Home » Public Forums » GMCnet » [GMCnet] I give up. (Onan)
|
|
| Re: [GMCnet] I give up. (Onan) [message #192235 is a reply to message #191667] |
Tue, 04 December 2012 18:27   |
Robin Hood
Messages: 1078
Registered: April 2011
Karma: 3
|
Senior Member |
|
|
Update!
Tom Phipps is kindly joining me tomorrow to mess with my Onan. I have
cleaned a lot of the caked on gunky oil and gotten after it in general
with degreaser and Simple Green, plus a ton of shop towels.
I installed the replacment fuel pump and the fuse, and jumpered the
board 5 to 9, andd was rewarded with the sound of the new pump
priming.
I tried starting it without the board jumpered, but it catch and then
quit just when you thought it was about to start running. I
rejumpered, and it started.
I let it run for a minute, and stopped it. Then I took off the jumper
wires, and tried it.
It started and stayed running! Huzzah!
I let it run for another 30 seconds and then stopped it.
To do! Cut a gasket for between the carb and intake. Check that I've
got 120VAC out of the hot wires. Adjust throttle if necessary. Once
we've established that Mr. Onan is basicly up to the task, I'll order
a carb rebuild kit, perform an oil change, and in general clean it up
and do the things that are easier to do whilst it's out of the coach.
I do NOT want to have to pull this thing out anytime soon! It's going
to be enough trouble getting it into my Royale; I'm going to have to
take the generator out of its power drawer and install it into the
power drawer in the Royale. (The ambitious theives removed the entire
power drawer from the Palm Beach's frame).
Huzzah I say!
--
Robin Hood
Jackson, MS
2003 Buick Lesabre
1968 Pontiac Catalina
1978 GMC Royale motorhome
1977 GMC Palm Beach motorhome
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192272 is a reply to message #192235] |
Wed, 05 December 2012 08:39 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| Robin Hood wrote on Tue, 04 December 2012 19:27 |
Update!
<snip>
I installed the replacement fuel pump and the fuse, and jumpered the board 5 to 9, and was rewarded with the sound of the new pump priming.
I tried starting it without the board jumpered, but it catch and then quit just when you thought it was about to start running. I
rejumpered, and it started.
I let it run for a minute, and stopped it. Then I took off the jumper wires, and tried it.
It started and stayed running! Huzzah!
I let it run for another 30 seconds and then stopped it.
<Big SniP>
Huzzah I say!
--
Robin Hood
|
We all knew you could do it.
Now you do - too!
Cowa FBunga
Matt (and a large cheering crowd)
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192280 is a reply to message #192272] |
Wed, 05 December 2012 10:28 |
Robin Hood
Messages: 1078
Registered: April 2011
Karma: 3
|
Senior Member |
|
|
Thanks, Matt. :) And everyone else who has provided advice along the way.
Tom Phipps came by this morning. I gave him a rundown of what-all I
have done. "Here, see, I think it runs now!" I said. I pushed the
button and not much happened.
"Hrm. Here, let me jumper it just to prime the pump..." *nothing*.
"Uh... Tom, do I have power to my pump?" Tom pulled out the meter.
"Well, yeah... but its' weird. It says there's NEGATIVE 12 volts here.
How can that be?"
Me: "Oh hell. I hooked up my battery wires backwards." Alas, the fuel
pump was a victim of my lack of attention. Tom drove me to NAPA and I
paid for a new one out of my own pocket (it was my screwup after all).
I am now an expert at the installation and removal of Facet pumps on
Onans, this being my third.
Once we were ready to try again, Tom determined that the carb was
flooding. Furthermore, while the motor is turning over, it's SPITTING
fuel vapor OUT the carb, and driving fuel UP the shaft that the
throttle linkage rides on.
See, that's something I don't understand. My theoretical understanding
of a four cycle engine is that it acts like an air pump.
intake>compression>power>exhaust. I didn't think there should be ANY
air going back the OTHER way, OUT of the carb.
We unhooked the power the fuel pump, and when the fuel-air mixture
finally got right I guess, the Onan fired and ran for a bit until it
ran out of fuel from the carb.
Anybody got any advice? I don't mind buying a new carb if I have to,
nor do I mind doing a rebuild using one of JimK's kits. I'd like to
better understand what I'm dealing with, though.
