Cat C9 Engine Starting Problems

[David Schroeder]

We are new to diesel motorhomes, Beaver and BAC (previously had a Damon Challenger).  This Spring we purchased a 2009 Beaver Monterey Sunset with the Cat C9 425 engine.  We made a couple of short trips in Florida before heading out for our first cross-country trip in May.  During the short trips, we had no problems and loved our new rig.  Unfortunately, we were only a few hundred miles into our longer trip before the problems started.  We had Regen problems, but three days and two Freightliner visits later (with a much lighter wallet) we were back on the road with no further problems.  However, we soon started having problems with the engine starting.  We continue to have intermittent problems with the engine starting...sometimes starts right up, sometimes starts with "boost" and mostly, doesn't turn over at all.  When it does decide to start, it is often after we have turned the key on and off two or three times.  We've replaced the batteries (regularly shows a low battery on the info screen), the Bi-Directional Relay (which seems to have resolved some generator problems), and the 12-volt starter solenoid.  We are still having problems with the engine starting.  You can start the engine from the engine compartment, but generally not from inside the motorhome.  We're hoping that someone out there may have some suggestions so that we can get this fixed and love our RV again.  Thanks for any help you may be able to offer!

[Steve Huber]

David,
Couple of clarifying questions:
When engine does turn over is it at normal cranking speed or is it slow?
Does it always start from the engine compartment? Normal cranking speed?
When you use Boost to start it was engine turning over at all or slowly before you applied boost?
Have you measured the chassis battery voltage at the batteries?

BTW, I took the liberty of adding a signature for you. Feel free to modify it under Form Profile.
Steve

[Dave Atherton]

Thanks Steve, answer to first question. To start a Diesel engine the starter must turn min.
150 rpm's. Use of boost switch will reinforce the speed of the starter. First place to look at
Key switch ( there has been several bulletins in this area. I would remove key switch and use
A jumper wire and see if engine will spin and start ) think early days ,bad guys hot wire car
To steal. next would check power from front key to start relay think is front door left driver
side electric panel. Dave Atherton Retired Cat Mechanic

[David Schroeder]

The engine runs at normal speed in both instances.  It doesn't seem to be an engine problem...seems more like electrical/starter problem...but I'm no mechanic.  And, so far, it does always start from the engine compartment.  You can always hear it click, but often, no turnover from inside the coach.  With the old batteries, it was a slower crank with the boost, but it hasn't started at all with boost recently, and with the new batteries.  The batteries appear to have normal output.
Thanks,
Dave

[Dave Atherton]

David, I understand that engine starts from back of motorhome but has a problem starting
from front key switch. What I'm relating to removing wires from back of key switch and using
jumper wire to wires coming to key switch. If engine spins over than starts, you have found your
problem. Yes I do understand this a electric problem and the key is in the electric circuit.
Dave Atherton Retired Cat Mechanic

[Steve Huber]

David,
You said the engine display was showing low battery voltage. Is this still the case and does it show thr actual voltage. If you are getting a low voltage indication but the voltage at the chassis batteries is good (~13V), your problem may be a bad connection.
Steve

[David Schroeder]

We just put new engine batteries in a few weeks ago, but continued to get a low battery indicator.  We replaced the coach batteries today and initially still got a low battery indicator, so we started the engine from the engine area, then drove around for about thirty minutes.  When we returned, the low battery indicator was no longer displayed and the generator started quicker than it has in the past, but the engine still would not turn over with the key.  The voltage readout was 13.8.  Any advice is sincerely appreciated.
Thanks again,
Dave

[Dave Atherton]

David, Batteries cables held in place via connection and a nut. Have found when sliding batteries
Back into motorhome a cable being stiff would slip on post connection which would allow enough
low voltage ( ground ) to not engage starter. Again would suggest above post with key switch.
You have indicated the rear start works ok. I do believe the starter switch is a GM switch and didn't
They have problems with many cars and pickups. My Cat bulletin keeps going to starter key switch.
Will dig deeper into cat bulletin and see if more info is on subject. What we are trying to do with
problem go with the easy and simple things first without spending money and not have you
Keep putting parts on. Dave Atherton Retired Cat mechanic

[Steve Huber]

David,
Agree with Dave Atherton that it sounds like the ignition switch is the culprit. Most everything else, battery connection, starter solenoid, etc is used regardless of whether engine is started from front or rear.
Steve

[Arden Smith]

Had problems with mine similar to stated above. I found the relay in the cabinet by the drivers side to be sticky or not having enough  voltage to energize it. Tapped it with the handle of a screwdriver, none metallic to avoid shorting, and the solenoid pulled in and the coach started with the switch. Replaced solenoid and solved problem. Should have left the solenoid in longer to truly troubleshoot why it wouldn't pull in. It is a 100% duty solenoid and they can get hot to the point of being sticky, but I wanted to get down the road.
PS. This might not even be the same, as mine is a 300 hp Cat.

[Dave Atherton]

Arden, good point about the solenoid but the way it's posted above by David the engine starts ok
from the rear but not the front key switch. Are you saying there are two start solenoids and one
Solenoid is bad.  Dave Atherton retired Cat Mechanic

[LaMonte Monnell]

I thought there were two solenoids for engine starting? One in the front left panel drivers side compartment for the key switch, and one in the back for when you use battery boost switch or rear start button. Maybe I am confusing myself here and how it all works.

[Dave Atherton]

LaMonte, yes there is a start solenoid in left front bay on the bottom and power connects to left buss bar
When power up, will energize the right buss bar. top left buss bar is key switch power and direct across
on top is the ECM power. Going back to David's problem engine will not start off key switch. I do believe
lower right side there are several relays that second one from top is ties into start system also.
Dave Atherton retired Cat mechanic.

[Arden Smith]

I believe the key is supposed to turn on the solenoid which in turn turns on the electrical system including the dash panel.

[Dave Atherton]

Arden, that is correct providing the diode jumper wire  is good on the little terminals of solenoid
otherwise, no it will not. Let's go back to the above post, now that we both understand how the
start system should work and again lets start at the key switch and work away from that point.
David hopefully you been reading these post and the help membership providing direction to solve
your problem. Dave Atherton Retired Cat Mechanic