1979 Onan 6.3 KW Genset


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saintanne

New Member
Ok, so I'm a little confused about this.

Bought a 1979 GMC TIOGA motorhome two months ago with a NON working Onan genset (6.3KWatt). The previous owner relayed the following story:

Apparently, the generator worked fine until one time when it shut down mysteriously. He said he tried starting it back up but without luck. He also said that he was burning out fuses trying to restart it (didn't say whether he just laid on the start button for 10 minutes, or not). Later, he realized that he had simply run out of fuel. After refueling, though, the generator wouldn't even turn over. His assumption on selling it to me is that he had burned out the starter.

Fast-forward two months. I pulled the generator out of the motorhome and hooked the battery lead coming from the generator directly to my charger/200 amp starter. This generator has two start switches: one on the genset itself, and the other in the cab up front. Neither of the switches, when activated, caused the generator to do anything. Then, to check the starter itself, I touched off on the positive terminal of the starter. It turned over beautifully.

Ok, so at the moment, I understand this is NOT a starter issue. What should I check next? Is it possible that the electronic fuel pump burned out and that the genset wont even turn over if the fuel pump doesn’t work? I’ve never owned one of these before, so I’m at a loss! Any help out there?

Thanks a million! SA
 
C Nash

C Nash

Senior Member
Re: 1979 Onan 6.3 KW Genset

First off be sure you have over a 1/4 tank of fuel in the Tioga. Quick ck is just remove the inlet fuel supply line to the gen and turn over to see if any fuel is being pumped, Be sure and catch the fuel and don't let it spray on anything that would set it on fire. If the pump is not working see if you have voltage to it. Could be wiring/ fuse or switch problems. Is the filter ok? Carb might be sludged up. Good luck
 
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LEN

Senior Member
Re: 1979 Onan 6.3 KW Genset

Under the switch start switch on the gen there is a controller board, bet that's the trouble. And I don't have clue as to how to test it. Maybe just getting a look can tell if it's burnt. Once you get the start circuit going it go's back to spark, compression, fuel. While apart I would put in a new set of points and plugs and maybe even the coil if it's hard to get to.

LEN
 
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saintanne

New Member
Re: 1979 Onan 6.3 KW Genset

Thanks for the pointers. I did pull the cover off the control board, but electronics isn't my strong point. I will look again and inspect carefully for any burnt resistors, capacitors, and any other "ors" that I might find.

Points and plugs are on my mind as well, because they are a pain to get to. Forst, I want to make sure I can get the thing to at least turn over...

Does anyone out there know if there as an automatic shutoff feature on this thing that I'm overlooking? I want to know what the possible fault sources are before I dig around too deeply!

Thanks again!
 
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LEN

Senior Member
Re: 1979 Onan 6.3 KW Genset

From your first note you did get the motor to turn over so the starter works. Pull the spark plug wires and turn the motor over and see if you have spark. If no then you have to find the problem, wire, points, condencer, or coil or still the board. If spark then squirt a little gas into the carb and turn over the motor if you get a short start then run down gas lines, pump, filter for problem. Pull the wires from the board and reseat. Check the start switches to see if contact is made.

LEN
 
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saintanne

New Member
Re: 1979 Onan 6.3 KW Genset

Ok, finally an update....

I pulled and replaced the plugs. The old ones looked fine, but I replaced them anyway. Wires look great, though I know looks can be deceiving.

As I looked things over more carefully, it seems that the 5A slow-blow glass fuse, found on the face of the Genset near the starter button, was blown. I went to the hardware store and bought three of them. Threw one in, hit the start button, and again blew the fuse. The starter actually did make an attempt at turning before the fuse blew.

Once again, I touched off my 200 amp starter/charger directly to the starter hot lead and it turned over....

