LMTV M1078 Wont start.

[Issati]

Hi everyone,
Thanks in advance for anyone that could help me
I have 2 HUMVEEs and when opportunity presented itself, I had to get this LMTV.

Its a 1997 M1078 with 608 miles from a random collector.
The engine, transmission and transferase all seem to be new, It was purchased from GovPlante in 2015 with not running title for about $8800 from a Texas base.
He claimed he never worked on starting it, all he did was fix the door and bought it new driveshafts as they were bent.
I got it for the same price from him 2 weeks ago and have not been able to start it.

here is what I have done so far,

It had about 3-4 quarts of oil in the engine , drained the entire oil, (did not change the oil filter yet) and put in 20 quarts of 15/40 diesel motor oil
Drained the diesel fuel tank fully and replaced with 20 gallons of diesel 2 fuel.
Transmission dipstick shows empty, have not added any oil to it yet.
Got 4 new Hawker NSN Heavy Duty Battery
Replaced all 24 Volt Relays on passenger side in the cabin with new relays.

It seems like everything is there but it just doesn't start.
The cluster instruments all light up and the beeping sound is heard but pushing the start button doesn't do anything at all. The relay sound is also not heard when pushing the start button.

Any advise will be greatly apricate it

 

[Ronmar]

Does the trans controller power up shound have a N N on the display? You need the neutral start contacts from the trans control unit to crank the engine.

it is a 12/24v power system and uses 4 different types of relays. 12v coil, 24v coil, 4 pin and 5 pin... these need to be the correct coil voltage and the correct number of pins for their specific locations...

i would add enough oil to the transmission to at least see something on the dipstick before trying to start the truck.

 

[Issati]

The transmission shows Mode O or Mode 0 and not N N,
I made sure all the Relays are correct as far as 12v and 24v relays goes, However, I placed all relays with 5 pins ones as I was under the impression that 5 pins works equally in a 4 pin socket.

I wasn't sure what kind of oil is in the transmission of the truck now and what to top it off with. From my research it looks like the government uses the same oil for transmission and engine.

 

[coachgeo]

...
I wasn't sure what kind of oil is in the transmission of the truck now and what to top it off with. From my research it looks like the government uses the same oil for transmission and engine.

at this point I would put cheap transmission fluid in and a tranny flush chemical. if you get her running then drain repeat a few times then replace with ALLISON approved automatic tranny fluid. There is several threads in here on the proceedure to swap over to auto trans fluid. Makes tranny much happier.

 

[Ronmar]

You have the right idea with the relays...

Ok, it sounds as if you have a transmission fault(Mabe low oil). Switch it on and when you have a display press the up and down arrows at the same time to get into code reading mode. The display should show D1, then a two digit number, then a second two digit number. This sequence will repeat. Press the mode button to move to memory position D2. There are 5 memory position. Write these codes down and note wether the mode light is lit when each code is displayed(indicates a active fault, not just a stored fault in memory).

the fault codes are in the manual, or list them here and I can define them.

open the drain plug on the bottom of the transfer case and see what comes out. My guess is it will be 15W40 motor oil. I personally don’t like to introduce unknowns to a troubleshooting situations. I would not mess with changing/mixing/flushing the trans oil till I get it running and driveable... if it is 15W40, add that to get an indication on the dipstick...

 

[Coffey1]

Tranny is same as engine
And it will do funky things with no oil in it.

 

[tennmogger]

What Ron said! You have committed that fresh motor oil, might as well commit to a new oil filter and not risk contaminating your new oil. I would look in the filter for trouble, just for grins. Expect close to 7 gallons of oil to be needed with a new/empty filter so 20 qt is a little light. Check out K-19 (start enable/disable relay), then K-11 (fuel solenoid) if it cranks. But, as Ron said, if the transmission is not happy, the truck is not happy.

 

[Issati]

You have the right idea with the relays...

Ok, it sounds as if you have a transmission fault(Mabe low oil). Switch it on and when you have a display press the up and down arrows at the same time to get into code reading mode. The display should show D1, then a two digit number, then a second two digit number. This sequence will repeat. Press the mode button to move to memory position D2. There are 5 memory position. Write these codes down and note wether the mode light is lit when each code is displayed(indicates a active fault, not just a stored fault in memory).

the fault codes are in the manual, or list them here and I can define them.

open the drain plug on the bottom of the transfer case and see what comes out. My guess is it will be 15W40 motor oil. I personally don’t like to introduce unknowns to a troubleshooting situations. I would not mess with changing/mixing/flushing the trans oil till I get it running and driveable... if it is 15W40, add that to get an indication on the dipstick...

