Really need assistance with LMTV

[reelclassic]

I have a 2003 Stewart Stevenson. I put the 3126 engine back together and it turns over and runs only when spraying starting fluid. It will not start on its own fuel.
The CTS system has been removed. I get a buzzer only when I turn on the ignition switch on the frame under the cab next to alternator. When I turn on ignition switch in the cab next to the steering wheel i get no power. The ECM powers up. I was checking to see if anyone knows of a relay that may be stopping the ECM from telling the truck not to start. Could use some ideas. Really looking forward to driving it for the first time!

Thanks

 

[gavland]

it is a Cat engine so any cat shops mite be helpful, but check to see if your fuel shut off on top of injection area is turning fuel on and off.
if same as 3116 should have a 6" cable running to electric switch on drivers side top of engine.
have to look at my engine again to make sure but a start!!

 

[Suprman]

The trans ecu will prevent the truck from starting if everything is not in order. If you get no power to the dash switch you have fuse, relay or wiring issues. The trans ecu does not prevent dash power. Do you have the truck out of VA that was partially disassembled?

 

[reelclassic]

Thanks for helping out. Do you know what the wire number is. I have a wire with a tag #42 about six feet long not sure where it plugs in. I can turn on my ignition at the switch next to the turbo (turns everything on and buzzes) but when I turn on the ignition near the steering column does nothing. If the switch is on and buzzer going off - I turn on the switch next to steering and turns everything off and buzzer stops.

Any ideas? I appreciate any assistance.

 

[Suprman]

I found on my m1078 there are wires that over time appear to have been abandoned with different mods or upgrades installed. And there are some jumpers in places that are definetly not original. You may be able to use the first variant TMs for stuff like dash power wiring. First place I would start is the power panel. Wiring issues are going to be something that's very had to give definite repair advice on the forum. It's more of a hands on troubleshooting thing. You need to start with manuals.

 

[reelclassic]

Any suggestions of where I can get a manual? Wiring diagrams.

 

[Suprman]

Not really. First variant manuals are available top of the forum and online. I haven't seen any A1 parts or troubleshooting TMs yet. Look at the first gen manual figure out the path to the power switch. Does the light switch have power? It's independent of the power switch. Have you made sure the power panel is properly populated? Is the power panel in good shape? Cracks in the board can break traces and cause power loss.

 

[Javiator8]

Having start issues myself, the truck would crank and start if we jumped the fuel shut off. We began to look at relays, upon finding the start inhibit relay was a 1 relay instead of a 4 relay we swapped with the 4 from the radio position also started testing relays and found one bad. now the starter doesn't even bump over. cbs are good, and wtech 2 says n n. HELP???

 

[snowtrac nome]

first off to the guy with the 3126, your truck is governed and shut off electrically at the injectors, fuel pressure is regulated by the hydraulic electric unit injector pump which uses oil pressure to pressurize the fuel in the injectors. it sounds to me like you have a bad fuse or relay. as for javitar8 I suspect you have a 3116 and if the tcm doesn't power up via the vcm box behind the passenger's side kick panel you wont be able to crank. also not all those relays look the same some have a 12 volt coil and others have a 24 volt coil

 

[CaptainPLaneT]

h

 

[Ronmar]

Hope the guy with the 3126 got it, it was 3 years ago

For Javiator8 N N on the trans controller indicates it is getting power so that is a good sign.

The TM troubleshooting is pretty detailed and relatively easy to follow. In your case you want TM 9-2320-365-20-1. You will find all of them up at the top of the forum listed under present conflict vehicles. The no-crank and crank-no-start troubleshooting starts around page 2-150...

 

[CaptainPLaneT]

Indeed Sergeant Major Ronmar...Thank You for your rapid guidance. Indeed I got a TM on Amazon for $32 with shipping. Starting on Page 2-150 I did soon find the circuit breaker page on 2-177 with a diagram. I will try this first thing in the mornoing! I really appreciate your assistance. I will let you know how it goes.

