Ok so I could use some advise cause I'm ready to blow thing up! I love this truck but FML!

About 4K miles ago I replaced both valve cover gaskets, internal harness, glow plugs, and pig tails after an initial inspection showed the pig tails were beginning to show signs of overheating and potential short. Had 4 glow plugs that were also showing resistance and mushrooming so....All was replaced with OEM ford parts. Connections made, soldered, tested and checked for resistance. There were no issues with engine start up prior to the repair and I just happen to find the issue while inspecting.

So fast forward about 6k miles and I start to notice upon start up I'm seeing a fluctuation in voltage and idle but only during a min or so maybe longer on cold mornings. Wtf? Ok so checking I go. Batteries good alternator good, ground good, GPR good.

Now I'm scratching my head..are my glow plugs intermittently going on and off? I measure voltage at the GPR at start up and sure enough the voltage fluctuates while the GPR is providing voltage to the glow plugs and then stops when the PCM shuts the GPR off.

More investigation reveals, pigtails are melting again.

Ok..breath...

I haven't taken the covers off yet so I'm not sure what the condition of the harness is inside, also don't know if the glow plugs are 100%. At this point the pigtails need to be replaced again and the valve cover gaskets didn't fair to well.

So...what am I missing? I can't keep replacing parts like this..

Any suggestions are welcome.

 

Check voltage at the GPR again. You should have the exact same voltage coming out of the GPR as there is going in (on the big posts). Any voltage drop at all through the relay, and it is bad. Low voltage means higher amperage, and that is what burns things up.

 

Did that and found voltage drop...so question is...did the glow plugs or the GPR cause the issue? I'm ordering parts today to replace everything again including the GPR.

Second guessing OEM parts now..

 

The tests I've read say that up to 0.3V voltage drop is acceptable.

What brand of gaskets, harnesses and pigtails did you buy?

 

I'd suggest first verifying that the GPR and GP are functioning properly. If they are and you need to replace everything again go with OEM SD parts. Its a little bit of work to change over, but its actually a little cheaper and a more resilient design.

 

Wow I always said if over .1 I'm replacing. Maybe I'm too strict.

 

Voltage drop on the GPR was considerable at +\- 3V and fluctuated at idle before the PCM shut it off. All parts are OEM Ford parts when I replaced things last. Although I did not replace the GPR which was a mistake. ($500 Mistake)

I ordered all new OEM gaskets, glow plugs, pigtails, and inner harnesses again, and a White Rogers Relay this time. The OEM relay just seems like a weak link.

 

That may be my new rule, cause this sucks...

 

Cheaper better...you got my attention..what's all different in the SD?

 

The SD setup only has one plug per side instead of two and the wires are suppose to be heavier gauge. (the glow plug wires anyway) If you do this solder the joints together and shrink wrap them.

 

Update , pulled the glow plugs, all of them tested and showed .5 To .6 Ohms resistance.

Pulled the complete harness to test and replace pigtails but now I'm wondering about just replacing the old harness completely.

Anyone test or replace this main harness?

 

Are you speaking about the joint at the pigtail?

 

No, The whole complete setup for the SD's. If your going to replace your complete harnesses, use the SD stuff, its tougher. A lot of guys have done it just make sure you solder all the wires, no butt connections. Its even cheaper.

 

So SD main engine harnes, valve covers gaskets, and internal harness.. Sound about right?

 

Not the engine harness. Just the valve cover gaskets, UVCHs, and the two pigtails with the SD plugs to plug into the gaskets. You will solder those two pigtails to your engine harness.