M1078 Won't Start

[cavetech]

I have a nice M1078, but it often (usually) won't start. Sometimes I go to start it and it fires right up. Often it won't start. I flip the master power switch on and push the starter button and nothing happens except a faint click seemingly in the dashboard. The starter does not turn over.

My batteries are good. Battery and starter connections are good and clean.

It might start one time and run fine and the next time I try to start it, nothing but the faint click in the dashboard.

I am really stuck and I can't find any mechanic to even work on it.

Has anybody experienced this? What the heck do I even look for?

I want to make the parade in Perry, FL on the 28th very much, but I'm afraid I'll get stuck.

Thanks, Steve

 

[NDT]

Thermal switch on starter bypassed? Connectors properly seated in Allison VIM and TCM? Fresh relays in appropriate locations in PDP?

 

[Suprman]

When it won't start, use a screwdriver to jump the aux start relay on the drivers inner frame rail. With the dash power switch on if you want it to start. Otherwise it will crank but no fuel.

 

[cavetech]

Thermal switch on starter bypassed? Connectors properly seated in Allison VIM and TCM? Fresh relays in appropriate locations in PDP?

I'm sorry, but I don't understand what you are suggesting. You are obviously knowledgeable about the 1078, but don't understand your abbreviations.

Thanks, Steve

 

[TNriverjet]

Thermal switch on starter bypassed? Connectors properly seated in Allison VIM and TCM? Fresh relays in appropriate locations in PDP?

VIM = ?
TCM = trans control module
PDP = power distribution panel (passenger side panel on dash)

 

[NDT]

I'm sorry, but I don't understand what you are suggesting. You are obviously knowledgeable about the 1078, but don't understand your abbreviations.

Thanks, Steve

Thermal switch is where two very small white wires go on the starter motor. Cut them off and connect together if not already done. The Transmission Control Module (TCM) is the transmission brain, which has connectors that can come loose. The VIM is the Vehicle Interface Module which can also have loose connections. The TCM and VIM assure the transmission is in neutral prior to allowing the starter to operate. The PDP is the Power Distribution Panel, in front of your passenger seat, there are relays there which make the starter operate, which can be defective or have corroded contacts. Hope that helps. If all else fails, the starters on these trucks cause a lot of grief as well, but are expensive to replace. Good luck.

 

[cavetech]

Thermal switch is where two very small white wires go on the starter motor. Cut them off and connect together if not already done. The Transmission Control Module (TCM) is the transmission brain, which has connectors that can come loose. The VIM is the Vehicle Interface Module which can also have loose connections. The TCM and VIM assure the transmission is in neutral prior to allowing the starter to operate. The PDP is the Power Distribution Panel, in front of your passenger seat, there are relays there which make the starter operate, which can be defective or have corroded contacts. Hope that helps. If all else fails, the starters on these trucks cause a lot of grief as well, but are expensive to replace. Good luck.

This I understand and I thank you for the simplified explanation. I think I can do this. Tomorrow will be interesting.

Thanks, Steve

 

[scottmandu]

Make sure the neutral relay is being activated by the TCM. Make sure the relay is also the correct relay.

 

[cavetech]

I spoke with a National Guard mechanic who knows the truck. He suggested replacing two relays in the breaker panel on the dashboard. I'm looking for them to buy right now. They are K19 and K1.

 

[Suprman]

I have new 24 volt relays

 

[Smike740]

I spoke with a National Guard mechanic who knows the truck. He suggested replacing two relays in the breaker panel on the dashboard. I'm looking for them to buy right now. They are K19 and K1.

I have the same issue occasional, maybe 1 out of every 20 times I get nothing when i push the start switch. Then it goes right back to working fine.

Please let us know if the relays solve your issue.

 

[cavetech]

I have new 24 volt relays

Thank you.

I have found the 24v relays.

