M998--new glow plugs burnt out and swollen in 2 hours

HI--bought 1986 m998 from gp--It came with nartron box and yellow controller--all glow plugs were bad and swollen--replaced with new military surplus glow plugs and all were bad and swollen within 2 hours---now the wait light flashes 5 or more times when start switch turned on--when this box goes bad does it keep power on to the glow plugs and cook them--this trucks runs at 120 deg.--could have bad thermostat--will the cold temp make the controller keep the glow plugs on--thanks George

anyone have any ideas--thanks

There is a timer and glow plug controller on that engine. It is fitted in a variety of vehicles and, when it went faulty on my friends motor home it messed all the glow plugs up just like yours has. Get the timer and controller checked out. Also check the voltage to the glow plugs as correct per the T.M. for your truck. They don't (or should not) run at full battery voltage for all the starting period.

I know where the controller is--where is the timer--thanks

On the HMMWV the timing function is controlled by the circuitboard in the EESS box under the dash. I posted some of the Nartron patents that describe some of this in this thread: "PCB circuit diagram of KDS controller".

Absolutely the box can go bad and keep the glowplugs energized all the time. You can find lots of info just by searching: HMMWV glowplugs, EESS etc. Keep in mind that the wait light does not indicate when the glowplugs are energized; it is simply telling you to wait before starting the engine.

Thanks--that is very good info--

cwc said:

Keep in mind that the wait light does not indicate when the glowplugs are energized; it is simply telling you to wait before starting the engine.

Click to expand...

So, you are saying that the glow plugs come on every time we start the Humvee, even if the WAIT light does not come on? I didn't see that in the TM. Or do I not understand what you just said?

No, saying that the wait light being off does not mean the glowplugs are off. The wait light goes off, but the glowplugs could still be energized, either because of the timing functions or a malfunction.

CWC--looks like most of the circuitry is contained in the controller on the engine and not in the box according to the patent--may just have a bad controller and the 100 deg. water in the engine may keep the after glow circut on--what do you think cwc

You sure you put 24volt glow plugs in it?
What's the # on plugs?
Where did you buy them ? EBAY?

I had a GP truck that did the same....bad EESS. Put in new S3 and new glow plugs...all good.

My Nartron box had the glowplugs on all the time, so I tried to figure out the interaction between the GPC and EESS box. The connections are shown in Technical Manual TM-9-2320-280-20-3 on page 1159/1170. I found that my connections were actually as follows:

GPC Pin 1: wire 573A - EESS Pin H - no internal connection
GPC Pin 2: no connection
GPC Pin 3: wire 459B - EESS Pin B - temperature signal to EESS - connected to terminal on board
GPC Pin 4: wire 570A - EESS Pin C - no internal connection
GPC Pin 5: wire 93A - ground
GPC Pin 6: wire 583/54A - EESS Pin A - 24VDC RUN command - also goes to Injector Pump solenoid

So only three GPC connections were actually connected: 24VDC, ground and temperature signal to EESS. You are right that the earlier Patents assign a lot of functionality to the engine-mounted GPC. I think the system I have is best reflected by the last of the patents, 6148258, although there are so many possible alternatives listed it is hard to say how they were actually built. From the discussion on page 21, it appears that the signal characteristic from the GPC would be a voltage. It is easy to see how bad grounds would throw that off, hence the emphasis on the grounding harness in all of the threads on the topic. Anyway, for the Nartron EESS system I don't think there is much logic happening in the GPC on the engine, it is in the EESS box under the dash.