As it started to get cold last fall I found my X getting hard to start. Discovered it had thrown P0672, P0674, P0676 and P0678 codes. All of the glow plugs were replaced at 225K miles, mileage last fall was about 298K. I didn't touch it at the time - I just parked it in my garage and plugged it in. I've driven it all winter just fine.

Finally got around to do an ohm check on the GPs today (at the connector outside the valve cover) and found the following:

cylinder 2 no reading / open
cylinder 4 33 ohms
cylinder 6 27 ohms
cylinder 8 33 ohms

No real surprise here. Next weekend I'm going to pull the valve cover and check the connections inside and probably replace the 4 GPs at the same time.

However, since the truck had less than 75K miles on new glow plugs when 4 on one bank failed, I'm suspicious. The probability of all 4 GPs on one bank going south at the same time seem very low to me.

My question is this - can a faulty GPCM eat glow plugs?

 

I doubt that the GPCM will "eat" the GP's. Since all of one side (of the GPCM) are in trouble I suspect that that side of the GPCM is bad. The two plugs represent one side or the other bank of GP's.

 

Prolonged time that the glow plugs are on will burn them out prematurely. I suppose the GPCM could be defective and keeping them on longer than they should be.

 

The other possibility with them all being bad on one side is a failing UVCH.

 

This looks like a bad UVCH to me... very common. How do the injectors read? UVCH link in my signature.

 

The injectors have not been an issue. No injector-related codes, just those for the GPs. I've put 15,000 miles on the truck since the end of August - as long as it stays plugged in and/or in the warm garage overnight and doesn't sit outside and get too cold during the day, it starts and runs just fine.

Even if it chills down a bit, it will start, run rough for a few minutes until the drivers-side bank comes up to temp, then smooth out OK. A few times this winter I left the heat off in the garage and neglected to plug it in. It would not start in the morning. After 30 minutes plugged in, it fired right up. Fortunately, I have not had to let it sit parked outside and unplugged for more than 4 hours all winter.

So while I'm not ruling out a UVCH issue, it just doesn't seem likely.

 

First and foremost you need to put some basic info in your threads and or your signature. I see you have an Excursion but that is all I know unless I want to dig into your profile, which none of us should have to do if you are asking for help.

I won't speak to your ohm readings for your glow plugs but I can tell you from experience the GPCM has two separate power leads in the plugs that power the glow plugs. If one of these is bad (seen several, mine included) you will have a failure of a complete bank of GP's like you are seeing. Ford sells new plugs to fix this issue but I just tore into my plug and replaced the bad power terminal. If you pull the plugs off the GPCM and you see burnt plastic, brown or black color or signs of arcing, this is or at least it contributes to your issue. You will know which is the power leads because they are significantly larger than the wires that feed the GP's.

Good Luck.

 

Dave,
Are you saying that it is rare for the GPCM itself to go bad and more likely a wiring issue? I replaced mine some time ago and all was well after that, but in the process I found that the plug one side was a little crooked. Might it just have been the infamous loose connection all along?

 

No, I wont say that it is rare because I truly don't know but I have seen the loose connection more than once and the way they are potted I would believe it is a connection issue more than the GPCM itself. I do know in electrical that a bad connection adds additional "stress" to a component because it can not operate in the parameters it was designed to operate in. Considering how expensive the GPCM is I thought I would throw this out there for I also changed one on my truck when in hindsight I believe it was not my problem.

I hope it helps and saves someone some heartache and money.