Cummins Comfort Guard APU Issues. Help!!

Erratic stalling issue with "unknown" fault code.Electric fuel pump went out and got replaced in June, at Cummins. Ran fine for awhile.

All filters have been replaced twice since then. Generator brushes are brand new.

Here's what I mean by erratic. Starts up fine and may run awhile, 5-6 hours. Then it'll stop abruptly with a fault code. Fault code thrown is "unknown reason". So you restart the apu and it may run for a couple minutes. Then stop abruptly again. Sometimes on re-start, it'll just crank and crank.

A couple thoughts I had.....was that it was starving for fuel. However, fuel filter is full and you can visibly see it circulate.
Those who know anything about electrical components know that, sometimes when a component gets too hot resistance can build up in the circuit and make it fail until it cools down.
this acts kinda like that. However, the engine stops abruptly. Not like an engine does when it runs out of fuel.


I'm stumped, but trying not to go back to Cummins.

Any ideas?

 

Also, does anyone know where I can buy those air ducts for the APUs?

The Comfort Guard APU has 6 air outlets on the unit, but they only installed 3 and left 3 capped.
I want to maximize it's capabilities, but can't figure out where to buy the air vents.

 

ya mean, in the tank??

 

I wound up getting crappy fuel economy for a lil while on the big engine. Got my PM service and new filters all the way around and problem went away.
I think I got bad fuel at the Broadway Flying J in Belgrade, MT.

Anyway, APU is down again for a diff. issue. Generator is going through brushes at a rate of one set per week. I think it's time to get the armature turned.

 

Why did you have the Blue Beacon do that?

Anyway, I'm pretty certain it's a lot simpler than that. I've gone thru 3 sets of brushes in 3 weeks. And it's not both that are wearing out, just the one....every time.

 

UPDATE: So, it turned out that the rotor was bad on the generator. Got that replaced. They also found that the water pump on it was leaking and replaced that.

So, I got it back. It for 3 times for an hour each b4 faulting. Code 36. After that, it would run for 3-5 minutes b4 stopping with code 36. But then, on re-start, it'd just crank and crank....throwing code 32.

I've checked the fuel system, replaced fuel filters again. There's no blockage in the fuel system, even getting steady flow in the return line.

 

How much did it cost you to get it replaced? Oh wait, you said warranty. I have over 7100 hrs on mine.