Thank you so much for helping me
Filled the transmission with 15/40 oil first but I don't have an N-N on the transmission. When I first turn on the master switch I get a " 0 MOD ON 0 " for a second then, it shows only " Mode on 0 " (so left zero disappears)

Here are the stored codes, there was no light turned on next to any of them. I dont know if my transmission has the light at all. (Please see the picture.)

d1: 21-12 <----> THROTTLE POSITION SENSOR, FAILED LOW
d2: 45-26 <----> N SOLENOID CIRCUIT OPEN
d3: 45-23 <----> H SOLENOID CIRCUIT OPEN
d4: 45-22 <----> G SOLENOID CIRCUIT OPEN
d5: 45-21 <----> F SOLENOID CIRCUIT OPEN

I am not sure what these mean or if I even looked them up correctly.
I hotwired the started solonoid and the engine ran correctly, the pressure built up in the system and the car didn't smoke or sound wearied, however the car did not move as I couldn't get it to select the D or R or even N option on the transmission. it would just show, MODE ON 0.

Any help is much appreciate it.

 

[Ronmar]

It says mode on right in the middle of the display, so those appear to be active faults. Looks like you have open circuits somewhere or a failed trans controller... i would start by hand over handing the cable harness from controller to trans. There is a connector right behind the grill on drivers side of the tunnel wher the cable passes thru the floor. the harness runs aft from there.

It needs one particular solenoid to enter neutral, so that may be why it isn’t giving a neutral start contact and the NN display...

You can try and clear the Codes and see if it records the same or new codes... When in code read mode, press and hold the mode button for 10 seconds untill the controller beeps twice...

 

[Issati]

It says mode on right in the middle of the display, so those appear to be active faults. Looks like you have open circuits somewhere or a failed trans controller... i would start by hand over handing the cable harness from controller to trans. There is a connector right behind the grill on drivers side of the tunnel wher the cable passes thru the floor. the harness runs aft from there.

It needs one particular solenoid to enter neutral, so that may be why it isn’t giving a neutral start contact and the NN display...

You can try and clear the Codes and see if it records the same or new codes... When in code read mode, press and hold the mode button for 10 seconds untill the controller beeps twice...

So I got some good news,
As advised, I removed the steering wheel and checked the back of the transmission keypad and it was not plugged-in !!!
Connected it back and cleared all the cods, and I got the N-N. (filled all engine and transmission to their correct dipstick's mark)
The truck is still not starting, I hot wired the starter and I was able to put the car in D and in R so I was able to drive it 10-20 feet forward and back.
The breaks seem to be holding the car and no matter what I did I was not able to release them. The beeping sound doesn't go away and once the tanks reach 90 PSI, inside of the cabin on the passenger side, there is some air being release from a valve that has D on int.


So it seems like I still have 2 problems.
1. the car doesn't start with its start button,
2. the air system has an issue holding the breaks.


Any help will be much appreciate it.

 

[Ronmar]

Cool! You need to study air brakes... the park brakes are mechanical springs. When you release the park brakes you are applying air pressure to the park chambers to compress those springs to release the brakes. You need enough air pressure(60-70 PSI) to compress the springs.

Are there glad hand covers on the rear? The rear ports need to be sealed. The front glad hand covers are vented. The front ports must be vented or a leaking checkvalve in the system could keep the service brakes applied.

do you have an air compressor? You can unscrew the vent fitting off of the front emergency glad hand cover(1/4” NPT), screw in an air fitting and connect an air compressor to that front emergency(red) gladhand. This will charge the air system and make it way easier to chase leaks and check operation without the engine running. Charge the system to 120PSI... air applied at the front emergency gladhand will also release the park brake so chock the wheels...

air under the passenger dash is for CTIS, fan control and middle axle lockup on a 6X6. You can disconnect and cap the line there to take those leaks out of the equation untill you get the system to full pressure and the brakes checked out.