--
Robin Hood
Jackson, MS
2003 Buick Lesabre
1968 Pontiac Catalina
1978 GMC Royale motorhome
1977 GMC Palm Beach motorhome
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192281 is a reply to message #192280] |
Wed, 05 December 2012 10:47 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
Robin, the Onan is an opposed twin cylinder waste spark ignition 4 cycle
engine. When one plug fires, so does the other one. Because of the points
being camshaft driven, it only fires every other revolution. When converted
to pertronix flywheel triggering, it fires both cylinders every revolution.
Sometimes during the overlap period when both the intake and exhaust valves
are off their seats at the same time, It can fire the mixture in the intake
manifold, and spit back through the carb. I know this is TMI but you said
you wanted to learn. (grin)
Jim Hupy
Salem, Or
78 Gmc Royale 403
On Dec 5, 2012 8:28 AM, "Robin Hood" <loxley@gmail.com> wrote:
> Thanks, Matt. :) And everyone else who has provided advice along the way.
>
> Tom Phipps came by this morning. I gave him a rundown of what-all I
> have done. "Here, see, I think it runs now!" I said. I pushed the
> button and not much happened.
>
> "Hrm. Here, let me jumper it just to prime the pump..." *nothing*.
> "Uh... Tom, do I have power to my pump?" Tom pulled out the meter.
> "Well, yeah... but its' weird. It says there's NEGATIVE 12 volts here.
> How can that be?"
>
> Me: "Oh hell. I hooked up my battery wires backwards." Alas, the fuel
> pump was a victim of my lack of attention. Tom drove me to NAPA and I
> paid for a new one out of my own pocket (it was my screwup after all).
> I am now an expert at the installation and removal of Facet pumps on
> Onans, this being my third.
>
> Once we were ready to try again, Tom determined that the carb was
> flooding. Furthermore, while the motor is turning over, it's SPITTING
> fuel vapor OUT the carb, and driving fuel UP the shaft that the
> throttle linkage rides on.
>
> See, that's something I don't understand. My theoretical understanding
> of a four cycle engine is that it acts like an air pump.
> intake>compression>power>exhaust. I didn't think there should be ANY
> air going back the OTHER way, OUT of the carb.
>
> We unhooked the power the fuel pump, and when the fuel-air mixture
> finally got right I guess, the Onan fired and ran for a bit until it
> ran out of fuel from the carb.
>
> Anybody got any advice? I don't mind buying a new carb if I have to,
> nor do I mind doing a rebuild using one of JimK's kits. I'd like to
> better understand what I'm dealing with, though.
>
> --
> Robin Hood
> Jackson, MS
> 2003 Buick Lesabre
> 1968 Pontiac Catalina
> 1978 GMC Royale motorhome
> 1977 GMC Palm Beach motorhome
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192286 is a reply to message #192272] |
Wed, 05 December 2012 11:19 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
|
Senior Member |
|
|
Cheering loud for you in Seattle ! I know exactly what you went through ;)
Sully
77 royale
Seattle
Sent from my iPhone
On Dec 5, 2012, at 6:39 AM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>
> Robin Hood wrote on Tue, 04 December 2012 19:27
>> Update!
>> <snip>
>> I installed the replacement fuel pump and the fuse, and jumpered the board 5 to 9, and was rewarded with the sound of the new pump priming.
>>
>> I tried starting it without the board jumpered, but it catch and then quit just when you thought it was about to start running. I
>> rejumpered, and it started.
>>
>> I let it run for a minute, and stopped it. Then I took off the jumper wires, and tried it.
>>
>> It started and stayed running! Huzzah!
>>
>> I let it run for another 30 seconds and then stopped it.
>> <Big SniP>
>>
>> Huzzah I say!
>> --
>> Robin Hood
>
> We all knew you could do it.
> Now you do - too!
>
> Cowa FBunga
>
> Matt (and a large cheering crowd)
>
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192287 is a reply to message #192284] |
Wed, 05 December 2012 11:23 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
|
Senior Member |
|
|
Agree with A. You got a float needle/ seat problem or maybe the pump is providing too much pressure and overpowering the needle/seat
Sully
77 royale
Seattle
Sent from my iPhone
On Dec 5, 2012, at 9:17 AM, A. <markbb1@netzero.com> wrote:
>
>
> Robin Hood wrote on Wed, 05 December 2012 10:28
>> ...Once we were ready to try again, Tom determined that the carb was flooding. Furthermore, while the motor is turning over, it's SPITTING fuel vapor OUT the carb, and driving fuel UP the shaft that the throttle linkage rides on.
>> ...
>> Anybody got any advice? I don't mind buying a new carb if I have to, nor do I mind doing a rebuild using one of JimK's kits. I'd like to better understand what I'm dealing with, though.
>> ...
