LMTV 1078 A1 Not Starting

[dbeasty]

My 2003 LMTV A1 stopped starting.

Some history:
Generally it was starting like a dream, until the panel or electrical work was done on it.. ( this is the episode #2, the episode #1 ,., was diagnosed as loose battery cable, and supposedly the pushing in the fuses reset buttons..)

I was troubleshooting why the wipers, horn and sprayer do not work.
I opened the dash..,and what looked like turn signal connector and was trying to check P18 voltage per troubleshooting steps.

Now the connector plastic 3x4 was initially disconnected, and there was a 24 volts coming to what I concluded P18 aka 4 connector and 12 volts to #2 even though I did not hit any wiper function or the switch to start engine which is somewhat suspicious.

Anyhow I connected the the 3x4 connectors and the CTIS went to blink mode and bunch of more electronics went online and after that the LMTV decided not to start ANY more.

Objective:
I do not not want to turn in into another LMTV starting thread.

I can try to follow you troubleshooting steps from previous posting and the manual for A0.

Rather I would like to figure out what are the differences with the A1 vs A0 in terms of startup and troubleshooting for example how the ECU effects the whole process and how to take it out of equation and so forth.


Specific questions:
1. I would live to get a photo of A1 the fuse/relay panel diagram, since mine is somewhat warped and hard to read.

2. Would like to get an equivalent step for what I recall was K1 relay workaround to make the LMTV start. ( I do not think I do have K1 relay ), providing there is one..

3. I have a battery turn off switch next to batteries, but there is down below a dash a switch which seems to be next to ECU diagnostic CAT port, what is that switch for?

 

[Suprman]

The switch down left by the diag port is a master power switch. Cuts power via the relay in the box mounted right side of the battery box. There is also a manual shutoff on the bottom of that box sometimes. Do you have a crank but no start or no crank? Dash power with the dash switch? 12 and 24 volts to the main posts on the power panel? What type of work was done to it?

 

[dbeasty]

Thanks for helping me and explaning the main power switches.
Please see below answers, hope the formatting will be a OK..

Do you have a crank but no start or no crank?
David: No crank, no voltage drop across the start switch.

Dash power with the dash switch? 12 and 24 volts to the main posts on the power panel?
David: Yes the power lights up with the dash lightning button, measured 24, 24,12,12 on the main posts of the power/relay/CB panel.

What type of work was done to it?
David: I just esentially got it.
It has brand new charged batteries engine oil change in shop. The back up camera was installed to lighter power, that was when the starting stopped first time (no crank same), but was resolved in the shop , by tightening the battery cables, and "resetting" the CBs ( after that it was starting nicely) untill I tried to connect the 3x4 panels for wipers in the dash next to steering wheel ( noted in the original post).
I have not checked if the starter bypass is needed, I suspect for that I would have to be able to raise the cab, which is not working at the moment ( due to what I think is missing hydraulic fluid and the hydraulic pump not right since it blows like a whale, makes some cranking noises, but did not lift the cab, but that is a different issue.)

 

[Suprman]

I would start by checking all of your battery cable connections again. Make sure all is tight and clean. Some of the angles like to come loose. There are power connections that come up under the board that are bolted on. You can check that those are tight. Starter connections should be checked make sure they arent loose.

 

[dbeasty]

1. Did check the battery cable terminals; they did look tight and clean, could not wiggle them, will go tight tem up with wrench just in case.

2. There are power connections that come up under the board that are bolted on. You can check that those are tight.
David: Are you refering to the relay/cb power panel? How do I access the connections below?
Do I unscrew the panel and check it or do I get to the panel below?

3. Starter connections should be checked make sure they arent loose.
David: I did go under the truck, did try to check the best I could, but I think without the cab raised I might have hard time reaching the starter.

 

[Suprman]

There are screws on the metal framework the board is bolted to. The whole thing comes up the board stays bolted to the metal frame. So when you turn in the dash power switch the dash comes on but you just can’t crank? Can you manually raise the cab with the hand pump? You will need to get that working if you want to troubleshoot your truck.

