| Bad fuel smell [message #106963] |
Sun, 28 November 2010 19:27  |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
Karma: 0
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Heres a weird issue I can't figure out.
When running low on fuel and going down hill the cabin fills up badly with a strong oder of unleaded. Its like your sticking your head in the tank!
Going uphill no problem.
Engine running strong.
Pulling over at a gas station checked for leaks nothing. Couldn't smell a hint of gas when level.
Fulled the tanks up at the station and no smell at all up or down hills.
On the way back started running low on fuel again and started smelling fuel downhill. However by the time the fuel started getting really low we were on level desert ground no up or downs so no oder?
Any ideas!!!! This drove me nuts!!!!!!!!! Sure glad we don't smoke! LOL
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: Bad fuel smell [message #106974 is a reply to message #106963] |
Sun, 28 November 2010 20:23  |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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| MrRadioActive wrote on Sun, 28 November 2010 17:27 |
Heres a weird issue I can't figure out.
When running low on fuel and going down hill the cabin fills up badly with a strong oder of unleaded. Its like your sticking your head in the tank!
Going uphill no problem.
Engine running strong.
Pulling over at a gas station checked for leaks nothing. Couldn't smell a hint of gas when level.
Fulled the tanks up at the station and no smell at all up or down hills.
On the way back started running low on fuel again and started smelling fuel downhill. However by the time the fuel started getting really low we were on level desert ground no up or downs so no oder?
Any ideas!!!! This drove me nuts!!!!!!!!! Sure glad we don't smoke! LOL
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What was the temperature outside? Do you have fuel injection? I am wondering if the fuel is getting warm... slowly during driving. This heating is accelerated by fuel injection as the gas passes over the back of the engine to the TBI and is returned to the tank. Some fuel pumps for carburator engines had a return from the pump to the tank to releve pressure at the carburator. That also can heat gas.
There are a zillion gas lines on these puppies. Most like to leak all the time or when full. But if pressure is building in the tanks, and the vapor separator is stuck, then the next vent spot is the cap. Our '78 tended to do this when pressure went up. The little fuel fill cave is right beside you, in a not very well sealed area. The window, right above also can leak fumes.
When trucks would pass they would really stir up a stink... inside.
Test 1 if you are still on your trip, pull over and crack (sloooooly- you can get a bath) the cap and let out the pressure. Drive on and see if it is better for a while.
Test 2 Take the bottom hose off of the separator valve (found in the left-rear wheel well, up high, near the front bogie wheel), put another short hose on it and see if you can blow air through to the canister. Air should pass fairly freely. If you want to test the valve itself, you can take off the top hose, too.
Ideally, the vapor is vented into the canister and sucked into the engine and used to go down the road. As a side bar, this valve can also let liquid gas into the canister under the shotgun seat, but that can only happen when the ball is not floating at all, and tanks are full or filling.
The GMC Motorhome suppliers have newly designed vapor separators. Most Corvette parts suppliers have the original triangle shaped separator.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Bad fuel smell [message #106976 is a reply to message #106974] |
Sun, 28 November 2010 20:34 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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When was the last time you replaced the rubber connectors on the fuel tanks?
On Sun, Nov 28, 2010 at 6:23 PM, George Beckman <gbeckman@pggp.com> wrote:
>
>
> MrRadioActive wrote on Sun, 28 November 2010 17:27
>> Heres a weird issue I can't figure out.
>> When running low on fuel and going down hill the cabin fills up badly with a strong oder of unleaded. Its like your sticking your head in the tank!
>> Going uphill no problem.
>> Engine running strong.
>> Pulling over at a gas station checked for leaks nothing. Couldn't smell a hint of gas when level.
>> Fulled the tanks up at the station and no smell at all up or down hills.
>> On the way back started running low on fuel again and started smelling fuel downhill. However by the time the fuel started getting really low we were on level desert ground no up or downs so no oder?
>> Any ideas!!!! This drove me nuts!!!!!!!!! Sure glad we don't smoke! LOL
>
>
> What was the temperature outside? Do you have fuel injection? I am wondering if the fuel is getting warm... slowly during driving. This heating is accelerated by fuel injection as the gas passes over the back of the engine to the TBI and is returned to the tank. Some fuel pumps for carburator engines had a return from the pump to the tank to releve pressure at the carburator. That also can heat gas.
>
> There are a zillion gas lines on these puppies. Most like to leak all the time or when full. But if pressure is building in the tanks, and the vapor separator is stuck, then the next vent spot is the cap. Our '78 tended to do this when pressure went up. The little fuel fill cave is right beside you, in a not very well sealed area. The window, right above also can leak fumes.
>
> When trucks would pass they would really stir up a stink... inside.
>
> Test 1 if you are still on your trip, pull over and crack (sloooooly- you can get a bath) the cap and let out the pressure. Drive on and see if it is better for a while.
