Fuel starvation

[jasm158]

I HAVE A BOGGING PROBLEM AT HIGH RPM AND HEAVY LOAD, SEEMS AS THOUGH IT RUNS OUT OF GAS AND THE PUMP CANT KEEP UP, I HAVE BEEN HAVING THIS SAME PROBLEM FROM THE BEGGINING, TOUGHT IT WAS THE CARB(1406) BUT I HAVE MADE THIS THING AS RICH AS CAN BE(CHANGED JETS RODS SPRINGS) WITHOUT FLOODING, I STARTED OFF WITH MECHANICAL PUMP THINKING NOT ENOUGH PRESSURE, NOW HAVE A HOLLEY BLUE AND STILL RUN INTO PROBLEMS, BEFORE I FORK OVER MORE CASH FOR ANOTHER CARB, HERE IS MY QUESTION: IS MY FUEL SYSTEM ROUTING TO RESTRICTIVE?

FROM TANK(WITH NEW PICKUP) TO PAPER FRAM FILTER, DOWN TO HOLLEY PUMP, 3/8 LINE OUT, APPROX 6 FT RUN THEN REGULATOR THEN AFTER REG. IS A NOTHER FILTER THEN THE CARB...TOO MANY FILTERS? FILTERS CANT MOVE FUEL FAST ENOUGH? SHOULD I RUN ALL NEW 3/8 LINE...ANY ADVICE WOULD HELP..SORRY FOR THE CAPS IN ADVANCE

 

[Jims86]

Could be a timing issue also. This same thing happens when after top dead center is mistken for before top dead center. Check the timing before you spend any Mo' Money!

 

[chengny]

Some diagnostic tests - from GM service manual.

Since you are currently supplying a carburetor with an electric fuel pump, you'll need to pick the ones that apply:


FUEL PUMP FLOW TEST (Electric)

1.Disconnect the EFI fuel feed line, then connect suitable hose to line and direct end into suitable container.
2.Apply battery voltage to the fuel pump test terminal. The fuel pump should supply 1/2 pint or more fuel within 15 seconds.
3.If fuel flow is below minimum, check for fuel restrictions. If there is no restrictions, check pump vacuum and/or pressure.

FUEL PUMP FLOW TEST (Mechanical)

1.Connect hose from carburetor fuel feed line to a suitable unbreakable container and crank engine.
2.Fuel pump should supply 1/2 pint or more in 15 seconds.
3.If flow is below minimum, check for fuel restriction. If there is no restriction, check pump pressure and/or vacuum.



Fuel Pump Pressure Test (Electric)

1.Remove air cleaner and plug THERMAC vacuum port on throttle body unit.
2.Remove fuel line between TBI unit and fuel filter. Use a suitable back-up wrench to hold flare nut on throttle body when removing line.
3.Install fuel pressure gauge J-29658 or equivalent, between throttle body and filter.
4.Check pressure reading with engine running. Fuel pressure should be between 9 and 13 psi.
5.De-pressurize fuel system, remove pressure gauge and reinstall fuel line.
6.Start engine and check for fuel leaks.
7.Remove plug from THERMAC vacuum port and install air cleaner.


FUEL PUMP PRESSURE TEST (Mechanical)

1.Disconnect the fuel line at the carburetor.
2.Install a low pressure gage onto the line.
3.Start the engine.
4.Fuel pump pressure should be (4 to 6.5 psi) .
5.If pressure is less, check for restrictions in fuel tank sender filter, lines or hoses.
6.Reconnect the fuel line.

From me:

Since the low flow issue is present only during periods of heavy load, pay special attention to the suction side of the pump. If there are any sections of rubber hose in the suction line be sure that the hose is of the proper material, sufficiently sized and has no tight bends or obvious kinks.

 

[jasm158]

Could be a timing issue also.

This was one of my very first thoughts... I just need to put a timing tape on current crank damp. ....i will check back

Thanks for the info....its not fuel injected, i keep the pressure around 5 to 6 pounds...with gauge.

 

[wheelerboy12]

change your fuel filter... had the same type of problem, three days to figure that one out. hope this helps!