GPCM or Injector Issues?

duncanb09 · Apr 27, 2016

So my 03 F250 has been having a hard time starting lately... Once it does get fired up it runs real rough until at normal operating temp. Today me and a buddy tested out the GPCM out with a reading of 0.5 ohms, and measured the glow plugs through the harness (not sure if this was the correct procedure) each plug on the passenger side was reading 0.3 while almost every plug on the driver side was reading 0.5-0.6. We went out and bought a new GPCM, installed it, and was still doing the same thing (didn't start. would get going a little but die as soon as you stopped cranking the starter) Now my question is, is there a better way to test the glow plugs like measuring the resistance off of the nut of the glow plug, and would it be likely that it could be a FICM or Injector issue?

When the truck was running a couple days ago, it was real hard starting but when it got to normal operating temp the rough idle and loss of power went away. White smoke on start up with rough idle.

swinky · Apr 27, 2016

If it is running rough till operating temp it's definitely not glow plugs. Check ficm voltage then get back with us.

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duncanb09 · Apr 28, 2016

Will do, wont have time tonite to check it but I should be able to tomorrow

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duncanb09 · Apr 30, 2016

FICM is reading 47.6 when keyed on and 30.1 when its running...

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ithumpwheniwalk · Apr 30, 2016

duncanb09 said:
FICM is reading 47.6 when keyed on and 30.1 when its running...

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From what I've read, if the voltage ever drops below 45v the ficm is bad and is bound to fail. Needs repaired (if possible) or replaced. This is with the engine running, btw.