Question about Coleman Powermate Premium Plus 6250W Portable Generator

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Generator is stalling

Our generator is stalling out after about 30 minutes. It is skipping also. I had inadvertantly run it with SAE 30 non-detergent for about 30 minutes, then turned it off and changed it to SAE 30 heavy duty.

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  • jforgette Dec 26, 2008

    I have the same problem, engine sputters out and often dies after about 20 minutes of running fine, except mine is an after-market propane conversion, so none of the gasoline fuel remedies offered seem to apply here.
    The engine is a 10hp Briggs, electric start. I'm going to check the low-oil sensor as suggested tomorrow... otherwise it could be something in the ignition/spark system? Or maybe the worn generator brushes... I'll check them all and see...


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My answer:

Not knowing your model # and how old your generator really is - as related to TOTAL RUN HOURS - I can only give you several possibilities of what the problem might be even though I don't know the make & model and what the rated WATTAGE output is.

I also don't know what LOAD you are putting on the Genset or at what RPM you are running the engine at as to half throttle or full throttle setting?? I take it that it's a Briggs & Stratton 4-stroke single cyl, or is it a Honda 4-stroke single/twin cyl engine?

Since it runs good for 30 mins, and then starts to cut out - I doubt that the OIL is a problem even though you ran straight 30 weight - seeings most small engines run 10-30 weight oil as a rule.

I seriously doubt you did any damage to the engine at all unless it was ran low on oil - in which case it should have a LOW OIL cutoff switch mounted in the lower engine case close to the CHECK OIL port.

If the LOW OIL switch is working properly and adjusted properly then you shouldn't be getting cutout unless this switch is mis-adjusted. (ie: mechanically set too low as then when the oil level is indeed at it's proper level the switch would be already shorting out to ground) (See your operators manual for proper setting)

A way to check for proper operation is to temporarily disconnect the (usually) BLACK wire from the LOW OIL switch when the engine starts to cut out. If the problem goes away completely then the LOW OIL switch is either mis-adjusted or else it is going bad from vibration. (Again see your operators manual for proper adjustment and/or check out procedure)

Electronically this LOW OIL switch should be the only thing that would protect the engine from damage should the oil level fall below recommended level. Other then that it may have an electronic REV LIMITER if it's a bigger and more expensive model, but usually not.

I doubt the Maintenance-free Magnetron® electronic ignition is at fault, but could be weak and going bad. Always a possibility, but I would 1st rule out everything else first. Since the Genset runs for 30 mins and then starts to cut out I would look more for like a fuel vapor lock (partially closed or clogged gas cap vent), a possible dirty fuel filter, possible water moisture in the gas tank or in the carb bowl, possibly dirty carb in general along with it's dirty Float Bowl, Float Pin, Float and Needle Valve, and any Adjustment Screws that go Into the Carb Body. That covers everything from a fuel standpoint.

You do know that all Gensets should be started and run for at least 10 mins every 30 days - right? If you didn't know this - now you do! Every good operators manual should state this.

It just doesn't sound like it's starving for gas unless it's building up a (vacuum) or vapor lock in the gas tank.

Having covered everything from an Electronics/electrical standpoint engine wise - there is only one other thing left Genset wise.

What it really sounds like to me (and I personally HAVE SEEN this happen myself firsthand) is that the generator brushes are nearly shot - as in almost worn out. They may be getting too too hot - as from excessive current draw at point of contact, and thus the generator sensing circuitry itself is doing an electrical CUTOUT!!

An added protective Genset circuit feature in that the generator itself may indeed be linked to the engine as a type of REV LIMITER on the Maintenance-free Magnetron® electronic ignition. Again - your operators or service manual should have a pretty good troubleshooting section in it unless you don't have that anymore or never got one if you bought it used to begin with.

It has to be one of the scenarios listed above.

Please post me a reply as to the found problem there, and the resolve to it by following my recommendations above. Also please rate my troubleshooting fix as well.

Best regards and thanks,


Posted on Sep 01, 2008

  • Frank JR
    Frank JR Sep 02, 2008

    Hi Mike,

    Thanks for the feedback on the Genset.

    Subaru engine should be pretty straight forward unless you got a bum
    engine to start, but I doubt that very much, and I hope for your sake this is not the case. 30 hours
    is nothing - depending on how it was broke in when brand new - all gas aside here. Again -
    following the owners manual, as every engine is slightly different.

    As to what you said about the gas tank, and emptying it out and then
    refilling it, etc and then the problem starting right after that -
    that's the KEY POINT right there!!

    Now I know for sure it's Carb related as to the Float, etc.

    The gas tank fuel line does have an in-line fuel filter correct? If it
    doesn't you definitely need to add one for dirt protection!!

    Depending on how you emptied the gas tank (tilting the Genset on end
    maybe?), and what was inside it after you refilled it (as I have no
    idea just how clean your gas/fuel is over there to begin with - all
    water in the gas aside), you may very well have gotten either water
    moisture or dirt in the Carb bowl, or else dirt in the Float Pin, Float and Needle Valve assy, or any Adjustment Screws that go Into the Carb Body.

    Worse case is that you misaligned the Float itself somehow inside the
    Carb Float Bowl, and now the fuel level inside is either running up too
    high or else too low and causing either a TOO RICH or else TOO LEAN a
    fuel mixture - thus causing the engine to maybe run way too HOT.
    Hopefully the engine is not trying to seize up on you!

    It's hard to say unless the Carb first is broken down, checked for
    proper Float action setting, and/or cleaned out accordingly if dirt is
    present in the bottom of the Float Bowl.

    If all looks good there Carb Bowl wise then you will next need to check the air/fuel mixture Jet Adjustment Screws.

    Let me know if you need that adjustment procedure after you first check
    everything else out I sent you previously and what I sent you here

    Keep me posted and I'll follow up as well.

    Best regards,



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This is jforgette, my neighbor's generator was almost brand new, so I didn't think the worn brushes applied. But we tried the low-oil shut off idea. He thought the oil was full enough, but I told him to fill it to beginning of threads at bottom of fill hole. It only took about 1/4 cup. But... believe it or not, THIS SOLVED THE PROBLEM of dying after 20 minutes of running.

So Frank had the solution for me... thanx!!

Posted on Jan 02, 2009


Thank you for the quick, and extremely thorough response. I failed to provide any background information as you noted. The generator is a Coleman Powermate 5000 Running Watts 6250 Maximum Watts 10 HP Subaru OHV/OHC gas engine with 5 gallon gas tank.

It only has about 30 hours on it. I got it from someone who brought it over from the Mainland (I live in Saipan near Guam). He brings generators over periodically and sells them (saves the buyer a little on shipping), as the power situation here is characterized by frequent outages. Anyway, he used this one for about 6 hours, then sold it to me and installed it.It worked fine until this past weekend. Besides the oil change, I did fill it up with gas at the same time (I poured everything out of the gas tank perhaps there was some water in it). After that is when the problem started. It skips or misfires?, then dies after about 30 minutes as I mentioned. I try restarting it but it stops after shorter periods of time, about 15-20 minutes.

Anyway Frank, I will go through your list and see if I can remedy the problem.

Again, Thank You for your prompt and very detailed response.


Posted on Sep 01, 2008

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