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pirlbeck's avatar
pirlbeck
Explorer
Nov 18, 2016

Onan 2500 KVD problems

New to me 2009 Lance 845 with an Onan RV QG 2500LP generator with 40 hours total run time starts very hard and runs rough. It also appears to have an engine oil leak. When we looked at this unit the owner said that he did not remember when the generator was last run, but after a lot of cranking he was able to get it to fire and keep running. I did notice at that time that it was not running smooth, but I thought it may improve with some run time. After I got the camper home I tried to get the generator running and while it finally fired after a lot of cranking, it would not stay running when the start switch was released. It acted the same when trying to start it from the remote panel and from the control panel on the generator itself.

Last night I pulled the generator out of the camper and tonight I hooked propane and a battery to it and fired it up. It started pretty quick and it kept running after the start switch was released. I am not sure what changed that it will now keep running.

I do now know that the rough running is being caused by too rich of fuel mixture because it will smooth out and run very smooth if I close the fuel tank valve until it is almost closed. The air filter looks like new and running it with no air filter makes no difference. I have it hooked up to a tank with a brand new regulator that I tested the pressure on with a manometer and while it is a little high at 13WC, it runs the very same as it did with the camper tanks and regulator. If this was a gas powered unit I would be looking for either a carb adjustment or a carb problem, but with propane I don't know. Anyone have any thoughts on this?

Also there is an oil leak somewhere on the bottom side of the engine.....any common areas to leak on these?

If it matters the Model number is 2.5KVD2089B Spec-B and the sn is D090241978

Sorry about the length of this.

Thanks!

17 Replies

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  • pirlbeck's avatar
    pirlbeck
    Explorer
    Nov 19, 2016
    I pulled the demand regulator this morning and took it apart and everything looks like new in it. The needle valve seems to seal fine and the diaphragm is very flexible and it is not damaged in any way. I put it back together and reinstalled it and the engine runs exactly the same......way too rich.

    Next, I pulled the carb/mixer off and used carb cleaner and a blow gun on any open passageways and orifices. Not really anything that comes apart, so I could not do much other then that. I also checked/adjusted the valve lash.......and it still runs the same. Turn the tank valve almost off and it smooths right out. Also tried a regulator I could take a cap off and adjust the pressure. I adjusted it down to 10"WC (static) and still the same thing.

    Looking like I am just going to start throwing parts/money at it. Searching online, it looks like a new carb/mixer is going to run $450.00 or more. A demand regulator would be $150.00-200.00. I can't see where there is anything wrong with the demand regulator, but you never know and it is cheaper, so maybe start there.

    I hate just throwing parts at something and hoping it fixes it......but I don't know what else to try. Maybe on Monday I can get ahold of someone from Onan/Cummins and see if there are any TSB's or known problems that would cause this.

    Anyone here that could give me some guidance or know of someone I could talk to?

    Thanks!
  • pirlbeck's avatar
    pirlbeck
    Explorer
    Nov 19, 2016
    OK I got the manometer tee'd in to do some more checks.

    Static pressure with tank valve on and engine off it is close to 16"WC. Seems hi to me, but this is a regulator I am using just for testing. I will check pressure of the camper system when I re-install the generator.

    Engine running with tank valve all the way open it is down to 8"WC, which seems low but that may be due to how rich the engine is running so it is drawing a lot more fuel then normal.

    When I start shutting down the tank valve it starts to really smooth out close to 0"WC and it actually runs the best a negative 1/2" WC. Am I correct in thinking it must be the demand regulator? I am not sure how this system works, as I have never messed with LP fuel systems, but everyone in the trade refers to what I would normally call the carb as the "mixer", so I take that to mean it does not meter the fuel at all, it just mixes it. That leaves the demand regulator to determine fuel mixture or "demand"

    I would really like to find a supplier for this part besides Onan as typically there parts are overpriced in my opinion.

    Thanks!
  • pirlbeck's avatar
    pirlbeck
    Explorer
    Nov 19, 2016
    marcsbigfoot20b27 wrote:
    I have a 2500 LP Onan also (Year 2000, maybe spec K?). 6 months ago it was hard to start, was surging badly at no load and had trouble managing a sudden load.

