LOST JEEPS :: View topic - Glow Plug Failure and GP Controller/Harness

To follow up on recent post..... Glow plug was replaced with one from my stock of used OEM ceramic ones at a specialty diesel shop and code went away. Couple weeks later, CEL was on again. This time they scanned with Starscan and got a code that is either the harness or GP controller, plus one of the newly replaced glow plugs had failed. They also found the harness was installed backwards (Geordi?) and reinstalled it correctly.
Its pretty easy to install the GP harness backwards. The GP leads are not labled. And personally, it doesn't matter. If one GP is bad you should replace them all.

Jeep is running without a CEL, now, for the moment

Question is, can a "failing" GP controller and/or harness cause premature failure of the OEM Bosch ceramic glow plugs?
Not likely. Glow plugs are like the filament of a light bulb. Turn it on and off too many times and eventually the filament burns out.

(Shop claims there is no way to "bench test" the GP controller.) I am wondering if a failure mode could include not consistently regulating the current correctly, allowing it to go too high and intermittently frying plugs.
Correct. The only way to properly test the glow plug system is with a oscilloscope.

Anyone have any thoughts? Anyone have a good used controller/harness they would be willing to part with?

Thanks,

DOC

Author:	DOC4444 [ Fri Feb 24, 2017 7:34 am ]
Post subject:	Glow Plug Failure and GP Controller/Harness
To follow up on recent post..... Glow plug was replaced with one from my stock of used OEM ceramic ones at a specialty diesel shop and code went away. Couple weeks later, CEL was on again. This time they scanned with Starscan and got a code that is either the harness or GP controller, plus one of the newly replaced glow plugs had failed. They also found the harness was installed backwards (Geordi?) and reinstalled it correctly. Jeep is running without a CEL, now, for the moment Question is, can a "failing" GP controller and/or harness cause premature failure of the OEM Bosch ceramic glow plugs? (Shop claims there is no way to "bench test" the GP controller.) I am wondering if a failure mode could include not consistently regulating the current correctly, allowing it to go too high and intermittently frying plugs. Anyone have any thoughts? Anyone have a good used controller/harness they would be willing to part with? Thanks, DOC

Author:	racertracer [ Fri Feb 24, 2017 8:35 am ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
Hello Doc, I experienced the same issue, but mine was on my 2006 CRD and not on my 2005.Besides doing all that you did to locate the issue and couldn't, I finally I replaced the harness and it went away. replacing the harness was a bear, especially when getting the connectors over to the other side the transmission.

Author:	jws84_02 [ Fri Feb 24, 2017 8:45 am ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
You replaced with used parts......?

Author:	DOC4444 [ Fri Feb 24, 2017 9:15 am ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
Hi Raff, thanks for your reply. So, you were having glow plugs repeatedly fail, like in a few weeks? Were they the OEM Bosch ceramic or steel? How did you decide to replace the harness vs. the controller? Or, did you replace the controller, still had the problem, so you replaced the harness? Could you see anything wrong with the harness after you removed it (signs of chafing, etc)? Thanks again, DOC

Author:	flash7210 [ Fri Feb 24, 2017 9:20 am ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
DOC4444 wrote: To follow up on recent post..... Glow plug was replaced with one from my stock of used OEM ceramic ones at a specialty diesel shop and code went away. Couple weeks later, CEL was on again. This time they scanned with Starscan and got a code that is either the harness or GP controller, plus one of the newly replaced glow plugs had failed. They also found the harness was installed backwards (Geordi?) and reinstalled it correctly. Its pretty easy to install the GP harness backwards. The GP leads are not labled. And personally, it doesn't matter. If one GP is bad you should replace them all. Jeep is running without a CEL, now, for the moment Question is, can a "failing" GP controller and/or harness cause premature failure of the OEM Bosch ceramic glow plugs? Not likely. Glow plugs are like the filament of a light bulb. Turn it on and off too many times and eventually the filament burns out. (Shop claims there is no way to "bench test" the GP controller.) I am wondering if a failure mode could include not consistently regulating the current correctly, allowing it to go too high and intermittently frying plugs. Correct. The only way to properly test the glow plug system is with a oscilloscope. Anyone have any thoughts? Anyone have a good used controller/harness they would be willing to part with? Thanks, DOC I doubt that the GP harness is bad. I mean, its just wires. Unless the insulation is worn off or the connectors dont fit tightly then it should be good. Stop messing around with used parts. Especially glow plugs and the glow plug controller. There is no way to be certain that any of those are good enough to last a long time. Everything you need is right here: http://www.idparts.com/glow-plug-system-c-29_94.html And get rid of those ceramic glow plugs. Yes they work better in the cold, but there is also a chance that the ceramic will break and cause engine damage. Get the metal plugs.

