I had a similar problem did all the same testing...i had no codes, i ended up pullin the idm driver and doing the ohms test from the driver plug. everything was fine, replaced idm (injection Driver Module) driver and it fixed the problem if you want to test from the driver all the way to the injectors, follow this link GB Remanufacturing - Tech Bulletin #103

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btw the idm location.....remove inner fender driver side....sick your arm on in there....youll feel it lol it is closer to the firewall tho...pretty high up on the fender.

I am about to go on the road to make some deliveries and will be off line till next week. Thanks for the suggestions so far. I will do some checking as soon as I can.

the deals told my uncle the same that ecm and module where fine they eventually said they were wrong but he stayed on em it was under warrent and they don't like spending time tracking down stuff like this under warrenty we all know this yet we have no choice but to keep going back we love our truck when they are running proper

heres a question, were the glow plugs carried over from the old motor? or are they new? or ???? i know you said you checked the harness and the light stays on for up to 2 minutes depending on temp but that doesnt mean anything if the gp's are bad, that just means the controllers good and the relay's good and the harness is good

I put an ammeter between the GPR and the harness to test the glow plug current draw. The draw was correct and the relay is activating properly. I tested the glow plugs before installing them in the used engine by putting power to them and watching them heat. I wish it was a simple glow plug problem. I have been on the road and since it is the truck my boss drives I haven't had time to pull the injector module plug and do the pin out test yet but it is my next test.

i think im having the same problem you are with my buddy's truck. glow plugs, relay and wiring harness is new and the controller is good but they still will not heat up. i was told there could be a fuseable link from the controller to the gp relay, ill let you know what i find. :c:

The glow plugs on ours are heating. It is not possible for them to draw the correct amount of current without heating.

im assuming oil level is good?

Yes it is. IO just checked it yeaterday. We are running delo 400 oil. The engine always starts good warm and as long as the block heater is plugged in it starts fine.

Updates??