Glow Plug Miracle Healing . . . ?

drew502

drew502

Member
As I reported in the "Glow Plug Replacement" thread, I have an 04 Sprinter/2500/140WB passenger model that was at the Dealership because it had a check engine light (engine control unit indicator lamp) on. The Service Manager indicated (in no uncertain terms) that the #1 glow plug shorted out and triggered the check engine light (i.e. no other codes present). He said that since the glow plug had shorted, I would need to replace the glow plug module as well as the glow plug. I elected to pick up the Sprinter and replace the glow plug myself and replace the GP Control Unit with SurleyOldBill's mod'd unit. Well low and behold, the CEL has been out for the past 2 days. Seems like if the #1 GP had shorted and the fuse blew in the GPCU, that the CEL light would stay on until the GPCU was replaced. Perhaps it was a miracle healing?
 
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220629

Well-known member
drew502 said:
As I reported in the "Glow Plug Replacement" thread, I have an 04 Sprinter/2500/140WB passenger model that was at the Dealership because it had a check engine light (engine control unit indicator lamp) on. The Service Manager indicated (in no uncertain terms) that the #1 glow plug shorted out and triggered the check engine light (i.e. no other codes present). He said that since the glow plug had shorted, I would need to replace the glow plug module as well as the glow plug. I elected to pick up the Sprinter and replace the glow plug myself and replace the GP Control Unit with SurleyOldBill's mod'd unit. Well low and behold, the CEL has been out for the past 2 days. Seems like if the #1 GP had shorted and the fuse blew in the GPCU, that the CEL light would stay on until the GPCU was replaced. Perhaps it was a miracle healing?
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You are the miracle worker. A shorted glow plug will cause the built-in fuse in the Glow Plug Module to blow. The fuses are integral to the unit and not replaceable so the dealer is correct from their repair option that you needed a new module.

SOB's external fuses replace the need for the integral fuses. By installing the modified, externally fused module you have repaired the damage.

I'd appreciate it if next you'd work the miracle of changing water into MB 229.51 specification engine oil. vic

118GlowPlugsWnotes.jpg

119GlowPlugs.jpg
 
glasseye

glasseye

Well-known member
All of which begs the question, "If a glow plug shorts, and in doing so it destroys the glow plug control module, why fuse it?":idunno:

In any case, thanks so SOB for making this mod available. :bow:
 
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shortshort

Dis member
The light for that comes and goes on mine. It's a likely a high resistance indicator and not a short indicator. It's also not the #1 plug as the software has a fault and always reports #1, this from reading the forum. It would probably makes sense to swap the plugs BEFORE you (I) get an actual short and need to replace the module.
 
drew502

drew502

Member
Aqua Puttana said:
You are the miracle worker. A shorted glow plug will cause the built-in fuse in the Glow Plug Module to blow. The fuses are integral to the unit and not replaceable so the dealer is correct from their repair option that you needed a new module.

SOB's external fuses replace the need for the integral fuses. By installing the modified, externally fused module you have repaired the damage.

I'd appreciate it if next you'd work the miracle of changing water into MB 229.51 specification engine oil. vic

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View attachment 45520
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I was unclear in the way I wrote my initial post; here is what I meant to say:

Even though I decided to not have the dealership do the repair (and planned on replacing the glow plug and the GPCM at some point), I did NOT do any repairs. I simply brought it home and drove it for a couple of days. So, it seems to me that the GPCM does not yet have a blown fuse since the CEL light is out. That said, perhaps shortshort has the correct theory. I was attempting to poke at the dealership's conclusion(s).
 
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2

220629

Well-known member
drew502 said:
I was unclear in the way I wrote my initial post; here is what I meant to say:

Even though I decided to not have the dealership do the repair (and planned on replacing the glow plug and the GPCM at some point), I did NOT do any repairs. I simply brought it home and drove it for a couple of days. So, it seems to me that the GPCM does not yet have a blown fuse since the CEL light is out. That said, perhaps shortshort has the correct theory. I was attempting to poke at the dealership's conclusion(s).
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That is a different story, but there's also an explanation for that.

On the OM647 engine (NAFTA 2004 - 2006) the glow plug fault is tied to the MIL or CEL on the premise that no glow plugs equals poor ignition upon starting WHEN IT IS COLD ENOUGH TO NEED THEM. They are monitored by a comparator circuit. If the ambient temperature is high enough then the glow plugs aren't called upon to do their thing. If they aren't called upon to do their job then they aren't noticed as being bad by the ECM. Most likely that is your situation. When you next store your vehicle where ambient temperatures are below 40F or so then I expect that your MIL will return.


glasseye said:
All of which begs the question, "If a glow plug shorts, and in doing so it destroys the glow plug control module, why fuse it?":idunno:

In any case, thanks so SOB for making this mod available. :bow:
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Since you asked...

A short in a glow plug can cause excessive current and result in higher than designed operating temperatures. A glow plug is basically an electric heating element. Heating elements can be damaged by internal resistive heater overtemperature. That damage can result in the metal expanding which can mushroom out or rupture the tip and make removal difficult. I believe that the fuses are there to prevent that from happening. The internal fuse also protects the individual glow plug wiring which would just burn up before blowing the 125 amp main glow plug module fuse mounted on the positive battery post. Just my opinion though. vic
 
surlyoldbill

surlyoldbill

Well-known member
glasseye said:
All of which begs the question, "If a glow plug shorts, and in doing so it destroys the glow plug control module, why fuse it?":idunno:

In any case, thanks so SOB for making this mod available. :bow:
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Only the hard-wired fuse in the module is blown. Everything else is hunky dory.
I've been toying with the idea of stealth fuses INSIDE the module, for those purists that don't want to alter the appearance of OEM equipment. ATC fuses should fit, but the fuse clips will be difficult.
 
