I posted about this before, and after over 3 weeks, my truck still will not start.
94 F150 w/302, has 93 ignition
It gets spark but it weakens out a bit after turning over a few times.
Fuel pressure is correct, and all injectors are functional.

I've replaced:
PIP sensor
ignition module
ignition coil
spark plugs
spark plug wires
distributor cap and rotor

I've checked:
all wires and connectors(no corrosion and no cuts or bad wires)
fuel pressure
injectors
diagnostic codes(no codes, I get 11, 111)
timing(right on the dot to where it should start, even have played with it while trying to start)
all grounds have been cleaned, replaced, and have added a few more
over all vacumm lines, none are broken or leak

I've kept the battery charged up the whole time. I've tried switching tanks(dual tanks). I've done every electric test in my Haynes manual and nothing is bad, all connections are fine. I took the electrical harness off, checked it over from end to end cleaning off what little corrosion was on the plugs. Oil pressure does buid up some while cranking over.

All I did to start this was take the intake manifold off to replace a leaky gasket(was leaking coolant out the front). The truck ran very well before that.

Could it be the PCM(computer) is messed up? And for some reason its telling it not to run? I'm completely lost. Everyone else I've talked to is stumped as well.

 

did you replace/check fuel relay and the fuel pump maxi fuse?

did you spray ether into intake?

 

I ment ECM, not PCM. And I can't edit the post.

quicklook2, Yes, I replaced the relays. And I tried the ether in the intake, nothing happened.

I've just talked to a few other people over the phone. They said if everything else is fine, then the ECM could be the problem. When I called a junk yard about a price, they said its a common problem. They don't charge too much for it, $45 with trade in and if it doesn't work they will let me try another or get my money back and my old one.

 

i think you need to get a case of beer, turn on game 7 tonight and just zone out.

this has got to be aggravating, like trying to figure out what your partner wants.

hope it is the ecm.

 

ECMs rarely go bad. Take the distributor out, and make sure there is no slop in it. Grab the shaft and wiggle it back and forth to see if it moves. If it does then you need a new distrbutor. You say it ran before this happened... Did you make sure that no1 is at TDC on the compression stroke?

 

The distributor works fine. I've checked it over before, no slop. When I replaced the PIP sensor, I had to take it apart. And yes, I've checked to make sure no1 was TDC on the compression stroke. I've done that a few times just to make certain people quit suggesting it.

Anyone know of a list of substitute ECM models? So far with my searching, nothing even comes close to my model. I have yet to go to the junk yard yet.

model # F20B-14A624-BAX

I think I might try to replace some of the capacitors on the board. I've read that when they get older that they may not function correctly in filtering power supply voltage. It could cause the ECM to keep resetting, work improperly, or to not function at all.

 

Hi Rc,
Are you sure thats fuel on your plugs? Light it with a match to make sure its not antifreeze trapped in the cylinders.

Have you tried diconnecting the exhaust at the end of the manifold to make sure its not plugged.

Also, verify your firing order and plug wiring. Its happended before that someone wired the plugs the wrong way around on the cap...

Lastly, is air being drawn into the intake?

 

Popa Tim, it was gas. The exhaust was replaced with 3" to a Flowmaster 40 Series. Verified firing order and plugs are on correctly. Air is being pulled in.

Thanks for trying to help everyone. I spent 4 hours online today and found out about the capacitors on the ECM. My brother makes guitar pedals so I replaced all the capacitors on the board, re-installed it, and the truck almost fired right up. The spark was very strong, like it should be. After advancing the distributor a hair, it fired right up! After timing it, its now running better than it ever has. Idles very smooth, too.

If you have the same problem, and all else checks out, replace the capacitors on the board. Its very cheap to buy them. Actually, its a hell of alot cheaper than buying even a used ECM that has a 50/50 chance of being bad itself. If you don't have soldering skills, find a buddy or someone who does. Heres an informative site http://www.tmo.com/howto/ecu1g/caps.htm Don't go by the values on that page as its for a different ECM. The values are always on the sides of the capacitor. I recommend replacing the smaller ones on the board as well. Also, as another side note, you don't need any fancy desoldering tools. Just heat the hole up and stick a tooth pick through it.

 

rc dan

good job!

what made them go bad?

quick

 

Capacitors all go bad with age and use. Generally, heat and moisture kills all electronics. The type of capacitors on the board have a gel inside of them. Over time, it dries up. With all the use it has had and all those hot summer days, 11 years isn't bad at all. As I said before, most go bad alot sooner.

 

I used your computer info to convince myself to get a new computer for my 1995 F-150 that was stalling intermittently without giving any trouble codes. I replaced the computer with a refurbished one and have had no problems now after driving over 200 miles in the past 4 days, so that appeared to fix the problem.

 

I previously posted a message that when I replaced the computer it fixed my stalling problem. Actually the problem was the distributor. I ordered a rebuilt one (cheap) but it didn't fit. I then got a new Motorcraft distributor. It works fine now. The problem was intermittent. I can only assume that the PIP was putting out a signal but that the waveform was not quite right.

 

Is it possible that any of these solutions could fix my hard to start when warm problem. I dont really know how to check the ecm or the distributer? What do you have to do?

 

My problem occurred both cold and hot. It was a distributor problem. I would sometimes get a trouble code indicating "intermittent or missing PIP signal". Good luck on finding your problem. If you get a new distributor I recommend getting a new Motorcraft distributor. They are available online from RockAuto.Com. I originally got a rebuilt one and it didn't fit so I had to get the new Motorcraft unit.

 

Hey, I started having problems with my truck missing when going uphill or hitting just small bumps. When I was back in a gravel pit, it stalled out and wouldn't start again for an hour. I couldn't get any codes and checked every connection I could think of. I ended up taking the dizzy cap off and cleaned off the points. It fired right up, but still missed. The next day, I went through all the checks for the ignition system and found nothing wrong. Then, I looked at the spring tension on the rotor. It was compressed a bit so I stretched it out some, put it back in, and have had no problems since.

Its also a good idea to wipe out the dirt in the distributor every once and a while. I think the dirt build-up might contribute to signal errors from the PIP.

BTW, I felt really stupid when I found out that when I replaced the caps on the ECU, that it was not the ECU. Infact, I had my hands on the Air Bag Module. Seems like it would be obvious seeing how it has less wires going to it. Now, a few of the capacitors were bad on it, so replacing them didn't hurt anything. But, what really gets me, is why it just decided to fire back up after 3 weeks of "no start". I still think it was computer related. I dunno.