Is this a case of a bad starter solenoid or something? I am blowing fuses on the genset, but my charger/starter is able to turn the engine over.... Perhaps the genset is a bit more sensitive to resistance than my charger? I pulled the faceplate of the genset off again and looked things over carefully. Checked for continuity in the start switch (all seemed ok). Looked for any "stray" wires that might inadvertently be shorting out.... Nothing. Should I be thinking new starter switch?

Any thoughts?
 
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saintanne

New Member
Re: 1979 Onan 6.3 KW Genset

Pulled the starter relay switch. Not exactly sure how to test it, but it has only one spade connector for control. I assume that if I touch this off to 12V, I should hear it click?? Is that right? If I touch off to 12 V, will I fry it?

Thanks!
 
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saintanne

New Member
Re: 1979 Onan 6.3 KW Genset

Hope these postings help SOMEONE out there....

Starter relay works fine. It did, indeed, click when I toughed off the 12 volt supply. I also tested for continuity between the battery input and output when relay was activated. All good. In pulling everything apart, I noticed that one very important connection was badly corroded. The line that powers the genset motherboard was nearly rusted off! I cut it fresh and re-attached with electrical grease. Re-greased/sanded all other connectors and grounds.

I put a 30A fuse into the fuse holder just for kicks. Now, when I hit the start switch, one component of the motherboard smokes. Might have fried it, I don't know, though it still seems to work. The starter does not turn over, but the starter relay kicks on as it should. I think I'm left with two possibilities (or both). 1) Starter and/or starter solenoid, 2) Motherboard component(s).

How does one check a starter beyond what I've already done?

SA
 
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LEN

Senior Member
Re: 1979 Onan 6.3 KW Genset

Ok remove the plugs and try the start switch again, if it rolls over then most likely the starter is dragging or the ground or hot side wires are corroded but will pass a light load. If it doe not roll over try jumping from one side of the solenoid to the other with jumper cables(do this in one quick motion so there will be little arcing), if the motor/starter rolls over solenoid is bad, if it doesn't starter or battery is bad or plus or minus battery leads. If you have another battery jump the starter form it not going through the solenoid(this should test the starter itself). If the board is smokin I would say it is done.
 
TexasClodhopper

TexasClodhopper

Senior Member
Re: 1979 Onan 6.3 KW Genset

Oh no, Mike! You've gone and done it now. You've let the smoke out of something electronic and now you are going to have to go get some more smoke to put back in there. I don't know what you were thinkin', but it sure wasn't the right thing to do. Don't you know there is a smoke shortage? Haven't you been reading the papers about the overuse of smoke all around the country. Now you've gone and let out some perfectly good smoke.

What are we gonna do with these RV newbies? Good grief! :clown:
 
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Guest

Guest
Re: 1979 Onan 6.3 KW Genset

well tex ,, we can always got to cali ,, when the big brushfires hit ,, and get all the smoke we need ,, btw i don;t mean any harm to all of those that have to go thur that every yr ,, by no means :approve:
 
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saintanne

New Member
Re: 1979 Onan 6.3 KW Genset

Oh, c'mon now. You don't think I'm THAT stupid. I bottled the smoke as it came out. Thinkin' I might just sell some of it.... Any interest?

For the moment, I'm pulling the generator completely and in its place, installing three deep cycle batteries in parallel and an inverter. Ought to be able to last a while on that, anyway. Until I get the genset running, I'll be without AC when off shore-power, though. Enough to run a microwave and battery powered lights for a while, I would think.

Thanks for the input. I haven't given up on this yet. Summer's here, and it's time to camp! I'll take it up again in a couple weeks.


SA
 
G

Guest

Guest
Re: 1979 Onan 6.3 KW Genset

well Mike ,, u will fit in very well around here ,, since u had a good come back to a answer ,, that is what we do ,, kid around ,, and do the best we can at ansewering questions ,,, but we do get a little goofy now and then ,, but since u have the sense of humor (as proved) then u'll do ok ,,, agian welcome
:approve: :approve: :approve: :) :)
 
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