>
> Test 2 Take the bottom hose off of the separator valve (found in the left-rear wheel well, up high, near the front bogie wheel), put another short hose on it and see if you can blow air through to the canister. Air should pass fairly freely. If you want to test the valve itself, you can take off the top hose, too.
>
> Ideally, the vapor is vented into the canister and sucked into the engine and used to go down the road. As a side bar, this valve can also let liquid gas into the canister under the shotgun seat, but that can only happen when the ball is not floating at all, and tanks are full or filling.
>
> The GMC Motorhome suppliers have newly designed vapor separators. Most Corvette parts suppliers have the original triangle shaped separator.
> --
> '74 Eleganza, SE, Howell + EBL
> Best Wishes,
> George
> _______________________________________________
> GMCnet mailing list
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>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Bad fuel smell [message #106979 is a reply to message #106963] |
Sun, 28 November 2010 20:46 |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
Karma: 0
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Senior Member |
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We are back but this gmc was changed over to TPI when I bought it. We went back to the carb after the TPI was about 30 yrs old and wasn't working correctly. We put in a new holly about 500 miles ago.
The fuel separator I may replace. Mine leaked horribly. I rebuilt it. Drilled out the cracked broken tube and put in a brass barb. I sealed it with epoxy thats gas friendly. It doesn't leak at all anymore. Maybe I'll replace it. When I bought the GMC I didnt know anything about them and couldn't find a replacement. But of course now I know a lot more and saw them for sale.
I don't sell anything near it, and its not leaking but I may replace it.
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: [GMCnet] Bad fuel smell [message #106987 is a reply to message #106979] |
Sun, 28 November 2010 21:18 |
Charles
Messages: 455
Registered: January 2004
Karma: 0
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Senior Member |
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Michael,
I think the vent tube from the filler neck runs straight to the
fuel tanks. If it has a low spot somewhere along its run
fuel might be settling there and when you go down hill it
moves forward and you then get fumes. Do you have
fumes in the cockpit when you fuel the coach. If you do,
then this could very well be the problem.
Charles
----- Original Message -----
From: "Michael" <radioactive626@msn.com>
To: <gmclist@temp.gmcnet.org>
Sent: Sunday, November 28, 2010 8:46 PM
Subject: Re: [GMCnet] Bad fuel smell
>
>
> We are back but this gmc was changed over to TPI when I bought it. We went
> back to the carb after the TPI was about 30 yrs old and wasn't working
> correctly. We put in a new holly about 500 miles ago.
> The fuel separator I may replace. Mine leaked horribly. I rebuilt it.
> Drilled out the cracked broken tube and put in a brass barb. I sealed it
> with epoxy thats gas friendly. It doesn't leak at all anymore. Maybe I'll
> replace it. When I bought the GMC I didnt know anything about them and
> couldn't find a replacement. But of course now I know a lot more and saw
> them for sale.
> I don't sell anything near it, and its not leaking but I may replace it.
>
> --
> 1973 23' Sequoia
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Charles Wersal
Duncanville, Texas
26 foot 1975 Glenbrook
Pandora's Box
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| Re: Bad fuel smell [message #106994 is a reply to message #106963] |
Sun, 28 November 2010 22:21 |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
Karma: 0
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Senior Member |
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No smell when filling. I mean you can't smell anything abnormal. Just going down a hill, when the tank is low on fuel. It was cold out when it happened.
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: Bad fuel smell [message #107038 is a reply to message #106963] |
Mon, 29 November 2010 12:27 |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
Karma: 0
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Senior Member |
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I'm going to start by changing the fuel vapor seperator as I rebuilt myself the one thats on there. I'm fairly sure its working the way I repaired it theres not much to it. But I'll replace it. I also need to order a new hose anyway for the filler neck might as well do both at the same time.
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: Bad fuel smell [message #107043 is a reply to message #107038] |
Mon, 29 November 2010 12:47 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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You are using the stock type non vented cap? If you are using a vented cap or if a small hole were drilled in the stock style cap to vent it there will be a gas odor coming from the cap. There are times the odor would be stronger then other times depending on the fume concentration in the tanks. This may not be your problem but something to consider
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Bad fuel smell [message #107050 is a reply to message #106963] |
Mon, 29 November 2010 13:35 |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
Karma: 0
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Senior Member |
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I do have a brand new vented cap. Didn't seem to smell it with the other cap on it. Maybe it vents alot more when the tanks are low?
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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| Re: Bad fuel smell [message #107085 is a reply to message #106963] |
Mon, 29 November 2010 21:49 |
RadioActiveGMC
Messages: 1020
Registered: November 2010
Location: Hot AZ desert
Karma: 0
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Senior Member |
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Ordered a new 45 degree filler hose, and new fuel vapor separator and will keep my fingers crossed!
***"Gettin There"-1973 23' Sequoia-
Michael, Onans smell, "Go solar/wind power!"
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