Home » Public Forums » GMCnet » Moving Generator Fuel Pump (Generator Vapor Lock?)
| Moving Generator Fuel Pump [message #182634] |
Fri, 31 August 2012 17:57  |
GeorgeRud
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Registered: February 2007
Location: Chicago, IL
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In today's Daily Pose, JimB discussed moving the Facet fuel pump that supplies fuel to the generator closer to the fuel tank in an effort to combat vapor lock in the generator. Since electric fuel pumps like to push fuel rather than pull fuel from the tank, it may not e a bad idea.
Has anyone had experience with vapor lock on their generator? I haven't used mine enough to really say, but mine has run for several days straight without problems. I don't really need another project, but I think JimB does have a valid point.
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: [GMCnet] Moving Generator Fuel Pump [message #182742 is a reply to message #182641] |
Sat, 01 September 2012 10:17  |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
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| mjbourgon wrote on Fri, 31 August 2012 16:45 |
Good afternoon from Sunny New Mexico
I had vapor lock on my Onan and visited with Jim Bounds about best way
to hopefully eliminate this problem. He suggested locating a fuel pump
close to fuel tank. I took Jim's advise and seems to work just fine.
Pretty simple project just a bit of a tight space to work in. Makes
good sense to push the fuel instead of trying to suck it out of tank.
No big deal and cheap project. I bought pump at Auto zone for about
$50.00. Good luck
Marcel in New Mexico
1976 palm beach stretched 2 feet
On 8/31/2012 16:57, George Rudawsky wrote:
>
> In today's Daily Pose, JimB discussed moving the Facet fuel pump that supplies fuel to the generator closer to the fuel tank in an effort to combat vapor lock in the generator. Since electric fuel pumps like to push fuel rather than pull fuel from the tank, it may not e a bad idea.
>
> Has anyone had experience with vapor lock on their generator? I haven't used mine enough to really say, but mine has run for several days straight without problems. I don't really need another project, but I think JimB does have a valid point.
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Marcel,
I am very interested in this topic, as my Onan has been acting the same way. The last two trips we took, it has died each time (both ways), while running the roof AC, while driving. Each time, it ran for a shorter period of time. On one occasion, it quit about half an hour after filling the gas tanks and on another, within five minutes of topping them off. After the third incident, I pulled the pump off and did a picnic table overhaul at the RV park. On the way home, it only ran for about 20 minutes before it died.
The coach has been run exclusively on 10% ethanol gas for the four years we have owned it and for at least the last couple of years that Bruce T. owned it. You can't get any other kind of gas in our part of the country. This symptom has never happened before, and I have regularly run the Onan while driving.
My question is; Did you lust add a second pump, closer to the gas tank? Or did you replace the original pump entirely. The reason I ask is that either of those things could have corrected the problem if it was a bad fuel pump.
When it quit in the Flying J parking lot in Lordsburg, in July, I went right outside, pulled the generator out, removed the board cover, and jumpered from 9 to 5. The pump came on, but the tone didn't change, like it does when it pumps up pressure. After letting it run for a short time, I hit the start switch and it fired up, only to die in a few seconds. I repeated the process and got the same results. I put the cover back on, slid the generator back in it's hole, and we proceeded to Silver City, where it was, thankfully, cooler.
I have since replaced the fuel pump and tested it in my driveway. So far, so good, but the real test won't come until we get a chance to take another trip, probably next month. I guess if the new pump does not fix the problem, I will start looking at the coil or condenser, and maybe relocate the fuel pump per Jim Bounds' recommendation.
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: Moving Generator Fuel Pump [message #182770 is a reply to message #182634] |
Sat, 01 September 2012 14:06 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
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On a related note, I've read about people installing an electric fuel pump solely for the purposes of priming the Onan carburetor. I'm in the process of installing TBI fuel injection on my rig, which already has a supplemental low-pressure pump.
Could I just re-wire that one to supply the Onan via a momentary contact switch by the generator control panel? If so, is it necessary to do a T in the supply line, or return line, or just "let 'er rip" until the Onan's running?
