Manual Override of Glow Plug Controller

[artmac]

I have a '92 M998 with a 6.2. I have put new GPs (1 wk ago), box and TSU (7 mos. ago) in. I am having trouble starting it and do not want to buy another box/TSU.

I know this has been discussed before but I have not found the specific instructions to do this after about 2 hrs of searching (I found great instructions for a CUCV).

Please help me install a manual override of the controller. It is most appreciated.

 

[snock]

You can override them with a 9V battery and a pushbutton switch but you need to know what you're doing. As a temporary measure I drove the gates of the MOSFETs in the box with a 9V battery to power the plugs to get the truck started. You can't use the vehicle power because the MOSFETs are on the high side and thus need the gate drive voltage referenced to their source pins. You could do this with the old boxes with the relay in them rather than the MOSFETs but the only problem there is that all of those that I have seen have been dipped in epoxy. If your glow plugs read a low resistance less than or around 2 ohms if I recall correctly then there isn't any sense in replacing them. Just get another control box. When I finish my house construction project I have going on I think I am going to start repairing these and/or design a new PCB to drop in them because they are a big headache and known good units are fetching big $$$ now.

 

[streetsalvation]

Hey Artmac, I figuring you mean you would like to hard wire the glow plugs to a toggle switch to bypass the need for a smart start box? If so, I am also interested in that possibility in the future. It makes sense to my simple thought process that an individual could wire all the glow plugs to a relay and use a momentary switch to activate for 7 seconds prior to starting. If that is not what you are thinking, more along and push my comment aside.

 

[artmac]

Snock, thanks for the reply but you went way over my head. I like the idea of fixing the box instead of tossing it and I would be first in line if you go that way.

Streetsalvation, you nailed what I was saying with the exception of I believe you must keep the box for the push button to work (the relay is in the box).

As I said above, the CUCV crowd had this nailed by using a blue wire to the push button and a ground on the other side of the push button. You just held the button down (as you suggest 7 secs. - don't know if that is the correct time length) and that cycled the GPs and start the engine.

I just assumed the HMMWV crowd had a similar solution that I could apply. Maybe that is why I couldn't find it in my search.

OK everyone (or someone) impress me with a simple explanation to my problem or want.

 

[artmac]

So am I right in saying that there is no solution to using a pushbutton to time the glow plugs instead of relying on the smart box?

Please confirm.

 

[Retiredwarhorses]

Replace the box, make it right...a lot of other components and operations run through it. If the box really goes Tango uniform, you can loose charging of the battery's and a host of other issues.

 

[Carrera911]

So am I right in saying that there is no solution to using a pushbutton to time the glow plugs instead of relying on the smart box?

Please confirm.

It is pretty easy to add a push button for the glow plugs. Just order a 24 volt starter relay off of Amazon and mount it in a convenient spot, maybe the battery compartment or on the firewall. Also order a momentary on push button switch, meaning it only makes the connection when pushed. Tie the two glow plug banks together and run it to one of the big lugs on your new starter relay and the other side of the relay to the 24volt positive on the battery. To make the relay engage, it needs 24 volts to the two smaller terminals on the relay. Give one of the small connections a constant 24 volts positive and run the negative off the battery to the switch and then off the switch to the other small terminal on the relay. When the button is pushed it will make the relay engage which can handle the 60+ amps that the glow plugs require.

 

[McSpeed]

It is pretty easy to add a push button for the glow plugs. Just order a 24 volt starter relay off of Amazon and mount it in a convenient spot, maybe the battery compartment or on the firewall. Also order a momentary on push button switch, meaning it only makes the connection when pushed. Tie the two glow plug banks together and run it to one of the big lugs on your new starter relay and the other side of the relay to the 24volt positive on the battery. To make the relay engage, it needs 24 volts to the two smaller terminals on the relay. Give one of the small connections a constant 24 volts positive and run the negative off the battery to the switch and then off the switch to the other small terminal on the relay. When the button is pushed it will make the relay engage which can handle the 60+ amps that the glow plugs require.

I really like this idea as an emergency back-up. Mine is dead in the garage right now and I need to at least get power to the GP to start and move it out of the way. Last time I drove it I noticed the light didn't come on - but the engine was up to temp from having driven it just prior to that. I went out to put it in the shop for the night and no- light, but I assumed it was still warmed up from earlier. But, temps had dropped outside into the 20s and it had been sitting for over an hour. It did crank, but was a bit rough. I moved it in and shut it down. Couple of days later go to move it to get to my other junk in the shop and no GP light - no click/thunk - thud. Once before I had a goofy short cycle light. But, after checking the connection on the TSU plug - it worked.

Anyway, mission critical this morning is to go get it to move so I can sort out my shop - I'm going to make up some ground straps, re-check all connections - verify batteries are fully up to charge...and if it doesn't work then I'm going to hot wire it so I can move it. I've got a spare 24 volt battery pack that I'm wondering if I can just wire it to the GPS, then start the engine.

 

[sue]

As I understand it, the glow plugs run off 12 volts
you could run them on 24 but be very quick
about it. People have hard wired them to 24 volts
and then wonder why they fail and are swollen up
upon removal.

 

[McSpeed]

Good news for the time being. My TSU was/is bad. The top just popped off it. I was able to adjust the pins and press it back on and it lit up and started like normal. Still want to get the emergency bypass set up. 12 or 24 volt??? I assumed it was 24.

