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Author Topic: Onan generator turns over slowly  (Read 967 times)


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Onan generator turns over slowly
« on: October 18, 2017, 11:56:17 AM »
Hi all. My 04 Onan 4000 barely cranks over, often too slowly to start. But when I jump it with a battery pack (bypassing the starter solenoid, it turns over much faster and starts no problem. I have cleaned the solenoid contacts and the battery connections. The voltage at the generator is virtually the same as the main voltage (13.5/13.6).

Any suggestions?


« Last Edit: October 18, 2017, 12:03:07 PM by Sun2Retire »


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Re: Onan generator turns over slowly
« Reply #1 on: October 18, 2017, 03:53:23 PM »
The fact that you can jump it and its fine tells the whole story,, your battery is not up to the job or the connections are suspect (each end).>>>Dan (A voltage reading does not tell the whole story,, it only shows surface charge.. You need a load test)
« Last Edit: October 18, 2017, 03:55:21 PM by utahclaimjumper »
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Re: Onan generator turns over slowly
« Reply #2 on: October 18, 2017, 06:24:30 PM »
Yeah, those voltage readings you posted indicate that the batteries were being charged when you took the readings. Since the generator turns over as it should when its being jumped, I also suspect a weak battery. A fully charged 12 volt battery will indicate 12.6 to 12.7 volts after it's been disconnected from a charger, and has sat for an hour (or so) with no loads on it.

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Re: Onan generator turns over slowly
« Reply #3 on: October 20, 2017, 04:40:11 AM »
When you say that you are "bypassing" the solenoid, if you are placing the positive cable to the (+) side of the solenoid, you are not really bypassing it.  If you are placing the positive cable from the power pack to the large solenoid post nearest you (+), then all you are doing is applying dc power that would have been applied by the house battery if it was working properly.  The solenoid has two large posts. One of those posts is for the positive battery cable that comes in from the house battery. The other large post goes to the starter. In order to "bypass" the solenoid you have to directly tie the two large posts. In the old days, we would have used a screwdriver blade to bridge the two posts, enabling 12 dc current to flow, sending current to the starter.  If you hear the solenoid clicking, you know most likely it is working, however, there is also the possibility that it could also click if the coil inside is unable to make full contact to connect the two large posts sending power across. You can touch it with your hand while you crank the generator and you can feel it clicking. The clicking sound made by the solenoid generally indicates insufficient 12 vdc power. I agree with others that it is mostly likely the house battery, if that is what powers the generator, but you also not discount the negative and positive cables.