Home » Public Forums » GMCnet » I've got the Vapors
| I've got the Vapors [message #145497] |
Tue, 04 October 2011 17:09  |
captjack
Messages: 271
Registered: February 2010
Location: Sebastopol, California
Karma: 1
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Senior Member |
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Just had a wonderful 3000 mile trip through southern Utah and visited all the parks and monuments.
I've decided to rename my coach "Prince of Darkness". No matter what I've done so far, when the temp rises and the road is warm, I've got the vapors. So, by traveling when it's dark, all is good. (I've painted my tanks white, installed a pump and filter at the tanks, and shielded the exhaust pipe).
So, the next step is to install in-tank fuel pumps. Hopefully that will bring joy.
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: [GMCnet] I've got the Vapors [message #145510 is a reply to message #145497] |
Tue, 04 October 2011 17:55  |
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hnielsen2
Messages: 1434
Registered: February 2004
Location: Alpine CA
Karma: 0
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Senior Member |
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Jack
It may help.
I installed 1/8" aluminum diamond plate under my tanks.
We run Howell F I with in line fuel pump.
Works for me.
Howard
----- Original Message -----
From: "Jack Christensen" <captjack@sonic.net>
To: <gmclist@temp.gmcnet.org>
Sent: Tuesday, October 04, 2011 3:09 PM
Subject: [GMCnet] I've got the Vapors
>
>
> Just had a wonderful 3000 mile trip through southern Utah and visited all
> the parks and monuments.
>
> I've decided to rename my coach "Prince of Darkness". No matter what I've
> done so far, when the temp rises and the road is warm, I've got the
> vapors. So, by traveling when it's dark, all is good. (I've painted my
> tanks white, installed a pump and filter at the tanks, and shielded the
> exhaust pipe).
>
> So, the next step is to install in-tank fuel pumps. Hopefully that will
> bring joy.
> --
> Jack Christensen - K6ROW,
> '76 Glenbrook/Clasco - "The Silver Bullet",
> '65 Clark Cortez,
> Sebastopol, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: I've got the Vapors [message #145668 is a reply to message #145497] |
Thu, 06 October 2011 00:03 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma: 2
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Jack, I had lots of fuel problems on my nearly completed 8-week trip from Arizona to Montana, Alberta, and BC until the weather cooled down a little. I think I had multiple problems and I ended up replacing my electric fuel pump, the relay that powers it and the safety oil pressure switch to solve the sudden engine stops. The stumbling continued once in a while when it was hot however until JimK suggested that I install the thick Felpro gasket under the carburetor. There were signs that my dual mufflers and open crossovers might be contributing (one side of the intake looked like it was getting hot). Since that Felpro gasket went in I have not had the problem again and I am sure that the engine starts much better now after stops when the engine is hot.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
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| Re: I've got the Vapors [message #145671 is a reply to message #145668] |
Thu, 06 October 2011 00:18 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Ok we all know vapor lock is fuel heating up. I have never had a vapor lock problem on a GMC but COOL is the RULE.
Here is what I have done to maintain cool.
1. Run a 180 degree thermostat
2. Block the exhaust crossover in the intake manifold.
3. Cover the fuel line between the fuel pump and the carb with fire sleeve or reflective foam tape.
4. Never buy Alcohol diluted fuel. If you are going to Kalifornia bring your fuel with you and get out of the state before you run out of fuel.
5. Exhaust heat shield between the exhaust pipe and the fuel tanks. Mine are OEM. GM put them on there when they built the coach because it was going to Kalifornia.
You can do a lot of other stuff like paint tanks etc. and if I ever have them out I will paint them white. So far I have not had any problems even up Trail Ridge Road (11,000 feet) or up to the Eisenhower tunnel (10,000 feet).
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: I've got the Vapors [message #145672 is a reply to message #145671] |
Thu, 06 October 2011 00:20 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Ken Burton wrote on Thu, 06 October 2011 00:18 |
Ok we all know vapor lock is fuel heating up. I have never had a vapor lock problem on a GMC but COOL is the RULE.
Here is what I have done to maintain cool.
1. Run a 180 degree thermostat
2. Block the exhaust crossover in the intake manifold.
3. Cover the fuel line between the fuel pump and the carb with fire sleeve or reflective foam tape.
4. Never buy Alcohol diluted fuel. If you are going to Kalifornia bring your fuel with you and get out of the state before you run out of fuel.
5. Exhaust heat shield between the exhaust pipe and the fuel tanks. Mine are OEM. GM put them on there when they built the coach because it was going to Kalifornia.
