Home » Public Forums » GMCnet » Gas Be Gone
| Gas Be Gone [message #203255] |
Mon, 01 April 2013 09:42  |
DrPepper
Messages: 80
Registered: February 2013
Location: Goose Creek,SC
Karma: 0
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As most of you know I just got this unit, and about 2 weeks ago I filled her up(42 Gallons). Sine then I have driven 110 miles, and run the generator for 4 hours. One the third day of camping, the generator stopped working. I was upset because I thought I had a generator issues, so we called it quiets early, and started to drive home(40 miles). So My Gas Gage always show Full, but I figured I would top her off and She Took 46 Gallons, OMG.
So I figure I used up 20 gallons max for 150 miles and 4 hours of Gen Time, where did the other 26 gallons go?
She is parked in a heated garage, and I see no signs that I have a leak even while running.
It was parked at a Shop outside for 2 weeks, maybe it was stolen?
Can you siphon gas form a GMC? I bought a locking Gas Cap Just in Case. lol
Is there any other Way to lose that amount of Fuel?
I wonder how hard it would be to get the Gas Gage working again?
Phillip Udel - I Own a 1975 Avion
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| Re: [GMCnet] Gas Be Gone [message #203263 is a reply to message #203255] |
Mon, 01 April 2013 10:38  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Phillip,
My short list of things to check before driving the coach from Ohio to California was mostly about safety. Unfortunately I should have replaced every rubber fuel line too as each stop at a gas station turned into a reenactment of the Exxon Valdez disaster.
If you don't know when the fuel lines - fill hoses, vent lines, gas hoses - all of 'em - were changed then they need to be done now. Today's gas eats yesterday's rubber and you are seeing what the result is.
The bad news is you'll have to drop your tanks.
The good new is that there are a lot of options available to you, but you must be certain to use only fuel hose that is rated for today's fuel. And once the tanks are down you can replace the senders if they prove to be bad. Some of the crafty geniuses here have devised electric fuel pumps that fit inside each tank just like modern cars. Others have placed a single electric pump on the frame rail. Some choose to eliminate as much rubber as possible by utilizing a metal tube that is easily bendable. While the tanks are down some choose to paint the underside white to reflect some summertime heat - others will install a second heat shield for the same purpose.
There are also two gizmos, a fuel separator and vapor canister that were originally mandated by smog laws but are beneficial to the coach that ought to be looked at while working on the tanks. These are available from our vendors if you need to replace them.
Also, while the tanks are down Some have taken to cutting access holes in the floor so they might service the top of the tanks.
As I look at this not I see that it's long on generalities and short on specifics. Others will help with the details.
Larry Davick
A Mystery Machine
Fremont, CA
1976(ish) Palm Beach
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Gas Be Gone [message #203264 is a reply to message #203258] |
Mon, 01 April 2013 10:46 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| WD0AFQ wrote on Mon, 01 April 2013 08:17 |
It ain't funny but I had to chuckle anyway.
I suspect you drove closer to 200 miles, used 35-40 gallons, and the Onan sucked up the rest. They get better out on the road. That is all I can say. 
Welcome to the group. I get 7-9 mpg on the road towing a car.
Dan
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Adding to what Dan says, it is possible that the 42 gallons wasn't a complete fill-up. Sometimes it is hard to fill the tanks all the way. (Due to the Plumbing to and venting of the tanks.) That is one reason why your fuel mileage needs to be calculated over a much longer period than a single tank.
That said, you seem to be getting poor, but not unheard of, mileage. Did you happen to leave the parking brake on? (I did that once... was getting about 3 mpg but it was not really noticeable other wise.  ) Check for dragging brakes.
There are things to look at as you learn your coach. Many can effect apparent mileage.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Gas Be Gone [message #203281 is a reply to message #203264] |
Mon, 01 April 2013 11:42 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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I got a measured 5mpg on my first big trip!
but youre getting like 3?
check the jetting on your carb!
Maybe send it to Dick patterson...
and YES get the fuel gauge working or you will be stranded!
