear them when I used the battery as a power source. Incidentally, voltmeter shows 11.9v at the IAC with the key on and the noid light stays on during cranking. It's red, by the way. I am going to re-install the original gauge cluster, do the key dance and see what DTCs it shows. I'm now questioning whether the replacement ECM is functioning correctly. Seller stated it was from a running 1991 or 1992 Cherokee with 4.0 w/AT. Of course, he could've said it would turn lead into gold, too!

To recap, I have good spark at the plugs, good fuel pressure at prime, 35psi, and while cranking (40psi), fuel injectors getting power(per the noid light) with correct amount of resistance, 11.9v at the IAC, I am stonewalled.