By Larry Carley
Technical Editor

Believe it or not, fuel pumps have a higher return rate than almost any other automotive part. According to the Fuel Pump Manufacturers Council (FPMC), about 10% of all the fuel pumps that are sold by jobber parts stores are returned. But it isn’t because there’s an epidemic of defective fuel pumps. FPMC members say that up to 80% or more of the returned pumps work fine when they are tested by the manufacturer. Most of the pumps are coming back because somebody misdiagnosed the fault and replaced the wrong part, or they assumed the vehicle had a bad fuel pump because the engine wouldn’t start.

Parts that are returned for any reason is an ongoing issue in the parts business because it costs everybody time and money. Parts stores don’t like returns because it requires extra work, processing and handling — and it may cost them repeat business if a customer loses confidence in the parts they sell.

Manufacturers don’t like returns because they have to eat the cost of the returned part (plus shipping), plus all the paperwork that goes with it. Returns can also hurt their relationship with the warehouse and jobber customers, and possibly undermine their reputation as a supplier of quality parts.

Do-It-Yourselfers don’t like returns because it means replacing the same part twice, and making another trip back to the parts store for another pump, or yet another part if the second (or third, or fourth) pump doesn’t fix their problem. Today’s tank-mounted fuel pumps are hard to reach, and can take up to several hours of hard work to replace.

Professional installers are less apt to make these types of mistakes, so fuel pump return rates are usually lower — but not always. Some technicians are very good diagnosticians and correctly identify the fault the first time. Others who are not as skilled might make a guess and hope for the best. The hard part is convincing the latter group of technicians that they need more training — or that they need to use the knowledge they already have to rule out other possibilities before they replace a “bad” fuel pump.

The only way to know if a fuel pump is good or bad is to test it. On-vehicle testing requires measuring two things: fuel pump pressure and fuel pump volume. If a fuel pump can’t deliver the required pressure or adequate volume, the engine may not start or may not run right.

Testing fuel pressure requires a fuel pressure gauge and some adapters. Many technicians have these tools, but don’t always use them to save time or effort. Fuel pressure is easy to read on vehicles that have a fuel pressure service fitting on the injector rail, but not so easy on engines that require splicing a tee fitting into the fuel supply line. If fuel pressure is below the minimum specifications, the pump may be weak. Or, the fuel filter may be clogged, the fuel pressure regulator may be defective or the fuel pump may not be receiving enough voltage to run at normal speed. All of these possibilities need to be investigated before the pump is replaced.

Electrical problems can also affect fuel delivery. These include a bad fuel pump relay, loose, corroded or burned wiring connections to the fuel pump, or even low charging voltage.

A good fuel pump should also be capable of pumping at least 750 ml (3/4 quart) of fuel in 30 seconds. If it can’t, there’s a problem. The pump might be worn, or a clogged fuel filter might be restricting fuel flow to the engine, or the pump might not be getting enough voltage to run at full speed. Again, all of these possibilities need to be investigated before any parts are replaced.

Currently, there is no easy way to bench-test a fuel pump in a parts store. But that may soon change. Several companies are developing easy-to-use fuel pump testers that parts store employees can use to check a customer’s old fuel pump. The tester can also be used to verify the operation of a new pump before it leaves the store, and to resolve any warranty issues that arise after a pump has been replaced. The tester cycles a nonflammable solvent through the pump to measure both pressure and volume. The results are compared to OEM specifications, and if the pump meets the specifications, it removes all doubt as to whether the pump is good or bad. The new equipment should be available later this year, and should go a long way toward reducing unnecessary fuel pump replacements and returns.

The FPMC is also looking at things their members can do to reduce fuel pump returns. The FPMC has hosted several jobber and installer focus groups to better understand the issues, and to discuss ideas for solving these issues. One thing everyone agrees upon is that parts store employees, DIY customers and professional technicians all need access to more service information.

Several FPMC members say they plan to package more detailed diagnosis and installation instructions with their replacement pumps (if anybody will read them). Others say they are stepping up their educational efforts by providing more in-store and in-shop training — especially in “problem” locations where return rates are unusually high.

The FPMC also plans to launch a new fuel pump information website where anyone can go for detailed fuel pump application, diagnosis and installation information. The goal is to have the website up later this year (we’ll keep you posted).