HMMWV Start Box Glow Plug ByPass Fix

[Dcmock]

That sounds simple my question is, the 24v power coming into the box, is this going to the circuit board and do I cut it so it doesn't go to the circuit board anymore or just splice into it

So ive got everything done in the box but I have not found a constant 24v for yhe power in, I tried using multimeter with the box removed and there isn't 24v coming into the plug

 

[Jrn576]

Greetings Brothers and Sisters
I have owned many Humvees and noticed a re occurring problem, either the glow plugs fail to come on at all, OR worst case scenario, they stay on all of the time and burn up.
I have went thru this repeatedly and came up with a fix that I am happy with.
I took my latest variant smart start box ( which happened to be bad ) and opened it up, and then, using a multi meter on continuity, I isolated the glow plug output, which is a #8 green wire - this wire comes from the computer board, thru the cannon plug at the upper fire wall, on the other side of the cannon plug, male side, this wire separates into 8 circuits ; going to each glow plug.
Cut the green wire at the circuit board and place a yellow heavy gauge eyelet 3/8ths on the green wire.
Using another dead start box, remove the 24 volt solenoid that controls the engine on and off, it is the only one in there.
This donor solenoid can be bolted to the corner cover of the box I was putting back in the truck.
Place the green wire on the 3/8th lug, of the donor solenoid
Run another yellow eyelet wire to the main power input at the computer board - now you have an input 24 volt and an output to the glow plug set.
Using a low voltage marine grade horn button, mount this next to the test port or the inboard side facing you as mounted in the truck
1 side of the horn button will go to the main 24 volt input line, the output from this button will go to the trigger side of the donor solenoid
Test fit your pieces so that everything fits in the box when it is bolted back together before mounting the solenoid and horn button.
I added a 24 volt LED light in the humvee style next to the horn button, the positive lead goes to the glow plug lug on the solenoid output, the negative goes under the mounting bolt of the solenoid. - Remember LEDs are polarity sensitive
Now when you want to activate your glow plugs ;
1) Turn on your ignition switch
2) Depress glow plug button for (4) seconds ; counting 1 thousand 1, 1 thousand 2 etc.
3) Rotate ignition switch to engage starter
*Note the Picture : #1 is the solenoid mounting bolts
#2 is the warning light that the glow plugs are activated
#3 is the power button - I used a sealed marine grade horn button. Voltage / Amps does not matter, as it is only engaged for (4) seconds.

If anyone is interested in this any further, please PM me, and I can take my box apart and post photos of the exploded view. - I did not do this as I built it, as it was a quick fix to run the truck, however, I mentioned it to some friends and they liked the idea so I thought I would share.

Joe

Hi Joe, so a few months ago I followed your instructions and put my glow plug power control through another solenoid and onto a plunger switch on the dash. This worked absolutely perfect for about 7 months.
I went for a ride the other night, and the next morning I went to start her up and heard a buzz and gurgle when I depressed the plunger. No change in the battery gauge, no draw. I tested the plunger, good. I tested the solenoid, no good. I replaced the solenoid thinking that was it, no dice. I opened up the start box and something burnt up. I have attached pic, do you, or anyone reading this, know what part that is and if it can be replaced? Possibly more damage down the line? Full box replacement likely?
Any advice would be much appreciated.

 

[jhighsmith]

Hi Joe, so a few months ago I followed your instructions and put my glow plug power control through another solenoid and onto a plunger switch on the dash. This worked absolutely perfect for about 7 months.
I went for a ride the other night, and the next morning I went to start her up and heard a buzz and gurgle when I depressed the plunger. No change in the battery gauge, no draw. I tested the plunger, good. I tested the solenoid, no good. I replaced the solenoid thinking that was it, no dice. I opened up the start box and something burnt up. I have attached pic, do you, or anyone reading this, know what part that is and if it can be replaced? Possibly more damage down the line? Full box replacement likely?
Any advice would be much appreciated.

The 60amp original alternator ran main power through this box, the newer bigger alternators run to the battery. The starter box controls the guage readouts. If you lost all other guages than something burned up on the circuit and the box is likely no good. I doubt this is a result of modifying you box with the glow plugs as everything you did is isolated from an active circuit. If you mounted the new solenoid and push button switch where they don't bang into or touch anything, perhaps the wire to the glow plugs became energized and could have grounded out but if you taped it up or cut it short as not to ground out then that's not the cause and possiblyjust failed. I would get another starter box "regardless of the type-older is better for me" and do it again. People throw the boxes away because the glow plug controller fails, the rest powers the guages. You don't need the water neck sensor if you control the glow plugs manually. Or get a functional box, the prices are completely insane on some of this stuff, it's a simple system to bypass and it's been done for decades so I'm confident doing it to my trucks. I've had several boxes "stick on" where the glow plugs always stay energized causing expensive glow plugs to instantly fail and swell up making it a nightmare to get back out, breaking off and having to pull injectors to get the pieces back out only to do it again and then find out that after the second or third set of glow plugs was staying on.
Let me know how it works out

 

[Jrn576]

