Quadrajet Evaporation

[DougA]

How long will a quadrajet sit before it's out of fuel? If I let my car sit about 5-6 days,have to crank and crank,to get the gas back up. Just wondering what's normal,or do I have a leak? Thanks.

[von]

Today's gasolines evaporate really fast. If a Q jet fuel level gets below the level that the accelerator pump will work (around 1/2 full) then it gets hard to start a cold engine. My Q jets, after being rebuilt and well plugs sealed, etc., typically will get hard to start after only about 3 days of sitting. Then it takes about 4 or 5 seconds of cranking to get the fuel level high enough to start the engine. That's with the float level set at 1/4"

[DougA]

I forgot to mention I'm using 100ll av gas.

[77cruiser]

5- 6 days for me too, now I have an  in tank electric pump.

[Frank400]

5- 6 days for me too, now I have an  in tank electric pump.

  And did the electric pump solve the long cranking ?

[77cruiser]

Seems to have just give it a pump  to set the choke & fires right up.

[markedmondson]

After sitting a week or less, my Q-Jet car needs to crank before firing.  After he rebuilt it, Cliff assured me the fuel bowl has no leaks.

We have E10 in North Texas.  I understand the rate of evaporation depends on several things, including the amount of ethanol, temperature, barometric pressure, design of bowl vents, car's susceptibility to heat soak.

I consider the cranking routine as part of the charm of owning an old analog car.  Consider it an opportunity to prime the engine before it starts. 

[Cliff Ruggles]

Even if the carb bowl goes dry the fuel pump should re-fill it quickly.  Having to crank for more than a few seconds and maybe one or two cycles may indicate that the fuel is draining back to the tank and the lines feeding the pump are dry.

Fuel has always evaporated in a vented system and vented carburetor, nothing much can be done about that, but it should not drain all the way back to the tank and have to be re-primed every time you let it sit a few days and need to re-start the vehicle....Cliff

[markedmondson]

Good points Cliff.

By priming the engine, I meant building some oil pressure while cranking before it fires. A tongue-in-cheek benefit.

In my case, after a week or so, the starter will crank 4-5 seconds before the engine fires.