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Author:	DOC4444 [ Fri Feb 24, 2017 12:19 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
Much appreciate the replies. When I last talked to Keith (admittedly over a year ago), he was still running the ceramics because all the steel ones work so poorly. His opinion is the ceramics are pretty safe UNTIL they fail electrically. They are then prone to shatter soon thereafter. Reportedly, KJ CRD will not start below 40 degrees F with steel glow plugs unless block heater is used for at least 3 hours. DOC

Author:	flash7210 [ Fri Feb 24, 2017 1:31 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
The problem is that there are no NEW ceramic glow plugs available anywhere. So what do you do when the supply of "good" used ones runs out? Several varied reports of the effectiveness of the metal glow plugs. Some say that the 7v Etecno plugs suck under all conditions. Some say that the 5v Bosch plugs (with proper programming) dont work as well when below freezing. Some say the 5v plugs work great under all conditions. Some say there have been some bad batches of plugs and quality control issues. Some have unknowingly been using 5v plugs with 7v programming and not had any problems. I have been using the 7v Etecno plugs and have not had cold start problems and I dont use the block heater. But I live in Florida so none of that matters to anyone else. Whats wrong with using the block heater? Thats what its there for.

Author:	lars0247 [ Fri Feb 24, 2017 9:18 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
I had two glow plugs fail at the #3 cylinder. I checked voltages during cycling at each of the plugs, and nothing was amiss. The issue was due to a crack behind the intake or exhaust seat, I guess hot glow plugs and coolant don't mix. After replacing the head and gasket in 2015, I've not had any failures since. Hopefully this is not your issue. Suggest pressurizing your cooling system with air overnight at about 12 psig, and removing the four glow plugs, and then cranking the engine. If coolant spits out from one of the glow plug holes, you've got a bad leak. Don't stand in front of the holes as if there is coolant, it is going to come out hard.

Author:	racertracer [ Fri Feb 24, 2017 9:22 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
DOC4444 wrote: Hi Raff, thanks for your reply. So, you were having glow plugs repeatedly fail, like in a few weeks? Were they the OEM Bosch ceramic or steel? How did you decide to replace the harness vs. the controller? Or, did you replace the controller, still had the problem, so you replaced the harness? Could you see anything wrong with the harness after you removed it (signs of chafing, etc)? Thanks again, DOC I replaced the controller and nothing changed. I then began to test the wiring harness by moving it in different places and noticed that the area just above the injectors and behind the plastic "Y" trough at the top of the engine had all sorts of electrical contact issues and I couldn't pinpoint a problem wire...... injector codes popped up, along with the glow plug codes. I found a donor 2006 CRD with a good harness in Massachusetts that i replaced mine with and the codes went away. I'd begin to look around the "Y" and behind the fuel head areas for a broken wire..... also check the grounds.

Author:	DOC4444 [ Mon Feb 27, 2017 8:57 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
Thanks Raff!

Author:	wilco549 [ Tue Feb 28, 2017 2:55 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
DOC4444 wrote: Reportedly, KJ CRD will not start below 40 degrees F with steel glow plugs unless block heater is used for at least 3 hours. DOC I have steel plugs and mine will start at 5f without block heater. It does need a good battery and admittedly does start better with the block heater.

Author:	joelukex4 [ Tue Feb 28, 2017 5:28 pm ]
Post subject:	Re: Glow Plug Failure and GP Controller/Harness
flash7210 wrote: Whats wrong with using the block heater? Thats what its there for. If possible always use the block heater. Its easier on the engine and the glow plugs. Yes I do still have my original ceramic GP's and will replace with new when they fail.

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