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: Gas Be Gone [message #203283 is a reply to message #203255] |
Mon, 01 April 2013 11:45 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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A gummed , dry, or stuck spark advance can really kill MPG. So can same on Qjet metering rods pn the primary side. The combination would really eat gas.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Gas Be Gone [message #203287 is a reply to message #203255] |
Mon, 01 April 2013 11:57 |
DrPepper
Messages: 80
Registered: February 2013
Location: Goose Creek,SC
Karma: 0
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I think it was Dick Patterson that built the motor and put the EI system in, this that the guy from Canada? I am %100 positive no more that 150 miles, I wrote the mileage down at the DMV when I did the title work. I know the Gen was only 4 hours, because I wrote that down two.
I did three short trips, about 10 miles each to my house from the Shop. Then I drove it once to the state part yesterday for 82 miles.
That is under the 150 miles est. So it's like 2.5 mpg. lol
With a total 2.5 hours of driving time.
The Hoses are 12 years old, so it would be good to change them.
I might have drop the tanks anyway to replace the Fuel sending units if they end up being bad.
I really thought it was a leak, when I go back to the shop today I am going to look and smell again.
Does the Gas Filler Tube have that anti-theft screen in it?
Phillip Udel - I Own a 1975 Avion
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| Re: Gas Be Gone [message #203288 is a reply to message #203283] |
Mon, 01 April 2013 12:02 |
DrPepper
Messages: 80
Registered: February 2013
Location: Goose Creek,SC
Karma: 0
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Ya, I need to look at that too, lucky for me I have some NASCAR mechanic in the same shop, I sure they would lov to help.
| JohnL455 wrote on Mon, 01 April 2013 12:45 |
A gummed , dry, or stuck spark advance can really kill MPG. So can same on Qjet metering rods pn the primary side. The combination would really eat gas.
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Phillip Udel - I Own a 1975 Avion
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| Re: Gas Be Gone [message #203291 is a reply to message #203255] |
Mon, 01 April 2013 12:32 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I have had the same experience. but was just bad gas mileage.
I was towing, against the wind, and somewhat up hill. was getting 3 to 4 mpg.
I have since rebuilt the carb, and am going do something about the distributor and tune up before I use it this year.
after I did the carb, I have not put too many miles on it, but I did notice that it is using alot less gas. but like he said, need to do a longer test.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Gas Be Gone [message #203292 is a reply to message #203255] |
Mon, 01 April 2013 12:33 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| DrPepper wrote on Mon, 01 April 2013 10:42 |
As most of you know I just got this unit, and about 2 weeks ago I filled her up(42 Gallons). Sine then I have driven 110 miles, and run the generator for 4 hours. One the third day of camping, the generator stopped working. I was upset because I thought I had a generator issues, so we called it quiets early, and started to drive home(40 miles). So My Gas Gage always show Full, but I figured I would top her off and She Took 46 Gallons, OMG.
So I figure I used up 20 gallons max for 150 miles and 4 hours of Gen Time, where did the other 26 gallons go?
She is parked in a heated garage, and I see no signs that I have a leak even while running.
It was parked at a Shop outside for 2 weeks, maybe it was stolen?
Can you siphon gas form a GMC? I bought a locking Gas Cap Just in Case. lol
Is there any other Way to lose that amount of Fuel?
I wonder how hard it would be to get the Gas Gage working again
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Phillip,
There are two real easy ways to loose that much fuel without starting the engine.
Yes, someone could siphon the top half of the tank pretty easily.
Even a microscopic leak could loose that much fuel in two weeks.
And as others have said, it takes very little to destroy the fuel economy of these old beasts.
As to the gages/sending units....
That is a classic stupid on GMs part. The system is low (2~3Ω) empty and ~90Ω full. So, when something gets bad (the typical condition) the indicator goes to full. I fought with bad connections under the coach for a few years while the senders were still effective. Start working with a meter and the ends of the harness near the selector valve. The color codes are in the service manual.
New sending units are ~150$us/ea.
I am currently running with two rebuilt senders. The job was not simple or trivial. If one has any income source at all, the repair would probably not be cost effective. I won't even write any more than that until I have enough miles on these to be confident that they are a successful repair.
Matt - headed for the Cape Fear Museum
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: Gas Be Gone [message #203298 is a reply to message #203293] |
Mon, 01 April 2013 13:02 |
DrPepper
Messages: 80
Registered: February 2013
Location: Goose Creek,SC
Karma: 0
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Member |
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Ya, I thought about that today, The best way I could think of was to use the Onan Gas port with a fuel pump.
