so i keep getting intermitent glow plug codes with my truck. sometimes it takes a while to start other times it starts within a couple seconds of cranking. it has a shake to it when its in gear stopped and it has a really bad shake between 1250 and 1750 rpms, so bad that i put it in overdrive to get rid of it. if i have anything in the pull out cup holder it will almost bounce out. i got a code for the number 6 injector once but i cleared it and its yet to come back. i pulled it out and inspected it and and cant see any clear evidence saying that its bad. i dont know if the motor in it burned out or what happend. the ficm tests good and the batteries dont show any signs of being bad. i havnt had them load tested at all though. where should my next step of trouble shooting be?

 

Get the batteries load tested first. Check the FICM cold. What were the exact voltages? You tested under all three conditions? I would also go over the wire harness coming from the FICM going to the injectors, make sure all of the clips on the injectors are tight. Did this happen out of the blue? A glow plug wouldn't cause these issues. I mean, maybe if it was 30* out, it would stumble a bit, but after it warmed up it should go away.

You can test the glow plugs and the glow plug control module with ease.

To eliminate this, unplug the GPCM (glow plug contro module) and see if anything changes.

No codes that stay? Just the one for the injector and now gone? Could be that injector is bad. Sometimes they don't even throw codes.

 

on the ficm test i was geting around 62 volts dc. and that was cold. i wasnt able to test it while cranking because i didnt have anyone to turn the key for me. i looked at the number 6 and 8 glow plug harness and they are a little loose. looks like someone tried to take it off with a screwdriver or something. but from the looks of glow plug ot looks like that shouldnt really madder but im somewhat new to diesels so i wouldnt exactly know. if i ohm through my glow plugs with my lowes special voltmeter i get good continuity. this problem did start at random. i was driving uphill at like 20 mph and it started running rough. i did have a previous problem similar to this and it all just blew over. i figured some air just got into the fuel lines or something. previously it lasted maybe 10 mins. the previous code was for the number 6 injector i cleared it and it hasnt come back since. i did notice that the oil was never changed before i got this truck and it was nice and thick and black so i dont know if maybe some sludge got stuck in the injector causing it to act all goofy like this. how can i test my gpcm?

 

The oil will be black like that after 1 minute of run time on these, always does.

62 volts aint right at all.... wtf? It should be around 48V at all conditions. Most of the components on the boards are only rated for 50V...

You can test the glow plugs and the glow plug control module. Shoot me your email address in a PM, I've got the PDF document with all of the specs for those parts to test.