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HMMWV Glow Plug Gospel

A

Army Kid

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jcappeljr said:
Someones got to have the answer.
Click to expand...
Still sounds like the start box not allowing glow plugs to get power. I have seen several new ones go for $125 to $200 online. But, at this point, probably time to just hot wire the glow plugs I think. Take all 8 of em to 24volts through a switch , hold power on for xx seconds, then crank it over. I have seen a few trucks now that wired in a momentary push button to light em up...gets rid of the pcb/gpc combo, etc.
If you get hot glow plugs & it still wont start, then you have other concerns, but, since you cant get the wait light to stay on for more than a blink, I'm bettin this is the root cause.
 
glassk

glassk

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http://www.hummerknowledgebase.com/index.html the knowledgebase has grounding info under electrical,. hope it is ok to post this,
Troubleshooting the Glow Plug System:
A flakey glow plug controller will cause one of two problems:
  1. The glow plugs don't work at all. This is the most common failure. Usually difficulty starts when ambiant temperature is below about 70F (21 C) though this varies from engine to engine.
  2. The glow pulgs are energized all the time. This generally destroys the glow plugs. This failure mode is uncommon.

Glow plug system failures:
  1. Most common: the bulb is either bad or not making good contact. (I've seen this more than I'd like to have!)
  2. Glow plug controller cycles but doesn't make the glow plugs go on. (Casued by burned glow plug contactor contacts.)
  3. Older Hummers sometimes (due to defective glow plug controllers) have bad glow plugs. AC-9s fail easily. AC-11s are much more resistant to failure, but can fail. AC-62s don't fail.
  4. There are a bunch of fusible links in the glow plug circuit. If a glow plug has failed, you must check the fusible link to ensure it is OK.
  5. The glow plug controller serves as the main power connector for the Hummer's electrical system! It is connected directly to the battery, thorough a fusible link. All other power then taps off from there. Strange problems can occure if the terminal nut is loose.

If ambiant temperature is over about 22 C, or 72 F, your truck should start regardless of whether the glow plugs are working or not. At least all the trucks I know of will start.Peter H.
 
jcappeljr

jcappeljr

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I ordered a new box and temp sensor from the hummer guy,pulled 1 glow plug.It was fried.I am going to order new glow plugs tommorow.What are the best glow plugs to get.I was told Kascars non swelling.They are $20 each.Are they the best ?
 
jcappeljr

jcappeljr

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Installed the new smart start box and temp sensor.Replaced the glow plugs with Kascars non swelling,3 are swelled.Had to order a glow plug removal tool.I hope it works.These old glow plugs were a couple weeks old.I guess the bad box fried them.Waiting for the removal tool.
 
jcappeljr

jcappeljr

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FINALLY.....After 2 sets of glow plugs,4 control boxes,3 glow plug controllers,brand new batteries,new Kascar grounding harness,Rebuilt engine,and 1 glow plug removal tool,she fired right up.I learned alot.I finally installed a new smart start control box,with matching temp sensor,Karscar non swelling glow plugs,And grounding harness.Dont buy the cheap glow plugs,spend the extra money for good ones.The first set of glow plugs were only a week old.3 of them swelled,so I bought the removal tool.It worked great.Thanks for everyones help,especially The Hummer Guy on here.
 
B

bfdvollie

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We are having issues with starting if it's been sitting. It takes a long time to crank and finally kicks and blows white smoke. We thought it was bad GPC so we found one of the old styles, replaced it and then tried again, but still does it. No issue after initial start up, fires right up.
 
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909Hmmwv

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Just chiming in that I had the same problem... I'd like to somewhat apologize for resurrecting a zombie thread but no matter how many ways I google problems I always seem to stumble back upon this one.

So its a 91 6.2l, was running like a charm and decided to clean it out real well one day. Drove it to a car wash, sprayed it all down, fired right up and got home. 30 minutes later I went back out and the controller (nartron) was making weird spaz noises (griding, whirring noises and if i smacked it, the noise would change). I figured I knocked a wire loose cleaning so I started looking, sure enough I found a glow plug wire dangling loose and the tip snapped off (in the harness). Decided to just replace all 8 glow plugs, put in a grounding harness, and she fired right up when I did so.

