M998 Wait Light Quick Flash

[GMVguy]

Just noticed a new problem on the Humvee. When switching from stop to run on a cold morning, the Glow Plug Wait Light just flashes quickly, whereas before it would stay lit for a few seconds, until the plugs were warmed up. I wait several seconds anyway, and the truck starts up fine, but am wondering why the light just flashes instead of accurately indicates the status. Any ideas?

 

[Retiredwarhorses]

Either Glows plugs are toast or EESS/TSU is faulty...I would check GP's first...

 

[GMVguy]

Either Glows plugs are toast or EESS/TSU is faulty...I would check GP's first...

Ok, I will test em. Strange though, as they only have 200 miles on them. Truck has been sitting on a base for 8 years though, so things are bound to happen with that long period of non-use. If glow plugs test fine, I was thinking it could be a wiring short or something like that...

 

[GMVguy]

The only thing that happened out of the ordinary recently is the other day, it was raining heavily and the truck wouldn't start. I attempted starting it several times, sometimes holding the switch in the Start position for 10-15 seconds. White smoke would blow out the exhaust pipe, but the motor wouldn't start. I figured some moisture had gotten in the intake system, so I sprayed a little ether in the air cleaner and she fired right up.

Before that, the wait light operated normally. But ever since then, the wait light issue has occurred: only flashing for a second and then a few seconds later it will quickly flash again. After waiting a normal period of time, the truck starts fine. Would those several long starting attempts have caused the issue?

 

[Bradyrw625]

It's either bad glow plugs or a bad glow plug controller. Do you still have a PCB box or has it been switched out?

 

[GMVguy]

Here's what I have (Nartron box). The problem only occurs when cold, so it seems the glow plugs are not heating up.

 

[85 USMC M998]

I have a yellow lable KDS and had a issue with the light flashing rapidly (14 times) and the glow plugs would not fire w/o disconnecting the TSU. Called KASCAR and they told me the 14 flash code was a glow plug or TSU issue so TheHummerGuy is spot on. I checked the GPs out, they were fine so I ordered a new TSU. It ended up being the TSU. BTW I have the yellow band TSU. For $40 shipped I am back in business.

 

[CATONY]

I'm having some of the same issues. One of my glow plugs is definitely bad and I'm having a **** of a time getting it out. Where is the GPC or TSU located?
How do I know if I still have one?
I have a 92' m988 HMMWV.
Thanks for your help.

 

[DatGuyC]

I replaced all of mine and I don't remember any of them being especially horrible to get out, but they all did have anti-seize around them from the military. The tsu is located on the coolant crossover tube on the passenger side.

 

[CATONY]

Well 7 of the 8 came out fine but one is swolen it's stuck and I even used the jj&a removal tool. At this point it looks like I'll have to break it and fish it out.
Where is the PCB located?
Thanks again for your help.

 

[85 USMC M998]

Drivers side firewall, half the side of a shoe box.

 

[85 USMC M998]

Sorry I need to clarify my last statement it is on the driver side but on a horizontal plane of the firewall

 

[Sand]

Either Glows plugs are toast or EESS/TSU is faulty...I would check GP's first...

Whats it mean if it only does the quick flash once in a while?

 

[Retiredwarhorses]

Whats it mean if it only does the quick flash once in a while?

well, if the engine is hot? It will flash once very quickl, bec you dint need glow plugs on a warm/hot engine, if its stone cold? It’s not lightning off the glowplugs, you on,y need glow plugs on “cold starts”