So, if Usage is out, and Theft is out, that means leak somewhere.
maybe I will put 3psi to the tanks and fill lines and see if they sprout a leak. Hmmm, I wonder if I can do that with breaking something.
| Mike Miller wrote on Mon, 01 April 2013 13:33 |
| DrPepper wrote on Mon, 01 April 2013 09:57 |
...
Does the Gas Filler Tube have that anti-theft screen in it?
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Doesn't need one.
Look at the route of the fill tube.... and the height of the cap compared to the tank.
It would be VERY hard to siphon gas from a GMC. It would be hard even to pump it out without tapping into a line under the coach. I think you would know if they did that! 
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Phillip Udel - I Own a 1975 Avion
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| Re: Gas Be Gone [message #203305 is a reply to message #203255] |
Mon, 01 April 2013 14:23 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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if the tank selector is old. it will draw from both tanks.
I have the same selector valve in my jeep wagoneer and it is old with aux tank. and it is trust me, now with the electric fuel pump, it will dry out both tanks.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Gas Be Gone [message #203318 is a reply to message #203255] |
Mon, 01 April 2013 16:33 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Ouch... that's a lot o' gas for that kind of usage. My coach's fuel lines had just been changed 12 years ago by the PO, but apparently they weren't really rated for the ethanol-laced gas we have to buy today. I knew I had a SERIOUS gas leak, though generally I could put around 35 gallons in before it started dumping out between the tanks. So I ordered the hose to replace all the gas lines (with ethanol-rated hose, of course). The "old" 12 year old lines didn't really look all that bad - the problem was that there was a spot where the vent line from the rear tank went through an adapter to take it from (IIRC) 3/8" hose to 1/2" hose. It appears that whoever did the hoses last time must not have had the 8" or so of 1/2" fuel line, and just left the old (original?) stuff in place. It was SO far gone it was scary, and I'm sure it cost me a whole lot more spilled gas than I want to think about (especially when taking a long curve to the right).
The fuel line to the generator were in horrible shape as well, so I know I was losing gas there as well. Even with all the leakage I was able to get about 8.5mpg on a 5,000 mile round trip, much of it going too fast, and driving at too high an altitude for my carburetor to deal with, so I'm pretty happy with it. I can't wait to install the FI system I've put together for it, to see if I can crack that mythical 10.000mpg ceiling.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: [GMCnet] Gas Be Gone [message #203330 is a reply to message #203287] |
Mon, 01 April 2013 17:56 |
Emery Stora
Messages: 959
Registered: January 2011
Karma: 4
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Senior Member |
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On Apr 1, 2013, at 10:57 AM, Phillip Udel <admin@salemcorp.com> wrote:
>
>
> I think it was Dick Patterson that built the motor and put the EI system in, this that the guy from Canada?
I don't think that Dick Paterson (only one t) ever puts EI on the engines he rebuilds. I have to assume that the prior owner installed it.
Emery Stora
> I am %100 positive no more that 150 miles, I wrote the mileage down at the DMV when I did the title work. I know the Gen was only 4 hours, because I wrote that down two.
>
> I did three short trips, about 10 miles each to my house from the Shop. Then I drove it once to the state part yesterday for 82 miles.
>
> That is under the 150 miles est. So it's like 2.5 mpg. lol
> With a total 2.5 hours of driving time.
>
> The Hoses are 12 years old, so it would be good to change them.
> I might have drop the tanks anyway to replace the Fuel sending units if they end up being bad.
>
> I really thought it was a leak, when I go back to the shop today I am going to look and smell again.
>
>
> Does the Gas Filler Tube have that anti-theft screen in it?
>
>
> --
> Phillip Udel - www.gmcfabrication.com I Own a 1975 Avion, Still removing the Mothballs after sitting in storage for 10+ years
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Gas Be Gone [message #203331 is a reply to message #203330] |
Mon, 01 April 2013 18:19 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Emery, do you think he might be thinking of the Springfield distributor?
