Home » Public Forums » GMCnet » Onan issues (Onan)
| Onan issues [message #307986] |
Wed, 28 September 2016 21:28  |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
Karma: 0
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I've been working on the Onan on the GMC I bought in August. I've replaced the air filter, spark plugs, changed the oil and oil filter, and checked the fuel filter. I can get it to turn over from outside or inside but she never even gets close to catching. I sort of feel like it's not getting any fuel. I put a jumper from 5 to 9 on the control board and I get nothing. I should be hearing a fuel pump correct? Also, there is one wire on top that doesn't seem to go anywhere (see pic). Where should this be?
As you can see from the board picture, in trying to remove the connections I pulled several of the male connnectors too (like #3) Don't know if this board can be saved.
-James Palmer, Traverse City, MI
1976 Eleganza
[Updated on: Wed, 28 September 2016 21:29] Report message to a moderator |
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| Re: Onan issues [message #307989 is a reply to message #307986] |
Wed, 28 September 2016 21:42  |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I just checked the spare Onan I have in my garage and that wire is not connected to anything on it either. The fuel pump should make some noise when you jumper 9 - 5. If it doesn't, it is probably gummed up and inoperable. It is a simple device and can be disassembled and cleaned up easily. Try spraying some starting fluid in the intake. If the engine starts, you can rule out an ignition problem.
If it hasn't been run in forever, the carburetor likely needs to be gone through. If you're careful, you may be able to reuse the gaskets. Make sure the gasket between the carb and the intake has not shrunk up to where there is a big vacuum leak.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Onan issues [message #307990 is a reply to message #307989] |
Wed, 28 September 2016 21:50 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
Karma: 0
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That's good to know about the wire on top. Sort of strange. I have been planning on opening the carb but the fact that I'm not hearing anything at all when jumped made me stop and wonder if it needed a new fuel pump. I already removed the filter and cleaned it. What more can be done on it?
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: Onan issues [message #307993 is a reply to message #307986] |
Wed, 28 September 2016 23:03 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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Palmerdad wrote on Wed, 28 September 2016 21:28I've been working on the Onan on the GMC I bought in August. I've replaced the air filter, spark plugs, changed the oil and oil filter, and checked the fuel filter. I can get it to turn over from outside or inside but she never even gets close to catching. I sort of feel like it's not getting any fuel. I put a jumper from 5 to 9 on the control board and I get nothing. I should be hearing a fuel pump correct? Also, there is one wire on top that doesn't seem to go anywhere (see pic). Where should this be?
http://www.gmcmhphotos.com/photos/data/10/medium/wire.jpg
http://www.gmcmhphotos.com/photos/data/10/medium/board.jpg
As you can see from the board picture, in trying to remove the connections I pulled several of the male connnectors too (like #3) Don't know if this board can be saved. That spare wire might have gone to the fuel shut off solenoid removed by a PO. Don't worry about it, it was only there for installations where the fuel tank is higher than the carb. Not needed for the GMC, like your appendix, it can only cause trouble.
Buy some starting fluid. Remove the air filter. Jumper pin 5 to pin 9. Push the start button, and while the starter is turning the engine, spritz some starting fluid into the carb air filter inlet. When it sputters, let go of the starter button and remove the jumper. Then fix your fuel pump.
Remove the fuel pump. Take it apart. Be very careful not to break the check valve keeper (hard lesson one) or you will have to make a new one. See below.
Turn the pump upside down and pour the acetone in it. Let it soak. Mine took a week to dissolve the shellac that had the piston glued to the cylinder. YMMV. Keep the the cover gasket away from the pump while it is soaking, the acetone will ruin the gasket (hard lesson two). When the piston loosens up, remove it and clean the cylinder and the piston. Put the fuel pump back together and install it. Jumper pin 5 to pin 9 and listen to the tick tick tick of the pump. If the carb needle valve is stuck open, gas will drip or run out of the carb air filter inlet. If not, the pump will slow down and stop after it gets primed and fills the carb bowl.
When the fuel pump stops ticking, or at least slows down a lot, try to start the Onan.
