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Yankee_Clipper's avatar
Mar 20, 2017

Onan Marquis 7000 generator starter failure

Went to start the generator before our annual trip to spring baseball in Lakeland. I could hear the starter motor engage, but the Bendix gears were just tearing themselves apart. Okay, 20 years is adequate for a starter motor, but there's always a glitch. In this case, the starter is in the inboard side of the tray the generator is mounted on, such that one can get a hand on it, but there is no way to get to the bolts without dropping the whole assembly several inches (or as the length of cabling allows). I will see who might have to tools or jack capable of supporting the generator tray in order to unbolt the tray and lower it enough to get to the two mounting bolts of the starter and one electric input wire. I will report on how this repair goes. BTW - the trip to Lakeland was cool and windy, and we did not need the generator on this trip. Joss.
  • Hope you get it figured out....I just had major work done to my generator at Cummins Ocala.
  • Yes, please do and get pictures if you can. It will help others!
  • A year or two ago I had to replace the starter on my Onan 4KY, which also involved dropping the generator as the starter motor was completely inaccessible without removing the outer case of the generator.

    For me, at least, it was a tedious task, but fairly straightforward conceptually. Basically, disconnect the fuel line, the AC output wires (which in my case required removal of the voltage regulator and other control modules from the generator to get access to the connections), the chassis ground connection, the 12V power connection, and the wires for the remote control. After that, I supported the generator with a floor jack and took out the bolts holding it in its mounting cage, and then carefully lowered it with the jack. Reinstallation is just everything backwards.

    I would suggest measuring and, if necessary, parking on ramps or whatever to provide plenty of clearance for the generator under the skirting of your motorhome so that you can move it entirely out if needed. Add a few inches for the jack, assuming you use a floor jack or transmission jack or similar. Maybe you won't need to pull it all the way out, but it is good to have that option if needed without undoing half your work should it become necessary.

    I'd also suggest getting the fuel level in your tank below the point of the generator pickup so there's no chance of siphoning many gallons of fuel out of the tank when you disconnect the feed line. I plugged the end of the line with a stopper (a cork, in my case), but it was still good to know I wouldn't have a major spill regardless.
  • At this point I have acquired a replacement motor. I found one on Amazon for $31, and although I was looking for a Bendix without a plastic spiral gear, there were none that I could find (even the Cummings replacement for $124).
    I have a friend who has more tools than I do (unusual) including a transmission jack. We plan on giving this project a whirl this weekend, subject to change without notice!! Think kind thoughts for this one...tip of the hat to DrewE!
  • Finally was able to get the starter changed out. Fortune smiled on me, and a friend who is a general manager of a cotton gin allowed me to use their maintenance pit facility. This facility allowed me to stand and view the generator try from below. On my configuration, there are two access portals in the tray holding the genny, and I was able to use a flexible ratcheting wrench to reach the bottom retaining bolt and battery connector. From the top, over the back of the genny I was able to reach the top retaining bolt.
    Caution: the flywheel housing is not threaded, there are hex bolts holding the starter to the housing, and gravity is not on your side. The magnetic pick-up got used a couple of times, but no parts were lost.
    Hint: un-torque the battery connecting nut first, as that sucker was torqued on and after I had loosened the retaining bolts the started wanted to wobble while I was trying to get that nut off. Those access ports are not very big, and my hands left me very little room to wrestle with the starter!
    Good news: the genny fired up on the first try and is running normally.
    The whole process took me about 1 1/2 hours. Total out of pocket was the replacement starter for $31 on eBay.
  • The next time take your starter to a lawn mower shop. Some Briggs & Stratton engines use the same starter gear, only it's steel.

    Richard