 

[shawnshumvee]

So does any one know if the Glow Plugs are 12 or 24volts? I search the TM's and Im coming up with the glow plugs are 12 volt but run on a 24 volt system?
Nevertheless, My Rig is down again and i have traced the issue down to the fact that I'm not getting power to the glow plug wires. So searching the form i have gathered a lot of info on how to by pass the Glow plug system (using a push button) and i'm thinking about doing it but need to know if i should pump 24 volts directly into he plugs or use 12 volts? My Humvee doesn't run a glow plug controller. it was eliminated by the upgraded PCB. All glow plugs are good also!

 

[springer1981]

I'll take a guess. I asked about my volt meter pulsing after my engine started when I first got my HMMWV. I was told it was called "After Glow". Reading your questions and what you posted and based on my experience this is how I believe it works. The controller pulses 24v to the 12v glow plugs to avoid overheating and damaging the plugs. If they are cycled at 50% with 24v it would be approximately the same as running them 100% at 12v.

This means simply using a momentary contact push button switch, a solenoid and holding it on would likely overheat them each time. That doesn't mean it won't work but it will likely reduce their longevity. It could also heat beyond what the engine really needs to start, not sure how bad that would be as I am not a diesel mechanic.

 

[springer1981]

Someone suggested in a PM that it may not work as I hypothesize. The suggestion is that the volt meter doesn't pulse during the warm up period before the engine is running. Not knowing exactly how the volt meter (actually charging meter) is wired in, it is possible that it is showing the what the alternator is doing and not the draw on the battery prior to starting.

The controller as I understand it uses MOSFET's and is still likely pulsing the glow plugs at 50% duty cycle. After the engine starts you see this in the volt meter during the "After glow" period.

 

[shawnshumvee]

So it would be Smart just to run 12 volts to the glow plugs? I don't know. All i know is i don't have any power gong to my Glow plug wires. it was running perfect, then the Next day... no start. It has to be the PCB because I i don't have a Controller or anything else that would stop power going to the Glow plugs. Im confident if i could get power to the glow plug wires it will run! i have fuel, Compression exhaust ( which doesn't matter right now) but no fire to explode the fuel so that is why i'm not running. Basis fundamental laws of the I.C.E ( Internal combustion engine.)

 

[springer1981]

My post has some terminology that may not coincide with the manual or your understanding. Specifically when I say "controller" I mean what ever device is controlling the power to the glow plugs. I don't specifically mean a device they call a controller vs the black control box listed in your documentation.

To your 12v question I think it would be better to power them with 12v however there is more to it than that. I don't know what the current draw is but it was suggested in an earlier post that a 60 amp solenoid would work. This is in a 24v system, in a 12v system the current would be twice as much.

I am new to the diesel world but I am not new to mechanical work or electronics. I'm not suggesting you do anything but trying to understand the logic of this. To me, I would try to fix it using the correct parts. If it were my vehicle I would likely be taking apart the controller to figure out how it works and trying to repair it. But that is me.

 

[shawnshumvee]

No I get it. It looks like it is going to need a PCB. I just wanted to do the bypass to make DARN sure it’s the PCB. I’m also new to diesel but its really not much different than gasoline. Both are ICE. Moreover, I know if all for laws (fuel, fire compression and exhaust) are not present the Engine will not run. And it’s apparent that I lost power to the glow plugs and with out power they can not glow and explode the fuel, thus completing the fist and second stroke of the 4 stoke system. As far as I see it the only thing that controls my glow plugs is the PCB.

 

[McSpeed]

I will take a pic and post it when the new TSU comes in...but my TSU looked okay - but when I wiggled it the first time the WAIT light came back on and I heard it all click in. Then it went dead. When I probed it this weekend I noticed something wasn't right - that is when I saw the whole top portion of it loose and it came apart. The pins the wire harness plugs into solder onto a circuit board inside - but mine were all broken free. For the time being, I bent and pinched the six pins tight and pressed it back in...and BINGO - it all lit up and I drove it all over the place yesterday.

Here is a TIP my brother-in-law who is active Army motor pool gave me. He said if you block the exhaust and crank...IT WILL START without glow plugs but it will cough and smoke for a while. But it will get you out and on your way.

Haven't tried it - but he swears it works.

He says you don't want to be the guy covering the exhaust as you end up covered in the exhaust.

 

[shawnshumvee]

I will take a pic and post it when the new TSU comes in...but my TSU looked okay - but when I wiggled it the first time the WAIT light came back on and I heard it all click in. Then it went dead. When I probed it this weekend I noticed something wasn't right - that is when I saw the whole top portion of it loose and it came apart. The pins the wire harness plugs into solder onto a circuit board inside - but mine were all broken free. For the time being, I bent and pinched the six pins tight and pressed it back in...and BINGO - it all lit up and I drove it all over the place yesterday.

Here is a TIP my brother-in-law who is active Army motor pool gave me. He said if you block the exhaust and crank...IT WILL START without glow plugs but it will cough and smoke for a while. But it will get you out and on your way.

Haven't tried it - but he swears it works.

He says you don't want to be the guy covering the exhaust as you end up covered in the exhaust.

Now that’s very Intresting to say the least, but I’m sure that trick isn’t good for the engine? Nevertheless it will come in handy when in a pinch. It reminds me of popping the clutch on a manual transmission when the starter has failed. Some times Tip & Tricks are a God sent.

 

[86humv]

The SSI black 12469158-1 box in photo works with temp sensor 12469158-2....either the black top Nartron, or the yellow band KDS.
Only Black box that needs no sensor is the Green label KDS.

 

[sue]

Who’s army is he in?, 12 (twelve) volts.
Below approximately 100 degrees water
temp ( temperature taken at the center
of cylinder head)the glow plugs will
cycle to improve cold temp idle.