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twostepen · 05-02-2018, 10:48 AM

We own a 2002 Monaco Diplomat w just over 67k miles. Have owned it for 5 yrs.
On occasion while the coach is in motion the engine completely shuts down.
Regardless of speed. Cost to the shoulder the key has not been touched mind you.
No warning lights on dash r lite up. The shift pad is still lit up.
I turn the key off and restart just like nothing happened shift to drive and we r going.
The shift pad still being lit up w power tells me it’s not an ignition solenoid.
Cummins says that the ECM (engine control module )controls fuel shut off and there is no shut off fuel Solenoid.
Any help would be greatly appreciated
Thanks in advance

vito.a · 05-02-2018, 11:20 AM

Just thinking this through. A diesel engine runs on compression with no spark plugs. Your engine needs fuel and air to run. So something is probably turning the fuel off, or it's getting air in through a fuel line leak.

Just a guess: Most of these engines have a lift pump that comes on when you first turn the key on (like a primer pump) and then the engine driven pump takes over. The issue is the lift pump develops an air leak and the larger engine driven pump can sometimes pull air in through that leak. This develops air bubbles and the engine will stall.

Make an appointment with a good Cummins Coach Care store and tell them the issue.

Good luck!

winniman · 05-02-2018, 12:24 PM

Probably not relevant, but this winter we were driving in my friends 07 pathfinder on the freightliner chassis, 5.9 cummins. The alternator went, and we were losing voltage as the motor battery was draining. We had the dashboard digital readout telling us what the voltage was. When the voltage dropped below 10 volts, the engine cut out, and we coasted to the shoulder. We started the genny, and jumped the engine boost relay with a cable, and kept going. Àny chance you are somehow loosing voltage to the engine computer. The alternator guy told us once the computer voltage gets too low, it just shuts down. It did for sure on us. If your battery voltage is good, maybe there is a bad connection to the computer, and it looses voltage. Im no mechanic at all, just trying to give you a clue to something similar that happened to us. Good luck.

CountryB · 05-02-2018, 12:28 PM

The problem does sound electrical.

The ECM needs power for the engine to run (the fuel injectors are electronic) so you could monitor the power to ECM and see if it cuts out. I would not recommend you do this while driving as it is dangerous to lose engine power going down the road.

However, it might take some road vibration to cause the shutdown. So testing while sitting still may not reveal anything.

I agree that you would be better off going to shop where they can pull the history from ECM and see if any there are any clues. The shop would probably drive the coach with their scanner connected and monitor the vital circuits.

But if this is something you want to try to diagnose in your driveway, you could rig up something to monitor 12V power on some of the circuits to see if power is lost just before engine dies. For example you run a temporary wire back to ECM and tie into the power feed where the other end of wire is connected to a light bulb that you can watch. Perhaps another temp wire connected to ignition switch, etc. so you can see what circuit is losing power when the engine quits. You would need to refer to a wiring schematic to see what circuits/systems need power to keep the engine running.

twostepen · 05-03-2018, 10:03 AM

Going to take her in Monday to Cummins Coach Care in Kansas City and see if they can figure it out.
More later

twostepen · 05-03-2018, 10:07 AM

Gonna take her into Cummins Coach Care in Kansas City on Monday and see if they can diagnosis the problem.
More later.

JohnBoyToo · 05-03-2018, 11:09 AM

Our's had that same issue, would just cut off like I turned the key off - no power steering, and brakes would bleed down !!!!
very, VERY scary @ 60 mph on a high overpass turn in New Mexico !!!

Had some type of short, that blew a large fuse... replaced the fuse with a auto reset fuse while on our trip with plans to have it checked out when we got home... but nothing found and if it still occurred, I didn't know about it !!!

our guess is that the previous fuse was marginal....

mackwrench · 05-03-2018, 01:47 PM

My gut tells me to start at the ingition switch. Then I'd work back towards battery grounds, engine ground and ecm ground....
But, that just my wag....

After engine shutdown do you still get normal dash warning lights...and they go out when restarted?

Hopefully issue will duplicate itself with Cummins

twostepen · 05-04-2018, 04:48 AM

That’s the bite as soon as it comes to a stop there is nothing lite up on the dash but the shift pad still has power because it is still lite up
I turn the key off and then it restarts and runs like nothing happened.

twostepen · 05-04-2018, 04:56 AM

That’s just it the dash warning lights are not lit up.
The shift pad has power and is lit up.
Once the coach stops moving I turn the key off and it restarts and runs like nothing happened.
Thxs

barmcd · 05-04-2018, 06:29 AM

I don't want to insult your intelligence, but are you sure the engine is off and not just stuck at idle? Having the engine idle and not respond to pedal commands is a classic symptom of a bad accelerator position sensor. A restart usually clears the issue--at least for a little while.

twostepen · 05-04-2018, 08:18 AM

I wish that it was just idling.
No the engine is completely shut down.

Chief Alen · 05-04-2018, 08:30 AM

You sure ALL the fuel filters are clean.

Some diesels have " hidden " filters .

Some times the main ground wire connection needs cleaning.

barmcd · 05-04-2018, 09:10 AM

Quote:

Originally Posted by twostepen

I wish that it was just idling.
No the engine is completely shut down.

If the key is on and the engine is not running and there are no lights on the dash, I'd suspect the ignition switch. If it were just an engine problem, you'd have idiot lights for low oil pressure and the like lit on the dash.