| Fuel filler system - possible to upgrade? [message #203190] |
Sun, 31 March 2013 11:14  |
dgsav
Messages: 13
Registered: January 2010
Location: Lancaster, CA
Karma: 0
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Junior Member |
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My early '73 23' coach has at least two leaks in the fuel filler and limiter (vent) system. Several hoses in the system appear to be original, right down to the rubber filler tee to the auxiliary (front) tank (this tee should have been replaced by the GMC recall that swapped out the original vapor canister for the fuel separator). I much prefer the concept of just three hard tubes in the updated (approximately 1975-on?) second design system rather than the several hard tubes with several hard-to find rubber couplings and tees in my original first design system.
Questions: is it feasible for me to replace the first design filler tubes with second design tubes? If so, where could I get the second design filler neck, filler tube, and limiter (vent) tube for a 23' coach?
David
'73 23' x-Painted Desert TZE033V100223
[Updated on: Sun, 31 March 2013 11:36] Report message to a moderator |
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| Re: Fuel filler system - possible to upgrade? [message #203233 is a reply to message #203190] |
Mon, 01 April 2013 00:07  |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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| dgsav wrote on Sun, 31 March 2013 09:14 |
My early '73 23' coach has at least two leaks in the fuel filler and limiter (vent) system. Several hoses in the system appear to be original, right down to the rubber filler tee to the auxiliary (front) tank (this tee should have been replaced by the GMC recall that swapped out the original vapor canister for the fuel separator). I much prefer the concept of just three hard tubes in the updated (approximately 1975-on?) second design system rather than the several hard tubes with several hard-to find rubber couplings and tees in my original first design system.
Questions: is it feasible for me to replace the first design filler tubes with second design tubes? If so, where could I get the second design filler neck, filler tube, and limiter (vent) tube for a 23' coach?
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The old hoses do leak. Some have replaced the rubber hoses from the tanks with steel and other materials. I just redid my hoses.
The separator valve and canister is a must have in my opinion, when I had a separator fail my tanks had so much pressure on warm days, while driving I could see the gas gauge go down after filling. I had to stop and very carefully release pressure at the cap. The gauge would then go back to full ( that is some tank bulging.) the canister keeps fumes and the separator stops raw gas. The canister let's you burn the fumes to go down the road. The tanks must vent. In addition as you drive tanks can need air to replace the used fuel. The canister filters that air so you don't get crud in the tank. (a hole to the outside or a hose off a canister invites dirt and is a smelly and possibly dangerous situation.)
The actual fill tubes are not something I have ever seen replaced. I have seen coaches with an side fill for one tank. I find the fill tube angle better on my 74 when compared to a 78 I had. The 74 fills better and the nozzle doesn't hit the inside of the fill box. The tee and elbow were fine on mine, but are available at JimKs I believe.
The hoses by the drivers elbow can be a pain to change.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Fuel filler system - possible to upgrade? [message #203260 is a reply to message #203190] |
Mon, 01 April 2013 10:27 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| dgsav wrote on Sun, 31 March 2013 12:14 |
My early '73 23' coach has at least two leaks in the fuel filler and limiter (vent) system. Several hoses in the system appear to be original, right down to the rubber filler tee to the auxiliary (front) tank (this tee should have been replaced by the GMC recall that swapped out the original vapor canister for the fuel separator). I much prefer the concept of just three hard tubes in the updated (approximately 1975-on?) second design system rather than the several hard tubes with several hard-to find rubber couplings and tees in my original first design system.
Questions: is it feasible for me to replace the first design filler tubes with second design tubes? If so, where could I get the second design filler neck, filler tube, and limiter (vent) tube for a 23' coach?
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David,
I am pretty sure it is possible because I believe it was done to my coach. Mine has the metal T in the fill system. I finally bit the bullet a year ago and replaced everything rubber under the coach. Most was replaced with metal. What rubber was used was J30-R14.
The smart move is to plan to take the tanks down. There is a lot of rubber up there and if it hasn't been replaced, it should be.
There are actually five systems back there. The fill, the delivery, the fill vent, the vapor vent and the genset (APU) feed (the rear - main tank only). There is also a very good chance that there is plugged stub on the main tank that nobody is really sure why exists.
While you are under there, take the selector valve and check it out, mine was leaking and that made for some interesting problems in fuel management.
The fill vent system (the part that goes back to the fill neck probably has a T near the fill T. If it does, move it as far forward and up as High as you can easily. This one mod will make your future fueling experiences much more productive and pleasant.
There is a fellow that makes a habit of breaking down GMCs for parts and just now I can't recall his name, but someone will (I hope). That may well be the best source for the fill plumbing parts.
Matt - still working my way back north - Slowly.
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: Fuel filler system - possible to upgrade? [message #203312 is a reply to message #203260] |
Mon, 01 April 2013 16:01 |
dgsav
Messages: 13
Registered: January 2010
Location: Lancaster, CA
Karma: 0
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Junior Member |
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| Matt Colie wrote on Mon, 01 April 2013 08:27 |
There is also a very good chance that there is plugged stub on the main tank that nobody is really sure why exists.
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The original GMC fuel vapor recovery system had a liquid-vapor separator canister mounted inboard of the mid left wheel (front rear). This silver (judging by photos) flat canister is not to be confused with the round black charcoal canister(s) on the right front frame near the engine. This early vapor canister had 4 hoses – one vent hose from each fuel tank, one vapor hose to the charcoal canister, and one fuel drain hose back to the main tank. My early ’73 would have left the factory with this system.
There was a fuel system recall mid-to-late 1973 that replaced the 4 hose liquid-vapor separator canister with the smaller 2 hose check ball separator we all have today. The recall kit tied the 2 fuel tank vent hoses together with a tee and removed the fuel drain hose altogether, leaving just one fuel vent hose into the new separator and one vapor hose out to the charcoal canister. The recall instructions specified to cut the fuel drain hose a few inches from the main fuel tank and plug it with a 3/8 bolt and a hose clamp. Pretty sophisticated factory fix, eh? When I first saw this on my coach, I thought it was a kluge from a previous owner.
Another part of this recall was to replace the front tank filler rubber tee with a metal tee and short hoses. My coach still has what is probably the original rubber tee (has the proper GM part number) and amazingly, it is in good shape, unlike many of the other filler hoses. I have no idea why it wasn’t replaced when the vapor recovery system was converted. Maybe the dealer mechanic didn’t feel like partially draining the tanks to do the job?
Sometime around 1975, probably when they went to the second design fuel filler system, they removed the fuel drain fitting from the main tank. The 1975 service manual section on the fuel system shows both the first design (Type 1) and second design (Type 2) filler system layouts and one can see where the drain fitting was erased in the second design drawing.
This second design is what I’d like to put on my coach. Just compare all the couplings (leak points) in the first design with the much simpler second design.
Thanks for the input regarding plumbing pieces; i'm hopeful that someone does have such parts available.
David
'73 23' x-Painted Desert TZE033V100223
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