I have read 3 to 5 posts on this issue but I hope mine a bit different.

Took my truck to the local auto parts store and they do error code testing for free. THey said that it was throwing codes showing glow plugs 1, 3, 5 & 7 are bad. From what I have read, it is most likely the GPCM? or harness?

The truck starts fine and seems to run fine as well. I bought new glow plugs but don't want to tear off the valve covers if I don't have to.

Any and all help would be greatly appreciated.


Our Family is trying to leave on vacation in 2 days and need to get this taken care of.

 

Helps if you state what kind of truck and engine you have. I would post your question in either the 7.3 or 6.0 section of this forum. It sounds like the harness but I dont know.....

 

I'm sorry I am a NOOB here. My truck is a 2001 FORD Excursion 7.3.

 

It is most likely the GPCM , & may only be a shunt problem ..If it's cool where you are , you would know right away if half the GP's were not working ...

Did he give you the code ?..

 

It is 70's to 90's here at the moment. State of Washington.

 

Don't believe the Excursions had shunts on them...

Without looking I can definitely tell you it's the GPCM or Glow Plug Control Module that has failed. You won't notice it now since it's relatively warm out, but you will notice it when it's freezing out.

The GPCM is the silver box with a green and black connector going to it. It's a simple part you can get off of fleabay: Glow Plug Control Module | eBay

 

I just ordered a GPCM from my local PS for $165.00. I had them run a code test again and it now shows all 8 Glow Plugs throwing errors. I hope it is the GPCM.

 

What was the code .?

 

For California only, the glow plug system monitor will start when the glow plugs are commanded on for over 30 seconds and the battery voltage is between 11.5-14 volts. A glow plug code will be stored in continuous memory if one or more glow plugs are not being powered.

Note: Look very carefully for poor connections, burnt looking or loose fitting pins that will cause high resistance and set a code.

The Glow Plug Monitor Self Test (California only) is a functional test of the glow plug system performed on demand with the engine running and the A/C off. The PCM will activate the glow plug relay and monitor the glow plug circuits. A fault must be present at the time of testing for the test to detect a fault. If one bank is reading less than 39 amps, a fault will be detected and a Diagnostic Trouble Code (DTC) will be output on the scan tool. If a fault code is set, it is a hard fault.

 

Had Parts Store test again and now all 8 Glow Plugs are throwing codes.
I forgot to get the codes from them.

The truck is running fine.

We are about to leave for a 3 hour drive pulling a 11k Toyhauler.
I need this truck not having issues.

 

Whats the plan if the GPCM is not the problem ?

 

My 7.3L had the same issue. A quick GPCM replacement and it was on its way. I did not have hard starts until the temps went down into the low 50's. I'll see if I can find it.

If you look around there is a way to test the glow plugs from the connectors on the GPCM. It seems unlikely that all 8 are bad. now on my 05 it went the other way. 4 of 8 were bad, 3 on the PS and 1 on the DS.

Cheers

 

Found it. I have it in pdf form. I cannot seem to upload it, but I found it here.

http://www.thedieselstop.com/faq/949...les/032136.pdf

Page 4 shows the wire orientation to ring out the glow plugs from the connectors on the GPCM.


Hope this helps.

Cheers

 

Why don't you grab a multi-meter, unplug the two connectors on the GPCM, and ohm out each glow plug to see if you're getting a good reading?



Test each of the glow plug pins on the connector against battery ground and look for a reading of less than 2 ohms. If anything is suspicious, move to the valve covers, unplug the flat connector on the inboard side of each valve cover and test the forward two and rear two pins on each side against battery ground. Still looking for a reading of less than 2 ohms. If you still get one that tests high, it will be time to pull the valve covers and check the glow plug itself, the wiring under the valve cover, and the pass thru connector that is part of the valve cover gasket.

Since your truck will throw a code for any individual glow plug that goes out, it's unlikely that all 4 failed at the same time, but it is possible damaged wiring or pins caused the GPCM to act up or fail.

If you replace the glow plugs, don't use autolite brand. The tips have been known to swell up and get stuck in the head.

1,3,5 & 7 are the passenger side cylinders.

Unless you're going somewhere it's really cold, your truck will start and run just fine with those 4 glow plugs not lighting up. If there are no other problems, and you don't mind the light, this issue can easily wait until you get back from vacation.

 

Its the GPCM Chris , parts store said so ...

One bad GP can cause this , without any testing I hope for the OP's sake it solves the problem ...