The same glow plug constantly roasting mystery..

[TOBASH]

RWH is one of the most reliable sources of information here. He has seen and repaired almost everything.

The OP has chosen to ignore his advice.

My suggestion is reconsider and follow Retired War Horses information to the letter.

I speak from experience. My M1165 now runs beautifully. RWH played a major part in that.

Change your PCB/EESS or rebuild as per my posted instructions. Use only quality glow plugs. Don’t argue with a man who holds contracts and rebuilds HMMWV for a living.

IMHO

 

[Humpty]

Considering how the IP operates it is highly unlikely it would deliver more fuel to just one injection line, this would also likely be detectable by a "miss" or knock.
It is also unlikely the harness is delivering more current to one glow plug
with multiple injectors and glow plugs, and inspection of the pre combustion chambers all that could be left would be a compression test.
I would think if that was way off you would have smoke from unburned fuel and an engine miss.
It is also unlikely you have an intermittent stuck valve, basically the only clearance from the piston and the valves is the thickness of the head gasket, it would have to "stick" just a few thousands off of the seat, but I suppose that is slightly possible.
I have to say you have a very strange issue.
If the compression test does not show anything and if it runs well, if it were me I would just stick a new glow plug in and not connect it and enjoy driving the truck, it will start fine on 7 and if it blows up then source a 6.5L GEP the cost compared to the benefits would not be much higher than going into the old 6.2L for repairs.
I am curious about one thing, how did you know it burned up the one glow plug??

Thank you. This is the kind of straight forward, knowledgeable advice and info I was looking for.

Shortly after I bought the truck I was driving it to Harbor Freight.. stopped at a red light.. people honking and waving.. I'm the coolest kid in town. Light turns green I hit the accelerator and POP! Like a .22 round followed by a PSSST PSSST PSSST PSSST PSSST as fuel and air was shot out the glow plug hole. The threaded part was still in there, it just shot out the inside. Never found that inside part beyond the tip that was still plugged into the connector. Used a bore scope to look around inside via the injector hole for traces of glow plug and found none. I then replaced ALL the glow plugs with the dreaded Land of the Red Dragon because .. well.. they're glow plugs and I have buddies who've run cheapo glow plugs in their civvy 6.2's for decades with no more or less issues than any other variety.

I metered the lead to the glow plugs to make sure the start box wasn't constantly laying on the 24v. It provides just under 24v during the wait light cycle, then after startup shortly after the generator comes up to full power it'll cycle in about half second bursts and then stops within about 20 seconds or so.. so I was pretty confident it wasn't my start box cooking anything.

Few weeks later, same situation. I'm at a red light.. hit the accelerator when the light turns green.. POP! PSST PSST PSST PSSST PSST PSST Same cylinder.

I buy another set of the evil Chinese glow plugs and instead of replacing them all, just replace the one and keep the other 7 as spares. The truck has smoked a bit since I got it.. particularly on acceleration and it was suggested I replace the injectors.. so I grabbed a cheap set of injectors off eBay and installed them. Truck seemed to smoke less but still smoked. I started wondering if the issue was that I'd just replaced old injectors with crap injectors and after a month or so broke down and bought a brand new set of Delphi injectors. It was as I was installing those injectors I could see that the glow plug on that cylinder was roached.. and by roached I mean burnt looking and about half missing.

Glow plug count 3.

I installed another glow plug and went looking for more answers. The suggestion that makes the most sense (to me, anyway) is that the glow plug is getting wet and that fuel is burning directly off the glow plug roasting it. I drove just a few blocks away for lunch, came home and popped the glow plug out to look and it was roached.

Glow plug count 4.

