Cat C9 Engine Starting Problems

[David Schroeder]

Yes, I have been reading the posts...And thanks to all of you for the ideas.  I got my cousin, who is a diesel auto mechanic to come out and give me a hand; this is definitely not my area of expertise, but I'm learning a lot.  We have tracked power in and out of solenoids, relays, etc. and believe we've isolated the problem.  We had a power drop out of the starter solenoid at the rear of the coach, so we replaced that, but that didn't resolve the problem.  We tracked good power to the starter, so we have removed it and it is being checked, and possibly rebuilt/replaced.  We'll post our outcome.  Thanks again for all of the input.  We will probably replace the ignition as a preventative measure as well...the GM ignition switch does make me nervous based on recent reports.
Regards,
Dave

[Edward Buker]

David,

If the coach always starts from the rear start then that would typically rule out a problem with the starter. If you measure the voltage at the solenoid on the starter while using the rear start switch a few times to see what voltage is triggering that solenoid repeatedly. Then repeat the test using the key switch. My guess is you are not getting enough voltage to the starter solenoid using the key switch. As Dave mentioned it could be a voltage drop in the switch or elsewhere. You could add a Bosch type relay in the rear of the coach and wire in a short path of adequate voltage from the battery compartment with suitable gauge wire and use the key switch just to trigger the relay if you cannot find the voltage drop source in the long path from the front of the coach. This is basically another rear start circuit triggered by the key switch. Some coaches are already wired this way with a rear relay triggered by the key switch. Hope this helps.

Later Ed

[David Schroeder]

An update for everyone...
Had the starter and starter solenoid checked out.  As it turns out, the solenoid was bad along with the starter pawl.  Apparently a gasket was missing which allowed water into that area causing parts to rust.  It appears the gasket was never installed at the factory.  With everything cleaned up and replacement parts, it seems to be starting consistently.  We still plan to replace the ignition switch as a preventative measure based upon GM's problems with that part.
Thanks again to all who contributed.  Hopefully, we are back in business.
Regards,
Dave

[Steve Huber Co-Admin]

David,
Hard to argue with success but unless there are 2 starter solenoids, I can't see how replacing the solenoid and starter pawl fits the symptom of always starting from the rear start  button but not from the ignition switch. I must be missing something...
Steve

[Edward Buker]

Steve,

I think the rear start shorter wire path provided enough voltage and current to throw the starter solenoid even with the rust issues and the front was not enough. With that corrected they both work. Good to be fixed and not worrying about starting issues.

Later Ed

[Dave Atherton]

David, Ed , Steve, Lee, wiring problems are a real troublesome as Ed will relate his background,
Motorhome builders seem to follow path to some place but forget the road map. Myself glad
David you are up and running but like Steve have a hard time understanding end result. Cat tech
Info. clearly spells out Code 93-40 start circuit off key switch fault problems, starting at key switch
and working away from that point. Think what is different there is a standard all of its own to
builder, this is where the twist comes into play. Ran into problems with engine grounds removed,
three on engine for Cat standards for example. Everyone looks at problems in many cases the
way there motorhome is same but sometimes not the same. End results David is up and
running. As time wears on and more miles more electrical problems will be popping up in a
different way.   Dave Atherton Retired Cat Mechanic