The 60amp original alternator ran main power through this box, the newer bigger alternators run to the battery. The starter box controls the guage readouts. If you lost all other guages than something burned up on the circuit and the box is likely no good. I doubt this is a result of modifying you box with the glow plugs as everything you did is isolated from an active circuit. If you mounted the new solenoid and push button switch where they don't bang into or touch anything, perhaps the wire to the glow plugs became energized and could have grounded out but if you taped it up or cut it short as not to ground out then that's not the cause and possiblyjust failed. I would get another starter box "regardless of the type-older is better for me" and do it again. People throw the boxes away because the glow plug controller fails, the rest powers the guages. You don't need the water neck sensor if you control the glow plugs manually. Or get a functional box, the prices are completely insane on some of this stuff, it's a simple system to bypass and it's been done for decades so I'm confident doing it to my trucks. I've had several boxes "stick on" where the glow plugs always stay energized causing expensive glow plugs to instantly fail and swell up making it a nightmare to get back out, breaking off and having to pull injectors to get the pieces back out only to do it again and then find out that after the second or third set of glow plugs was staying on.
Let me know how it works out

copy all. So after poking around, I found that one of the transistors leading to/from the internal solenoid had blown. I’m first going to put in a new transistor. The internal solenoid is still good. If my plugs are not burnt, it may have only been a failed transistor. I’m going to see if that does it.
If that doesn’t do it, I’ll be in sync with your thoughts.
thx, I’ll update after I get the component installed.

 

[jhighsmith]

copy all. So after poking around, I found that one of the transistors leading to/from the internal solenoid had blown. I’m first going to put in a new transistor. The internal solenoid is still good. If my plugs are not burnt, it may have only been a failed transistor. I’m going to see if that does it.
If that doesn’t do it, I’ll be in sync with your thoughts.
thx, I’ll update after I get the component installed.

You can do a continuity test on your plugs or test for resistance while the engine is cold. I bought a glow plug extractor which helps tremendously. In alot of cases you can work the plug in and out, it seams to reshape the element. Each time it'll come out alittle further. If one breaks of, tap it into the combustion chamber and pull the injector. You can stick a telescopic magnet in the hole and extract the busted element

 

[Jrn576]

You can do a continuity test on your plugs or test for resistance while the engine is cold. I bought a glow plug extractor which helps tremendously. In alot of cases you can work the plug in and out, it seams to reshape the element. Each time it'll come out alittle further. If one breaks of, tap it into the combustion chamber and pull the injector. You can stick a telescopic magnet in the hole and extract the busted element

yeah, been through this in the beginning. I bought and used that extractor already, life saver! Hopefully the transistor blew without affecting the plugs. Waiting a few days for a new one. Updates to come soon. Thanks.

 

[Jrn576]

yeah, been through this in the beginning. I bought and used that extractor already, life saver! Hopefully the transistor blew without affecting the plugs. Waiting a few days for a new one. Updates to come soon. Thanks.

update:
After replacing the blown transistor, I still was not getting any power to the secondary glow plug solenoid. So I ended up getting with an electrician, buddy, and we found that no power was coming from the transistor bar, which he assumed was caused by a bad diode somewhere on the board. As I’m sure you know, there are many trace ways on that board. So what we ended up doing was just taking power from one position and moving a wire over to the transistor block. See pics to help explain. Once we just moved that one wire we kept everything the same as per your instructions in previous thread and everything seems to be working… Including gauges, lights, etc.
thanks for the help. Now to troubleshoot my A/C.

 

[jhighsmith]

update:
After replacing the blown transistor, I still was not getting any power to the secondary glow plug solenoid. So I ended up getting with an electrician, buddy, and we found that no power was coming from the transistor bar, which he assumed was caused by a bad diode somewhere on the board. As I’m sure you know, there are many trace ways on that board. So what we ended up doing was just taking power from one position and moving a wire over to the transistor block. See pics to help explain. Once we just moved that one wire we kept everything the same as per your instructions in previous thread and everything seems to be working… Including gauges, lights, etc.
thanks for the help. Now to troubleshoot my

update:
After replacing the blown transistor, I still was not getting any power to the secondary glow plug solenoid. So I ended up getting with an electrician, buddy, and we found that no power was coming from the transistor bar, which he assumed was caused by a bad diode somewhere on the board. As I’m sure you know, there are many trace ways on that board. So what we ended up doing was just taking power from one position and moving a wire over to the transistor block. See pics to help explain. Once we just moved that one wire we kept everything the same as per your instructions in previous thread and everything seems to be working… Including gauges, lights, etc.
thanks for the help. Now to troubleshoot my A/C.

update:
After replacing the blown transistor, I still was not getting any power to the secondary glow plug solenoid. So I ended up getting with an electrician, buddy, and we found that no power was coming from the transistor bar, which he assumed was caused by a bad diode somewhere on the board. As I’m sure you know, there are many trace ways on that board. So what we ended up doing was just taking power from one position and moving a wire over to the transistor block. See pics to help explain. Once we just moved that one wire we kept everything the same as per your instructions in previous thread and everything seems to be working… Including gauges, lights, etc.
thanks for the help. Now to troubleshoot my A/C.

That's good news, if you figured the box out the A/C shouldn't be any issue

 

[rubespada]

Tnks for the info.Some person has done a complete bypass of the smart start box ?

 

[jhighsmith]

Chopped all the cannon plugs off?

 

[Milcommoguy]

Tnks for the info.Some person has done a complete bypass of the smart start box ?

I think it was camotek