HMMWV Glow Plug Gospel

[IroncladGA]

I am troubleshoot my HMMWV glow plug problem. I finished driving it on a multi-hour road march a couple of weekends ago. I left it sitting since. I was trying to start it a couple of days ago, and noticed that the glow plug light would instantaneously go out and the relays would not cycle.\ and no draw on the volt meter. I suspect it is the PCB and/or glow plugs. Because a video is worth a thousand words, I have posted a video of my issue here . The video is low quality and shot in the dark. Initially it looks like there is just a blank screen, but the action is all between the 12 and 13 second mark, when the glow plug light comes on for a fraction of a second.
I found this old post from fobrat http://www.steelsoldiers.com/hmmwv/29724-hmmwv-troubleshooting.html where he says:

"As far as the glow plug system a good way to truble shoot it is that when you turn the start switch to run and you have no wait light the PCB box is bad, when it flashs the controler is bad, when the light comes on like it should and there is no draw on the voltmeter the glow plugs are bad, and when the wait light comes on for a second and gos off it also means the glow plugs are bad. The glow plug system cannot be bypassed cause the relay is inclosed in the PCB box. "

I have italicized the part that seems to apply to me in this case, but my question pertains to the reliability of fobrat's statement. Can it be taken as gospel, or is it just an old steelsoldier's tale? If anyone has had this situation before, have you found that replacement of the plugs without replacing the PCB gets you back on the road? Don't have a problem replacing both, but for the short-term sake of my wallet, I'd prefer to isolate and replace only the broken components.

I went through and grounded the whole system to reduce the likelihood of frying components again, but wish I would have done this to begin with...

Any advice/experience greatly appreciated!

 

[IroncladGA]

Video link here, forgot to post above [media]http://www.youtube.com/watch?v=hc24YmPRV1o&feature=youtu.be[/media]

 

[emmado22]

What PCB does that apply to? There are several versions.

 

[richark998]

Before you start buying parts, check the plug in connections on the box. Just unscrew the collars a couple of turns and slide the plug in and out several times to wear through any oxide or stuff that may be on the pins. If the ground is good like you said, the connectors can still cause trouble. Good idea to coat the pins with a silicone dielectric grease. I had a similar problem with mine a couple of months ago and every few starts I had to open the hood and reseat the connectors. I finally took them apart and cleaned them properly and coated them and have had no trouble since.

 

[nattieleather]

Wow...if I handn't been paying attention I would have missed that blip on the screen...

I would double check all your grounds and the connectors like richark998 said.

 

[Wile E. Coyote]

Also, check your engine ground. One guy brought his 1985 HMMWV around with glow plug problems and I took a test light, clamped one end to one of the nuts retaining the PCB and the other to the engine block then turned the ignition to run. The light lit up - metal-to-metal...the light lit up. No engine ground.

Anyway, long story short - cleaned up all the grounds and life was good.

Apart from the poor connections at the PCB caused by oxidization (as previously mentioned), I've also had the harness itself go bad right at the engine-compartment connector to the PCB. What happened in my case was one of the wires had been strained/stretched or just had too many bounces under its own weight, and the steel wire inside the rubber insulation had broken, despite the fact the rubber insulation betrayed no hint of such. Quick tug-test on the suspect wires revealed the break, but only after many frustrating days dealing with the phantom intermittent.

As also previously mentioned there are several generations of the PCBs and Glow Plug controllers (the module that screws into the water crossover near the front of the engine.) Two generations of those controllers are bad, bad, bad. One appears to be 'skinnier' than its later counterparts because it's a mechanical type and controls the on/off via the action of the glow plugs via a bi-metallic strip similar to the way an old 4-way flasher works. The second is either the first generation of the electronic controller or just a bad lot from one of the contractors - not sure, really. The ones we're using at work now have plastic tops which are medium grey in color -- the 'bad' ones have plastic tops which are either black or white in color.

 

[IroncladGA]

It took me a while (partly because I had to get out of tax season), but here is what I did to get the HMMWV back up and running.

I created a grounding harness from 10 gauge wire, and connected the glow plug controller, electronic control box, engine block, alternator, and instrument panel to the grounding block. I then also cleaned all of the connections on the gpc, control box, temperature sensor and glow plugs and applied dielectric grease. That resolved the glow plug/starter issues where the glow plug relays would go off right away regardless of temperature. I did find that one of the glow plugs is broken and swollen, and I can't figure out how to remove it. I have terminated it, so it is running on 7 cylinders now, but does fine. In that process, I broke the engine harness plug, but I have it rigged up in a workable fashion for now, if anyone has a good lead on a replacement, please let me know.