Stupid me then decided to tidy up the engine bay and I noticed I had the ground to the gpc (natron) upside down, it just wasn't sitting flush and I was irritated I did that so I unscrewed it and decided to clean the contacts on the nartron since I was at it. The only problem was that I forgot to unplug the batteries. Put it all back together and I got the quick flash wait light!

Now I was kicking **** in the garage and just relatively pissed at myself presuming I fried the box so I ordered a new KDS and TSU (matched pair from Erik's).

Slapped em in (after unplugging the battery) and bam, still quick flash wait light. Tried taking out the tsu, same problem. Batteries are good tested them and threw a jump pack on just to be sure. Now I'm super pissed because it may well not have been the Nartron but I guess I have a back up now. I pulled 2 plugs and the second was swollen, so now I'm off to buy an ohm-meter and start ordering some new plugs (again).

Purely speculating that I did fry the nartron and in doing so fried the plugs and now the new KDS is doing the quick flash due to the faulty plugs.

tldr; new plugs, new harness, new KDS, new tsu.... still get the one flash wait light and no voltage drop indicating that glow plugs are cycling.

I was wondering since quite a few people seemed to have been having the same issue, if there turned out to be a resolution? After testing the plugs, my next guess will be an engine harness, as I still haven't replaced that. All the grounding points are solid, ground off all the paint and ensured fresh contacts etc..

edit: hmmm just read about a fuse located behind the instruments that is potentially tied to the KDS...
 
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Wile E. Coyote

Wile E. Coyote

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White smoke means you're getting fuel - it's just not burning because the combustion chamber temps are too low, so your glow plugs probably aren't doing anything - or a good percentage of them aren't doing anything. Because the Army introduced so many different combinations of GPC/ Temp Sensor and PCB/ EESS/ S3 underdash boxes - you can't mix and match what screws in to the water crossover for the most part and hope it will work. It won't. I'd start by disconnecting each glow plug and checking it with a good digital voltmeter on a low-range Resistance setting. Most usually show something like 1.2 - 2.3 ohms or so between the center conductor and body metal, but you're just interested in the ones that read open, because they're toast. Even if you have 5 of 8 that read okay - replace them all with a set of the 'non-swelling' options out there.

Lots has been written elsewhere about the ground problems - so do all those mods (and replace the plugs) before doing much else. Before even trying to start it with new glow plugs - look at the label on your underdash box - figure out what your vehicle has - then make sure what's screwed into the water jacket matches it. There's a lot of older USMC origin HMMWV out there with the original silver-label Prestolite black boxes (PCB = Protective Control Box) which only work with the grey/green-top or older black top controller that screws into the water jacket (apparently you're supposed to change out the black-topped ones, and immediately change out the 'skinny' ones, which are time bombs.) Also, those Prestolite boxes are really getting on in years now, and the relays inside them are only good for so many cycles - most of which have already been used up somewhere between 1985 and now.

If you have a later model Army HMMWV, you'll probably have a Yellow Label black box. Most seem to be the KDS manufactured ones, and the device that screws into your water jacket will need to have a yellow band around it to match the KDS box. If you have some other variation under the dash there's going to be some web-searching in your future because some ignore whatever is screwed into the water jacket (KDS Green and I *think* SSI Yellow) - where some will work with the KDS 'yellow band' sensor.

In my opinion, out of all of them, I have least trouble with the KDS Yellow label box and yellow band water-jacket temp sensor. And I have 100% failure rate on the KDS Green Label.
 
McSpeed

McSpeed

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I just had the short cycle light on a cold engine. Garage is 40 degrees

engine started well though and I was able to use the truck. I left it running the whole time. It is 9 degree Fahrenheit outside.

Ugh. So I’ll be crawling through all this info as well. Should it have started so earsily if the PCB box or relay box failed?
 
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