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By Larry Carley copyright AA1Car.com
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 auto parts stores are returned. But it is not because there is 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 would not start.
Parts that are returned for any reason is an ongoing issue in the auto parts business because it costs everybody time and money. Parts stores do not 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.
Fuel pump manufacturers do not like returns either 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 their warehouse and jobber customers, and possibly undermine their reputation as a supplier of quality parts.
Do-It-Yourselfers do not 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 does not fix their problem. 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 returns are less common with professionally installed pumps. Most technicians are good diagnosticians and can accurately identify a bad fuel pump. But some less skilled techs might incorrectly diagnose a no start problem and replace the ful pump unnecessarily. A good tech should rule out other possibilities before replacing a 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 cannot 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 cannot, there is 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.
If a fuel pump fails to meet OEM flow or pressure specifications, it is bad and needs to be replaced.
In an effort to reduce unnecessary returns, some fuel pump manufacturers have stepped up their training efforts of both professional technicians and auto parts store employees. Some are also including more detailed diagnosis and installation instructions with their pumps so installers will hopefully read the information and do the job correctly.
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