After I got the glow plugs working again, the fuel system was still problematic, and I wasn't getting any exhaust or diesel smell when trying to start, so I knew fuel wasn't getting through to the injectors. I replaced the fuel filter, tested that fuel was being pushed by the fuel pump through the fuel filter, replaced the hoses from the fuel filter to the injectors, but still wasn't generating exhaust, so I knew it was an injector/injector pump issue. I was afraid that when I refilled the fuel filter with diesel I introduced dirt that had clogged the injector pump, so I was really ticked off at myself. Nevertheless, I tried just about the only inexpensive repair that I could do myself to the injector pump, which was to replace the fuel return line from the cylinders back to the pump. It is a 1' piece of flexible hose 3/4" diameter. If it is leaky, it will prevent fuel from being delivered to the injectors (I also cleaned electrical connections, but don't really think that was the issue). Turns out that after replacing this, the thing cranked right up and has been starting with ease ever since (knock on wood).

 

[jcappeljr]

I am having problems with my m998.put the new engine in,New glow plugs,new glow plug controller,a nos control box.The wait to start light blinks for a second.I havent checked the power to the glow plugs yet.It will start with ether.Will the truck start with a bad control box ?Someone mentioned a grounding harness.Where do I find one ?thanks

 

[Army Kid]

I am having problems with my m998.put the new engine in,New glow plugs,new glow plug controller,a nos control box.The wait to start light blinks for a second.I havent checked the power to the glow plugs yet.It will start with ether.Will the truck start with a bad control box ?Someone mentioned a grounding harness.Where do I find one ?thanks

I posted on here awhile back on my starting issues. Net.. Old '85 PCB went bad, it started to ghost crank... then bought a NOS Nartron Smartstart PCB w/controller. Fought that thing for a few days. Installed a ground harness from Kascar (could make one, but this was easier... 535-A1- Ground Kit, 4 Wire, A, B, C, D, ) , then installed all new glow plugs. glow light on quick, then out, no start. Returned the PCB for refund. Bought a NOS KDS smartstart & controller, installed, Vroom.
NOS controller was junk.
Bought a old used one for $35 online as a backup... works great also.

 

[Retiredwarhorses]

I am having problems with my m998.put the new engine in,New glow plugs,new glow plug controller,a nos control box.The wait to start light blinks for a second.I havent checked the power to the glow plugs yet.It will start with ether.Will the truck start with a bad control box ?Someone mentioned a grounding harness.Where do I find one ?thanks

The ground harness can be made locally, run a 10ga wire from these points.
1. Gen ground
2.EESS mount bolt
3.the pass through inst gauge ground, this is on the engine side and inside the instrument gauge area far to the right, I generally replace this studded bolt while cleaning all the grounds.
4. Starter ground


all these connections come together and are terminated into a large solder less connector ,bolt it to the left rear head, there is a metric bolt hole there. Make sure to clean with some sand paper all the grounds to get the. Clean.
make sure you have a known good EESS, correct Engine temp sensor in water crossover and a nice new set of glow plugs...and make sure batteries are fully charged.
i go to Napa and buy the wire connectors, I think 3 are 1/4in lugs #8 and the starter is 3/8, the engine ground where they all come back too is like 2ga...you can play with wire size....I use #8 a lot too....it done make a diff.

 

[jcappeljr]

What is the eess ?The pcb ?Does anybody know were to buy a new pcb at a decent price.I am not sure if mine is working or if its the right one,It was missing from the truck when I bought it.I had a used one.laying around.That might be my problem.I was told the pcb and the glow plug controller must match.thanks for any help.

 

[Retiredwarhorses]

EESS is the Engine Electrical Start System....new name foe the Old PCB.
ebay has them at times, make sure you buy a KDS or Nartron unit, they normally come with a TSU, temp sensor unit that replaces the old Glow plug controller.....I would look for the new S3 variant, and make darn sure to install a ground harness. Also make sure your batteries are disconnected before you work on any of it or you will fry ur new box.

 

[jcappeljr]

were can you buy a ground harness.

 

[emmado22]

Make one, it is easy.

 

[GWP112]

I had one do the exact same thing the same way.... changed the PCB, wait light worked right and she fired right up.

 

[papakb]

The grounding harness is a very simple item to make up. I used some #8 wire from a stereo shop because of it's availability and flexibility. Some Thomas & Betts crimp lugs and your good to go. I have plenty of this wire if you have trouble finding it locally.

Kurt

 

[4x4Guy]

I've had starting issues as well, Wait light would come one cycle and all but not start. Replaced plugs now the light won't stay on, starts right up but no wait light. Goes on for a second and turns off, relay does click. Also replaced temp sensor, wondering if grounding could be an issue being the light was working fine priorto changing the plugs

 

[TedG]

Please Google: HMMWV grounding harness . Then find the site that has a very nice write up of making your own harness with pictures. Do this before first before proceeding with trouble shooting.

 

[jcappeljr]

I am getting agravated,New glow plugs,new batteries,# new glow plug contollers,new kascar grounding harness,4 used control boxes.2 boxes were bad.The other 2 when you turn the switch the wait light flashes about 4 or 5 times,then goes out.It smokes alot but wont start.It will start with either.According to this post that indicates a bad glow plug controller.I replaced it with 2 new ones.Same thing happens.I dont want to spend $600 for a new pcb and have the same thing happen.You can here the pcb make the click when you turn the switch.Now what..

 

[4x4Guy]

Thats exactly what I have going on, burned through a new set of plugs in 2 days...