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: Moving Generator Fuel Pump [message #182771 is a reply to message #182770] |
Sat, 01 September 2012 14:19 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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| habbyguy wrote on Sat, 01 September 2012 12:06 |
On a related note, I've read about people installing an electric fuel pump solely for the purposes of priming the Onan carburetor. I'm in the process of installing TBI fuel injection on my rig, which already has a supplemental low-pressure pump.
Could I just re-wire that one to supply the Onan via a momentary contact switch by the generator control panel? If so, is it necessary to do a T in the supply line, or return line, or just "let 'er rip" until the Onan's running?
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Mark,
There is no need to install a supplemental fuel pump to 'prime' the Onan. It already has an electric pump on it. All you need to do is install a "prime circuit" to turn it on prior to starting the Onan.
Here's an article by Jim Bounds on how to accomplish this:
http://www.gmccoop.com/onan_prime_circuit.htm
It works well.
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: Moving Generator Fuel Pump [message #182780 is a reply to message #182634] |
Sat, 01 September 2012 15:14 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
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Thanks, Carl... My coach has an Emerald series 6500 watt generator, but it apparently has an electric fuel pump as well (who knew?). That WILL save some extra hassle, to be sure. I've got to run a wire from my inverter to the same area (next to the Onan control panel), so I guess I'll add one more.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: Moving Generator Fuel Pump [message #182792 is a reply to message #182634] |
Sat, 01 September 2012 16:52 |
captjack
Messages: 271
Registered: February 2010
Location: Sebastopol, California
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I could tell when my engine was about to get vapor lock. First, the Onan would quit, then within a short time the coach would start showing vapor lock symptoms. I think I've resolved the coach problem with in-tank pumps, but I haven't addressed the Onan vapor lock problem yet.
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: Moving Generator Fuel Pump [message #182862 is a reply to message #182792] |
Sat, 01 September 2012 23:49 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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If you already have two in tank pumps then I suggest you already have what you need for the Onan.
First the plumbing. I am assuming you have 5 PSI pumps in the tanks. I would tee into the tank output line for the rear tank and run that to the Onan. In the Onan fuel line I would make sure that you have the Onan supplied cutoff solenoid. You can bypass or leave the OEM Onan facet pump. It is your choice. I have one of those facet pumps in line in my airplane that is normally off and used only as a boost pump. Several thousand hours of fuel have been pumped through it with power off with no problems.
On the electrical side, I would install a single diode in line in the wire from the coach engine to the rear in tank pump.
Note: that pump takes less than 1.5 amps to run so a good diode rated a 5 amps and anything over 50 volts ought to do.
Then I would add a second wire to that same pump with a similar diode in line. The other end of the wire would go to the same power source used for the solenoid and Onan supplied pump.
That is it.
Now when the Onan is running, the solenoid is open to allow fuel flow and the Onan supplies the +12 volt power to the rear in tank pump. When the main engine is running and the Onan is off, the Onan solenoid is closed and the +12 volt electrical power is supplied by the normal main engine source.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Moving Generator Fuel Pump [message #182872 is a reply to message #182742] |
Sun, 02 September 2012 07:12 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
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Carl,
That new pump will solve your onan problem and save your marriage.
In late July my onan started with the symptoms you describe.
I replaced the pump with a $44 one from O'Riellly's.
First trip after replacement we left Red Bluff, Ca. at 1:30 pm and 105*.
3 1/2 hours later I refueled at Grants Pass, Ore. It was still well over 100*
The Onan ran the a/c all that time without a stutter.
I had never in 10 years ran the Onan continuosly for that long.
Did the same thing in the same ambient temps on the return trip.
Had I not replaced the onan pump, I would be divorced or dead; justifiable homocide.
My wife hates the heat.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: [GMCnet] Moving Generator Fuel Pump [message #182888 is a reply to message #182872] |
Sun, 02 September 2012 10:03 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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| gbarrow wrote on Sun, 02 September 2012 05:12 |
Carl,
That new pump will solve your onan problem and save your marriage.
In late July my onan started with the symptoms you describe.
I replaced the pump with a $44 one from O'Riellly's.
First trip after replacement we left Red Bluff, Ca. at 1:30 pm and 105*.
3 1/2 hours later I refueled at Grants Pass, Ore. It was still well over 100*
The Onan ran the a/c all that time without a stutter.
I had never in 10 years ran the Onan continuosly for that long.