The start circuit mixes in a few different circuits so here is a quick rundown.
when you turn on the main switch the crank lockout relay K24 must energize. You can hold a hand on it while switching on the main switch to feel for the click. This relay de-energizes once the engine builds oil pressure to keep you from cranking a running engine. The start button provides a path to ground thru the energized contacts(87-30) of K24. This ground path goes to the start relay K1 to energize it. K1 gets it’s DC power from CB21 via the neutral start contacts in the vehicle interface module(black plastic box under passenger dash). If this power is present thru the VIM, K1 should energize when you push the start button. You can feel for this while pushing the button. You can also check for power at CB21 and at pin 86 of relay K1 with the power on and NN on the trans display.

K1 switches 24v down to the coil of K8, the aux starter relay on the drivers frame rail. The other side of the coil passes thru a thermal switch on the starter(sometimes) and on to ground. If K1 clicks, K8 down on frame should also click/energize. K8 provides the contact closure that powers the starter solenoid and cranks the engine...

 

[Issati]

Cool! You need to study air brakes... the park brakes are mechanical springs. When you release the park brakes you are applying air pressure to the park chambers to compress those springs to release the brakes. You need enough air pressure(60-70 PSI) to compress the springs.

Are there glad hand covers on the rear? The rear ports need to be sealed. The front glad hand covers are vented. The front ports must be vented or a leaking checkvalve in the system could keep the service brakes applied.

do you have an air compressor? You can unscrew the vent fitting off of the front emergency glad hand cover(1/4” NPT), screw in an air fitting and connect an air compressor to that front emergency(red) gladhand. This will charge the air system and make it way easier to chase leaks and check operation without the engine running. Charge the system to 120PSI... air applied at the front emergency gladhand will also release the park brake so chock the wheels...

air under the passenger dash is for CTIS, fan control and middle axle lockup on a 6X6. You can disconnect and cap the line there to take those leaks out of the equation untill you get the system to full pressure and the brakes checked out.

The start circuit mixes in a few different circuits so here is a quick rundown.
when you turn on the main switch the crank lockout relay K24 must energize. You can hold a hand on it while switching on the main switch to feel for the click. This relay de-energizes once the engine builds oil pressure to keep you from cranking a running engine. The start button provides a path to ground thru the energized contacts(87-30) of K24. This ground path goes to the start relay K1 to energize it. K1 gets it’s DC power from CB21 via the neutral start contacts in the vehicle interface module(black plastic box under passenger dash). If this power is present thru the VIM, K1 should energize when you push the start button. You can feel for this while pushing the button. You can also check for power at CB21 and at pin 86 of relay K1 with the power on and NN on the trans display.

K1 switches 24v down to the coil of K8, the aux starter relay on the drivers frame rail. The other side of the coil passes thru a thermal switch on the starter(sometimes) and on to ground. If K1 clicks, K8 down on frame should also click/energize. K8 provides the contact closure that powers the starter solenoid and cranks the engine...

Lots of good information here, thank you so much
I don't live where I have the truck parked and so unfortunately I can only work on it on the weekends.

I have both front and rear Hand Covers placed on and sealed, is this not correct? Do I need to open and remove the front two?

I do have an air compressor on this and the air pressure reaches around 95 on the front and over 120 on the rear. close to 150 I would say, (the gauge only has it marked to 120)
This is a 4x4 and not a 6x6 but it does come with a CTIS which I dont think is working currently. I unplugged it for now.

I will need to check the rest of the information you gave me on Starting it on the car on Saturday. All I remember is that when I switch on the master switch K24 does click for sure, but that is the only relay that clicks from that point on when I try to start the truck I don't get any other clicking.

 

[Coffey1]

Yes the passenger side glad hand should have a glad hand cover that has a vent built into it.

 

[Ronmar]

I have both front and rear Hand Covers placed on and sealed, is this not correct? Do I need to open and remove the front two?

both front glad-hands need to be vented. If the blue one is sealed and you have a bad 2way check(common issue), it will pressurize all the service brakes just like you stepped on the pedal...

If the red one is sealed a leaking 2way check will prevent you from setting the park brake...

 

[Issati]

I will check the glad-hands tonight, and report back tomorrow,

any ideas why my left and right tire's air breaks look different.
what was suppose to be there?

 

[Coffey1]

You have to remove that chaging bolt.
That bolt holds the break off.

 

[Coffey1]

Brake lol

 

[Ronmar]

like Coffey said the bolt sticking out is a caging bolt, used to mechanically compress the park brake springs to release the park brakes for towing when you don’t have air to compress the springs...

 

[frank8003]

WOW, learning much in here

 

[Coffey1]

I watch u tube and stay at a holiday inn Express lol.