[DK on the road]

I thought i was low on fuel in my main tank and I had sucked air. It was warm out and I was running the for the air conditioners.  It was running and I was down to about 15% on my fuel tank.  I slid in all slides and refueled.

1) is the fuel pick up for the gen set higher than the engine ?
I have known this to be at 25% on earlier motor homes 

Now full, it ran fine. I even changed the filters, and added gauges to see pressure at the pump and suction prior to my new Racor filter. 

The next trip, again now at more than 1/2 the tank full, it slowed and stalled again. After my wife came and found me and told me it stopped, I went back to try and restart it. I went through 3 start cycles, while I held the prime switch on and it tried but wouldn't start. I decided to bleed all injector lines and hold the prime switch and after 3 start cycles it still didn't start. The next start cycle it started to get fuel and after closing each (and making a mess) it started.  If I hold the prime switch on when it slows, it will regain RPM and continue to run.  I have power to my fuel pump at all times, as measured with a continuity light, while its stalling showing 5 PSI just prior to the injection pump. 

2) is 5 psi enough ?
3) am I over riding the electric shut off switch by holing the prime switch on ?

Is my electric switch at the injection pump failing ? It looks newish by a previous owner.

Is this an electrical problem ? I once thought it was a fuel delivery problem

Your thoughts are appreciated

[pairodice]

Is the fire extinguisher in the bay still connected? Ours was connected and basically if the canister is empty it will not allow the engine to remain running. Call Newell, they can help!

[bestgenman]

You’ve given a fair amount of information here and my bet initially is a filter restriction. “Slowed and stalled” supports no fuel.  If you have fuel pressure of 5psi (don’t know exactly where you gauge is mounted) , there should be enough fuel to the injection pump.  If the gauge is at the output of the primary and the fuel passes through the secondary, you might change that filter.  This is where a picture is worth a lot.

I’m not sure at what level the pickup runs of of fuel but since you filled there is a good possibility of filter clogging material in the generator suction that passed beyond your primary.   And, if the fuel quality is low (dirty or alge laden) it may take a couple of filter changes.

Since it stopped while carrying a fair load, it doesn’t make sense that it is an electrical problem unless it stopped on high temperature and 784 should have a controller indicating the shutdown cause.  If it starved for fuel then it would stop and no oil pressure would be your indication.  Again here, what did the controller report?

The lift pump may be failing also.  It shows pressure while you are attending but during a run it may be loosing pressure (again, a no fuel problem).  If you’re sure the fuel is good and I’m assuming the main engine is happy with the last fuel load, then swap the pump.  Any 12V 5psi pump will work.  My 5psi rated pump only shows 3psi but works fine.  

These kind of problems are very difficult to diagnose remotely.  I hope this helps.

[DK on the road]

[attachment=5935][attachment=5935][attachment=5935][attachment=5935][attachment=5935][attachment=5935][attachment=5935][attachment=5935]Thanks for the quick response. to answer some of the questions;

The extinguisher is mounted and full with its sensor in tact, but the wires that must be to notify the operator are hanging loose and disconnected from something. I'll call Newell and see if I can figure out where and why they are disconnected.

The fuel system goes, tank to gauge at inlet, and gauge, (vacuum/pressure gauge) at outlet of racor to measure differential across 2 micron filter. None noted. This should all be vacuum.
From racor to electric pump, pump to original spin on filter, spin on filter to gauge at inlet to injector pump.  This gauge shows 5 PSI.

I'm going to start by exchanging parts, I don't thinks its the small electric fuel pump, Maybe it gets warm and fails. But it always ups pressure when i try to revive the RPM with the prime switch held on. I'll start with the electric fuel solenoid.  It's after this, if it continues, I'll be stumped.

PS, I've never attached so I hope I've sent the right pictures

[folivier]

Looking at the hose going to the secondary filter (not the Racor) I see cracks, is it possible that those cracks are letting air into the fuel system?

[bestgenman]

Dave, good job on the pictures, it looks very well plumbed.  The differential pressure setup is a good service tool.  In looking at your set, I believe it is a Power Tech with a kubota engine and the electrical device at the back of the injection pump is an actuator for isochronous governing.  These are notorious for sticking.  Coach 785 was in my shop with the same problem several years ago.  The air conditioning would add a unit,  the engine wouldn’t pick up the load and the additional load pulled the set down.  I’m betting the same thing is happening here.  About the only fix is replacement, call Power Tech.
They aren’t difficult to replace, just two bolts and an O-ring if my memory is working correctly.  Any adjustments are made with the controller unless they have used a programmable controller (no user adjustments).
On 785, I changed the actuator back to a solenoid and reset the injection pump to “droop governing”. I know this all sounds complicated but it isn’t really.  It’s a “been there, done that” kind of thing.  I can talk you through it if you desire to tackle.

What is the ball valve without the handle being used for?

[DK on the road]

Thanks for the info Gordon and Forest.

I may contact you about "droop governing". Or can it be explained here? I'm not familiar with that term.

The initial fuel supply goes thru the SS 1/2 ball valve "with no handle". I didn't have a handle on the ball valve, but don't think i need it shut off accidentally either. I installed the valve so that the Racor and other filters could be removed without adding vice grips to the supply line and compromising the tubing and controlling fuel while doing maintenance

Forest, the cracks are paint cracks. The hose is OK, it has pressure not suction on it. Somebody tried to doll up the inside of the generator area and painted hoses also. All the other lines are new but that one.

[DK on the road]

Looking at the hose going to the secondary filter (not the Racor) I see cracks, is it possible that those cracks are letting air into the fuel system?

Sorry Forest, That line with paint crack is to the remote oil filter, not pressure or vacuum for fuel.

[DK on the road]

Update;

I replaced the solenoid that sits behind the fuel pumps while were out on the road and having fun with friends. I ran it for about 2 hours with what I thought was a full load, both electric burners on, 2 heat pumps running, and the oven on as a test. No problem.

Later that night, the wife was cooking. After about an hour of usage, it went into slow (30 seconds or so), stumble (10 seconds or so), speed up (3-5 minutes or so), stumble, slow (2 minutes), speed up (3 minutes), stumble (20 seconds or so) then shut off.  This sequence of stuttering takes about 10 to 15 minutes total.  

It seems like a fuel problem, but all the gauges say we have 4 to 5 psi. seconds before it shuts down completely

I'm leaving tomorrow for a month and will be stopping for an appointment at the Mother ship in 2 weeks and Ill have them look at it.

[ccjohnson]

Sounds like a dirty fuel filter. If you have a bad tank of fuel you may be in for quite a few filter changes to get it straightened out. Each subsequent filter should run a little longer before plugging as you are lowering the concentration of gunk in the tank. Or drain & flush/clean out tank.