Hi, The starter on my Generator will crank and spin the engine freely with the plugs out. When I install the plugs it has good compression but will only spin the motor a 1/2 revolution or so then stop. It sounds like the starter cannot overcome the engines compression. If I repeatedly bump the starter the engine will hiss a bit as compression releases and then turn about another 1/3 revolution and stop the same way again. I have replaced the starter, starter solenoid, and the battery. As a test, I have connected good 12v (with good amperage) to both the starter terminal right on the starter and also to the starter terminal side of the starter solenoid (hard to get to). Both of these tests resulted in no change at all. Is there supposed to be a compression release of some sort on these engines? Cant figure this out. ANY help is appreciated and thanks very much.

What made it quit in the beginning? Did it stop while running?

How good is your "good" 12V source? The starter likely needs more than 100A to turn over at first. Maybe the ground between the starter and the generator or the generator and the motorhome is not sufficiently good?I had somewhat similar symptoms for my generator (an Onan 4KY), and it turned out to be the starter motor (and replacing it cured the problem). The actual fault with the motor was one of the four brushes was disconnected, making it run at half power, which was barely enough to get my generator to turn over most of the time. Eventually I burned out a winding or two on the rotor of the motor when it was a wee bit harder starting due to cold weather, and so had to replace the starter. On the 4KY, mucking with the starter motor requires dropping the generator for access, so it's a good bit of labor for an otherwise straightforward repair.

Kcharles.. It did not. Just like an Ebay Auction.. It was running fine when it last ran.. but I let it sit a long time without starting it. It does not seem like a seize. It is a "spongey" compression like resistance that it cannot push past on it's own.

Drew..My 12v source is a 12v battery charger/booster that I have tested up to 200 amps setting. all connections on positive side have been cleaned. bad ground is something I haven't explored. Good idea. I can possibly use jumper cables from starter mounting flange to the battery negative. Will do that now. I did actually replace the starter motor with new. I really have the same issue I had prior. Interestingly there were FOUR of the plastic "bendix" type drives inside the starter mounting hole that had been bouncing around in there for a while. Apparently previous owners had starter issues as well. It really was starting and running well prior to this last time I let it sit too long.

Does it crank over with one plug out? If yes, which one?

Onan Marquee Generator wont crank with plugs installed?

Class_A_DP_1
Explorer
Feb 27, 2016
Drew..

My 12v source is a 12v battery charger/booster that I have tested up to 200 amps setting. all connections on positive side have been cleaned. bad ground is something I haven't explored. Good idea. I can possibly use jumper cables from starter mounting flange to the battery negative. Will do that now.

I did actually replace the starter motor with new. I really have the same issue I had prior. Interestingly there were FOUR of the plastic "bendix" type drives inside the starter mounting hole that had been bouncing around in there for a while. Apparently previous owners had starter issues as well. It really was starting and running well prior to this last time I let it sit too long.
Class_A_DP_1
Explorer
Feb 27, 2016
Kcharles..

It did not. Just like an Ebay Auction.. It was running fine when it last ran.. but I let it sit a long time without starting it.

It does not seem like a seize. It is a "spongey" compression like resistance that it cannot push past on it's own.
DrewE
Explorer II
Feb 27, 2016
How good is your "good" 12V source? The starter likely needs more than 100A to turn over at first. Maybe the ground between the starter and the generator or the generator and the motorhome is not sufficiently good?

I had somewhat similar symptoms for my generator (an Onan 4KY), and it turned out to be the starter motor (and replacing it cured the problem). The actual fault with the motor was one of the four brushes was disconnected, making it run at half power, which was barely enough to get my generator to turn over most of the time. Eventually I burned out a winding or two on the rotor of the motor when it was a wee bit harder starting due to cold weather, and so had to replace the starter. On the 4KY, mucking with the starter motor requires dropping the generator for access, so it's a good bit of labor for an otherwise straightforward repair.
K_Charles
Explorer
Feb 27, 2016
What made it quit in the beginning? Did it stop while running?

Forum Discussion

Onan Marquee Generator wont crank with plugs installed?

About Motorhome Group

Related Content

HELP with Honda Generator install.

Generator ready - how much for 5.5 installed?

generator

Generator

Generator