won't start when it is warm\hot..please help

[bhawk]

94 Ranger 4.0.
We've been battling a no start condition when warm\hot for the last several months and everything we have changed\repaired has failed to correct the problem. The truck will always start and run when it is dead cold. But if we run the engine for say 15 minutes and shut if off, it won't start until it gets cold again.
When it won't start I have hooked up my timing light to a plug wire and I get lots of spark as it turns over.
I now have a fuel pressure gauge and it shows the fuel pump builds 32 pounds pressure right away and it holds pressure after the engine is shut down. When the engine won't start the fuel pressure gauge shows between 30 and 40 pounds pressure, so it can't be a fuel supply problem.
I wanted to eliminate vacuum leaks so we just finished putting in new gaskets on the lower intake, upper intake, fuel supply manifold, valve cover gaskets, flushed and cleaned all 6 injectors, and replaced the fuel pressure regulator. Also since the no start condition started to occur, we swapped out the MAF sensor, throttle position sensor, IAC from engines known to work. Still no start once the engine heats up. I will go to the shop in about 20 minutes when the engine cools and I expect it will fire up and run.
WHERE DO WE GO FROM HERE?? 02 sensors??, coil pack??? computer??? Why does it not start hot but start cold and run decent once it starts. Please HELP, I am near giving up, but I can't let this beat me.

 

[bhawk]

An update.
Still starts when it is dead cold, but won't start after it runs for about 4 minutes or more. Have to leave it sit for a few hours or more before it will start again.
So, I replaced the ignition control module (ICM) with one from a working truck. No difference, still no start.
Then, I replaced the coil pack from a known running truck. Again, no start when it is hot.
I put a spark plug into a couple spark plug wires and held it against the exhaust manifold while my son cranked the engine. I gets lots of spark at those 2 plugs. I guess I will try every plug later tonight or tomorrow.
I get lots of fuel pressure on my gauge, but I guess I never really know if a fuel injector is spraying fuel into each cylinder. IS there any way to tell if the fuel injectors are spraying during my no-start condition???
What about the O2 sensors??? or the crankshaft position sensor???? or the PCM???

 

[chazzone]

Is it throwing a code? I'd check the coolant temp sensor (not the one for the guage). This is usually the problem when there is a cold/hot start issue.

 

[bhawk]

Will the engine run or start if I disconnect the coolant temp sensor? I was thinking that if I disconnect it maybe it will tell the PCM that the coolant is cold and it may start? But not sure if I'd be damaging anything by trying to run it disconnected.
The sensor was new last year. I replaced it to try and get the high idle down, but to no avail then.
I am reading now on how to pull the codes without a code reader. Will post results later today. Thanks.

 

[disciplerocks]

Was having the same problem a couple weeks ago. Did a search. Coolant temp sensor (2 wire) is the most common problem. Then bad MAF, crank position sensor, or ecu. Mine ended up being the ecu. Do the coolant sensor first, it will be easiest. Mine was about $17.

 

[bhawk]

I just pulled some codes by using the jumper wire technique. I got a number of flashes of the CEL that I can't read, doesn't seem to be any consistency to them, maybe a separator code whatever that is, but, I could read one code as it comes up twice in a row..The code is 118, which literature says is engine coolant temp sensor problem.
So, maybe I'm onto something.

 

[bhawk]

Problem solved. thanks for your help chazone and disciplerocks.
Turned out to be the engine coolant temp sensor. I let the engine cool and pulled the codes again. I got 2 codes, a 116 and a 118. Both related to faulty coolant temp sensor.
So, I went to my parts truck and pulled an original Ford sensor off. Installed it and the truck runs good and started when it was hot.
The faulty sensor was only a year old. Got it from OReilly's last year for 17 bucks. It was an all plastic model, BWD I think. Anyway, they are junk obviously, given that an old Ford sensor, 19 years old still works and has me going again.

 

[disciplerocks]

Glad to hear it.

 

[clifford97]

rail plugs!

 

[polar765]

my 4.0 ranger did the same thing ,a new computer solved the problem ,replaced everything else before trying the computer

 

[bhawk]

Where did you get your computer, and how much cost? Just in case I ever have to go there.

 

[disciplerocks]

Mine was $10 from the u-pull.