 

[coachgeo]

Indeed Sergeant Major Ronmar...Thank You for your rapid guidance. Indeed I got a TM on Amazon for $32 with shipping. Starting on Page 2-150 I did soon find the circuit breaker page on 2-177 with a diagram. I will try this first thing in the mornoing! I really appreciate your assistance. I will let you know how it goes.

32 dollars is possibly cheaper than printing up all the free PDF pages of that manual that are available online. (they are located in the first forum of this steel soldiers discussion board)

 

[Ronmar]

I just realized that I have probably been taking for granted that others understood what a link looked like. it might not be obvious to some that the stuff printed in yellow in a post is a link like coach geos above post has a link to the manuals section of the forum. In there under present conflict vehicles is a thread with all the M1078A0 manuals. They are in .PDF and are searchable which is really handy if you are looking for something specific... from now on when I post a link I will announce it.

here is a link to the thread containing the M1078(A0) manuals.
https://www.steelsoldiers.com/showthread.php?118919-M1078-TM-s

 

[Javiator8]

All good now thanks for the help

 

[BHathaway52]

What ended up being the problem if you don't mind me asking? Have a M1083 with 3126 that batteries died on and it sat for a while now it is a crank/no start. Thinking I may have a failed ECU, but exhausting all other options before I go there.

Thanks!

 

[NDT]

What ended up being the problem if you don't mind me asking? Have a M1083 with 3126 that batteries died on and it sat for a while now it is a crank/no start. Thinking I may have a failed ECU, but exhausting all other options before I go there.

Thanks!

We are seeing a rash of folks with early 2000s A1 trucks where the hold up battery in the ecu dies. If the engine runs with either, that is a sign of this. Check your fuel prime, if good it's time to find a mechanic with a Cat ET scan tool.

 

[reelclassic]

My truck would spin over but I could not get it to start. Turns out the Heui pump on the 3126 CAT in my truck was bad. It has to reach a certain PSI in order to start.

 

[Suprman]

Unfortunately with the electronic cat, diagnosis can be tricky without specific equipment. An off the shelf heavy duty vehicle code reader will pull basic codes. Some trucks have a power line filter on the supply to the engine computer. Seen those go bad. May pop a breaker in the panel. If the engine computer has power and you cant communicate with it then its probably bad. Easy to find a replacement computer. Not so easy to get the proper flash for it.

 

[BHathaway52]

Got mine going, thanks to another thread on here. You guys rock! Ended up being a failed EMI Filter not allowing power to the ECM.

(EMI Filter and ECU are on left side bolted to the rear of the block below the fuel filters. EMI Filter is the smaller black box with two, threaded, two pin connectors attached to it. Apparently these had an issue of rusting out internally and are not needed; can be bypassed and done away with.)

Diagnosis I used:

- Placed inductive voltmeter on the injector wiring harness at the front corner of the valve cover and did not have any power going to my injectors. (Picked up this trick from Adept Ape on Youtube in his crank/no start video for CAT engines) The inductive volt meters say they will only read AC current, but I tested after I got the truck going and it will flash if power is being sent to the injectors. Be careful it's 90-120 volts!

- Disconnected the rear ECM connector or P1 on CAT diagrams. (All inputs come through P1 connector and all outputs to engine go through P2) Check for power at pins 70, 52, and 53. 70 is switched power from key switch, 52 and 53 are unswitched power from the battery. This unswitched power comes through the EMI Filter first then to the ECM. Switched power tells the ECM to turn on and unswitched power gives it the energy to power up. I had power at pin 70, but not pins 52 and 53. (Side Note: Pins 65 and 67 are your grounds for the ECM)


- Disconnected the EMI filter and bypassed it with jumper wires to test. Connect A to A and B to B; you will see the letter on the end of the connector. I just stripped both ends of some wire and shoved it into the pins, don't let them touch each other. Now had power at pins 52 and 53 for ECM power-up. Was then able to start the engine right up! Clipped the wires at the EMI Filter connectors and butt connected them together permanently.