Starter Chatter

[jkitt]

I have a T750 which I purchased this spring. I noticed then a "chatter" when trying to start the machine but only when it was cold. I replaced the starter and as the warm weather of summer came I had no issues. Now that it is cooling off (northern Alberta) I have the same issue. I just replaced the battery yesterday thinking that would solve the problem but it didn't. Ground and starter connections are tight. I'm not sure where to look next. Has anyone had this problem and solved it?

 

[flyerdan]

Just off the top I would imagine that it is something like a relay or safety interlock that is acting up. Normally temperature problems tend to show up when things warm up (a thermal open, etc.) but some corrosion might worsen with the slight cooling contraction.
Having a new starter and battery should spin it right over, if you can use a remote starter and have it fire right up that would indicate that the issue is somewhere between the key switch and the terminal on the starter.
Unfortunately, there isn't a book in the manual thread for this one, but if it's close to a wheeled machine you might be able to use the wiring diagram to sort it.

 

[Tazza]

Just off the top I would imagine that it is something like a relay or safety interlock that is acting up. Normally temperature problems tend to show up when things warm up (a thermal open, etc.) but some corrosion might worsen with the slight cooling contraction.
Having a new starter and battery should spin it right over, if you can use a remote starter and have it fire right up that would indicate that the issue is somewhere between the key switch and the terminal on the starter.
Unfortunately, there isn't a book in the manual thread for this one, but if it's close to a wheeled machine you might be able to use the wiring diagram to sort it.

I'd try swapping the starter relay in the fuse box with another one, just to rule that out.
You have changed pretty much everything that could cause it apart from the main ground connection.

 

[jkitt]

I'd try swapping the starter relay in the fuse box with another one, just to rule that out.
You have changed pretty much everything that could cause it apart from the main ground connection.

Thanks for the reply. I tried swapping relays. No difference. I cleaned the 3 ground connections on the battery cable, cleaned the ground to frame connection and the also cleaned and tightened the battery clamp. No difference. Shorted out the solenoid, cranked fine but would not start. (It had started before by doing this). Checked the battery voltage in my new battery, 12.9 volts. Tried starting it. Voltage dropped to 11.5 V. Boosted with two batteries from my Cummins and shorted the solenoid. Started fine. One thing new however when I was trying to start it (26 F this morning), after it would chatter for a couple seconds the display panels would die. Maybe a ground connection to the cab is what I'll check next unless there are some other ideas out there.

 

[foton]

Thanks for the reply. I tried swapping relays. No difference. I cleaned the 3 ground connections on the battery cable, cleaned the ground to frame connection and the also cleaned and tightened the battery clamp. No difference. Shorted out the solenoid, cranked fine but would not start. (It had started before by doing this). Checked the battery voltage in my new battery, 12.9 volts. Tried starting it. Voltage dropped to 11.5 V. Boosted with two batteries from my Cummins and shorted the solenoid. Started fine. One thing new however when I was trying to start it (26 F this morning), after it would chatter for a couple seconds the display panels would die. Maybe a ground connection to the cab is what I'll check next unless there are some other ideas out there.

if the starter chatters I would say it is either a positive or negative connection somewhere because you are not allowing enough amps to move. Is there any splices in the battery cables that could be giving a resistance issue. Maybe use heavy wire bypassing existing start cables, bypassing as much as you can(like relays) to figure out which side the fault is on.(+ or - )

 

[Tazza]

if the starter chatters I would say it is either a positive or negative connection somewhere because you are not allowing enough amps to move. Is there any splices in the battery cables that could be giving a resistance issue. Maybe use heavy wire bypassing existing start cables, bypassing as much as you can(like relays) to figure out which side the fault is on.(+ or - )

As you said there is no chatter when you jump it at the starter, you know your main battery connections are good, it has to be something between the starter and computer, bad fuse connection or poor connection somewhere?
Being a later model machine, i don't believe the starter connection is connected to the physical switch, but to the computer via the starter relay.
I wonder if you could use a multi-meter or test light on the starter pin and get someone to crank and see if the light pulses at all, showing erratic power. If it does, trace it back towards the computer and see where the pulsing stops.