>> --
>> Robin Hood
>> Jackson, MS
>> 2003 Buick Lesabre
>> 1968 Pontiac Catalina
>> 1978 GMC Royale motorhome
>> 1977 GMC Palm Beach motorhome
> The needle valve is stuck open or otherwise not sealing. The float is probably stuck. Maybe some light "percussive maintenance" as close to the float pivot as you can get.
> Rebuilding the carb might help prevent future recurrences.
> --
> '73 23' Sequoia
> UA (Upper Alabama)
> "Time is money. If you use YOUR time, you get to keep YOUR money."
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192296 is a reply to message #192280] |
Wed, 05 December 2012 12:11 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Float level and jet setting. Also, in some instances vibration will make fuel in the float bowl slosh. If the throttle shaft is that loose, a rebuild might be in your future.. and it will run more consistently afterwards too. Consider - on the intake stroke you have a mass of air moving into the engine through the carb. When the vale shuts, the air through inertia keeps moving for a bit. And hits a brick wall as it were. Since air is compressible it does so, and then rebounds. Get everything just wrong in this sequence and it will throw almost as much gas out the intake as it does into the engine.
Back in The Day, we used to wrap solder around the carbs on some Hondoo twin scooters to stop the vibrations, the added mass giving them a different resonant frequency.
--johnny
'76 23' transmode norris
'76 palm beach
From: Robin Hood <loxley@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, December 5, 2012 11:28 AM
Subject: Re: [GMCnet] I NEVER give up. (Onan)
Thanks, Matt. :) And everyone else who has provided advice along the way.
Tom Phipps came by this morning. I gave him a rundown of what-all I
have done. "Here, see, I think it runs now!" I said. I pushed the
button and not much happened.
"Hrm. Here, let me jumper it just to prime the pump..." *nothing*.
"Uh... Tom, do I have power to my pump?" Tom pulled out the meter.
"Well, yeah... but its' weird. It says there's NEGATIVE 12 volts here.
How can that be?"
Me: "Oh hell. I hooked up my battery wires backwards." Alas, the fuel
pump was a victim of my lack of attention. Tom drove me to NAPA and I
paid for a new one out of my own pocket (it was my screwup after all).
I am now an expert at the installation and removal of Facet pumps on
Onans, this being my third.
Once we were ready to try again, Tom determined that the carb was
flooding. Furthermore, while the motor is turning over, it's SPITTING
fuel vapor OUT the carb, and driving fuel UP the shaft that the
throttle linkage rides on.
See, that's something I don't understand. My theoretical understanding
of a four cycle engine is that it acts like an air pump.
intake>compression>power>exhaust. I didn't think there should be ANY
air going back the OTHER way, OUT of the carb.
We unhooked the power the fuel pump, and when the fuel-air mixture
finally got right I guess, the Onan fired and ran for a bit until it
ran out of fuel from the carb.
Anybody got any advice? I don't mind buying a new carb if I have to,
nor do I mind doing a rebuild using one of JimK's kits. I'd like to
better understand what I'm dealing with, though.
--
Robin Hood
Jackson, MS
2003 Buick Lesabre
1968 Pontiac Catalina
1978 GMC Royale motorhome
1977 GMC Palm Beach motorhome
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192298 is a reply to message #192280] |
Wed, 05 December 2012 12:34 |
|
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| Robin Hood wrote on Wed, 05 December 2012 11:28 |
<snip>
Once we were ready to try again, Tom determined that the carb was
flooding. Furthermore, while the motor is turning over, it's SPITTING fuel vapor OUT the carb, and driving fuel UP the shaft that the throttle linkage rides on.
See, that's something I don't understand. My theoretical understanding of a four cycle engine is that it acts like an air pump.
intake>compression>power>exhaust.
I didn't think there should be ANY air going back the OTHER way, OUT of the carb.
We unhooked the power the fuel pump, and when the fuel-air mixture finally got right I guess, the Onan fired and ran for a bit until it ran out of fuel from the carb.
Anybody got any advice? I don't mind buying a new carb if I have to, nor do I mind doing a rebuild using one of JimK's kits. I'd like to better understand what I'm dealing with, though.
--
Robin Hood
|
Robin,
Your understanding is correct, but it is a little bit simplified.
Summary: I don't think you have a problem.
Yes, the Suck,Push,Pop,Poey is correct, but the problem comes in the fine points. The valves require some time (in flywheel rotation) to open and close. Since the intake valve is often still closing when the piston changes direction, at low speeds (with low charge inertia) it is possible to have "charge reversion" where the charge air actually reverses flow direction for a very short period. This is a big problem for hot starts on governor controlled engines as the throttle plate is not restricting the flow.
