Fuel drain back?

[ghopp24]

86 K10 305. If my truck sits overnight or more than say 5hrs, I have to crank on it and pump the gas to start. If it only sits an hour or two it cranks as soon as i hit the key. Carb is new as well at the fuel pump and i broke into the fuel line between the bed and cab to put a filter. The filter is always full and no leaks. Anyone have any ideas?

 

[1987 GMC Jimmy]

I usually prime mine with two pumps before starting if it sits for more than half a day. It takes only a few seconds for it to start every time. The Quadrajet has about 10 or 11 thousand miles since reman, and the fuel pump has the same mileage on it, too. If you're sitting there pumping and pumping, something's wrong, but if you're just giving it a little boost, I think that's normal.

 

[Crispy]

At the firehouse we have a 77 Chevy step van that sits outside and i need to pump the throttle a couple times and it still cranks a little bit, not long, but definitely longer than a newer fuel injected vehicle. It will start immediately if cranked shortly after it was shut off. We also have a low mileage engine in it with an edelbrock carb. I think what you have there is normal as long as you arent cranking away excessively.

 

[Honky Kong jr]

Just because no fuel is present doesn’t mean it’s not sucking air or allowing it to siphon fuel out of the carb when it sits due to an air leak.

 

[ghopp24]

Thanks for the input..sucking some air is my guess since I have to crank on it more than 7 seconds , I would call that excessive, for it to hit after sitting a long while. . I currently have a broken ankle so it will be a bit before i can check the lines.

 

[RustyPile]

This subject has been discussed before.. The fuel cannot syphon OUT of a Q-jet.. Needle and seat sits above the bottom of the carb reservoir.. Law of Physics prevents syphoning.. If the reservoir is emptying between start ups, the metering well plugs AT THE BOTTOM of the reservoir are leaking.. OR something is causing the fuel to evaporate.... It's not uncommon to have to give the throttle a couple pumps before starting.. This "loads" the choke and introduces a small amount of fuel into the intake manifold for temporary enrichment...

 

[ghopp24]

Ok thanks. I'll check the carb. I used to be able to rebuild one blindfolded...20+ yrs ago..sucks getting older. Other than my starting problem she runs perfectly. Will start building a 400 after first of the year and put the 305 on the shelf.

 

[roadracerga]

You definitely have a siphon or drain back issue if it sits for a month or two fuel will evaporate. Fuel pumps can be an issue make sure it is not leaking into crankcase.