If he is, that is Dick Paterson's ignition, and it has the correct
mechanical advance and vacuum advance for a 455 with a quadrajet and
whatever cam that Dick installed in the engine. When we were at Dick's
place last summer, I asked him about fuel injection. At the time he was not
very "gung ho" on the throttle body type injection setups. He was more
concerned with fuel lines and adequate pressure to the carb as a way to
make the Olds engines run correctly on blended fuels. My thinking on this
whole fuel, carb vs injection flap is currently in a state of flux. I think
that pusher type electric pumps located either in the fuel tanks or as
close as you can get them, good tank venting, correct gas caps, and high
quality fuel lines that are alcohol resistant will go a long way towards
resolving most fuel related problems. But, that being said, I am collecting
the pieces to build a multi port fuel injection system triggered by a
reluctor wheel and sensor that will trigger the ignition as well as the
injectors. Gotta' have something to do in my spare time. (grin)
Jim Hupy
Salem, Or
78 Gmc Royale 403
On Apr 1, 2013 3:56 PM, "Emery Stora" <emerystora@me.com> wrote:
>
> On Apr 1, 2013, at 10:57 AM, Phillip Udel <admin@salemcorp.com> wrote:
>
> >
> >
> > I think it was Dick Patterson that built the motor and put the EI system
> in, this that the guy from Canada?
>
>
> I don't think that Dick Paterson (only one t) ever puts EI on the engines
> he rebuilds. I have to assume that the prior owner installed it.
>
> Emery Stora
>
> > I am %100 positive no more that 150 miles, I wrote the mileage down at
> the DMV when I did the title work. I know the Gen was only 4 hours, because
> I wrote that down two.
> >
> > I did three short trips, about 10 miles each to my house from the Shop.
> Then I drove it once to the state part yesterday for 82 miles.
> >
> > That is under the 150 miles est. So it's like 2.5 mpg. lol
> > With a total 2.5 hours of driving time.
> >
> > The Hoses are 12 years old, so it would be good to change them.
> > I might have drop the tanks anyway to replace the Fuel sending units if
> they end up being bad.
> >
> > I really thought it was a leak, when I go back to the shop today I am
> going to look and smell again.
> >
> >
> > Does the Gas Filler Tube have that anti-theft screen in it?
> >
> >
> > --
> > Phillip Udel - www.gmcfabrication.com I Own a 1975 Avion, Still
> removing the Mothballs after sitting in storage for 10+ years
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
> GMCnet mailing list
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> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Gas Be Gone [message #203340 is a reply to message #203255] |
Mon, 01 April 2013 20:04 |
Douglas Norton
Messages: 191
Registered: April 2008
Karma: 0
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Senior Member |
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I replied to the wrong thread (gas mileage question) It was intended to be posted here.
I had a 5 mpg car once. It turned out it had the choke on whenever I
was driving. I only drove a few miles to work in winter so the choke
forced the carb to suck fuel. If you have an intake manifold with the
exhaust crossover blocked off or if you have a bad linkage problem, the
choke could be your enemy. Just pull over, turn off your engine and
pull off the air cleaner cover when engine has just heated up and be
sure the choke is open. Just my two cents worth.
Not recommended
test I would consider: block off your fuel lines and run a fuel line to
a 5 gallon can strapped to your (front or rear bumper or wherever you
dare), drive about five highway miles and check to see how much you
used.
________________________________
From: Phillip Udel <admin@salemcorp.com>
To: gmclist@temp.gmcnet.org
Sent: Monday, April 1, 2013 7:42 AM
Subject: [GMCnet] Gas Be Gone
As most of you know I just got this unit, and about 2 weeks ago I filled her up(42 Gallons). Sine then I have driven 110 miles, and run the generator for 4 hours. One the third day of camping, the generator stopped working. I was upset because I thought I had a generator issues, so we called it quiets early, and started to drive home(40 miles). So My Gas Gage always show Full, but I figured I would top her off and She Took 46 Gallons, OMG.
So I figure I used up 20 gallons max for 150 miles and 4 hours of Gen Time, where did the other 26 gallons go?
She is parked in a heated garage, and I see no signs that I have a leak even while running.
It was parked at a Shop outside for 2 weeks, maybe it was stolen?
Can you siphon gas form a GMC? I bought a locking Gas Cap Just in Case. lol
Is there any other Way to lose that amount of Fuel?
I wonder how hard it would be to get the Gas Gage working again?
--
Phillip Udel - www.gmcfabrication.com I Own a 1975 Avion, Still removing the Mothballs after sitting in storage for 10+ years
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