And you may also have a float/needle/seat problem to deal with, but if that is the case, leave the pump running for most of a minute and see if fuel drips out of the carburetor. If it does, you do.
Matt
P.S. You are probably the first person to connect a battery backwards - In you garage - This week.
P.S.S. You may have damaged other things like the voltage regulator or some features on the control board. (If it were a boat, I would give you the long list of things to be checked and possibly repaired/replaced.)
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
|
|
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192323 is a reply to message #192321] |
Wed, 05 December 2012 15:44 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
| Robin Hood wrote on Wed, 05 December 2012 14:15 |
Upon further investigation... the liquid on my carb isn't leaking
fuel. It's water from condensation. The carb is ice cold, and I live
in the moist humidity of the Deep South. It's overcast and drizzly
even as I type this.
Anyway, so she starts, runs and stops, and puts out 120VAC! 
http://www.youtube.com/watch?v=H2dcMReUsqs
The jetwash at the end threw me for a bit.
So, this means that the generator is DEFINITELY worth investing
further time and money into. Carb kit just to be on the safe side. I
reckon I should take the covers off the cylinder heads so I can clean
them up. What else should I do whilst I've got it out of the coach? I
want to clean things up and not have to pull it out again any time
soon.
--
Robin Hood
Jackson, MS
2003 Buick Lesabre
1968 Pontiac Catalina
1978 GMC Royale motorhome
1977 GMC Palm Beach motorhome
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
I would definitely pay some attention to the other end of the generator (opposite of the engine) an clean thee brushes and brush holders. Not a bad idea to remove the heads and decarbon them and the tops of the pistons either. The gaskets can be reused. Steve Ferguson always suggests spraying them with a couple coats of aluminum paint before reusing them. IIRC, the torque on the nuts is 19ft lbs
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
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192324 is a reply to message #192323] |
Wed, 05 December 2012 15:45 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
PS, You should change the name of this thread to I DON'T give up! 
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
[Updated on: Wed, 05 December 2012 15:46] Report message to a moderator |
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192325 is a reply to message #192324] |
Wed, 05 December 2012 15:46 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
PSS, Oh wait! You already DID! (almost)
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
|
|
|
|
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192336 is a reply to message #192321] |
Wed, 05 December 2012 18:38 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
When you do finally install this Onan in your coach, use NEW rubber mounting isolators. The old ones usually have compressed and cause the Onan to drop down on it's mounts.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: [GMCnet] I NEVER give up. (Onan) [message #192364 is a reply to message #192321] |
Thu, 06 December 2012 07:31 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
If you haven't already, pop the heads and clean the carbon off them. Do it carefully and the gaskets are reusable. Clean it up, make sure nothing;s busted, Ty-rap <tm> the various wires up nice and neat. Carb ice is why airplanes have carb heaters. You see a substantial drop in temperature across the venturi, upwards of 40 degrees in some circumstances. With the air filter and bafflinfg back obn it's lessof a problem. And some Onans have the 'Winter/Summer" setting which moves a baffle to pick up intake air from the cooling stream where it's been warmed. Buttoned up and reinstalled in th coach it shouldn't be a problem. How far are you guys from Starkburg?
--johnny
'76 23' transmode norris
'76 palm beach
From: Robin Hood <loxley@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, December 5, 2012 4:15 PM
Subject: Re: [GMCnet] I NEVER give up. (Onan)
Upon further investigation... the liquid on my carb isn't leaking
fuel. It's water from condensation. The carb is ice cold, and I live
in the moist humidity of the Deep South. It's overcast and drizzly
even as I type this.
Anyway, so she starts, runs and stops, and puts out 120VAC! :)
http://www.youtube.com/watch?v=H2dcMReUsqs
The jetwash at the end threw me for a bit. :)
So, this means that the generator is DEFINITELY worth investing
further time and money into. Carb kit just to be on the safe side. I
reckon I should take the covers off the cylinder heads so I can clean
them up. What else should I do whilst I've got it out of the coach? I
want to clean things up and not have to pull it out again any time
soon.
--
Robin Hood
Jackson, MS
2003 Buick Lesabre
1968 Pontiac Catalina
1978 GMC Royale motorhome
1977 GMC Palm Beach motorhome
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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
|
|
|
|
Goto Forum:
Current Time: Fri Sep 27 12:28:26 CDT 2024
Total time taken to generate the page: 0.02247 seconds
|
GMCforum
Search
Help
Register
Login
Home
