Onan Marquis 7000 Generator Starter Revs But No Action

Are you priming before trying to start?
The start switch is a rocker type. Press the bottom and hold in for 15-20 seconds, then try starting.
Be sure there is over 1/4 tank of gas in the RV or it will not start. It is a safety feature that will not let the genny drain all the gas.

brisath wrote:
Using the starter switch on the generator, the starter revs very high but no attempt to turnover or start.

Are you saying the starter runs but does not engage the engine?

Your starter probably looks something like this



And if so it has a cheap plastic drive on it. From your words, it sounds like you are hearing only the starter spinning up. Correct? NOT the sound of the whole generator being cranked but not starting. Correct?

If I'm right in my understanding you have a good starter with a bad drive. But, on some of these ONANs, if you can jog the flywheel a little, a blocked or stuck drive may release and operate again.

That pic is from Amazon. I'm not sure the pic represents your starter. Somebody here can help you get to a service manual and a parts list. That said, the starters for several ONAN models seem to run between $35 and $55 on Amazon. If your generator design and installation allow changing the starter with the genset still in the coach, I'd replace starter with new.

That's if I understand your symptoms.

Thanks for the helpful replies. Gas tank near full, and the switch doesn't toggle to prime from what I can tell. J-D's suggestion seems to be the case, as it is spinning wildly (by the sound of it) and nothing seems to engage. I think I've found the starter on the back side of the generator where it is too hard to take off without dropping or maybe swinging(?) the generator down so I'll try that in the morning and take the starter off to look at the gears. We seem to have found a rebuild assembly from the Onan dealer for $50.

Those gear drives have a roll pin in it and kind of hard to take out and put in. Turn your flywheel by hand and see how hard it is to turn if its to hard to turn the gear drive just slips its a trait of that starter I have the same gen. It has no prime.
Bgm and nhm service manual

I got the starter off today and gears are all stripped off. It was a bit difficult to take off. I took out the first 3 of 4 bolts on each side of the tray and swung the generator down so I could get in behind it more easily. Unscrewed both bolts on the starter but it still wouldn't budge. After a lot of hammering and prying with a flathead screwdriver (which resulted in breaking of one of the bolt flanges) nothing was happening. Some WD-40 and wedging a wrench between the engine bock and starter allowed me to pry it to the side and it popped off finally. Because of the broken part on the starter housing, I'm going to replace the whole starter which is $157 from the Onan dealer. I'll try putting that in tomorrow and see what happens.

What is the best way to see if the engine flywheel is turning properly? I don't see a way to access it to turn it by hand so I can make sure the starter won't break again. Thanks for all of the help so far in helping me find that problem.

The top part of the housing may have to come off I can't remember. Or the wire mesh from the bottom by the muffler. If its to hard to turn the valves may need setting so the top has to come off anyway. If its real hard to turn pull both spark plugs out and the turn it to see how hard it is if its easy to turn with the plugs out you will have to set the valves to spec. I took my gen out its to hard to work on in the trailer.

Installed a new starter and it's not moving the flywheel. There is just a lower sounding buzz noise with not engine engagement. I tried it with the engine running too. I was able to reach my fingers into where the starter goes in and move the flywheel. It turns but it is not exactly easy to turn. I'm unclear on what you are suggesting Kpack. Any recommendations from here?

There are two tiers to the housing just take the top one off and make some full revolutions of the flywheel. Also with a multimeter check your volts when you engage the starter you could have a dirty connection on the start soileniod or battery. Check all your connections from the battery all the way to the starter when you push your start switch.

Thanks. I'll check that. Is there any trick to the grounding. The manual shows a tray bolt as a ground but I don't see any wires that look like a ground to a tray bolt.