YFA carb leak down
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YFA carb leak down
I have an 84 f150 with a YFA carb that has gone through many rebuilds and works fine. Old truck runs great. Starts great when I leave it for a day or maybe two. Withing two or more days it will leak down and I have to "spin" the engine a bit to get gas back in the carb bowl.
Guessing that maybe the valve in the canister vent system is not closing or something.
John McDonald
Guessing that maybe the valve in the canister vent system is not closing or something.
John McDonald
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Joined: Dec 2007
Posts: 8,521
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From: Lost
It's not really that usual for fuel in the carb bowl to evaporate after a few days, especially with winter fuel still in the system during warmer weather. Winter fuel has a lower vapor point temp, to assist in getting it to vaporize in colder temps. This means in warmer weather, it will evaporate quicker.
Stations that do not sell high volumes of fuel tend to have winterized fuel longer than higher volume stations. The formulation is made at certain times of the year, by the refinery, and retailers have little or no control on what blend they get at any given time.
However, it's quite possible that the accel pump has a very tiny hole/split/crack in the diaphram, and the fuel is slowly dripping thru and into the engine.
My truck was showing these same symptoms, and I discovered the fuel line between the frame and pump was split. I guess it was sucking air in, rather than fuel, so letting it sit for more than a few days required priming the carb in order to get it started back up. I'm pretty sure the check valve in the fuel pump is not quite sealing off after more than 12 years of ownership and never having changed it.
Replacing that piece of fuel hose cured my issue.
Stations that do not sell high volumes of fuel tend to have winterized fuel longer than higher volume stations. The formulation is made at certain times of the year, by the refinery, and retailers have little or no control on what blend they get at any given time.
However, it's quite possible that the accel pump has a very tiny hole/split/crack in the diaphram, and the fuel is slowly dripping thru and into the engine.
My truck was showing these same symptoms, and I discovered the fuel line between the frame and pump was split. I guess it was sucking air in, rather than fuel, so letting it sit for more than a few days required priming the carb in order to get it started back up. I'm pretty sure the check valve in the fuel pump is not quite sealing off after more than 12 years of ownership and never having changed it.
Replacing that piece of fuel hose cured my issue.
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