1995 F150, 300 straight 6 cylinder EFI
Recently I developed the dreaded no spark issue. It started out as an intermittent problem where the truck would "skip a beat" driving down the road. Then it developed into a hard to start and now it won't start at all. I have followed the Haynes manual to a T and it suggests it may be the computer. When the key is turned into the on position the fuel pump runs until it builds pressure, about 2 seconds then shuts off. this makes me think the computer is OK.

Here is what I have done.
New fuel filter, TFI module, coil, plugs wires and re-manufactured distributor. All the fuses and relays seem to be fine.

After all the parts I still have no spark at the coil. There is voltage at the coils plug but it does not "flicker" as the Haynes manual says it should. I disconnected the computer and still have no spark when cranking the motor over.

Any help is much appreciated.

 

I did the KOEO test and the only codes I got were 522 (Vehicle not in PARK or NEUTRAL during KOEO) and 111 (System pass).

 

Was it in P or N when you did the test?

The fuel pump doesn't shut off based on pressure - it's just a timer inside the EEC.

Did you TEST any of those new parts? Did you test any of the original ones before replacing them? I hope you kept them.

The Haynes procedure never mentions the EEC as a possible cause for no-spark because the EEC isn't involved in making the spark. The ignition system operates independently of the EEC; the EEC only provides an advance signal on the SPOUT circuit. But a fault in the wiring between the ICM & EEC can interrupt the ignition system, so read this:

 

Thanks Steve83,
It's a five speed. Re-tried the test and while pushing in the clutch the only code I get is 111 (System Pass)

My original TFI tested OK but I read that sometimes the test won't find intermittent problems so replaced it anyway. My original coil was within test specs but the coil wire was really corroded and almost gone, so was the connection at the coil. I had already performed the procedure you listed. Sorry, forgot to mention that one. I did not find any broken or exposed wires.

I had read in one of these forums that if you had no spark and disconnecting the PCM made the spark return that the culprit was most likely the PCM.

In the Haynes manual I got to step #77 on page 5-13. The spec voltage for the spout connector test was 3 to 8.5 volts but I got 1.3 volts. The manual said the problem was probably the PCM, I thought that was the computer. Re-reading the manual I noticed it said the voltage was AC. I was measuring DC so I will go back and check again. UPDATE, checked that test again and my voltage is even lower, .1 AC volts while cranking with the spout removed, measuring at the wire coming from the PCM.

 

That step isn't for no-spark; it's for DTCs 18, 212, & 213 (which is a KOER code, meaning the engine runs). You have to start at the beginning of that section and go to the specified step for your symptom. It's not 1-2-3-4... It might be 1-17-18-33-11-42 for you, depending on each result you get in each step.

 

Our book must be different. I understand that you don't go in 1-2-3-4 order but that it jumps around depending on your results. That is what I did. In my book that page/step is under checking the PIP module.

 

I have 3 editions, but the one I'm looking at is a blue cover ©94,95,96, and step 77 is in the middle of the L column on p.5-13 immediately above diagram 8.17 .PCM; not PIP. From what you've posted, it looks like you should have read steps 1,2,3,4,6 (Symptom 2),16-20. What steps did you follow that led you to 77?

 

Thanks for your patience Steve. Yes, PCM.
I started with the tfi-iv system checks/preliminary checks on page 5-9, fuel pump ran and shut off. Under ignition problem symptoms I went through steps 2-4 and I had symptom #2 which sent me to step #16.

Steps #16-20 passed. Installed new ICM and no joy. At this point the book sends me back to section 3 for general ignition system checks and I end up back at the same point. So I started going through all of section 7 trying to isolate the problem and look for other clues.

Ignition coil supply voltage-passed
Coil primary and secondary resistance within specs-passed
Ignition control module supply voltage check-passed
Ignition control module ground check-passed
PIP stator sensor checks (remote ICM)-passed, this sends me to step 72
PCM module check (spout)....step 74 I get 1.3 volts when I should get 3 to 8.5 volts.
(77) removed spout and checked voltage on PCM side of harness, voltage still too low.
(79) Resistance between PCM side of spout connector and PCM plug is less than 5 ohms.
(80) Resistance between spout connector and ground is greater than 10k oms

This is where the books suggests the PCM may be at fault. I read on another forum that if one disconnected the PCM and cranked the engine and the spark returned that the PCM was most likely the culprit. I did so but the spark did not return.

 

Right - as I said before, the PCM has nothing to do with the creation of the spark. But when you returned to Sec.7, you should have returned to steps 1-4 and repeated the process instead of "going through all of section 7".

Your problem is in the ignition system, but it could be mechanical. Or your meter might not be reading correctly, causing you to miss the electrical fault. And new parts aren't always good parts, so that ICM could be defective. What brand is it, and where did it come from? Or it might be the wrong ICM for your truck. Check a few online sources for that brand to make sure you have the right PN.

I realize this is frustrating, but you've eliminated the PCM as a possibility at least 3 ways. This is an ignition system problem.

 

OK, I found something different. While doing the voltage checks for the ICM I noticed that pin 4 on the harness only gives me .8volts in the run position and while cranking.

The Haynes schematic says that pin 4 goes to the starter relay but mine goes to pin 4 on the PCM. The schematic I found that appears to match is this one


Would low voltage on pin four of the ICM cause my problem?

 

ICM (C1021) pin 4 (R/LG) comes from fuse U, which also feeds the RFI capacitor, coil, & distributor. In that diagram, it's labelled "ICM PWR" at the ICM. It should have battery voltage at every terminal when the key is in RUN or START.

PCM (C185) pin 4 (Y/Bk) comes from the ICM pin 3. It may be START or IDM, depending on application. What color is your ICM? Both Haynes & Ford have contradictions/errors in their ignition diagrams & info, and I'm not sure if the diagram you posted is any better.

 

I have the third one from the top. Black remote mounted ICM which seems to match the one in the diagram. I checked and #4 on the ICM goes to the #4 on the PCM on my truck. I get .8 volts with the ignition in the run position and while cranking.

 

I didn't expect that. I was reading the part of the '95 F150 PCED that says they're all Push-Start ICMs. Since yours is actually a CCD, the EEC does affect the production of a spark. Pull the SPOUT connector & try to start it.

****EDIT****
I found part of the problem - on both the '95 Truck CD & the '92-96 DVD, the PCED numbers the ICM & distributor pins reverse of the corresponding EVTM. So ICM pins 3 & 4 are opposite, depending on which direction you go.

 

Done that, still no spark. I have also unplugged the PCM and no spark.

 

It's in the ignition system. I'm working on a revised (CORRECT) wiring diagram, but I'm having to compare the PCED, EVTM, Haynes, & my own truck's wiring to make sure it's right. It might take me hours, days, weeks...