M998 Was Alive, But Now Is Dead

[hawk-aggie]

I searched the forums, but.... forgive me for rehashing any previous post. Relatively new to the forum. Been lurking awhile, but now have an issue that has me stumped. I've gotten some ideas from some of the threads I've reviewed, but my knowledge has gaps. Below is my story - sorry for the length.
6.2 engine
Replaced fuel pump, fuel injector pump, fuel filter and separator, glow plugs, oil filter and oil, and transmission fluid. Had to pull the heads because of a blown gasket on one side and water intrusion to one of the cylinders on the other. While the heads were off, I seriously clean the grounding points. Lightly flex-honed all the cylinders. Reassembled everything. Installed new batteries. When all that was done, the thing cranked like a champ. Bled all the fuel lines, and it fired up! Progress. Took it for a 2 mile test drive. Ran well and didn't present any issues. Almost done and ready to be parked with the other M998s in the compound, but I'm getting ahead of myself.

The rear main seal sort of resealed itself for the most part, but the power steering pump had a small leak. Tightened up the hose clamps, wiped off the wet area underneath, and attempted to start it. It cranked well, the engine began to catch, but I let off the ignition switch a little soon. It died. Turned the ignition switch off, then back to run. Wait light came on for about a second, then went off AND the fuel gauge bottomed out as well - as it would if it lost power. Switched to start - nothing. Weird thing is I thought I could hear a slight crackling and thought I saw a whiff of smoke from the passenger side. (paranoia?) Turned the ignition switch off and those two alleged issues quit. I have yet to find any crispy wires, and I really don't want to do a "smoke" test. Thought the "burnt" smell came from the starter. Took it off and had it tested - all good in the starter world. Reinstalled starter. While I was up there around the starter, I removed the radio power cable at the lug connections on the outside of the battery box, and the connections appear clean with no corrosion. The wires at the end that radio cable were very dry and cracked, but there didn't appear to be any evidence of burning.

I decided to remove the KDS 2699 and replace it with another unit. (Unbeknownst to me, the truck has a yellow stripe glow plug controller and a green sticker smart box. Apparently, the last unit that had this one installed that combination and it worked for me until....). When I opened up the smart box, I found it got fried (see photo). Also, the component shown in the second photo was rattling around loose inside. Ok, that whole burnt thing would definitely be a problem, but what caused it?

I checked all the glow plugs. All were in the 1.2-1.5 ohm range. I installed a KDS-2695 yellow sticker smart box. Reconnected the batteries. Switched to "run" and nothing - no wait light, no cranking, not squat. I intend to remove the smart box and open it, but I haven't gotten back to it. I'd say there is a short somewhere, but right now I'm at a loss as to where to start. I HATE ELECTRICAL ISSUES!

I have not changed the glow plug controller, and I don't have that famous grounding harness installed.

Grill me or advise me - your choice. Any help or tips will be welcomed.

 

[Action]

Are the battery cable clamps tight?
The green label KDS box does not need a GPC or TSU connected. It uses some kind of timer. If it thinks it was just running and you shut off and try to restart, the plugs may not get power. The timer thinks the engine is still warm. IIRC

 

[hawk-aggie]

Are the battery cable clamps tight?
The green label KDS box does not need a GPC or TSU connected. It uses some kind of timer. If it thinks it was just running and you shut off and try to restart, the plugs may not get power. The timer thinks the engine is still warm. IIRC

Battery clamps are tight. Green label box is the one that got toasted. It probably thought, "hey, I just got fried." Does the yellow label KDS need the GPC or TSU?

 

[Action]

Yes, the yellow label box uses the yellow band sender.

 

[Mogman]

The SCR that got fried is part of the glow plug circuit, seems to be a rather common way to die, the diode got un-soldered by the fire.

 

[Mogman]

If you have no power at all after replacing the EESS then the relay in that yellow box could be bad, another common occurrence, at least that one is fairly easy to fix.
You should here it "clunk" when the key is turned to run, but even that does not mean it is actually transferring power

 

[hawk-aggie]

If you have no power at all after replacing the EESS then the relay in that yellow box could be bad, another common occurrence, at least that one is fairly easy to fix.
You should here it "clunk" when the key is turned to run, but even that does not mean it is actually transferring power

No clunk. What's the relay look like? I remember hearing the clunk on this unit untill the unit died.

 

[hawk-aggie]

Yes, the yellow label box uses the yellow band sender.

That is what is currently installed. How frequently do those go bad?

Also, do you know what GPC matches a Prestolite smart box?

 

[Mogman]

No clunk. What's the relay look like?