When it runs, use a meter to make sure it is putting out 120V and then see if it will run the roof AC.
As far as the broken tabs on the board, you need to talk to Johnny Bridges.
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| Re: Onan issues [message #308005 is a reply to message #307986] |
Thu, 29 September 2016 09:32 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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The board can be healed. It won't look pretty, but it will run the engine. If you have soldering skills, take a male connector the same size (Either 3/16 or 1/4, I forget which), peel the insulation off the crimp section, split it and clamp it across the hole in the board and solder it to the trace. You may have to heal the trace with a piece of shaped bare wire soldered to it. Thereafter, hold the tab with pliers while plugging the connector on, it will not be as robust as the original.
The option is to remove the tabs and connectors, and solder the pigtail wires directly to the board.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Onan issues [message #308006 is a reply to message #307993] |
Thu, 29 September 2016 10:05 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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Is it my imagination or is the glass fuse on the board blown in that photo?
Sully
77 eleganza 2
Seattle
On Wednesday, September 28, 2016, A. wrote:
> Palmerdad wrote on Wed, 28 September 2016 21:28
>> I've been working on the Onan on the GMC I bought in August. I've
> replaced the air filter, spark plugs, changed the oil and oil filter, and
>> checked the fuel filter. I can get it to turn over from outside or
> inside but she never even gets close to catching. I sort of feel like it's
> not
>> getting any fuel. I put a jumper from 5 to 9 on the control board and I
> get nothing. I should be hearing a fuel pump correct? Also, there is one
>> wire on top that doesn't seem to go anywhere (see pic). Where should
> this be?
>>
>> http://www.gmcmhphotos.com/photos/data/10/medium/wire.jpg
>>
>> http://www.gmcmhphotos.com/photos/data/10/medium/board.jpg
>>
>> As you can see from the board picture, in trying to remove the
> connections I pulled several of the male connnectors too (like #3) Don't
> know if
>> this board can be saved.
> That spare wire might have gone to the fuel shut off solenoid removed by a
> PO. Don't worry about it, it was only there for installations where the
> fuel tank is higher than the carb. Not needed for the GMC, like your
> appendix, it can only cause trouble.
>
> Buy some starting fluid. Remove the air filter. Jumper pin 5 to pin 9.
> Push the start button, and while the starter is turning the engine, spritz
> some
> starting fluid into the carb air filter inlet. When it sputters, let go of
> the starter button and remove the jumper. Then fix your fuel pump.
>
> Remove the fuel pump. Take it apart. Be very careful not to break the
> check valve keeper (hard lesson one) or you will have to make a new one. See
> below.
>
> Turn the pump upside down and pour the acetone in it. Let it soak. Mine
> took a week to dissolve the shellac that had the piston glued to the
> cylinder.
> YMMV. Keep the the cover gasket away from the pump while it is soaking,
> the acetone will ruin the gasket (hard lesson two). When the piston loosens
> up, remove it and clean the cylinder and the piston. Put the fuel pump
> back together and install it. Jumper pin 5 to pin 9 and listen to the tick
> tick
> tick of the pump. If the carb needle valve is stuck open, gas will drip or
> run out of the carb air filter inlet. If not, the pump will slow down and
> stop after it gets primed and fills the carb bowl.
>
> When the fuel pump stops ticking, or at least slows down a lot, try to
> start the Onan.
>
> When it runs, use a meter to make sure it is putting out 120V and then see
> if it will run the roof AC.
>
> As far as the broken tabs on the board, you need to talk to Johnny Bridges.
>
> http://www.gmcmhphotos.com/photos/data/6363/medium/image35.jpeg
> --
> 73 23' Sequoia 4 Sale
> 73 23' CanyonLands Parts Unit 4 Sale
> Upper Alabama
> "Highest price does not guarantee highest quality."
