No Spark. I'm stumped for tonight.

So i'm trying to finish up this 4.0 swap. Everything works but I have no spark. Head lights work, all the lights on the dash work, fuel pump works; i got good pressure at the rail, engine cranks over good, just no spark. So i got the good ol fluke out and manual out and started performing all the ignition system checks.

-Battery is fully charged.
-Cables are clean have have good connection at the Battery.
-I have B+ power and ground at the harness to the coil pack.
-The connector at the coil pack with the 4 prongs, there's 7.0 ohms of resistance between the B+ prong and the three coil ground prongs.
-There is continuity between the firing pistons' coil connections.
- Brand new spark plug cables and brand new correctly gapped spark plugs.

Everything at the coil pack looks OK

-ICM Harness has B+ power to it.
-ICM Harness has continuity the battery ground.

-ICM Harness between pin 5 and 6 that goto the Crank Position Sensor read 0.531 K Ohms and the spec calls for between 2000 - 3000 ohms.

If not check the crank position sensor.


-At the Crank sensor itself between prongs it read 0.531 K ohms.
-No analog wave created by the sensor when cranked, it stayed at 8.09 amps.

I figured it must be the crank position sensor. 48$ later I was wrong.
New crank sensor didn't help.

It's late, ~4am so I am calling it a night. I work second shift so this isn't too terribley past my bedtime. But I'm stumped for the night, it will be figured out eventually but any thoughts? I was thinking the spec calls for 2000 - 3000 ohms and the new crank sensor is still reading really low resistance at 0.601 k oms or 601 ohms. So that'd mean there's a short in the wiring before the sensor??? If it isn't and short and its not the crank position sensor and the coil pack checks out good then that leaves the ICM. That wouldn't be cool the manual starts off describing it as a expensive and delicate piece of electrical equipment, yea o'riley's lists it at 250$ and that's not FoMoCo. The manual doesn't give any tests for the ICM itself, only notes that if the other primary circuits are working properlyt than it is probably the ICM. Any ideas on anything I am missing?

I am having the exact same problem with my 4.0 swap!! I'm sorry to hear that someone else is having this same issue. I worked on mine for hours trying to figure it out last night. I'm going to look at it again today and if I figure something out I will let you know. In the meantime does anyone have any ideas?????

well in case there's other people out there with a similar problem I took the ICM into o'reilly's today and found out they have a tester for them there. they plug a harness into the ICM and it undergoes a series of tests, either pass or fail. My ICM failed two of the tests, Low rpm recognition i.e. cranking, and it failed reference voltage recognition test. So in other words my ICM is supposedly bad. They had to order an ICM and it'll be here on thursday so I'll find out if that will solve my spark problem thursday night.

So i got the working ICM. No spark still.

That is the problem with conversions that require rewiring....

Finding a problem.

Yeah, I only had one problem on my conversion,
but it still took TWO experience professional mechanics
with ALL the factory documentation for both the vehicle and
the engine donor, AND a MODIS scanning tester, 18hrs to find
the problem, a neglected ground lug that wasn't grounded.

and THAT prevented the Fuel pump relay from switching on.

Masking that problem was the fact that the injectors were
gummed closed because the engine had been sitting
(and the fuel drying out) for several years. so they had to
be flushed out with injector cleaner (at high pressure)
to get fuel to flow out of them.

AD

I know you are gonna say I need all the factory diagrams etc. but AllanD would you be able to list off the grounds? I thought I was positive I got them all. I am gonna try and have a guy I know from work that drives a 91 exploder to come out to the shop and park next to my bII and see what we got goin on. I am stumped, I got a buddy who is a sharp dealership mechanic thats gonna come out sometime to help me out if I can't find it.

Yes, if someone could list where each ground is located it would be highly appreciated. I have the diagrams but they don't state the exact mounting spot of the grounds. I have checked mine over and over again and can't see any hanging anywhere but maybe I am missing one.