LMTV not starting sometimes

[joshua180422]

First thing I did try searching for this. Sometimes when I try to start my truck it will start right up and sometimes it won't. Obviously the not starting is the time I am concerned with. It usually happens if it is kind of cold and I haven't ran it in a while. I will push the start button try for a split second then it will try again. So it will just keeping trying for a split second at a time. Even the lights on the CTIS will keep going on and off with the attempts. The batteries are fully charged. Not sure if I explained it right, I was a Army grunt!
I am doing a trip from Maine in a week from Pennsylvania, should I be worried about this?

 

[Kambaku]

What year is your truck? I don't think pushing the start button for a "split second" will do much. The operators manual says you can crank up to 30 seconds before letting the starter cool off a bit. It also says that you should fully depress the peddle, let up and then press 1/3 of the way down before hitting the start button.

 

[Suprman]

The older model starters have a thermal safety that does not always function as intended. There was a thread on bypassing the thermal sensor. Or your starter solenoid could be intermittent. And there is a starter relay in the breaker panel. And the vim module has lockout relays like neutral safety.

 

[Kambaku]

Oh, I guess I didn't understand the original question. It sounds like the starter is only engaging for a short time and then kicking out?

 

[joshua180422]

I push and hold the button but it only temporary engages. I think mine is a 1996 or at least that is what the title says. Thermal sensor? That sounds like it would be a sensor to not allow for overheating. Today it was 30 degrees at my house and it was having the issue.

 

[Suprman]

I would replace the starter relay in the breaker panel. They are only a few dollars. I have heard of the push button going bad also. Had a nice new looking starter go bad on me too. It's hard to get to I had to use a piece of pipe and big wrench to get in there and hammer on it till it started. When it's giving you a hard time, you can use a clip lead to jump the starter solenoid and bypass everything else. The solenoid positive is the one closest to the engine it's a pain to get to it. I would check the starter connections make sure all is on tight. Be careful though it's always live and there is no protection in between starter and batteries.

 

[Kambaku]

Will, re: your comment on safety, can you turn off the main battery disconnect and discharge the capacitors and get in there and work on the starter/solenoids safely?

 

[Suprman]

Only later gen A1 trucks have a batt disconnect. I don't believe it disconnects the starter lead though. You would have to disconnect the batteries to be safe. There are no capacitors that I know of in any of the trucks. Maybe small components inside trans or A1 engine control but nothing that will hold a charge. The starter connections are nuts and if they have come slightly loose the natural way to tighten them would be wrench or ratchet and socket. Both of which are metal and it's a tight space so really easy to touch ground and 4 big mil batts provide a boatload of current. You would basically weld the metal tool to ground and then it would all just go downhill from there.

 

[joshua180422]

I am trying to find the starter relay as we speak. Can you recommend any where to find it?

 

[Suprman]

Standard Bosch style relay. The diagram is on the back of the breaker panel cover. I believe that one is a 24 volt relay. Very common on the Internet. You can borrow one from a less used position that also has a 24 volt relay just switch them. Be careful though it's a bit confusing. There are 12v relays switching 24v circuits and vice versa. You have to read carefully.

 

[Ue413]

I had this issue...there is a button on your fuse board (lower left) that is called something like "starting interruptor?" (Not at my truck so cannot recall or look at exact phrase).

as far as I can tell, it is just an on/off switch. This was giving me the same symptoms as what you describe. I popped it out of the board, and monkeyed with the two wires that run to it, checked it out with multi-meter, and in that whole process, problem went away. I believe it was the connectors, and removing and replacing seemed to do the trick.

 

[tennmogger]

There were two major clues: the truck does not like to start when it is cold, and the CTIS lighs blink in unison to starter drop out. Starter loads battery, battery voltage drops, starter drops, batt V bounces back up, starter relay energizes again, etc, etc.

My guess, battery voltage is dropping. Either batteries are 'charged' but not holding a charge or there is a high resistance connection in the heavy cables.

Best test, a voltmeter right at the batteries, measuring the 24v WHILE trying to start. Analog meter is best. Long meter leads very handy.

 

[joshua180422]

Ok when I try to start it I put my hand on the relays. The one that is popping is the cranking lockout. Does anyone know if it could just be the relay or another issue? Also where can I get another relay. Leaving for Maine this Friday. I am getting nervous.

 

[Suprman]

They are over the counter 12 and 24 volt bosch style automotive relays. You can temporarily swap with a less used one to see if the relay is bad and go from there.

 

[joshua180422]

Switch the relay out with the relay from the radio power. Did not work at all. The batteries are fully charged. I am going to look into this thermal bypass.

 

[Suprman]

Go to the starter solenoid. Solenoid engagement positive is the contact closest to the engine block. Put an alligator clip lead on it and touch to the large positive terminal on the starter end. See if it cranks. If no crank listen for noise like the starter solenoid is trying to engage. If it sounds like the solenoid is trying, take a bar (to get in there its tight) and wrench or something and whack on the solenoid with the clip lead on the solenoid positive and the main starter positive see if it goes.

 

[joshua180422]

So I tried the thermal bypass and when I tried to start the truck nothing happened except some smoke from the fuse panel. So I give up. I am just going to start it by connecting the two posts on the solenoid.

 

[Suprman]

Smoke is a problem maybe you have a short somewhere. I would be careful with whatever you do that panel is expensive to replace.