You can do a lot of other stuff like paint tanks etc. and if I ever have them out I will paint them white. So far I have not had any problems even up Trail Ridge Road (11,000 feet) or up to the Eisenhower tunnel (10,000 feet).
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I forgot to add that I do have a P4070 boost pump but I have not needed it. It was on the coach when I got it. It went bad (maybe from not being used) and I did replace it.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: I've got the Vapors [message #145690 is a reply to message #145671] |
Thu, 06 October 2011 08:37 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma: 2
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Senior Member |
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Ken, when it is anywhere near hot out and I am towing my engine runs at around 200 degrees. Putting a 180 thermostat will not affect that at all.
I plan to put a 3 inch exhaust system in with a single muffler in which case the crossovers will not get anywhere near as hot as they do with two unbalanced mufflers.
Maybe the fuel line would help but right now the crossovers are my prime suspect.
I have just driven almost 4000 miles between Arizona and California up into Canada and have never had the opportunity to buy gasoline without alcohol.
Chuck Garton has the most instrumented coach in existence. He can measure fuel temps in the tanks and says that all that shielding from the road and the exhaust has had no effect on his fuel temps.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
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| Re: I've got the Vapors [message #145691 is a reply to message #145497] |
Thu, 06 October 2011 08:39 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I have a stock 77 455 mechanical pump only and don't have any vapor problems to date. I'd look at the crossover/mufflers end of the equation. If you over send fuel to the Qjet you overrun the needle and seat.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] I've got the Vapors [message #145707 is a reply to message #145687] |
Thu, 06 October 2011 10:32 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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We need to figure the difference in your coach and mine. I drove it home from Sarasota in 100+ degree weather without problems, other than when I fueled, there was pressure on the filler. Lots o hiss when the cap was removed. No vapor lock, easy ride at 65 - 70 per up I 75. Running it around this last summer, no problems. On a later trip I got one sputter outside Asheville in 105 degree 3P heat after idling for maybe five minutes at an intersection, but the sputter cleared and it ran smoothly as soon as I got around the corner and punched it. It's a '76 23 foot Norris upfiot with the bathtub in the rear. It was originally sold in CA, so it had the california switches and such in the vacuum lines. I don't know if the exhaust is shielded or not. It has headers fitted by Sirum some while back, and high temp wrap around the plug wires and metal fuel line on the engine. Single muffler in the rear. No idea whether the corssover is blocked
or not, I suspect not since it doesn't appear on any of the peprwork supplied by the PO. I fed it elixer of exxon for the trip, which from the look and smell was 10% alcohol anyway. Later trip when I got gas in Asheville to return home, no alcohol, and much better mileage.
How come so many vapor up and mine doesn't?
--johnny
________________________________
From: Michael <lilmyk@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Thursday, October 6, 2011 8:48 AM
Subject: Re: [GMCnet] I've got the Vapors
I recently drove from North Carolina to Northern California and experienced horrible vapor lock. It was also 100+ outside. I have steel plates welded to the frame under the fuel tanks (PO did that) and an electric fuel pump mounted in the engine compartment (I want to move it rearward). As far as I know the exhaust crossover is not blocked, I could literally watch the fuel vaporize and evaporate when it hit the carb. I ended up adding Marvel Mystery Oil and it helped to the point of almost eliminating the problem. It is not my long term solution, I would love to put pumps in the tanks or move the electric one closer, but I am a new owner and just have not had the time. I also had to change my fuel filters on the way back, they were so plugged up, I was starving the engine.
Michael
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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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| Re: [GMCnet] I've got the Vapors [message #145709 is a reply to message #145707] |
Thu, 06 October 2011 10:51 |
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Michael Leipold
Messages: 318
Registered: April 2011
Location: Greensboro NC
Karma: 2
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Senior Member |
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I have been discussing this at work and one of my coworkers has run into vapor lock issues with motorcycles. The motorcycle tank was designed to vent a certain amount, with the new fuels, the vent can not keep up with the amount of vapor needing to be vented.
Hence the pressure build up in the tank. Possibly some GMC's have better vapor venting than others, I know my little catch can in the wheel well looks pretty decrepit. I also know if I keep pumping gas, it will eventually start running out from under the back of the motorhome, not sure where it is leaking. Another thought is the temp of the gas entering the carb. The fuel pump can essentially act as a fuel heater, along with the line running up the engine, and so can the float bowl on the carb. I know, looking into my carb, with the engine off and the electric fuel pump on with the pedal depressed, the gas is just turning into vapor as it is pumped in.
I think our vapor lock issues are a combination of many things, some GMC's may be in better "original" condition than others.
I have thought about devising a scoop to route fresh air over the tanks, but have not gotten much further than the thought.
