Home » Public Forums » GMCnet » Daniel's Onan
| Daniel's Onan [message #369518] |
Thu, 21 April 2022 11:18  |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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After two and a half years of not being able to travel outside of Europe, due to Covid restrictions, Daniel and Marjon Jacobs are in the US on an extended vacation in their GMC, "The Flying Dutchman". The coach has been stored at Ken Booth's place in Lake Havasu, AZ and ken helped out with a few renewal items to get them on their way. After a few stops at various other GMCers, most of the issues with the coach have been worked out due to the gracious help of several fellow GMCers.
By the time they got to me place, in Tucson, the main remaining issue has been the Onan. At first, the Onan would fire up and run as long as the prime button was engaged. Release the prime button and it would quit. After pulling the cover off the Dinosaur control board and inspecting the connections, I took the main wiring plug apart, sprayed it with electrical cleaner, tightened up the sockets, and put it back together with a little dielectric grease. The result was that the generator would start and run without the prime switch being engaged and carry a light load for a short time.
After running for probably less than a minute, it would start to stumble and hunt and than die like it was running out of gas. The fuel tank is full, and the fuel pump has been replaced (at Steve Weinstock's place). The strange thing about this is that the 5 amp fuse on the board would blow at about the same time. WE tried several fuses, even a 10 amp, with the same result.
Any ideas???
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: Thu, 21 April 2022 21:43] Report message to a moderator |
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| Re: Daniel's Onan [message #369519 is a reply to message #369518] |
Thu, 21 April 2022 12:24  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Carl S. wrote on Thu, 21 April 2022 12:18<snip>
After running for probably less than a minute, it would start to stumble and hunt and than die like it was running out of gas. The fuel tank is full, and the fuel pump has been replaced (at Steve Winestock's place). The strange thing about this is that the 5 amp fuse on the board would blow at about the same time. WE tried several fuses, even a 10 amp, with the same result.
Any ideas???
I have an idea.....
When most prime circuits are wired in, they by-pass the fuse. If the fuel pump is gummed up, it can sit on the contacts and draw more power sitting there getting hot. This can also be a result of less than good power to the pump. So, check the connections that feed the fuel pump and if that doesn't get it, maybe you need to take the pump off and apart (not a big job) and clean it. The gasket is available at NAPA (at least).
Be sure to let us know.
Matt
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
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| Re: Daniel's Onan [message #369520 is a reply to message #369519] |
Thu, 21 April 2022 12:59 |
rjw
Messages: 697
Registered: September 2005
Karma: 4
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Matt Colie wrote on Thu, 21 April 2022 13:24Carl S. wrote on Thu, 21 April 2022 12:18<snip>
After running for probably less than a minute, it would start to stumble and hunt and than die like it was running out of gas. The fuel tank is full, and the fuel pump has been replaced (at Steve Winestock's place). The strange thing about this is that the 5 amp fuse on the board would blow at about the same time. WE tried several fuses, even a 10 amp, with the same result.
Any ideas???
I have an idea.....
When most prime circuits are wired in, they by-pass the fuse. If the fuel pump is gummed up, it can sit on the contacts and draw more power sitting there getting hot. This can also be a result of less than good power to the pump. So, check the connections that feed the fuel pump and if that doesn't get it, maybe you need to take the pump off and apart (not a big job) and clean it. The gasket is available at NAPA (at least).
Be sure to let us know.
Matt
Carl said "The fuel tank is full, and the fuel pump has been replaced (at Steve Winestock's place)" so should we assume the fuel pump is OK?
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
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| Re: Daniel's Onan [message #369521 is a reply to message #369520] |
Thu, 21 April 2022 13:47 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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The fuel pump is a brand new Facet replacement pump, just installed a few days ago. Daniel also stated that they went through the carburetor as well.
What does the 5 amp fuse protect? The fuel pump, or the board?
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: Daniel's Onan [message #369532 is a reply to message #369527] |
Thu, 21 April 2022 21:21 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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The 5 amp fuse protects just about everything electrical in the Onan except the starter If it run OK with the prime activated that means the fuel pump is OK NEVER use a fuse greater than 5 amp or you can / will easily burn the land patterns on the board
Some Onans have a fuel solenoid. Remove, soak / clean it. A cracked hose on the input side of the pump could leak and cause this The hose is under negative pressure and will not leak gas. It will leak air into it.
I would run the onan until it quits and them immediately remove the carb bowl. If there is no gas in it, you will know you have a fuel delivery problem.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Daniel's Onan [message #369533 is a reply to message #369532] |
Thu, 21 April 2022 21:35 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Okay, along with the other things we tried, mostly cleaning wiring connections, I disconnected the voltage regulator, taped off the wires, leaving the two connected to each other, and the generator started up and continued to run, even without the prime switch engaged. We then put it under load, checked the voltage and frequency (both just a tad low) and it ran until we shut it off even with the AC on.
Weird, huh?
It still is not quite right, adjusting the main jet screw on the carb didn't make any difference no matter how far in or out it was adjusted, and adjusting the governor rod didn't increase the RPMs any noticeable amount. Voltage under load is now at about 118.5 and frequency is at 57 HZ. But for now, it's good enough to be functional.
I will keep in mind the admonition to NOT use any fuse over 5 amps.
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: Daniel's Onan [message #369534 is a reply to message #369533] |
Fri, 22 April 2022 04:05 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I was thinking about the regulator but it appeared to be a fuel problem to me, so I pursued that. Sorry.
Put s 5 amp fuse in the primer circuit too.
118.5 volts under heavy load is no problem as long as the light load voltage does not exceed 132 volts. The spec is +10%, -5% of 120 volts.