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abittenbinder

Doktor A (864-623-9110)
drew502 said:
So, it seems to me that the GPCM does not yet have a blown fuse since the CEL light is out.
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The MIL (also know as CEL) is triggered by several 'cold starts' with open circuit or shorted to ground glow plug(s). Cold being defined as overnight cool down, even in summer heat.

Several hot starts in a row (hot being defined as operating temp) will cause the light to go off.

Once a shorted to ground glow plug destroys the internal fuse link a fault code is stored and remains until replacement and code erase.

BTW, the new generation MBenz replacement glow plug module has no internal sacrificial fuse links. It is now completely solid state.

Doktor A
 
drew502

drew502

Member
abittenbinder said:
The MIL (also know as CEL) is triggered by several 'cold starts' with open circuit or shorted to ground glow plug(s). Cold being defined as overnight cool down, even in summer heat.

Several hot starts in a row (hot being defined as operating temp) will cause the light to go off.

Once a shorted to ground glow plug destroys the internal fuse link a fault code is stored and remains until replacement and code erase.

BTW, the new generation MBenz replacement glow plug module has no internal sacrificial fuse links. It is now completely solid state.

Doktor A
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Thanks Dr. A.; this is interesting!

So, if I understand correctly: the current state of affairs is that I have one (or more) failing glow plugs, but since the CEL does not remain on, we can infer that an internal fuse in the GP Module has not blown. If correct, I'm glad I did not pay the dealership for the part and labor to replace the GP Module.

Will the new solid state GP Module work in a 04 TIN?

I'm still debating the merits of replacing all the Glow Plugs preemptively since the vehicle is only at 28k and hopefully the GP's are not stuck yet. However, some of the accounts of glow plug removal on the forum have given me the fear.
 
ECU

ECU

2006 T1n 118 Sprinter
I'm following this because I have had a couple of glow plug shorts. Replaced module and plugs with zero improvement in the check engine warnings. I forget the P codes for this after dealing with it for over a year.
The issue only comes up on cold days when I don't drive long enough for a decent warm up, before a shut down. The warning light will come on with the second start of the day in this instance only.
 
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abittenbinder

Doktor A (864-623-9110)
drew502 said:
but since the CEL does not remain on, we can infer that an internal fuse in the GP Module has not blown.

Will the new solid state GP Module work in a 04 TIN?
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On 647 Sprinters, the MIL (CEL) will come and go with glow plug issues regardless of shorted to ground failures or open circuit failures. Re-read my explanation above.

The new solid state module is for all 5 cylinder Sprinters.

Doktor A
 
drew502

drew502

Member
abittenbinder said:
On 647 Sprinters, the MIL (CEL) will come and go with glow plug issues regardless of shorted to ground failures or open circuit failures. Re-read my explanation above.

The new solid state module is for all 5 cylinder Sprinters.

Doktor A
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Are you saying that the CEL will come and go even with a blown fuse in the GP Module?
 
2

220629

Well-known member
I don't know the exact reason, but even when I had 2 glow plugs out my MIL would go off for the (edit: entire) summer and then return in Fall when temperatures went down (with no repairs effected) edit: and stay on for the entire winter. :idunno:
 
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drew502

drew502

Member
shortshort said:
That is what he said. The code stays, the light comes and goes. I posted this link a while back.

I understand this point; what I'm still not clear on is whether with this particular scenario, one can say definitively (w/o more specific testing of the GP Module) that there is in fact one or more blown fuses in the the GP Module?

Also, what is the advantage of the solid state GP Module and what are the pros/cons of the solid state GP Module vs SOB's mod'd GPM?
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shortshort

Dis member
drew502 said:
shortshort said:
That is what he said. The code stays, the light comes and goes. I posted this link a while back.

I understand this point; what I'm still not clear on is whether with this particular scenario, one can say definitively (w/o more specific testing of the GP Module) that there is in fact one or more blown fuses in the the GP Module?

Also, what is the advantage of the solid state GP Module and what are the pros/cons of the solid state GP Module vs SOB's mod'd GPM?
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The implication was yes, some of the fuses in the module blew, setting the code and intermittently illuminating the oh crap light on the dash.

I assume he means it is circuit breaker protected vs fused, so next time, after you swap the plugs and clear the code, you are done. From the sound of it, either way the module is coming out this time.
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abittenbinder

Doktor A (864-623-9110)
drew502 said:
what I'm still not clear on is whether one can say definitively (w/o more specific testing of the GP Module) that there is in fact one or more blown fuses in the the GP Module?
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A fault code for glow plug module excess current along with at least one glow plug short/open fault code

Or direct testing for one or more glow plug short to ground, is proof of a blown fuse link in an earlier type glow plug module.

The new solid state module is currently the only one available from MBenz or Chrysler.

Doktor A
 
mendonsy

mendonsy

Member
Andy:

Does the new GP module work with the T1N engines or is it strictly an NCV3 part???

Bill's GP module modification makes testing everything much easier.
You can directly inspect the fuses and you can also check each glow plug individually by pulling the fuse out and checking the wire resistance to ground with a meter.
A new glow plug measures approximately 0.7 ohms. A bad one measures <0.5 ohms.
 
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