[Archived]

Chris,

I wonder if it’s something with the fuel pickup in the tank. When you drive debris could be getting stirred up and clogging a screen or something. When setting still there may not be enough suspended stuff to cause a problem. Could you rig up a small temporary fuel tank near the generator for a test drive? Another thought is perhaps the action of the return fuel from the pusher is somehow effecting it. The fuel being heated could be helping a partially collapsed fuel hose to fully collapse. Or the return fuel is agitating dibris. The temp tank would verify one of these or at least a fuel supply issue.

[Dan]

I may be off base here, but the only difference I can think of between stationary and driving is air flow.

I cannot believe dirty fuel is an issue because our generator fuel pickups are well off the bottom of the fuel tank so we do not run a tank dry meaning if it was dirt or sediment the coach would suffer first.

Is there any way to measure the generator compartment for both pressure (using a manometer) and temperature especially in areas that might be more affected by a temperature variation? If there is no way to easily measure and record temps what happens if the coach is driven in 65 degree morning temps and 85 degree afternoon temps? Does it take longer to act up or does is not act up?

Is the compartment baffled and if so is the baffle damaged or crushed?

Is there a way to measure engine RPM from start up until the problem occurs? If the engine is lugging down would that impact voltage?

[Jerry]

This is a wild ass guess since it’s showing low voltage.

Gen battery? Is the gen alternator/regulator doing it’s job? Is it possible the solar panel is providing the only battery charge and does the solar panel automatically disconnect when the engine is running? Of course if it runs while dry camping at night it shoots that theory.

Another thing to try is start the gen from the gen itself and not the remote start, then drive to see if it still quits.

One more, do you have the autostart turned off to rule out any electrical gremlins?

[Davy]

I know Jon suggests we need to run our gens more. Not so sure if it’s a Kohler. The gen in my Marathon (1990 coach, not a Kohler) was bulletproof during my ownership period. I have an appointment to have my dead Kohler looked at in October. Third failure in 11 years, all on the electrical side. By the way, mine seems to use a little coolant, too.

[Jim]

I don’t run my generators enough, but so far the two Kohlers I have had had only one issue and that was a failed fuel pump on the last coach. I hope I don’t regret saying that because in the near future I am looking at 4 weeks of dry camping spread over 3 trips and I just turn the generator on when I get up and run it every day until I go to bed.

[Mark]

Another thought is tank venting. Could the engine fuel consumption be creating a vacuum in the tank and continue to overcome it while starving the generator? I have no idea how the tank is vented. As to Jon’s theory, What happens if you run the engine parked on high idle. Does that shut the generator down?

[Roscoeapproved]

I am going way out on a limb with this Wild A@@ Guess (WAG). Could it be a loose electricial connection that vibrates while driving but makes a good enough conection when parked. On my previous coach I found that the negative cable from the generator to the bus was loose. When I tightened it up, it stared a lot better. Now that is not your problem, but maybe the 120V wires in the generator or where they connect to the transfer switch could be loose???? Any connection inside the generator or where power is connected to the house systems might be giving an issue when the bus is moving.

I have a hard time seeing how this problem is cooling or fuel related or you would be getter a different error code.

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Jeff and Lindsay

91 Marathon XL

[Archived]

If the engine Rpms drop from a performance issue be it from fuel problem air problems or whatever the frequency changes. Frequency is directly proportional to shaft speed with no means for regulation.The voltage regulator will adjust the voltage to compensate for speed variations but it can only compensate so much (+or- 10%). When the rpms get too far off the voltage will fall out of the fault parameters.

I agree it could just be a loose connection but engine performance will also shut them down through the voltage monitor.

[Archived]

I serviced my gen when I bought the coach, did all the same things you did and had the same problem. Not saying this is your problem ,but mine was a loose ground wire to the fuel pump. Sometimes the difficult problems have a simple answer…..😕

[Archived]

thanks for the he responses. When I get time this week I’ll test out some of the suggestions. I’m leaning toward an engine performance issue that leads to a temp rpm decrease that leads to low voltage and shut down or a loose vibrating connection. Reading some Koehler stuff it appears the UU code is nonspecific and appears any time there is a decrease in voltage that leads to shut down.

Anyway to do an injector and engine treatment just to the gen to clean it out in case the issue is carbon build up. Small can of diesel hooked to the fuel pump with an additive. Suggestions as to best product?

My my plan is to:

• Turn off auto start and do a trial run
• Run gen with engine in high idle to see if the gen shuts down
• Check ground connections
• Check battery connections
• Expect to swear a lot

Gremlins!

[Archived]

Chris, if you suspect the engine needs to have the carbon cleaned out the best way to do that is load it to the maximum extent. Run all the A/Cs, range, outside grille, electric toe space heaters, etc. You can also monitor engine temps that way also because as it gets loaded and works hard you will see temps climb. I don’t think you need an additive.

I know it has been mentioned to run the generator hard and often but in reality the use of a 20KW generator to run a couple of A/Cs and a few other house loads is nowhere near its capacity and unless we try really hard we have a hard time approaching it 166 amp capacity.

[Fred F.]

Do you have a Racor main engine fuel filter? Have you taken it out and inspected it in the recent past? Just curious. If there is a lot of crap in the filter media and housing of the Racor, then the gen is getting the same stuff. Most converters don’t put a Racor on the gen fuel system or Aqua Hot/Webasto so that they can be inspected individually for fuel quality or water content, so you should be especially careful to monitor the engine one.

If you were here at the moment, I’d take the gen fuel filter off, empty it of fuel, fill it up with Diesel Shok, and run the gen to see what the results are. If may not be debris, but water in the tank messing with the gen. Upon driving, stirring up the water in the fuel tank could very easily explain your simptoms.

[Fred F.]

Chris,

If you want to try what Ben has suggested, Jon may still have Diesel Shok (we call it mink piss). I use it, so I’m a fan.

[Archived]

Don’t forget to check the large lead connections inside the gen electrical section control box for tightness.

[Doug]

I used 100% of the fuel treatment doing the test.

Still having a hard time getting my brain wrapped around debris or water in the fuel because the generator fuel pickup is set so high up that whatever is in the fuel tank is going to show up in the engine filters long before it reaches the generator filters.

Does it stop slowly or is the generator failure a sudden stop? An electrical cause of failure is usually sudden, even if it is something like a sensor.