Do not turn off the Onan under heavy load like with the AC on. It can blow the full wave bridge rectifier. Turn off the AC first.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Daniel's Onan [message #369538 is a reply to message #369518] |
Fri, 22 April 2022 10:20 |
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SteveW
Messages: 538
Registered: June 2005
Location: Southern California - Ora...
Karma: 1
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Good Morning Carl !!
That fuel pump came off of my spare (never used nor run by me) generator….
Oddly - on that generator - it had a manual / mechanical fuel pressure regulator.
I’m running that same pump on the 4K generator in my coach with no problems.
But - I didn’t investigate to confirm that the pumps were identical…. And I don’t know if facet has different pump specifications with all pumps in that same body. If it’s a higher pressure pump - that would explain the pressure regulator. Perhaps it would contribute to the weird carb issues you’re seeing.
Thanks for spreading good GMC karma.
Steve W
Steve W
1973 : 23'
Southern California
[Updated on: Fri, 22 April 2022 10:20] Report message to a moderator |
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| Re: Daniel's Onan [message #369540 is a reply to message #369538] |
Fri, 22 April 2022 10:23 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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SteveW wrote on Fri, 22 April 2022 08:20Good Morning Carl !!
That fuel pump came off of my spare (never used nor run by me) generator….
Oddly - on that generator - it had a manual / mechanical fuel pressure regulator.
I’m running that same pump on the 4K generator in my coach with no problems.
But - I didn’t investigate to confirm that the pumps were identical…. And I don’t know if facet has different pump specifications with all pumps in that same body. If it’s a higher pressure pump - that would explain the pressure regulator. Perhaps it would contribute to the weird carb issues you’re seeing.
Thanks for spreading good GMC karma.
Steve W
That's a possibility, Steve. It appears to be the same pump as I have on my Onan, but it bears looking into.
Thanks.
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: Daniel's Onan [message #369542 is a reply to message #369540] |
Fri, 22 April 2022 13:43 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Those Facet (Bendix) pumps have been around for years and are made at many different pressures with several different Brands on them. The OEM FACET (Bendix) boost pump in my airplane is 5 to 7 PSI. I believe the one on the Onan is 3-5 PSI.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Daniel's Onan [message #369547 is a reply to message #369518] |
Fri, 22 April 2022 20:09 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Are you troubleshooting with the Onan in the stored position? The fuel line from outer case to pump may have taken a set with disuse and kinked allowing some fuel but not full flow
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Daniel's Onan [message #369551 is a reply to message #369547] |
Sat, 23 April 2022 15:56 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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JohnL455 wrote on Fri, 22 April 2022 18:09Are you troubleshooting with the Onan in the stored position? The fuel line from outer case to pump may have taken a set with disuse and kinked allowing some fuel but not full flow
Seems to me it would be kind of hard to diagnose/work on an Onan in the stored position since the only thing you can see is the front plate.
It looked like Steve had run the line to an inline filter with a new hose, that was tied to the top of the back frame of the Onan. I don't think hose kinking is the issue. If anything it is running rich now that it keeps running, although the original symptom (starting, running for a few minutes, then dying) would have pointed to a possible kink in the fuel line. However the gen was out on the slides the entire time we were working on it.
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: Daniel's Onan [message #369555 is a reply to message #369518] |
Sat, 23 April 2022 20:18 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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There was a “screen door spring” to dress the fuel line with drawer action when new. Most of those rotted away by the new milenuim due to living in the road splash zone.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Daniel's Onan [message #369558 is a reply to message #369533] |
Mon, 25 April 2022 16:02 |
AndrewCudlipp
Messages: 3
Registered: June 2021
Location: Bremerton, WA
Karma: 0
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Junior Member |
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Carl S. wrote on Thu, 21 April 2022 19:35It still is not quite right, adjusting the main jet screw on the carb didn't make any difference no matter how far in or out it was adjusted, and adjusting the governor rod didn't increase the RPMs any noticeable amount. Voltage under load is now at about 118.5 and frequency is at 57 HZ. But for now, it's good enough to be functional.
I will keep in mind the admonition to NOT use any fuse over 5 amps.
That is not good. You are missing a very important seal inside the carburetor bowl. Unlike a Briggs & Stratton carb or any other small engine, the ONAN carb needs a gasket/washer/seal underneath the bolt head for the carb bowl AND INSIDE the floatbowl. It should look like this
[bolthead] |(fiber washer)---|(carb bowl flange)---|(second fiber washer)------threads of the bolt-------
I used a 7/16 I.D. nitrile Oring from a standard oring kit. Your generator is running extremely rich without this very crucial seal. It is funny because the original power drawer manual does not show this seal in the parts blow-apart-diagram but does mention it on the troubleshooting procedures.
When running rich like this the generator can do some funny things... my friend's was icing up the carburetor and intake manifold a shocking amount before we repaired it.
Also, running this rich can easily foul the spark plugs and lower the compression from the fuel washing out the cylinder walls. You may find the generator is hard to start, or will putter out.
Hope this helps... sorry for my terrible diagram. Once you get that seal sorted out the generator SHOULD STALL OUT with the main jet adjustment turned all the way in.
- AC
Super excited to be here!
1976 Eleganza II
1977 Eleganza II
1978 Royale (Moms)
[Updated on: Mon, 25 April 2022 16:05] Report message to a moderator |
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| Re: Daniel's Onan [message #369560 is a reply to message #369518] |
Tue, 26 April 2022 11:15 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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We had the same problem with Zhookoff's Onan, traced to an exposed wire at the shutoff solenoid. When this warmed up it touched the case and shorted.
--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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