Did the same thing in the same ambient temps on the return trip.
Had I not replaced the onan pump, I would be divorced or dead; justifiable homocide.
My wife hates the heat.
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Thanks for the words of encouragement, Gene. I'm pretty confident that the new pump will do the trick. Fortunately, my wife is pretty understanding about such things. We are both on a second marriage and learned a lot from our respective first ones. She doesn't tend to blame mechanical failures on me, personally. Besides, we have 'wind wings' on our windows and they do an amazing job of keeping the air flowing, even if it's hot.
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: [GMCnet] Moving Generator Fuel Pump [message #182891 is a reply to message #182888] |
Sun, 02 September 2012 10:28 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
Yesterday I let the Onan run until it died. I then had Helen push on the primer switch and listened to the pump; it kept running,
running, and running at the same "speed." At the time it was around 90° OAT and both tanks were nearly full.
This morning I had Helen repeat the test, the pump ran for about 10-15 seconds then slowed down to a tic - tic - tic.
This says to me that when it kept running, running and running either:
1) the pump stops pumping when it gets hot
2) the pump stops sucking when it gets hot
3) vapor lock is developing in the line from the main tank
Carl,
If you get the chance before you R&R the pump could you try the same test? If you don't have a primer switch jump pins 5 & 9.
Regards,
Rob M.
-----Original Message-----
From: Carl Stouffer
Thanks for the words of encouragement, Gene. I'm pretty confident that the new pump will do the trick. Fortunately, my wife is
pretty understanding about such things. We are both on a second marriage and learned a lot from our respective first ones. She
doesn't tend to blame mechanical failures on me, personally. Besides, we have 'wind wings' on our windows and they do an amazing
job of keeping the air flowing, even if it's hot.
--
Carl S.
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Moving Generator Fuel Pump [message #182922 is a reply to message #182891] |
Sun, 02 September 2012 12:27 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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| Robert Mueller wrote on Sun, 02 September 2012 08:28 |
G'day,
Yesterday I let the Onan run until it died. I then had Helen push on the primer switch and listened to the pump; it kept running,
running, and running at the same "speed." At the time it was around 90° OAT and both tanks were nearly full.
This morning I had Helen repeat the test, the pump ran for about 10-15 seconds then slowed down to a tic - tic - tic.
This says to me that when it kept running, running and running either:
1) the pump stops pumping when it gets hot
2) the pump stops sucking when it gets hot
3) vapor lock is developing in the line from the main tank
Carl,
If you get the chance before you R&R the pump could you try the same test? If you don't have a primer switch jump pins 5 & 9.
Regards,
Rob M.
-----Original Message-----
From: Carl Stouffer
Thanks for the words of encouragement, Gene. I'm pretty confident that the new pump will do the trick. Fortunately, my wife is
pretty understanding about such things. We are both on a second marriage and learned a lot from our respective first ones. She
doesn't tend to blame mechanical failures on me, personally. Besides, we have 'wind wings' on our windows and they do an amazing
job of keeping the air flowing, even if it's hot.
--
Carl S.
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Rob,
That's exactly the same test I did in the Flying J parking lot when the Onan died five minutes after filling the tanks with fresh gas (which, to me, precludes vapor lock). Same results as you had. When I did the same thing the next day, at Burro Mountain, it pumped up fuel, just as you described. I did a quick overhaul on the picnic bench, didn't find anything obviously wrong and reinstalled it, hoping for a better result. I was disappointed. On the trip home, we fired up the gen at a rest stop and it died 20 minutes later.
I have already replaced the pump:
http://www.gmcmhphotos.com/photos/onan-mount-replacement/p45340-replacement-fuel-pump.html
It is a Mr Gasket pump from Jim K.with the right pressure spec (2 - 3.5 psi IIRC)
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: [GMCnet] Moving Generator Fuel Pump [message #182948 is a reply to message #182891] |
Sun, 02 September 2012 20:25 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Rob,
The pump running and running, without slowing describes my old pump. I removed the line from the carb end while it was running and it pumped out what seemed like a lot of fuel. But it would not pressure up and stop.
Seemed like it was pumping plenty og fuel to run that engine; not so!
Replaced the pump and it has been running fine ever since.
Good luck with yours.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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