I put another glow plug in and didn't connect it.. just left the connector hanging. Getting no power whatsoever. I drove the truck around the block and parked it until today when the diesel compression gauge set arrived (Ahhnother most Honorable Chinese purchase) and thought I'd quick pull out the glow plug, disconnect the leads to the injector pump so so fuel went to the cylinders and do a quick compression test.. the glow plug that has never been powered and only driven around the block was swollen to the extent I had to do the "vice grip pull and twist" method to remove it. It was wet with diesel.. so there's definitely more fuel in that cylinder than should be.. I feel like that's because there's just enough compression to make a little bang but not enough to fully combust all the fuel in there. I'll pull the injector this afternoon and check cylinder compression. The only other thing I can think of would be if somehow the IP were pushing too much pressure on that one line. I don't know enough about how the pump works to know if that's even a possibility.

 

[Humpty]

RWH is one of the most reliable sources of information here. He has seen and repaired almost everything.

The OP has chosen to ignore his advice.

My suggestion is reconsider and follow Retired War Horses information to the letter.

I speak from experience. My M1165 now runs beautifully. RWH played a major part in that.

Change your PCB/EESS or rebuild as per my posted instructions. Use only quality glow plugs. Don’t argue with a man who holds contracts and rebuilds HMMWV for a living.

IMHO

Only I just pulled out a swollen glow plug THAT WAS NEVER EVEN PLUGGED INTO THE START BOX.

It's not an argument. I don't care if a guy has been doing this 1000 years. Maybe in 497 cases out of 500 the start box IS to blame. Hey, HIS money, he can use it to replace stuff that doesn't need to be replaced if he wants to. I on the other hand prefer to rely on actual data to make informed decisions when the price for the parts get steep. If it was a $50 part, sure whatever, swap it out.. what could it hurt? But when I've METERED the voltage from the startbox and confirmed it is fine. When I've METERED the evil Chinese glow plugs and 7 of them are fine but I've fried 4 in one cylinder? THAT'S NOT BAD GLOW PLUGS. THAT'S NOT A BAD START BOX. That's something going on with that cylinder.

 

[Mogman]

That is really odd, interested in the comp. test.
Do not discount the advice given by others regarding the aftermarket (chicom) glow plugs, they have reputation of giving nothing but trouble in the HMMWV world and have for a long time.
Although this may not be your present problem.

 

[REF]

The only thing I can think of that would blow the guts out of your glow plug is fuel detonating early in the cylinder, picture the fuel igniting way before TDC and the other 7 cylinders forcing that one cylinder on up over center with the injector adding more fuel when it should to make the PSI in the cylinder even greater. Engine ping in a gas engine is bad and will damage an engine over time but in a 25:1 compression diesel it is worse.

With a good injector I think you solved the first problem, but if you still have raw unburned fuel in that pre cup you may not be burning the injected fuel due to (my Guess) low compresion in that cylinder, could be valves or top ring again my guess. But still have a problem.

Rotary pumps use one piston / plunger for all 8 cylinders and a rotor to distribute to the cylinder that is to be fired much like a distributor and rotor. So not sure how it would put more fuel to one cylinder and not the others. But at my age I won't say it is impossible.

 

[Humpty]

That is really odd, interested in the comp. test.
Do not discount the advice given by others regarding the aftermarket (chicom) glow plugs, they have reputation of giving nothing but trouble in the HMMWV world and have for a long time.
Although this may not be your present problem.

I plan on buying a set of the hallowed “quality” glowplugs if for no other reason than to bench test them against some ching chong plugs to see if the hype is legit. Not sure where the U.S. Government sources their glowplugs but my truck roasted that one with less than 35k on the clock, and at least two of them were down below 1.5 so I’m not overly impressed. None were swollen tho. Maybe that’s the difference? The chinese ones swell and die and the “quality” ones just die?

 

[TOBASH]

Gotta wonder if that cylinder number on the injection pump is somehow farked. Also gotta wonder if the injector line is too long or too short or kinked.

 

[Humpty]

Gotta wonder if that cylinder number on the injection pump is somehow farked. Also gotta wonder if the injector line is too long or too short or kinked.

