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jaunderwood · 09-05-2015, 05:27 PM

2010 w22 with MaxxForce7 diesel - Start relay not getting ground when ignition switch turned to start position - Anybody know where the ground comes from?

Skip426 · 09-05-2015, 11:13 PM

What transmission series is the coach equipped with?
Keypad or column shifter ?
If the transmission control is a keypad then the ground is provided by the transmission control module , after neutral is selected.
With a column shift there would be a neutral safety switch, on the shift linkage or side of the transmission.

jaunderwood · 09-06-2015, 07:59 AM

Skip426 thanks for the reply. It has an Allison transmission with a column shift.

Skip426 · 09-06-2015, 11:22 AM

The safety switch should provide a relay ground in neutral and park, and may be the same switch as for the back up lights. I'll dig around and see if I can pull up exact info or a picture.

stink · 09-06-2015, 11:36 AM

If this is the starter relay on the starter than it gets it's ground thru the starter itself. This keeps the relay from closing if there is a bad brush or winding. Some separate relays also ground thru the starter but not sure on yours. Best to check wiring diagram.

jaunderwood · 09-06-2015, 02:21 PM

It is ign-run/crank relay 14 located in under-hood electrical center.

jaunderwood · 09-07-2015, 08:34 AM

My mistake, it is the start relay located in the underhood elect center.

Skip426 · 09-07-2015, 10:57 PM

I've been poking around For info on Allison trans with a gear shift, and the neutral safety switch may be on the side of the transmission , drivers side where the linkage attaches, you should check the electrical connections there, GM trucks for a few years had problems with water intrusion into the electrical connections causing all sorts of issues.

mgscott4 · 09-08-2015, 03:09 AM

Quote:

Originally Posted by jaunderwood

2010 w22 with MaxxForce7 diesel - Start relay not getting ground when ignition switch turned to start position - Anybody know where the ground comes from?

More information please, How do you know the start relay is not getting ground? If the start relay is not energizing, maybe the 12 volts to pull it in is not getting there, maybe the relay is bad, maybe the relay socket connection is dirty. Maybe it has nothing to do with the relay.

But, getting back to your original question, without a wiring diagram,I am only guessing , I thinking that the ground is supplied through the ECM, certain conditions have to be met before the ECM gives a ground signal to the start relay, such as "the shift lever has to be in park or neutral". But I am sure that there are more relays that have to be energized before the ground signal is applied to the relay, maybe a ECM signal, or a fuel pump relay, or IGN A, IGN B relay.

If I am troubleshooting relays, I need a good wiring diagram.

Just for the heck of it, swap the start relay with another relay with the same part number on it.

jaunderwood · 09-08-2015, 05:55 AM

Quote:

Originally Posted by mgscott4

More information please, How do you know the start relay is not getting ground? If the start relay is not energizing, maybe the 12 volts to pull it in is not getting there, maybe the relay is bad, maybe the relay socket connection is dirty. Maybe it has nothing to do with the relay.

But, getting back to your original question, without a wiring diagram,I am only guessing , I thinking that the ground is supplied through the ECM, certain conditions have to be met before the ECM gives a ground signal to the start relay, such as "the shift lever has to be in park or neutral". But I am sure that there are more relays that have to be energized before the ground signal is applied to the relay, maybe a ECM signal, or a fuel pump relay, or IGN A, IGN B relay.

If I am troubleshooting relays, I need a good wiring diagram.

Just for the heck of it, swap the start relay with another relay with the same part number on it.

This problem is on a 2011 Thor Serrano I recently purchased used. If you turn the ignition switch straight to start without pausing in the run position the starter will crank and the engine will start. If you pause any length of time in the run position prior to selecting start the starter will not crank therefore the engine will not turn over. I carried the unit to the local International Harvester / Navistar / Workhorse dealer for diagnosis and repair. They have been troubleshooting for two weeks without any success. They have replaced the ECM to no avail and they say the start relay is getting 12v but not getting ground. They have offered to mod the relay where it will get a constant ground. I just dont know if that is a good idea, but I might have to go that route to avoid bankruptcy at this rate. Thanks again for all your responses.

mgscott4 · 09-08-2015, 08:47 PM

This isn't Rocket Surgery, Any good tech with a wiring diagram should be able to troubleshoot it. Can you get a copy of the wiring diagram.

Last month I helped my nephew with an engine swap in a 2004 Silverado. 4.3l V6 to a 6.0l V8. Got it swapped and ready to start and it wouldn't start. I troubleshot the problem to a ground wire not connected on the top transmission bolt on the back of the engine block. I noticed the same ground wire was also used on my engine swap in a 1999 Astro van. So the point being, GM uses this bolt for a ground wire, ask the repair guys to check the ground wire on the top transmission mounting bolt on the back of the engine.