 

[Moostang]

I see a lot of starter problems on the older trucks. The starter solenoids go bad often. Have someone hold the button down and tap on the solenoid. Also have seen water get inside and rust them up and cause intermittent problems. On a side note, I have seen several with loose bolts holding the nose cone on but they usually still start fine.

 

[cavetech]

I see a lot of starter problems on the older trucks. The starter solenoids go bad often. Have someone hold the button down and tap on the solenoid. Also have seen water get inside and rust them up and cause intermittent problems. On a side note, I have seen several with loose bolts holding the nose cone on but they usually still start fine.

Sounds like good information. Believe it or not I actually knew to try the trick to hold the starter button down while I tapped the starter and solenoid with a hammer. Unfortunately it didn't work.

I just put my new relays in the panel. I hope they solve the intermittent problem.

Thanks, Steve

 

[cavetech]

OK, I have more information. I have replaced the K19 and K1 24v relays. The truck has been in a good mood and was starting reliably. Yesterday it wouldn't start.

Today I discovered it will start in Drive (not neutral). After starting in Drive it will also start in Neutral. But, for how long I don't know. I've got to fix this truck for the Perry parade on the 28th. Now it starts repeatedly in Neutral. But, it may stop starting at any time now and I can't risk getting stranded.

When I press the transmission up and down arrow keys at the same time I get a code of d1. What does that mean?

Should I bypass the neutral transmission ecu relay? If so, how???

What is happening and how do I fix it?

Thanks, Steve

 

[Rebuilder]

OK, I have more information. I have replaced the K19 and K1 24v relays. The truck has been in a good mood and was starting reliably. Yesterday it wouldn't start.

Today I discovered it will start in Drive (not neutral). After starting in Drive it will also start in Neutral. But, for how long I don't know. I've got to fix this truck for the Perry parade on the 28th. Now it starts repeatedly in Neutral. But, it may stop starting at any time now and I can't risk getting stranded.

When I press the transmission up and down arrow keys at the same time I get a code of d1. What does that mean?

Should I bypass the neutral transmission ecu relay? If so, how???

What is happening and how do I fix it?

Thanks, Steve

This is what I had to do when I had issues with my starting circuit. Remove the K1 Starter Relay, turn the main switch on and check for 24volts at terminal 30. If you have 24 volts you can jump 30 to 87 and it should start the truck. Doing this bypasses all the other relays in the starting circuit. It doesn't solve your problem but if it works you'll know your starter is fine and you'll have a way to start your truck until you can fix the problem.

 

[Rebuilder]

If you do want to bypass the neutral switch jump F to G in the VIM box which is under the dash on the passenger side.

 

[cavetech]

This is what I had to do when I had issues with my starting circuit. Remove the K1 Starter Relay, turn the main switch on and check for 24volts at terminal 30. If you have 24 volts you can jump 30 to 87 and it should start the truck. Doing this bypasses all the other relays in the starting circuit. It doesn't solve your problem but if it works you'll know your starter is fine and you'll have a way to start your truck until you can fix the problem.

I have the breaker panel open. K1 is a relay I have replaced, but which leg is terminal 30? I see the sockets the relay legs plug into, but none of them are marked. I don't see anything marked 30. What have I misunderstood?

Sorry, Steve

 

[Rebuilder]

I have the breaker panel open. K1 is a relay I have replaced, but which leg is terminal 30? I see the sockets the relay legs plug into, but none of them are marked. I don't see anything marked 30. What have I misunderstood?

Sorry, Steve

The numbers are on the blade side of the relay. 30 is the top one and 87 is the bottom one. The electrical schematics are near the end of the TM m1078_TM 9-2320-365-20-2 . They're a bit intimidating at first but well worth the time to learn how to read them.

To clarify.... to start the truck this way you jump 30 to 87 and remove the jumper right when it starts.

 

[TNriverjet]

This may be a good resource to help you decipher your transmission code.

http://www.beamalarm.com/Documents/allison_transmission_codes_manual.html