FAQ – Carbureted Fuel Pumps

After hard braking or cornering, or when parking on steep inclines, my fuel pressure falls and it takes a long time to come back up, why?
Fuel pump supply and/or pickup problems are commonly the cause of this dilemma. Most often, the use of a restrictive filter before the pump, one that is too small or too fine, or both, is at the bottom of things. This is a problem for all types of electric pumps and will result in either cavitation, if the pump pulls well and makes vacuum, or loss of prime and difficulty reestablishing same if it does not. Be certain the line connecting the fuel cell to the fuel pump inlet is the correct size and that the inlet filter is course and free flowing. Certain rollover vent valves have also been found not to function, allowing significant vacuum to form in the tank and forcing the fuel pump to drop prime. A lack of baffling and slosh control panels, common in early muscle car and pickup truck fuel tanks, is another significant cause of intermittent fuel pressure during vehicle maneuvering. I your tank is not properly baffled you will be required to maintain fuel levels at or above ½ full to minimize this problem. See tech bulletins #101, Fuel Filtration and #801, Fuel Tanks and Cells for additional information.

Right after installing my fuel pump, or after disconnecting the fuel lines for maintenance, the pump has to run a long time before building pressure again.
These are symptoms of the same problems outlined in question number 1 above. Cracking the line connected to the pump inlet, then the line connected to the carburetor or fuel rail may help purge air, be careful to avoid fuel leaks and prevent fire hazards anytime fuel is being handled!

My fuel pressure is steady until after the car leaves the starting line, then down track, it falls 2 PSI or more, what’s wrong?
Though this may seem to be a regulator problem, it is more often an indication of a fuel supply problem. If for some reason there is insufficient fuel volume available from the fuel pump to actually oversupply the engine, creating backpressure to the regulator, line pressure will begin to drop. A significant drop in line pressure will result in a drop in regulated pressure, affecting fuel flow into the float bowl. Do not automatically assume the pump is bad or inadequate, inspect and resolve any supply line issues to the pump, ensure that the tank is vented and the vent is functioning, and be sure to check the fuel pump wiring, along with the overall electrical system performance. Finally, contact Aeromotive for a proper flow test, one you can perform in the field, to verify if your fuel pump is performing properly or not.

I’ve installed an A-2000 Fuel pump, with the bypass from the pump connected to the fuel cell, along with a bypass regulator and return line from the carburetor. When I try to adjust the regulator at the fuel pump, it has no affect on system pressure, why?
When using a bypassing regulator at the carburetor, line pressure and regulated pressure are one in the same. The bypass on the fuel pump should not be connected when using a bypass regulator at the carburetor. The fuel pump return port should be blocked with a –8 AN port plug. The rule is, when two bypass regulators are connected to the same fuel pump, the regulator set for the lower pressure becomes the default regulator, with the bypass on the higher pressure regulator remaining closed and therefore not regulating. The recommended bypass regulator for use with fuel pump P/N 11202 is P/N 13202, and should be installed with a –10 AN return line for proper regulation.

I’m using an A-2000 fuel pump and can’t get the pressure to go below 11-12 psi, it keeps flooding the carburetor, what’s wrong?
The regulator on the A-2000 fuel pump, P/N 11202, is designed to control line pressure (inlet pressure) to a standard, non-bypass Aeromotive regulator, including P/N’s 13208, 13210,13203, 13201 and 13205. The pump bypass is not capable of flowing sufficient volume to regulate pressure below 12 psi and cannot be used alone (without a proper blocking or dead-head regulator under the hood) to regulate pressure to a carburetor float bowl. The bypass regulator feature built into the A-2000 fuel pump is designed to present extremely consistent, adjustable fuel “line” pressure to the inlet of a regulator under the hood.