BAC Forum
General Boards => Technical Support => Topic started by: David Schroeder on September 24, 2015, 12:54:34 AM
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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!
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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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.
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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.
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I believe the key is supposed to turn on the solenoid which in turn turns on the electrical system including the dash panel.
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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
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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
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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
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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
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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
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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
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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