Intermitten spark, then no spark
 

I recently replaced a bad 302 in my 94, f-150, 4X4. replacement 302 engine came from an 87 f-150, 4X2. Both automatics. The only thing i changed into the '94 was the block, its internals, heads and valve covers. Everything else stayed on the '94. The bad 302 started right up and ran before removing it, but had a bottom end knock and squeak.

Now to the weird part. When trying to start engine for the first time, I got a few pops, then nothing. The timing chain was replaced and is in time correctly. The distributor and rotor are close (haven't been able to nail timing down as it hasn't started yet) I checked for spark by pulling number one wire and grounding a sparkplug to a clean spot on the engine. Had spark but looked weak (white/yellowish). Then I checked the coil for spark. Still wasn't a good blue white spark. Tried moving the distributor a few degress back and forth, with no luck. However, now I am getting no spark out of the coil or distributor. I've tried several wires and plugs, and they are all new, so I have ruled them out.

the two wire connector going to the coil has 12 volts on both sides at "key on" and "start" positions. My next guess was a bad coil, so i tried another one I had laying around and got spark a few times out of it, and now nothing again.

Is there a ground for the coil system where it mounts? My only thought was maybe I lost ground to the coil when detaching the intake and engine harness. I hope i've given enough info. ANy help is greatly apreciated.

Thanks, Kevin.

Ignition module?

That is a thought of mine, but if it was bad, would i still be getting 12 volts to the coil?
-K

Maybe, there are many diff. ways for it to fail.

Ok, I've got another possible idea/question. Does anyone know if anything changed from 87 to 94 in respect to the cam/crank positioning sensor magnets? My thought is, if they have changed, maybe my cam or crank positioning sensor in the distributor is not picking up correctly (or has nothing to pick up) and therefor telling the ICM to not fire? Is this possible? I do not have any extra electrical connectors to plug in anywhere so I think I'm ok on that end.

And the plot thickens.....

I just noticed on alldata that Ford decided to change the firing order on 5.0's from '87 to '94. Doesn't sound like the '94 ECM is going to like that very much. Oh boy. I think my 3day project just got a little longer.

-

I know they did if you went from a roller to a flat tappet or the otherway around.
Mixing parts on a truck take knowing these little things or you get into a big compatability problem.
Btw, there are no crank or cam sensors on these motors.
The PIP in the distributor is the = of the crank sensor in later motors.
The fuel injection is sequencial and not batch fire between the two combinations.
The distributor top hat signal wheel may even be cut a little different between the two systems..

According to the Haynes repair manual the '94 and earlier 5.0s all have the same firing order. However in '95 the 5.0 firing order did change.