 

[dbeasty]

Thanks for the hint how to take the board off. Indeed there were two loose nuts, on the double connectors, tigten those. Went over the battery terminal and titghten check those, those are pretty much spotless.
Was able to manually raise the truck cab; but there were some periods of no pressure/empty pumping, so will fill the hydraulic fluid once I get some in the pump reservoar.

There are switches on the passenger side, in the engine compartment, which have on the signs OFF IGN, OFF ST, OFF BATT, I can send pic if that will help, what are those for? Are those to turn off engine once its running?

Access to the starter with the cab raised is still not good.., I did manually wiggle the connectors , they seemed to be a OK, but they are in no means spoteless..

Yes my dash power and lights come on, but no crank when I hit the starter switch. It was starting perferctly untill I connected the above mentioned 3x4 connector under the dash.. when I was trying to fix my wipers. Hence I think I must have blown some fuse or relay or.. maybe the ECU needs reset or something like that..

 

[coachgeo]

swap into place some relays from non crucial places with same amp/volts... (or go to napa to get some more) and put them in locations that have to do with starting. See what that gets you.

 

[Suprman]

Post pic of what you reconnected. May have been radio power and the cable and is bare somewhere. I would check all the beakers and relays.

 

[pontiac62]

My humble opinion disconnect the 3x4. Check your circuit breakers. She if she’ll start. You said the no start was when you connected the 3x4.


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M1081 LVAD

 

[dbeasty]

Thanks, I am going to play with the breakers and relays today, have some new ones and will swap some. The 3x4 has been disconnected ( sorry I did not mention that).

I will send a pic of that once I figure out the starting issue. It seems like it was "backfeeding" the panel with 24/12 volts which tha lit up the dash/CTIS lights and did some damage/tripped something etc..; agree that will nee some investigation; but there is no point to have wipers/horn/sprayer working without vehicle strarting.

Can somebody please post the A1 circuit power panel schematic photo from the lid ( mine is partly damaged), or better diagram for A1, since the layout is markedly different from A0, that might assit me in the troubleshooting process.

 

[Keith Knight]

I own a 2003 M1078A1, so I understand your troubles. I had to chase about 10-12 different electrical problems. A few of those prevented it from starting. My point is don’t get stuck thinking it had to do with the 3x4, something else could have suddenly started to cause it. For instance I found a loose connection on the starter Solenoid, another was the engine ECM died. Wish I could be more help. But get the volt meter out and start testing the basics.

 

[dbeasty]

Understood, not getting stuck on the panel/ direct cause / relationship.

I was not able to get the A1 starting by switching relays, CBs randomly.
Interesting thing is that the cover on panels says all relay's are 12 volts , but I have one 5 prong 24V volt one in panel go figure...( but swapping it did not make a difference ..)..
But its not over in panel, since I want to test the CBs and test the relays; would be goot to know which ones are critical ones, but just will test them all, so will get back to that.

I think I need to get more methodical and try to isolate the problem.

How do you access the starter, did you deflate the wheel, or removed components above/around it, I am having hard time accessing the starter/contacts, did you go from below. I would like to cleanup the connections on starter and maybe do some direct starter troubleshooting.

Also how did you figure out your ECM was bad; did you use some diagnostic tool as ECAT?

 

[Keith Knight]

If you want call me 863-781-0165

 

[dbeasty]

Thanks for help.

I did go an replaced all the CBs with the low tech standard ATC set; had to cramp the fuse beds a bit, and the truck started smooth.

I suspect the MAXI fuse size might be even better match, but not certain.

If its OK I will start another thread on getting the wipers/horn going, since I could use a reference as to what should be going on with my disconnected 4x3 connector ( will send pic etc).

 

[Suprman]

The 3126 a1 power boards can develop bad solder joints. The earlier ones used eco friendly lower lead content solder that does not appear to last as long as regular 60/40. Its a multi layer board so you have to be careful if resoldering it.