On the later boxes they use multiple "automotive" type relays, probably look like this although I have not seen one. only read descriptions of them.

 

[hawk-aggie]

View attachment 855867
On the later boxes they use multiple "automotive" type relays, probably look like this although I have not seen one. only read descriptions of them.
View attachment 855868

Any way to test them? I remember seeing one inside the box that got fried.

 

[Mogman]

Any way to test them? I remember seeing one inside the box that got fried.

If I was going to the trouble of opening up the box and it was used I would replace it even if it was working.

 

[Action]

That is what is currently installed. How frequently do those go bad?

Also, do you know what GPC matches a Prestolite smart box?

That is NOT a smart start box. That term seems to get used for every PCB.

 

[Mogman]

Also there could be other reasons you do not have any run power (check the fan and the wipers to make sure they are not getting power) it is definitely time to get out the schematic and volt meter and start doing some troubleshooting, seek help if you need it.

 

[TOBASH]

Did you replace the unit with the Battery cables still connected

 

[TOBASH]

You have all kinds of problems going on. Please take pictures of the labels on the boxes to show us, and take pictures of the glow plug sensor so we can see if they all match up.

A PCB is an early/old generation box. The EESS Is a new/later generation smart box. They are not the same. Each box has its own type of glow plug sensor and you cannot mix and match in many cases. The only box that does not require the glow plug sensor is the KDS green label box. Very versatile but they tend to burn out.

Please take pictures of the entire guts of the burnt out box.

 

[hawk-aggie]

That is NOT a smart start box. That term seems to get used for every PCB.

Noted - thanks.

 

[hawk-aggie]

Did you replace the unit with the Battery cables still connected

Nope

 

[dhaumann69166]

I forgot to disconnect my battery one time when messing with the PCB and when I reconnected the plug under the dash it made the inside of my PCB look identical to yours inside! Check to make sure you have 24v at the center hole of the top plug for the PCB. Also make sure you DON’T have 24v at any of the other holes on the plug. I have had the plug get corrosion inside and short out. At first it just wouldn’t have power at times then after a while started sending power in all directions.

 

[hawk-aggie]

Ok, here's more. You guys asked for some photos, so here they are.

First two are of the original green sticker unit. TOBASH wanted to see the complete burned out unit.

The next four are of the second unit I installed, and the associated GPC that was also installed at the time that both the green and yellow sticker units were installed. Unfortunately, I realized too late that there is something amiss in the electrical system and fried the yellow sticker box. That one component SEEMS to be the only damage. It's possible I could repair the box, if I knew what the component is exactly and the installation orientation. (I think it might be a diode that has to be installed one way only.)

I have two Nartron units available, with a Natron GPC. Before I install either of them, I'm going to crack them open to ensure they are intact. But first, I have to do some digging to find out what is causing the primary issue. To begin with, I really could use a portrayal or drawing of the engine and body connectors indicating the lettering for the pins.

We suspect that the starter is causing our electrical issue. On another of our HMMWVs, we had a defective starter overload the control module on a deep fording winch. The control module caught fire. That starter was giving us starting issues as is this one.

 

[hawk-aggie]

Haven't made much progress on finding the source of our problem. I'm tracing wires to make sure there aren't any shorts. I've learn some things. Still think the problem was the starter. Have a new starter ready to go back on, but have to deal with a broken mounting bolt first.

With regards to "smart boxes", I have one fried yellow sticker KDS, one fried green sticker KDS, and one fried Nartron. Just on a whim, I opened up the two Nartron units we had on the shelf. The first one looks new inside and out, and, yes, I have the matching GPC for it. I opened the second one (mentioned above), that we just purchased a few months ago from our surplus supplier, and it was fried. I can send it back for a refund, but we only paid $25 for it. Sometimes you hit, sometimes you miss. It costs half what we paid to mail it back. So, right now, I'm down to one uninstalled working unit (the Nartron) that I don't want to install until I'm very reasonably certain that I won't fry it as well.

(EDIT: Going to install the good Nartron on the second truck, rather than the first one. The 2nd truck is just 4 new glow plugs away from being tested after installing a ground harness and fixing the ground from the PCB to the starter. This situation with fried boxes leaves 5 of our HMMWVs without boxes.)

Any more tips would be welcomed. BTW, is there any one out there rebuilding these boxes?

BTW, the Prestolite box I mentioned in an earlier post will be relegated to the "antique" display. I haven't opened it to see if it's intact, but apparently is of such old technology that I'm not going to bother with it. (EDIT: Besides, it's closed with rivets rather than screws.)