Still stumped over '94 PSD

[Tim the 2lman]

Well first of all, thanks to all who have tried to help. I really appreciate your time and sharing your experience with me. One of my pet peeves though is not posting a resolution once it was found. So in the spirit of non-hypocrisy, here goes.

Got the new CPS and cranked it without the GP relay connected and watched the scanner. The numbers imediately started showing up on the scanner. Hooked in the GP relay cranked for about 5 secs and heard its first pop. Kept on the starter another 5-10 secs and bam....she roared to life. It runs like a top!! Unbelievable.

Haven't been that stoked and humiliated at the same time in quite some time. The moral of the story though is this, the Tach can still show evidence that the CPS is working even though it's not. When the key was just in the run position, the tach showed 0 rpm. When I moved the key to the start position and cranked it, the tach would rise to around 200 rpm. PCM also had no codes related to CPS unless I unplugged it. The rpm monitor on the scanner is what exposed the truth. Don't know why I didn't see that sooner. Oh well, maybe this will help someone avoid the same head scratchin i've gone through for the past month and a half.

 

[BigRigTech]

Have you tried a code reader to see if any faults are active?
Are you sure the oil pressure isn't bypassing bad injector o-rings?
Is the tach/scanner reading cranking speed?
Have you tried another known good IDM or PCM?
Any signs of engine oil in the fuel bowl?



....Really, anything over 300psi will start to bring these things to life...cranking 200-300rpm should show you 500psi or close to it. ..I just went through a no start on my buddy's 97, took me 10hrs to fix it....Bad PCM....I had 500psi while cranking, 70psi of fuel pressure but no cranking rpm on the tach or the scanner. I tested the CPS wiring and ruled everything out by the process of elimination until he bit the bullet and bought a $600 PCM....Man was I happy when it started......The old PCM was so bad that it fell apart when I pulled it out. Me - I would go in a different direction, forget about huei pressures as what you have is ok and start looking at the electrical possibilities...Another PCM or IDM would be my first test. Also, flip the fuse box over and see if any wiring is green - I've seen some nasty stuff there....Another issue I've seen is the truck not starting in Park but it would in Nuetral - the range selector on the trans was bad.....A few things to think about for now.

This is why I asked about the RPM's on the scanner - my buddy's truck would bounce the tach but the scanner rear zero rpm....I had a feeling you were headed in the same direction as you had the same symptoms......Now's it's fixed and hopefully everyone has learned a little more about the infamous Powerstroke CPS...

 

[Double-S-Diesel]

that may also explain the 425 on the HPOP, no rpm, no IPR

 

[Tim the 2lman]

That's just it Double S. With the IPR diconnected the HPOP pressures were much lower. Plus, I put an oscilloscope on the IPR signal from the PCM and had a valid signal that looked just like Ford's documentation said it should with the exception of amplitude. That was something their documentation didn't elaborate on. I guess I need to go back and look at the signal again now that it's running and post the results.

BigRig, don't you know that I glossed right over the "/scanner" part of your question. You were right on there. Had I verified both of them then we;d been done last week . All the feedback I had received seemed to indicate that if the tach was moving then CPS was good. Bad conclusion on my part.

 

[69oiler]

way to go Tim! now how about some truck pics?

 

[BigRigTech]

My buddy's tach would bounce but the Edge tuner I borrowed to read the code's read zero RPM, to confirm this I borrowed a Snap-on scanner from another friend and it read zero too....I had already put in a new CPS ( the old one was only 6 months old) and I verified the CPS wiring all the way back to the PCM....All good with under 1-ohm in each wire....I had power and grounds to the PCM so having ruled out everything involved I told Brian to order a PCM....I would have felt pretty bad if it hadn't worked as the PCM was $600 from Ford.....Hit the key and it fired right up......And it fixed his GP issue too....It starts on it's own now. I put 8 new Ford GP's and a GPR on it last spring and it still wouldn't start on it's own but he said we could frig with that this fall....Little did he know he would be towing the truck to my house on a trailer....