No spark

[FritzTKatt]

So last year (before I joined the corps) my 4.0 toasted itself. Long story short, everything was good to go, less the fuel in crank case problem... hehe... my buddy was taking care of it, but now it's time to resume control.

Had a new 4.0l from an exploder put in (don't know what year, yet), IIRC with about 80k on it. I spoke to the mechanic that did the swap on the phone, he said that the swap went well, but can't get spark. I don't know how competent or knowledgeable this guy is. Threw a crank sensor, cam sensor, used the ranger intake (it was different?). Says the injectors fire, and it compresses but no spark.

I know the ICM was good, had it tested out, but don't know about the ECM. Could never locate it (seriously). Mech thinks that's the only thing left in the whole spark... I kind of agree with him, the wiring is good, ICM is good, injectors shouldn't fire without crank/cam sensor?

What do ya'll think?

 

[tmcalavy]

Makes sense and shouldn't be too expensive to diagnose...as in used ECM or new...not that spendy.

 

[FritzTKatt]

Yeah, I'm just not sure where to go with it. I'm hoping ADSM has some good input, or maybe he can tell me some stupid little thing that was completely over looked. I'd much rather look a fool on the internet and have a running truck then spend more money, lol.

 

[Snoranger]

The ICM is pretty much a stand alone module. The ECM just controls spark timing.

Check for power and ground at the ICM. (I assume they're there if you have injector pluse, the ICM creates the PIP that the ECM needs to know whe engine RPM, but check anyway. It's grounded through the case and has a separate ign ground from the PCM at pin #4. Batt + at pin #8... Comes from PCM power relay.)
Check for power and ground pulses at coil pack. (4 wires input, red 1 is power, the other 3 are yellow with different tracers from the ICM that fire each channel. I don't remember the tracer colors off the top of my head.)