Fuelling probs...

[monza]

hi guys,

75 EB, 351, Holley 650cfm 4 bbl, Holley mech pump.

I have intermittent starting probs.

the spark is no problem - she turns over furiously.

I have a small glass fuel filter inline to the carb - so i can see fuel line content.

On some days the filter is full - mostly its half full - but sometimes its dead empty...

obv when its empty it takes time for the fuel to come thru and fire up.

it didnt used to be like this - she has always fired first time.

When she fires and i watch the fuel - i can se the pump kick in and fuel sputter into the filter AFTER she has been running for a minute or so.... which means when there is no fuel in the line I am just turning, and turning and turning until the fuel sputters thru...

I am not experienced in this stuff, but shouldnt there be some kind of vacuum effect which keeps the fuel line charged ? so the pump isnt dragging it from the tank every time ??

As far as i can assess the whole fuel line is empty - she starts on residual fuel (wherever that is) - then the pump has to drag new fuel all the way from the tank... but when i have no residual fuel i have a problem...

and i am frequently experiencing no residual fuel...

any help would be great.

thx dudes, Monza.

 

[Bully Bob]

You may have a bad check valve in the fuel pump.

One "shade-tree" test is to ***** by mouth, into the fuel line (at the fuel filter area, or carb, whichever is easiest to get to) & see if air passes back to tank.

Also, make sure your accel. pump is working, by looking down the carb air horn & moving the accelerator. (Eng. & key off of course) This is a starting prob. 75% of the time.

 

[monza]

You may have a bad check valve in the fuel pump.

One "shade-tree" test is to ***** by mouth, into the fuel line (at the fuel filter area, or carb, whichever is easiest to get to) & see if air passes back to tank.

Also, make sure your accel. pump is working, by looking down the carb air horn & moving the accelerator. (Eng. & key off of course) This is a starting prob. 75% of the time.

1. Okay - if i can blow air to tank do ineed to replace fuel pump - or just a valve ?

and what does the check valve do.

2. Bit more help here... 'carb air horn' - is that just straight down into the carb with air filter off ??

I take it I can adjust throttle at carb - no need to use pedal in cab.

How do i know if the pump is working - wht am i looking for ?

thx again,

Monza.

 

[Bully Bob]

"---- Okay - if i can blow air to tank do i need to replace fuel pump - or just a valve ?-----"

PUMP....check valve is supposed to hold pressure in the line after the pump.

"----carb air horn' - is that just straight down into the carb with air filter off ---"

YEP

"----How do i know if the pump is working. what am i looking for ?---"

You should see a stream of fuel shooting down into the depths of the carb.