Adv. 34D Eng. won't turnover

[CTC42]

3 out of 5 tries to start Cummins 275 Diesel on Freightliner XC chassis just clicks and will not turnover. When it does turnover it starts immediately. Batteries new and charged at 12.5V when starting. I removed and cleaned terminals on battery, starter and attached starter solenoid, separate rail solenoid, a terminal for battery wires in the battery compartment, and both ground and + terminals under the hood. I don't hear the bendix in the starter clicking in the starter when it doesn't start. Hitting the switch in the coach that connects the coach batteries to the engine , makes no difference. When I turn the ignition key (in the condition when it does not turn over), I hear an air valve momentarially open alternately under the coach near the front then the rear axle. When it starts there is no clicking it just turns over. Not sure what or where to look next.
There are bolts holding the starter on the engine that also hold the ground strap on the starter mounting bolt, that have about twice as many points as a Torx. What is the type of socket that will fit these, and where do you get them? A 12 point 3/8 socket is too small and a 7/16 socket fits over the bolt head.
We just acquird this MH used and this is just one of several major electrical problems. I'll make separate posts for each issue. Thanks for all that respond with answers based on experience with this Freightliner Chassis.

[CTC42]

3 out of 5 tries to start Cummins 275 Diesel on Freightliner XC chassis just clicks and will not turnover. When it does turnover it starts immediately. Batteries new and charged at 12.5V when starting. I removed and cleaned terminals on battery, starter and attached starter solenoid, separate rail solenoid, a terminal for battery wires in the battery compartment, and both ground and + terminals under the hood. I don't hear the bendix in the starter clicking in the starter when it doesn't start. Hitting the switch in the coach that connects the coach batteries to the engine , makes no difference. When I turn the ignition key (in the condition when it does not turn over), I hear an air valve momentarially open alternately under the coach near the front then the rear axle. When it starts there is no clicking it just turns over. Not sure what or where to look next.
There are bolts holding the starter on the engine that also hold the ground strap on the starter mounting bolt, that have about twice as many points as a Torx. What is the type of socket that will fit these, and where do you get them? A 12 point 3/8 socket is too small and a 7/16 socket fits over the bolt head.
We just acquird this MH used and this is just one of several major electrical problems. I'll make separate posts for each issue. Thanks for all that respond with answers based on experience with this Freightliner Chassis.

[John_Canfield]

Welcome to the forum!

I would get a partner to assist you in the coach to try to start the engine while you are using a meter to check the voltage at the starter solenoid and working your way back to the batteries.

You can measure a good voltage with no load but as soon as a load is applied the voltage can drop to a useless point with a bad connection or hairline break in a wire/connection.

Send a message to one of the moderators and ask them to cross-post this on the Freightliner Chassis forum for more exposure.

Doubtless you will get more ideas from the brain-trust here!