Yeah.. if things happen to be good in regards to the compression i’ll for sure be looking in the line and IP direction. In my cursory inspection of the lines i had’t seen any obvious kinks.. it appears to have the same patina of the other lines so nothing about it would suggest it wasn’t original to the truck. I’m wondering if maybe a hunk of that original glow plug might have gotten stuck in the exhaust valve? I only really have a rudimentary grasp of how things move around inside the engine but I have a strong feeling that if the compression is low much will be revealed when I get the intake off.

 

[Humpty]

My “universal” diesel compression gauge wasn’t so universal, but fortunately i was able to disassemble one of my old injectors and found an adapter in the kit that would thread into that so that worked out.

Who knows how accurate this gauge is, so i checked multiple cylinders. Method was to disconnect the wires from the injection pump to keep fuel from pumping into the cylinders, disconnecting the glow plug leads and cranking the engine over roughly 7 to 10 revolutions. One “revolution” by my mesurement equals one “rar rar”. On all tested cylinders the gauge stopped rising at that point. I repeated the test 3 times per cylinder and all 3 measurements were consistent.

The bad glow plug cylinder measured a hair under 300psi

The cylinder rigjt beside the bad glow plug cylinder measured 280psi

The cylinder on passenger firewall side 330psi

 

[87cr250r]

On the subject of glow plugs swelling, for the civy trucks most know not to run the Autolite plugs. They always swell. There are certainly design characteristics that do cause swelling.

And don't go calling glow plugs low tech insignificant items. The materials required to make a reliable glow plug were born from the space race. Good plugs have Inconel jackets.

 

[Humpty]

On the subject of glow plugs swelling, for the civy trucks most know not to run the Autolite plugs. They always swell. There are certainly design characteristics that do cause swelling.

And don't go calling glow plugs low tech insignificant items. The materials required to make a reliable glow plug were born from the space race. Good plugs have Inconel jackets.

My point is i’m replying to this post on a device made in China. You’re reading it on a device made in China. We don’t produce resistors or capacitors in the United States so most of the components in the start box are made in China. The vast majority of things we use every day are made in China or assembled elsewhere with Chinese parts. They build lots of highly complex things that work flawlessly for years but apparently glow plugs they just can’t crack the code! Your mileage may vary but for the last 20 years internet sourced Chinese parts haven’t let me down yet.

 

[Mogman]

With the pressures you list you have a 17% variance, as a general rule 10% or so is ideal, I am sure there is a spec out there but I do not have it for the 6.2L.
IMHO that is not an obvious red flag.
I think generally the pressures should be a little higher but for the most part one is looking for the variance, given the accuracy of the gauge and the setup

 

[Mogman]

I do understand and somewhat agree with your assessment of Chicom products, many of the parts used in US "manufactured" goods are made in China, Look at HD, just about everything on a Harley has been made in China or some other third world country since the mid 80s
But they do have a hand in quality control, I have found products made by the exact same manufacturer as OEM that are inferior, they use the same tooling as OEM but cheaper materials to save/make money.
At this point with no smoking gun I would invest in some OEM plugs from folks like Kascar, HPG etc and see what happens, and possibly souce a new injector line for that cylinder just because it is a possible variance.
As explained by another the IP uses, (actually 2 pistons, why it is called a DB-2) fed by governor control and is simply sent to each cylinder via a "distributor" so the likelihood it is delivering a different amount consistently to one cylinder seems very remote.
It seems that if one cylinder would be operating so much differently than the others to be able to "fry" a new glow plug that has never been activated without some obvious indication or measurable difference is awesomely intriguing.

 

[87cr250r]

Quality requires specification OR pedigree. Pedigree makes specification easy but can't be relied on forever. Apple engineers were very good at specification to get quality out of their Chinese made phones for example. With that said, we're working with aftermarket parts here. They don't have the big money engineering behind them to ensure the product is made correctly.

A side note, most of our passive and semiconductor electrical components are either made in USA or Taiwan.