>
> _______________________________________________
> GMCnet mailing list
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: Onan issues [message #308013 is a reply to message #307986] |
Thu, 29 September 2016 14:00 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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It may or may not be. Some low current fuses have the fusible wire supported between two larger wires with solder cups on the ends. You hafta hold the fuse up to light to see if the fusible wire is open. Also, normally when the fuse goes on Onans, it's due to a short someplace, which usually leaves a discolored place on the envelope. I'd pop an end up and lay my trusty ohmmeter across it.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Onan issues [message #308042 is a reply to message #307986] |
Fri, 30 September 2016 07:09 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
Karma: 0
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Member |
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Thanks everyone. You've given me some more things to check. Now I just need too find some time! I checked and the fuse is good, I think you may be seeing the light reflecting off the glass in the picture. Thanks again!
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: Onan issues [message #308099 is a reply to message #307986] |
Sat, 01 October 2016 16:45 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
Karma: 0
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Update. Got the fuel pump cleaned out and this time when I jumped 5 and 9 I could hear it ticking! The ticking slowed and stopped so I tried to start it and it came to life for a split second with a puff of black smoke before going back out. I jumped 5 and 9 again, this time the ticking never stopped and it started coming out of the air filter inlet. Tried to start it again but to no avail. I pulled the carb bowl and emptied it. This time I didn't jump 5 and 9 but just started it like normal. Again it seemed to come to life but as soon as I let go of the start switch it choked back out. Subsequent tries led to the same pattern. Start, engine starts for a second and dies, drain the carb bowl. Start, engine starts for a second and dies, drain the carb bowl.
Feels like I'm close but obviously not quite there yet! What should I try next?
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: Onan issues [message #308103 is a reply to message #307986] |
Sat, 01 October 2016 17:25 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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You have 2 issues
1). Carb float gummed and needle not seating
2) no power to ignition/ fuel pump from a non jumped board. The start position is overriding the safety shut down but does not when you release. It is doing what it is supposed to, but you need to find the fault. Look to low oil level or bad oil switch or bad connection to it.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Onan issues [message #308104 is a reply to message #308099] |
Sat, 01 October 2016 17:33 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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If there is an inline fuel solenoid before the pump it could be sticking. Tap it with a wrench..
C. Boyd
76 Crestmont
East Tennessee
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| Re: Onan issues [message #308107 is a reply to message #308099] |
Sat, 01 October 2016 18:01 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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Palmerdad wrote on Sat, 01 October 2016 16:45Update. Got the fuel pump cleaned out and this time when I jumped 5 and 9 I could hear it ticking! The ticking slowed and stopped so I tried to start it and it came to life for a split second with a puff of black smoke before going back out. I jumped 5 and 9 again, this time the ticking never stopped and it started coming out of the air filter inlet. Tried to start it again but to no avail. I pulled the carb bowl and emptied it. This time I didn't jump 5 and 9 but just started it like normal. Again it seemed to come to life but as soon as I let go of the start switch it choked back out. Subsequent tries led to the same pattern. Start, engine starts for a second and dies, drain the carb bowl. Start, engine starts for a second and dies, drain the carb bowl.
Feels like I'm close but obviously not quite there yet! What should I try next? Gas coming out of the filter inlet means the float is stuck. I told you it might do that. You should have wiggled the float up and down while you had the carb bowl off to free it up. If it persists in pushing gas out the air filter inlet, you will have to clean/refurb the carb. No big surprise if it has been sitting long enough to gum up the fuel pump. It didn't start until you emptied the float bowl because it was flooded. After that, the start was mostly right, and when you tried it without pin 9 jumped to pin 5...
You need to hold the start switch a little longer after it fires off. It needs to get to speed before the flywheel alternator puts out enough voltage to tell pin 8 that it is running. Without enough voltage to pin 8, it thinks the engine is not turning and turns off the fuel pump and ignition.
Some people believe that the Voltage Regulator going bad draws down the voltage to pin 8. If your house battery bank is the Onan start battery, here is how to stop that from happening:
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| Re: Onan issues [message #308132 is a reply to message #308107] |
Sun, 02 October 2016 09:21 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
Karma: 0
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Member |
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The carb float moved freely up and down after the gas ran through the filter housing so I thought it was good to go. Sounds like I need to look a little deeper into it and perhaps the needle as well. I'm determined to get this thing going!
-James Palmer, Traverse City, MI
1976 Eleganza
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