[mhessling]

Drove my 96 F250 home from the transmission shop the other day after a rebuild. Ran fine for the 60 mile trip. Parked it in the driveway then went to start it yesterday and it cranks but will not start. No Wait To Start light and no white smoke out of the exhaust pipe. Had the issue with the fuel heater a few years ago. It would blow the fuse but at least the engine would start and run although it only ran on a few cylinders (The fuel heater wire is disconnected and taped). This won't start at all. I have a remote start and usually it delays until the WTS light goes off before it tries to start but when i used it yesterday it hit the starter almost as soon as i pressed the button. Tested the glow plug solenoid and it works just fine. Pulled and checked all the fuses under the hood and everything was good. I saw in some previous postings that there could be a problem with the PCM. Is this the same as the injector control module? Replaced that last year as it all of a sudden started running really rough and had no power. The injector control module fixed that issue. I know when i had issues before with a broken glow plug relay it would crank and blow white smoke but wouldn't start. No smoke out ot the pipe at all this time. Gave it a little sniff of ether and it starts and runs on the ether but dies. I only tried that because i knew the glow plugs were not working. I know not to use starting fluid on a diesel engine with glow plugs. Any help would be greatly appreciated

 

[Patrick Feeley]

PCM and IDM (injector driver module) are different. PCM controls everything while the IDM provides the high voltage DC required to "drive" the injectors. Do check your underhood fuses anyway (use a DVOM). The PCM could be the problem, but it's possible you have a problem with the 5V reference voltage circuit that the PCM provides to some of the sensors that use it. It could be a wiring issue or a shorted sensor. The sensors that use the 5V reference are the TPS (also called AP), CPS, BARO, EBP, MAP, and ICP. For a shorted sensor, you can try unplugging each sensor (one at a time) and see if the WTS light comes on (you don't have to try and start it, just see if the WTS light comes on). The most common ones to short would be the EBP followed by the ICP. Not sure of your capabilities, but attached are a couple of documents for your perusal. Cheers!

 

[mhessling]

Update on my starting problem. Narrowed the issue down to the F22 circuit. When the truck wouldn't start I could turn the key on, pull F22 and tap it in the holes. This would cause the PCM and the IDM relays to toggle. After a few try's the glow plug relay would kick in and I would get the "Wait To Start" light. Turn the key and the motor would start and run till the next episode. The other day I went out in the morning to go to work. Started the truck and it ran for about 30 seconds then shut off. Same MO as before engine cranks but won't start. My F22 trick didn't do anything this time. Was able to get some wiring diagrams from a friend and started tracing signals. Decided it could be a grounding issue so I removed and cleaned all the grounds from the PCM and IDM. Turned the key and got the wait to start light, engine fired up, ran for about 30 seconds then shut off. Tried my F22 trick but didn't help this time. Traced some more wires and did some voltage checks. All seemed fine. Checked the R1 and R2 relays input and output, nothing found there. Got back in and turned the key and it fired right up. Tried it again today and it fired up and ran ok. I do electronic troubleshooting as part of my job and I know the most frustrating problem is one that won't stay broken. I'm back leaning towards the PCM again. I know it's probably coincidence but all these troubles started after the transmission rebuild. Just not sure what the transmission guy could have done that would mess up the engine.

 

[mhessling]

Just wanted to post an update although I'm a little behind. Finally determined what was causing my no Wait To Start light and crank but not start. It turns out that the Super Chip that was installed by the previous owner in 2000 had gone bad. As everyone know intermittent failures are the hardest to find. Found this one completely by chance as we were swapping computers. Hooked one up without the chip attached to the backside and it worked. Plugged in the chip and no work. Ended up having Hypermax burn me a new chip and all is well now. I guess sometimes it is better to be lucky than good. Thanks for all the suggestions. Wish I had checked it our back in the beginning.

 

[Patrick Feeley]

Glad you found the problem! That's why it is good to mention the specifics of your truck in you post or signature. I we had known that you had a chip, we would have recommended physically removing it as a first course of action. Cheers!