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Some gas tanks have an independent vent tube that runs along side of the filler neck. If a leak is in the vent tube or filler tube high enuf to disallow fuel leakage it mite allow water seapage from rear tire spary during rain.

At this point we need to eleminate or confirm the water issue as a possibility or the vapour lock. The electric fuel pump pushing fuel or fuel/water/debris on thru the sytem is only a band-aid for both problems.

Trog writes:
"I assumed it to be vapor lock given the new tank, blown out lines, and filter at the back."

Good control unit for diagnosis. If the problem is fuel then it's either vapour lock or water. Wonder if there is water from recent refueling???

Have thought more and still believe the weak valve and pressure pushing the fuel back is the most reasonable explanation.

As far as the electric pumps, they are as prone to alcohol or additives destroying the rubber parts as mechanical pumps so that may be part of the issue--particularly the older ones.

Might be interesting to fit a diesel fuel water separator if one is available at a reasonable price and see if that is actually what is happening. I know condensation is a big issue here in winter but not so much summer.

As to the low end gas station, wouldn't necessarily condemn it early. We had an incident here early last year where shortly after filling up at a large local independent station, cars were dying and had to be towed. Later reports of same thing from other stations. Found that about all stations locally (including major branded) are supplied from the same tank farm. Someone had opened a wrong valve, mixed diesel and gasoline together and filled all the route trucks that previous evening. The independent was one of the first to get his supply & also one of the first on a major commute route which is why the reports started there.

Customers made a stink with the majors having same problem & same gas and their explanation was just because it says X or Y on our sign, it just means the product meets our standards--not that we necessarily produced it. Moral in this case, you pay 10 or 20 cents more a gallon for the name.

Fortunately, the tank farm absorbed somewhere close to a million in pumping out and replacing gas plus repair costs for hundreds of cars which had to have their tanks removed and drained plus injector work in some cases.

I'm not ready to place blame anywhere in particular at this point. But i'm not convinced of vapor lock either.
As for the fuel suppliers i agree that we never really know where the fuel comes from. Maverick suppliers dumping at nite and so on and so-forth.

I am suspicious about individual gas stations and their susceptibility to rain gathering in their parking lot and running into the holding tanks under the ground or fractures in the holding tanks.

Guess rainwater is possible but would believe condensation more likely--believe most tanks pretty well capped. Don't know about Tennessee, but here in most parts of the state, because of the old tanks leaking MTBE (or somesuch name) and contaminating groundwater, the EPA forced gas stations to remove old underground tanks, replace with ones above ground or if under, something that won't corrode etc. If they didn't do that, had to close down AND remove tanks. New tanks have monitoring equipt, and because of air resources board, vapor recovery systems in some counties--so running rainwater or seepage would be low on the list of problems here--(the drought doesn't help either). Interestingly, none of this would have taken place if air resources and EPA hadn't forced them to sell the MTBE (which turns out to be a potent carcinogen) gas in the first place as a way to cut pollution.

I'm thinking that HH56's fuel/water seperator is the best idea so far. What if i cheat and just use a spare cARTER glass bowl filter mounted near the tank. Just need to come up with some kind of stone shield for the glass bowl and carry extra cork gaskets.

Quote:

I wouldn't use cork gaskets anywhere modern fuel is involved.

Here is my two cents.

I really think a marginal mechanical fuel pump can be the cause of a lot of the phantom vapor lock issues. It the valve seals are getting old, or there is grit imbedded in the sealing surfaces, or a partial clogged inlet screen, then the fuel pressure that it can both deliver to the carb, and the vacuum it can draw on the fuel line may be affected. So on normal/cool days it runs fine as the marginal pump doesn't have to try to overcome any possible issues with the fuel becoming vaporized in the line. But on hot days when the vapor issue in the fuel arrises, the marginal pump cannot over come that.

Where as a good fuel pump can over come that issue because of the higher fuel pressure, vacuum it can generate. Explains why on two of the exact same models running the same fuel that one is having the problem and the other may not. The lower the fuel pressure the higher the chances of vapor lock are.

"Ethanol is the one commonly distilled from corn or biomass and which is used in gasoline by Federal requirement an an oxygenate (source of oxygen), isopropanol is the one which we used to buy as "dry gas"."


Should we expect Ethanol to be significanlty less effective as a "dry gas" than isopropanol???

OR, let me pose the question a different way:

Should we expect long term use of Ethanol gasoline, as delivered from the gas station pump, to keep our automobile fuel system void of water and condensation?????

Probably no, and yes, respectively, assuming you don't get really heavily water-contaminated gasoline, and/or exceptional amounts of condensation.