Auto Service World
Feature   December 1, 2005   by Dean Askin

In the Tank

Changing a fuel pump is a dirty job that's got to be done right

Replacing a fuel pump is probably one of the most time-consuming, dirtiest jobs your shop can be called upon to do. If you’ve replaced a fuel pump and there’s still a fuel delivery problem, your first thought may be that the pump is faulty — but that’s not necessarily the case.

“You’ve got to figure out what caused the pump to fail in the first place,” affirms Laura Teste, Product Manager, Fuel Delivery Products for Federal Mogul.

The problem could be contaminants in the fuel tank, a clogged fuel line, or faulty wiring that caused a voltage drop to the pump.

Contamination in the fuel tank is the primary cause of in-tank fuel pump failures. That’s why the installation of a new fuel pump needs to start with completely dropping the gas tank and cleaning it thoroughly. A vehicle’s gas tank can pick up contaminants from the fuel distribution network — right from fuel storage tanks, down to the gas pump during the fuelling process.

“Typically the majority of problems come from mechanics who get pressed for time and they may not have cleaned the tank thoroughly to make sure there’s no dirt or contaminants in the system,” says Joseph Voda, Sales Product Manager for Electronics at Peachtree, Ga.-based Hella Inc., a fuel pump manufacturer.

Cleanliness is Everything

Whether a tank is easy to clean depends on what it’s made of. Plastic tanks can be drained and wiped out with a lint-free cloth that picks up sediment and debris. Metal tanks are harder to clean because moisture that accumulates on the inside of the tank over time actually attacks the metal. In its educational materials for technicians, the Federal Mogul Technical Education Center advises that the only way to properly clean a metal fuel tank is to send it out to a radiator repair shop.

Keeping everything clean is vital, Federal Mogul points out, because modern electric fuel pumps, which are manufactured to very close tolerances, can be damaged by the most minute of contaminants. It’s important to keep the new pump in the packaging until you’re ready to install it; put it on a clean work surface or a lint-free shop towel; and make sure your hands are clean.

Voda and others point out that if you install a new fuel pump in a contaminated gas tank, it’s bound to fail — but it’s not the pump that’s faulty. “If you have contaminants in the tank, changing the pump isn’t going to do any good if you don’t get rid of those contaminants,” Voda notes.

“It’s a lot of work to clean out a tank, especially dropping a tank and cleaning it out,” acknowledges Teste. “You have to convince them (technicians) that it’s worth the effort.”

What sometimes ends up happening is that perfectly good fuel pumps get returned to the manufacturer, which is then left with a replacement part that can’t be resold.

“Obviously there’s a dollar value attached to it, but more so it damages the reputation of the aftermarket,” says Teste. “You end up with a large number of installers going to the OE saying ‘I tried three pumps and then I tried the OE and it worked.’ They end up using three pumps as very expensive filters to flush out the dirt, and then they go to the OE from now on. It’s a real hazard to the aftermarket industry.”

Installation Essentials

There are three basic essential steps involved in installing a fuel pump and ensuring that everything is working properly: Dropping the tank and cleaning it out; doing a voltage test to verify whether the real problem is in the wiring to the pump; and replacing the intake fuel strainer when you replace the pump.

If you don’t do one of these things, you may install a new pump that appears to be faulty — but isn’t.

“What they can do is look for burned out electrical connectors. Burned wires or melted terminals … would indicate that the main body harness has failed, to cause arcing and would result in a voltage drop or loss of voltage to the pump, which would cause the pump not to run … the first instinct is to change the pump out,” says Teste.

Bad electrical connections are the second-most cause of fuel pump replacement jobs. It’s important to do a voltage test on all the connectors and components involved with the fuel pump. Poor electrical flow can make it appear that the pump is faulty, when it’s not. You’ve got to do a voltage test with a Digital Multimeter (DMM) or Digital Volt/Ohm Meter (DVOM) on both the power side of a circuit and the ground side of a circuit.

“Verify that power’s available to the pump. It’s kind of a logical sequence,” says Craig Weber, Technical Director at Elmira, N.Y.-based Purolator Motor Components LLC.

Weber adds that technicians need to make sure they’re installing the right pump to begin with. “They need to make sure they selected the appropriate pump for the application. That means making sure the pump has the proper delivery, the proper regulated pressure, and the ability to draw fuel from the tank.”

Another pitfall to avoid is not installing a new strainer when you install the new pump — not only does this lead to contamination problems that can cause the new pump to fail, it also will void the warranty on the part.

“The strainer, when we get a part back for warranty, is how we can tell if the tank was cleaned,” says Teste.

Either the new strainer will all ready be on the new pump, or you’ll have to install a new strainer separately. It depends on whether you’re working with a module unit (most come with the strainer already installed), or dealing with a replacement hangar assembly or pump-only application. In those situations, the strainer must be installed during the replacement process. As well, the strainer must be pushed on to the fuel inlet by hand. Try to screw on the strainer can cut the pump inlet, and you’ll end up with pieces of the fuel inlet in the strainer — contamination that will make the new pump fail. And pounding the strainer on can rupture it, which also will cause debris to get into the pump and make it fail.

A proper fuel pump replacement also means checking for clogged fuel filters and bent fuel lines, which both can restrict flow to the pump and make you think the pump is faulty. Reduced fuel flow can cause the pump to work harder, exceed its amperage limit, burn out the wiring, and make the pump fail.

How to Avoid Pump Comebacks

What it gets down to is getting to the root of the problem when you’re replacing a fuel pump. “If remove and replace is all you’re after without really making sure that you’ve really gotten to the root of the problem, you’re going to have a comeback,” affirms Voda.

You’ve also got to make sure that the technician doing the repair is properly trained to do a fuel pump replacement, he adds.

“The majority of comebacks that I’ve experienced are not generally from a certified mechanic. They follow through. The comebacks are usually from people in retail sales, or mechanics who haven’t been trained at all in the proper procedure of the fuel pump as part of a total system.”

Teste believes shops and technicians can set examples for each other to follow in fuel pump installation jobs. “Nothing breeds success like success, so if you have someone who’s successfully using these measures and they have a very low comeback rate, and high customer satisfaction, you’ll have other people adopting it.”

Take the time to do the job right even though fuel pump replacement is time consuming, says Voda.

“The obvious thing to do before the tank is sealed back up, is check out the operation of the pump. Plug it in to the wiring harness, lift the lever, see if you can get the gauge to read. These are the obvious step-by-step procedures that are time consuming, and in some instances, the shop may be pressed for less time than they actually have to give it.”

“It’s a matter of following through, getting to the root of the problem, having the education necessary and then being careful,” he adds.