Hi all,

I was driving my 1994 F-150 XLT with the 302 this past Sunday when all of a sudden, 20 minutes or so into the drive, I noticed some hesitation. This went away and then came back maybe 15 seconds later, and when I stopped at a stop sign, the engine died. It started back up for a second or 2, then died again and wouldn't restart. Someone kindly towed me to a nearby parking lot.

Some brief spark tests with a screwdriver told me I didn't have consistent spark coming out of the coil. When I pushed down on the Schrader valve on the fuel rail, fuel squirted out plenty high; this combined with no spark made me think it was most likely a spark issue. I didn't have any electrical tools with me so I tried replacing the coil and ICM, since, after reading up online, those seemed to be common culprits. No dice with those, and I got permission to leave it there for the week so I could come back this weekend to fix it.

Went back today with more tools and she started up when I got there and ran for a minute or two, then died. I tried to start it back up, and it started but then died after a few seconds. Out came the LED test light (Innova 3410). I suspected the PIP sensor, so I put one side on the positive terminal of the battery and the other on the top wire of the ICM (using a piercer). When cranking, the LED flashed continuously, as it is supposed to (to my understanding).

So, I put an in-line spark plug light on the coil just to verify I definitely had no spark, and it started again for a bit (it had been sitting while I went to the auto parts store to get a test light) and then died shortly after. No spark when cranking.

I tested the ICM (heard of some issues with aftermarket ones and was worried I got sold a bad one) by attaching one end of the LED test light to the passenger-side wire on the coil and the other on the positive terminal on the battery. Briefly had some weak flashing and then none. Tested the PIP again using the same method as before and still strong. This made me think the ICM was bad, so I went and got a Motorcraft one from "the zone," and (it had been sitting for a while again) it started right up, then died after a minute or two. I pulled the KOEO codes (probably should've done this earlier) and got 118, 122, 181, 212, 334, and 556. I cleared them but couldn't get it to start again before I went home and didn't have any new codes. Because 118 deals with the ECT and I had replaced the radiator and drained and flushed the coolant (using both a hose and a Prestone chemical flush) the day it died, and because I read about some people online having issues with no spark due to a bad ECT, I replaced the ECT. Unfortunately, no change.

I really don't know where to go from here, any help would be appreciated. Thanks!

Edits:
- Meant to add I read something about the SPOUT connector with code 212 so I took off the connector and tried it and still no luck.
- Also none of these codes were current, they were all in memory, and the engine runs great when it does start.
- I checked and the coil connector has ~12v

 

Are you sure you have the correct ICM? I went through this similar issue myself awhile back in my 95 5.0. Ford changed to computer controlled dwell sometime in 1994 and my truck had the wrong ICM. I would replace it, work fine for a bit then same problems as you're describing. Auto parts stores and online kept giving me the wrong ICM. I finally found the below info and got the right ICM and cleared it up.

I cut and pasted this from a forum somewhere (sorry I can't give proper credit). I saved this in my "Things to Try" folder as I was researching and it did the trick for me: There was also an explanation of CCD vs Push Start ignition if you're interested in that, I'll post it.
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"1994 was the first year for the Computer Controlled Dwell style ignition on these trucks. This requires the black colored ICM to work properly.
Even the Ford documentation is usually wrong for the replacement part number."

Apparently around 1994, Ford introduced the black colored ICM which is computer controlled dwell. Until then Ford used the gray colored ICM which was "push start" dwell.

If in doubt about which TFI module belongs on a particular vehicle, consult the ignition system-wiring diagram for the vehicle. If the wire going to pin #4 on the EEC-IV computer comes directly from pin #4 of the TFI module, it is a CCD system. If not, it is a Push Start system.

TFI-IV ICMs that utilize computer-controlled dwell are black in color."
Using the wrong ICM in your truck will cause problems which are hard to identify.

 

I’m fairly certain it’s the right ICM. The old one was black and it was running perfectly before, also it’s fender-mounted. I appreciate the response though.

 

Finally found where @subford listed the correct voltages at each of the ICM pins (see this post: https://www.ford-trucks.com/forums/1...150-5-0-a.html) and I checked them. All seem normal (well, with the distributor and PCM unplugged everything was at battery voltage, so I plugged those both back in and got the voltages he listed), except before it started (but after it had been sitting so I knew it would start), I measured ~20 ohms between the bottom pin of the ICM and the negative battery terminal. After it ran (only for about 15 seconds this time) and wouldn't start again, I measured ~30 ohms. I'm thinking (hoping) this is my issue. If anyone knows the exact locations of the grounds the ICM uses, that would be very helpful. I found a wiring diagram that shows that bottom pin on the ICM (labelled as ground) going to the distributor, so I'm not sure if this means the ICM just gets its ground from the distributor which is grounded since it's touching the engine? Any help would be appreciated, thanks!

 

Pushing on the schrader valve doesn’t tell you anything. Fuel will spray out pretty good at 20# but that isn’t the 30-35# it needs to run.

Interesting. I’m down to two of these trucks but at one point had three and have never had an OEM Ford coil go bad. I think I might have replaced the ICM on the ‘87 Bronco once but that was a long time ago.

Yes. You should have started by retrieving odes and putting a fuel pressure gauge on it. Those codes are all over the place: voltage too high and voltage too low. Code 118 is the ECT above max voltage so what voltage is the computer sending to the sensor? Hopefully it’s only the 5V reference signal. I’d suspect the ECM/PCM is bad. Time to open it up to take a look at the capacitors.

 

I appreciate the response.

Yes, I should've retrieved codes earlier. I do not have a fuel pressure gauge and figured if it didn't have spark than that would likely be the issue. Did you see my reply about the resistance on the ground pin of the ICM? I'm comfortable with soldering so wouldn't mind replacing the capacitors but don't wanna go down that road if grounding is the more likely issue, what do you think?

Also when I ran it yesterday it didn't throw any more codes. It only ran for 50 seconds though before it died, would this have been long enough to throw codes?

Thanks!

 

You could have stopped by the auto parts store and rented one.

I don’t know and never bought Ford service manuals for the ‘94 Bronco. I did use the search function here and found this from rla2005 in a 2016 thread.




Did you clear the codes? If not, where did they go unless the computer reset on its own which isn’t good.

 

I did clear the codes so I could see which ones reappeared. Thank you for the diagram! What exactly did you search (diagram is a little fuzzy and hard to read, I'm wondering if the original would be clearer)? I tried using the search bar but had way too many irrelevant results, mainly been finding posts through google.

Edit: Nevermind on a clearer version of the diagram, I found it on google. Am I correct in understanding that the distributor gets it's ground from the PCM? Is this then also what is grounding the ICM?

 

Realized I was being pretty silly when I checked the resistance and still had the battery hooked up. Unhooked, checked today and very low resistance from there to neg terminal on battery. Going to take out PCM and check capacitors.

If capacitors look fine is there another way I can test the PCM?

I already tried taking off the SPOUT connector and still no spark. I thought this meant the computer was fine but maybe not.

Should I still check the fuel pressure even though there’s no spark?

 

To me, it looks like the ICM grounds through the distributor. The distributor is grounded through its housing to the block.



If I remember correctly removing the spout takes the computer out of the equation. If you still do not have spark then it is a distributor/ PIP problem.