Home » Public Forums » GMCnet » Vapor lock and me (Lots of progress)
| Vapor lock and me [message #178733] |
Thu, 02 August 2012 15:12  |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma:
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Senior Member |
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There has been a lot of talk about vapor lock lately so I though I’d give you my 2 cents.
I live in Arizona, I frequently drive my GMC when outside air temperatures exceed 100 degrees Fahrenheit. It is almost impossible to find pure gas (no ethanol) anywhere so I don’t even try – happens by accident sometimes but not very often. I am currently in Branson, Missouri on a planned 8,000+ mile trip from the Tucson, Arizona area to Maine and back again. I have had virtually no problems with vapor lock on this trip.
When I say I have had no problems with vapor lock I mean that I don’t get stuck, the engine doesn’t stall, I can feel the occasional mild ‘stuttering’ after refueling but nothing that causes concern. I hope I am not jinxing myself with this declaration but I have to say it can be overcome – at least until I get fuel that has more than 10% ethanol.
I have driven my coach on extended trips during the summer for the past two years – Maine and back in 2010 and Banff and Vancouver and back in 2011. During those trips I did have vapor lock problems and I was frequently stuck trying to keep the coach running on hot days. Since last year the only major thing I did was (with lots of help and advice from Steve Ferguson) block the crossover ports on my stock intake manifold. Other than that, I use an full time electric fuel pump (Carter P4070 – no mechanical pump) mounted on the outside of the frame as suggested – it has helped but did not solve the problem completely.
Earlier this year we left Arizona on Sunday, April 27th, and crossed the Mojave Desert in 110 degree heat – very early for that kind of heat. The coach had exactly the same configuration as it does now. During that day I did have a couple of interesting things happen.
First, I stopped in Gila Bend, AZ to refuel and the temperature was at about 100 degrees – there was a lot of vapor pressure in the tanks and it took me a couple of minutes to manually bleed the pressure off so that I could remove the gas cap. Immediately after the refueling, vapor lock symptoms (stumbling and hesitation) happened getting back on the highway but quickly went away.
Second, I stopped in Yuma, AZ for more fuel before entering California – trying to save some money. Again I had to spend a lot of time bleeding the vapor pressure off the tanks before I could remove the gas cap. This time I decided that I would leave the gas cap loose because that vapor pressure had to be a potential problem I thought. I left the gas station and could barely keep the engine running well enough to get turned around and back on the highway. I had to stop and put the gas cap back on tight and, within a couple of minutes the problem went away and, has not returned. I have a new fuel-vapor separator and charcoal canister in case you are wondering – they apparently can’t keep up with the vapor produced in the tanks.
I suspect that the excessive vapor pressure in the tanks on that day was due to the gas not being formulated correctly for the outside air temperature – it was still the winter formulation.
Even on this trip, the only hint of vapor lock problems has occurred immediately after refueling. I would have to guess that the vapor pressure buildup helps to stop the fuel from boiling in the tanks. Although the vapor pressure is there when I try to remove the gas cap it is nowhere as high as it was in April.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
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