mechanical fuel pump

69bronc · Jan 17, 2005

I have a 302 w/ mechanical fuel pump. If I let it sit over night the fuel filter empties out and I have to crank it for a long time before it fires. Once the fuel gets back to the filter, (I have a clear one just b4 the carb) it fires right up.
Is there a check valve or something in the fuel pump bad? It has dual tanks so I don't know if the switch has anything to do with this problem.
Any help would be appreciated

Bronco Bull · Jan 17, 2005

The fuel pump could be bad, or there might be a crack.

Seabronc · Jan 17, 2005

I assume that the filter is somplace between the pump and the carb. If so, the only reason I can see for it to empty out, is a air leak in the hose between the pump and carb, the float valve is not seating properly or as BroncoBull said you may have a crack in the pump or the diaphram. If it is leaking at the pump diaphram check your oil for the possiblility gas in it. My pump worked with a leak in the diaphram for a long time, atleast long enough to put several quarts of gas in the oil. I didn't discover it until I did a oil change when about 10 quarts of fluid came out of a 5 quart system, talk about a driving bomb :huh: .

Good luck,

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Broncoholics · Jan 17, 2005

All early Broncos seem to do this. I think its the gas cap seal becasue I have a new carb, new lines & new pump. All my other carbs did the same thing. I haven't tried it yet but I think it would help.

Bronco Bull · Jan 17, 2005

I still think it's most likely a crack.

Bully Bob · Jan 18, 2005

Firstly,
Eng. should fire rigt up, even if you took the fuel pump "off" the night before !
(A cracked carb. bowl may be allowing its fuel to leak into the manifold & evap. over night... 1 Possibility)
Usually, a cracked bladder in fuel pump will leak out weep-hole (like the waterpump).
Fuel going backwards from the filter would have to push against many gal. of gas in the tanks. As mentioned, lines & connections are suspect. Fuel leaks usually leave a "trail."
Starting problem.... sounds more like an accelerator pump issue. Should get a healthy "squirt" if float bowl is full & acc. pump is good.

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