    Found by spraying carb clean on the air filter that it was running lean.....idle would smooth right out.

    Ended up yanking the demand regulator, getting a rebuild kit on Amazon for ~$60 and using only the diaphragm.

    Now it idles normal and runs perfect under load or not.


    Would you have a part number of the kit you bought? How were you able to determine that it was the correct kit for your generator?

    Thanks!
  • marcsbigfoot20b's avatar
    marcsbigfoot20b
    Explorer
    Nov 18, 2016
    I have a 2500 LP Onan also (Year 2000, maybe spec K?). 6 months ago it was hard to start, was surging badly at no load and had trouble managing a sudden load.

    Found by spraying carb clean on the air filter that it was running lean.....idle would smooth right out.

    Ended up yanking the demand regulator, getting a rebuild kit on Amazon for ~$60 and using only the diaphragm.

    Now it idles normal and runs perfect under load or not.
  • Bill_T's avatar
    Bill_T
    Explorer
    Nov 18, 2016
    I've had two starting/running problems with my Onan, vintage 2011. First was the oil level switch. With a full oil sump the gen. was running rough and was hard to start, then failed to run. Long story cut short, disconnected the oil level switch, gen. starts very quick and runs as smooth as new. Second problem, gen. would crank but not start. With the front access panel removed, the carb is in front of you, there was a small spring on top of the carb that was disconnected, hooked up spring and she fired right up.

    Possible oil leak could be the oil level switch. It screws into the sump. Location is to the right of the oil fill tube. On mine the wire to the switch is tie-wrapped to the oil fill tube. When the switch senses loss of oil level its contacts close grounding the circuit.

    Maybe this will help.
  • pirlbeck's avatar
    pirlbeck
    Explorer
    Nov 18, 2016
    Yes, I have the factory service and parts manuals for this unit. I have read about the problems with the demand regulator vent hose plugging by searching on this site, and this generator is new enough that it has the foam filter on the end of the vent hose. Because it has the filter, I did not check the hose for an obstruction.

    The parts that I think are most likely to cause this sort of problem are the demand regulator mounted on the unit and the carb, but the service manual says these two items rarely cause trouble. Here is what the service manual says about these two components.

    Demand Regulator
    The demand regulator assembly supplies fuel to the
    carburetor. It is usually not the cause of fuel system
    problems. All other possible causes should be
    checked out before adjusting or replacing the demand
    regulator assembly. Figure 8-24 illustrates
    the regulator with priming solenoid used prior to
    Spec L on Model KV or Spec B on Model KVD. The
    demand regulator on later models does not have a
    priming solenoid.

    LPG Carburetor (Begin Spec E, Model KV
    and Spec A, Model KVD)
    See Figure 8-27. An LPG carburetor is not likely to
    cause problems and should be replaced only after
    all other causes have been eliminated (see Section
    6. Troubleshooting). It is not necessary to adjust fuel
    mixture. These carburetors are calibrated at the factory
    and the adjustments are sealed.

    The LP pressure reading I mentioned was a static reading as I did not have the correct fittings to tee it in so I could check pressure while the generator was running, I plan on getting the correct fittings to tee it in today and then I can see at what pressure the engine smooths out when I turn the tank valve towards shut off.

    Thanks!
  • j-d's avatar
    j-d
    Explorer II
    Nov 18, 2016
    Welcome to the Forum!

    You've done well describing symptoms and what you've done so far.

    AND, Most Importantly, Model and Spec! We had a lot of generator experts for awhile, but our members were vague in their descriptions and lacking in that Model/Spec info, to where many of those experts bailed.

    Do you have the Service Manual for this generator? We can probably help with at least that, then you can at least follow their troubleshooting flowchart.

    I do know that mud daubers and spiders love LPG. Look for webs, mud, and nests, especially around the regulator and carburetor areas.

    It's a long shot, but there might have been an insect obstruction and you broke it loose pulling the generator. I'd hate to see you heave it all back in only to find there was still a problem.

    If it's rich, and LPG pressure is a little high, sounds to me, NON Expert, that regulator setting could be an issue too.

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