 

[Gcelevator]

How about the injector to be out of adjustment? Pressure wise

 

[Humpty]

With the pressures you list you have a 17% variance, as a general rule 10% or so is ideal, I am sure there is a spec out there but I do not have it for the 6.2L.
IMHO that is not an obvious red flag.
I think generally the pressures should be a little higher but for the most part one is looking for the variance, given the accuracy of the gauge and the setup

I’m going to try them again tomorrow with all the glow plugs out so the only chamber with compression is the one i’m testing. Also wondering if I shouldn’t have some pipe tape on the adapter that i have threaded i to the old injector base. Someone earlier in this thread said according to the TM there ahould be 380psi.. in a google search on the subject someone said they wouldn’t be concerned if all the cylinders were at 320 or better - and then of course we have the questionable accuracy of my gauge. I’m gonna pull the intake off this weekend and see what i can see down the intake holes. Hoping they’re just gummed up.

 

[Humpty]

How about the injector to be out of adjustment? Pressure wise

I considered that, which is why I replaced the injectors to begin with. Then replaced them a third time with Delphi injectors because I thought my cheapo injectors were perhaps sketchy. I also swapped the Delphi injectors and the issue didn't follow the injector which eliminates the injector from the equation.

 

[Gcelevator]

I considered that, which is why I replaced the injectors to begin with. Then replaced them a third time with Delphi injectors because I thought my cheapo injectors were perhaps sketchy. I also swapped the Delphi injectors and the issue didn't follow the injector which eliminates the injector from the equation.

I thought that probably the pressure where the injector have to cut off was too low allowing too much fuel to pass or the return line or section on that injector to be plugged. Have you inspected the pre combustion cup for cracks or deteriorating?

 

[87cr250r]

Pipe tape is for tapered threads only. You should use the injector washer on the adapter to head. I can't tell what thread you have to mate your gauge to the adapter. It's bottomed out which should never be the case for a tapered thread.

 

[Humpty]

Quality requires specification OR pedigree. Pedigree makes specification easy but can't be relied on forever. Apple engineers were very good at specification to get quality out of their Chinese made phones for example. With that said, we're working with aftermarket parts here. They don't have the big money engineering behind them to ensure the product is made correctly.

A side note, most of our passive and semiconductor electrical components are either made in USA or Taiwan.

One of my many hobbies is building all tube guitar amps based off of early Fender designs. If you know of a U.S. manufacturer still producing resistors, particularly carbon comp, I'd be interested in checking them out. I'm not aware of any made in the U.S. anymore beyond ever dwindling NOS inventories. Allen-Bradley was the last one I was aware of, and they stopped production I think in the 90's.

There is zero question that Chinese products *do* vary in quality. A Chinese made Floyd Rose "Special" guitar bridge is, in design, identical to the Original German made Floyd Rose but the metals used are crap. The Chinese also make a Floyd Rose 1000 with identical metals as the German made counterpart. The only difference between the two guitar bridges is they clean out the threaded holes in the German made unit. So without question there are absolutely different tiers of quality coming out of China.. just as there are vastly different tiers of quality coming out of the United States. Some stuff is great. Some stuff, not so much.. from BOTH countries.

The very first glow plug my M998A1 spit out was a super duper U.S. high quality glow plug. Does that make them bad? Absolutely not. I plan to bench test both a cheapo Amazon glow plug and one of these much lauded glow plugs. I'll hook 'em up to a bench supply to feed them 24vdc and cycle them both and see which one cooks first. See if either swell and after how many cycles. A true controlled environment test rather than colloquial observations and see if they're really worth the dramatic price difference. I bought my last set of 8 for $32.99 plus tax and got free shipping. The Wellman that folks speak highly of are $78.99 off Amazon, so I'd also get free shipping.. over twice as much. I'm curious to see how they truly compare. A cursory google search returns several people talking about how bad Wellman glow plugs suck. One guy said he had to have his whole head redone because they had swollen up so bad. I'm sure many people have had that issue with Chinese plugs. Is that a PLUG issue or something happening to the plugs that is far beyond their operational design? I strongly suspect it's the latter.