And for what it is worth, my exhaust is dual Dynomax Mufflers, with a side exit, perhaps it is adding too much heat to the situation.
Michael
1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive 
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| Re: [GMCnet] I've got the Vapors [message #145713 is a reply to message #145707] |
Thu, 06 October 2011 12:01 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma: 2
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Senior Member |
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The issue with the crossovers is caused by dual mufflers with different resistance to flow. If the pressures on either side of the engine are unbalanced it will balance itself via the crossover and heat up the manifold and the carb. The thick gasket under the carb helps. I suspect in my case that the different gas formulations in Montana and Canada contributed. I also suspect that maybe the old gasket under the carb was leaking when things got hot?? The new gasket is seated correctly and snugged down (not tightened) and I have had only the slightest hesitation after a couple of stops since I put it on (ambient temps near 100) and the engine hot starts very well in hot weather now.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
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| Re: I've got the Vapors [message #145714 is a reply to message #145497] |
Thu, 06 October 2011 12:06 |
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Michael Leipold
Messages: 318
Registered: April 2011
Location: Greensboro NC
Karma: 2
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Senior Member |
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is the thicker gasket available in parts stores?
from a corvette forum:
The gasket you use depends on which manifold you have. If you have the manifold that has a curved exhaust groove crossover running from one side of the manifold to the other just forward of the primary throttle bores, you have to use a special 3-piece gasket set consisting of a thin hi-temp gasket with a metal shield and a thin top gasket. If you do not have the crossover feature, you need to use the standard 1/4" thick gasket. No sealants are needed - the gasket will not leak if the carb is correctly tightened.
1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive
[Updated on: Thu, 06 October 2011 12:13] Report message to a moderator |
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| Re: I've got the Vapors [message #145718 is a reply to message #145497] |
Thu, 06 October 2011 12:40 |
captjack
Messages: 271
Registered: February 2010
Location: Sebastopol, California
Karma: 1
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Senior Member |
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Johnny Bridges raised an interesting point. His tanks get pressurized and he heard a hiss when he removed the fuel cap. This happens often with my other cars, but never with the GMC.
Pressure in the gas tank would increase the boiling point of the gas, a good thing. It would also eliminate the slight vacuum which develops when the electric (or the engine) fuel pump sucks gas from the tank, also a good thing.
On modern cars there must be something that allows the tank to pressurize. There must be some restriction or pressure regulator between the tank and the carbon canister.
I dropped the tanks and changed all the hoses in my GMC including those in the vapor collection system. I don't recall seeing anything which would restrict the flow of vapor from the tanks to the carbon canister. Hopefully it wasn't there, hiding somewhere in a hose, and I removed it.
One thought would be to block off the vapor hose to the carbon canister. I'm really reluctant to even try this since I'm ignorant of the possible ramifications, which could be dire, But modern cars allow this to happen in a controlled way. Finding out how that occurs is something I'm going to look into.
But, meanwhile, I'm going to pursue the in tank fuel pumps using the info on the GMC International site.
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: [GMCnet] I've got the Vapors [message #145729 is a reply to message #145709] |
Thu, 06 October 2011 13:57 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I want to compare my 'parts' coach to my driver. The parts coach has the original dal mufflers just behind the engine and it has the original manifolding. My surmise is, it's going to get a lot hotter in the engine compartment than the driver with a rear muffler and headers. The driver has a lot more room for air circulation.
I need to fix the brakes on the parts opne so I can run it on the road and do somemeasuring.
--johnny
________________________________
From: Michael <lilmyk@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Thursday, October 6, 2011 11:51 AM
Subject: Re: [GMCnet] I've got the Vapors
I have been discussing this at work and one of my coworkers has run into vapor lock issues with motorcycles. The motorcycle tank was designed to vent a certain amount, with the new fuels, the vent can not keep up with the amount of vapor needing to be vented.
Hence the pressure build up in the tank. Possibly some GMC's have better vapor venting than others, I know my little catch can in the wheel well looks pretty decrepit. I also know if I keep pumping gas, it will eventually start running out from under the back of the motorhome, not sure where it is leaking. Another thought is the temp of the gas entering the carb. The fuel pump can essentially act as a fuel heater, along with the line running up the engine, and so can the float bowl on the carb. I know, looking into my carb, with the engine off and the electric fuel pump on with the pedal depressed, the gas is just turning into vapor as it is pumped in.
I think our vapor lock issues are a combination of many things, some GMC's may be in better "original" condition than others.
I have thought about devising a scoop to route fresh air over the tanks, but have not gotten much further than the thought.
And for what it is worth, my exhaust is dual Dynomax Mufflers, with a side exit, perhaps it is adding too much heat to the situation.
Michael
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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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