Another LMTV No start thread M1078

[expeditionnw]

Working on a new to me 1998 m1078.

Have analyzed the TMs this evening till my eyes bled.

A little background on truck. Was a basket case. Air system missing key components, lots of stuff disconnected at the fuse panel. Missing all fuses and relays, missing turbo, fuel filter housing, voltage regulator. And fluids were drained.

Also missing start inhibit switch.


Got it pretty well reassembled now.

Issue is, it wont start when pressing start button. The starter is turning, just engages and disengages rapidly like the batteries are low. Can jump the starter relay pins at fuse panel and starter will turn normally.


Engine starts right up when jumped from the starter solenoid on frame, and clipwire to fuel shutoff.

Engine also starts right up when jumping starter relay in fuse panel (with clipwire on fuel solinoid)

So my cranking issue is between the start relay and my start switch.

I believe my fuel shutoff isnt getting power because my missing start inhibit switch. Checked TM tonight, The wires that go to it are lugs TL159 and TL158. I will connect those together and im sure will resolve that issue.

I Confirmed my fuse panel is in order, all relays present and in the right spots. panel wiring is clean, no corrosion, everything looks new and shiny.

Batteries are charged.

I Tested solenoid, its good. Can jump it both ways to start. even put a ground to it thinking maybe a spotty thermo switch. nope.

I also bypassed the oil pressure safety switch, it is working correctly.

Trans controller is lit up showing neutral. mode light engages when button is pressed. Wont change to D or R though. stuck in neutral.

I believe this is a Wtec3, as it has the RED display controller, and no black Allison box under the kick panel. has a aluminum 3 plug module under there.

What obvious thing am I missing here guys?

 

[Suprman]

Ground to cab panel or ground connection at battery. Run a temp ground from batts to panel binding post.

 

[NDT]

What codes is it showing? Thought you said you were parting this one out?

 

[expeditionnw]

Ground to cab panel or ground connection at battery. Run a temp ground from batts to panel binding post.

Thanks Will. Is there some sort of buss that the three 12v, 24v, and ground wires connect to the board, or do they screw right to the back of the access terminals on the board?

What codes is it showing? Thought you said you were parting this one out?

Didnt know it would throw codes that could be read without diag tools?
I planned to part it, but its a really nice truck. Im not sure it has ever been used.

 

[Suprman]

They go from the batt box to the polarity box under the spare tire then along the frame and up into the cab and bolt to the backside of the panel lugs. Bad batts can cause the same issue. I have seen someone leave a ground off the starter and that happen also.

 

[NDT]

Press the two buttons simultaneously on the wtec 3 and codes for whatever is causing shift inhibit will show. The diagnostic manual is attached to a post in the middle of mkcoen's M1078 thread. Where did you find the hydraulic motor? I could not find it for less than $1k.

 

[Suprman]

The wtec3 does a "continuity" test on the trans solenoids before engaging. Its less forgiving than the wtec2 control. Had one with a few nicks in the cab to trans harness was making the wtec3 control error. It came up with bad solenoid codes, since it saw abnormally high resistance in the test loop.
Will

 

[expeditionnw]

Press the two buttons simultaneously on the wtec 3 and codes for whatever is causing shift inhibit will show. The diagnostic manual is attached to a post in the middle of mkcoen's M1078 thread. Where did you find the hydraulic motor? I could not find it for less than $1k.

Good info, thanks! The motor didnt need replacing, just the end cap. $150 part, but I will likely just mill one.

 

[expeditionnw]

They go from the batt box to the polarity box under the spare tire then along the frame and up into the cab and bolt to the backside of the panel lugs. Bad batts can cause the same issue. I have seen someone leave a ground off the starter and that happen also.

So the cables just bolt directly to the panel lugs, huh. Everything else is so neat and orderly on the panel, I assumed there was some sort of extension buss i was missing. forcing them onto the lugs didnt seem right as there was already half a dozen wires on each already.

The wtec3 does a "continuity" test on the trans solenoids before engaging. Its less forgiving than the wtec2 control. Had one with a few nicks in the cab to trans harness was making the wtec3 control error. It came up with bad solenoid codes, since it saw abnormally high resistance in the test loop.
Will

I know the trans is drained, I wonder if theres a sensor there.

 

[NDT]

Is drained not WAS drained? You are running the engine with no oil in the transmission????????? Bad idea.

 

[Suprman]

You will def get an error with no fluid in the trans

 

[expeditionnw]

Is drained not WAS drained? You are running the engine with no oil in the transmission????????? Bad idea.

Agreed. It has a few gallons in it to keep it lubed. Per Allisons advice.

 

[expeditionnw]

Press the two buttons simultaneously on the wtec 3 and codes for whatever is causing shift inhibit will show. The diagnostic manual is attached to a post in the middle of mkcoen's M1078 thread. Where did you find the hydraulic motor? I could not find it for less than $1k.

NDT, I found the manual you speak of but it didn't open for me. Any chance you have it saved?

i pressed every combination of two I can think of on my controller, there aren't any codes ive been able to glean.

also, I added a few more gallons to the trans making 5 total. Near as I can tell, this is about what comes out on a fluid change. Was hoping to avoid this step as the trans will be flushed and serviced with transynd.

anyway, still won't start.

Ran a ground to the fuse box lug from the batt. No change.

Ive also noticed the power is killed to the fuel shutoff while cranking.

going to see if I can find the trans diag manual. Beginning to think that's where my no start problem lies.

 

[Suprman]

Hold up and down arrows it will go into diag mode and display numeric error codes. Usually it will do 1 then a code one digit at a time then 2 and the next code. Wtec 3 will prevent engagement with a fluid level that's low enough to not be able to operate or cause damage.

 

[expeditionnw]

I'm not getting any error codes. In fact, nothing is happening when the arrow buttons are pressed. Stays in N.
pulling the controller and see if there's a funky button connection.

 

[Suprman]

In n, press and hold arrow up and arrow down at the same time for 3 seconds. I have seen a lot of bad keypads. Water drips in around the running lights above the windshield. Had one that would put itself in drive without being touched. Lucky for me the parking brake worked well. Would have been truck thru fence.

 

[NDT]

I would fill the Allison full per the dipstick. I do have the Allison manual saved, but I forgot that it is for the WTEC II not the III you have. Both transmissions have an oil level sensor which will tell the trans to fault to DNS or Do Not Shift if the level is incorrect. I don't think the DNS also causes engine crank inhibit, that is never discussed anywhere. The TM fault tree helped me figure out several no start problems like you are experiencing on FMTVs. Once the Army had a single throw relay in a spot that needed a double throw. Check the part numbers carefully of the relays.

 

[expeditionnw]

Is there any published specs to ohm out one? I popped it open, these things really aren't serviceable. Is it's just a go-no go scenario?

 

[Suprman]

You can take the keypad out and take it apart it's small torx screws. Look for visible damage. Low voltage bad grounds will cause all kinds of trans issues so of you are having relay chattering on start and you have a bad ground or other electrical issue at the panel I would fix that first. I keep a spare keypad around, swapping it out is the easiest way to check it. The wtec3 keypads used to be cheap they are going up in price. If you need one don't go on eBay and buy a used one they are all worn out and you will be in the same boat. They keys need to be domed up slightly and have a distinct snap feel when pressed.

 

[expeditionnw]

NDT, yes I used the dipstick to fill it. Pending a gear cycle, it should be full.

Controller looked great inside. If there are no codes stored, will the controller still spit some kind of diagnostic queue?

as it happens, I do have another wtec3 truck with a known working controller. Guess I'll switch to parts swap mode. Hate that kind of "mechanicing"