Mallory Ignition Mallory ELECTRIC FUEL PUMP User Manual

ELECTRIC FUEL PUMP TROUBLESHOOTING GUIDE

The following pertains primarily to Mallory COMP Pumps equipped with Gerotor style pump systems, but also applies to many other fuel systems.

BASIC INFORMATION

The Mallory Gerotor style COMP Pumps are more forgiving than vane style pumps, but it is still important to insure they are properly mounted and receive clean fuel.

The correct mounting position is even with or below the tank and preferably behind or next to the fuel tank. All electric pumps push fuel far better than they can pull (suck) fuel.

Make sure that a low restriction filter is between the tank and the pump. A 40-micron element it sufficient to protect the pump from contamination such as dirt, rust, fuel cell foam, etc. Mallory has them available that will screw directly into the pump itself.

Electric pumps need a clean and stable power source. Run a minimum of 12 gauge wires to the pump if it is relatively close to the power source. Longer runs should utilize 10 gauge wire instead. With a trunkmounted battery, we recommend that you use a relay to allow for short power wires to be run. Do not pull power from a common terminal, especially if the ignition is wired to the same terminal.

The regulator used must be properly matched to the flow characteristics of the fuel pump. Refer to the compatibility information in the current Mallory Catalog. Small regulators and big pumps don’t work. Also, check to make sure the pump and regulator are designed for the type of fuel that is going to be used.

For the longest possible life from your Mallory or any other brand of electric fuel pump, it is highly recommended that you use a bypass style regulator. This allows the pump to run cooler, keeps the fuel cooler reducing the chance of vapor lock, draw less amperage, and supply constant flow of fuel. The minor inconvenience that running a return line to the tank presents is more than offset by the positives mentioned above.

Fuel line size is based on the length of the lines in addition to the intended use. The supply line to the engine is based on the horsepower of the engine. The return line size is based on the total volume of the fuel pump. Basically, to insure stable fuel pressure, the return line should be of sufficient diameter to handle the full volume of the fuel pump without the engine running. That means that the return should be as big or bigger than the supply line

Use liquid Teflon or a suitable pipe dope and not Teflon tape on all threaded fuel systems connections. Pieces of the tape can break off as they are being assembled and plug up lines, get stuck on small passages, and even seize up a pump if they are large enough.

Don’t buy cheap fittings. Use low restriction fittings, preferably CNC machined ones like those listed in the Mallory catalog. Tightly angled fittings can be just as bad of a restriction as too small of a line size. The larger the radius, the better and make sure that you buy quality fuel lines. Look at them closely and make sure they have a large inside diameter. That especially applies to some of the low cost dual feed lines being sold today. Some 3/8" OD lines are 1/4" or less ID.

FREQUENTLY ASKED QUESTIONS

Q.- Why can’t I adjust my fuel pressure down? Even

with the adjuster backed all of the way out, I still have too much.

A.- Start by checking to make sure the regulator is

suitable for the pump you have installed. Next, if it is a bypass system, check the return line size. If the return line is too small, the regulator isn’t causing the pressure, rather it’s the return line size is too small. This is especially a problem when the factory return line is used. Ford Mustangs are probably the most common offenders.

There are a couple ways to prove it. The easiest way is to remove the spring from the regulator. Without starting the engine, turn on the pump. The pressure gauge must read less than 3 PSI on a carburetor-equipped engine and less than 10 PSI with high-pressure fuel injection.

FORM 1485M

12/03

Made in U.S.A.

Printed in U.S.A.

MALLORY IS A DIVISION OF THE MR. GASKET PERFORMANCE GROUP 10601 MEMPHIS AVE. #12, CLEVELAND, OH 44144

216.688.8300 FAX 216.688.8306 www.mrgasket.com

Q.- When I first hit the throttle hard, the pressure

drops then comes back up. Why?

A.- The pump has to catch up to the demand. The

problem would not exist if the car had a return (bypass) style regulator. The fuel would always

be flowing.

Q.- When I adjust the fuel pressure, it’s fine when it’s

cold, but then it starts dropping off. If I let it cool off, the pressure comes back up. If I readjust it hot, then I have too much pressure cold. What’s going on?

A.- This is a classic problem when there is a liquid

filled gauge mounted on or near the engine. The pressure isn’t changing, it’s the gauge reacting to the underhood temperature. To prove it, start the engine with everything cold, then blow hot air from a hair dryer on the gauge. You can watch the pressure reading drop. It’s just the nature of liquid filled gauges and hot engines. Try to mount the gauge away from as much engine heat as possible.

Q.- I want to run a return style system, but there isn’t

another hole in the tank. What can I do short of welding in a fitting. Can I dump it back into the feed line?

A.- Run the return into the fill neck if you have to, but

you cannot either put it into the feed line or the bottom of the tank. Remember to keep the return line above the fuel level in the tank.

Q.- Every Spring, I have to take apart my pump and

regulator apart. I store my car in the winter in a garage. Why the sticky mess?

A.- The higher octane the gas, the quicker it

evaporates. If you leave fuel in the system, add one of the many additives available and put in a regular pump gas. Racing type gasoline evaporates quickly and leaves a sticky mess that will gum up everything. Just remember to put the right fuel in before you go out and stand on the throttle.

Q.- I took my pump apart, cleaned it up and tighten it

back up. Now it doesn’t want to run. What did I do wrong?

A.- When you put the pump assembly back on the

bottom of the motor, be sure to draw both of the screws up slowly and evenly. Do not over tighten them. Make sure all of the pieces go back on the same way they came off. Putting a grease pencil mark down the side of the pump housing is the simple way to make sure that you don’t put it together backwards. They’ll fit, but they won’t flow the fuel right.