Fuel pump replacement and fuel sending unit replacement
On car forums people always ask where the fuel pump is located so they can perform a fuel pump replacement procedure. Well, on a fuel-injected vehicle, it’s always in the gas tank.
Next, they ask if they really have to drop the tank to replace it. Yeah, in some cases you do. In other cases, the carmaker has installed an access panel in the back seat area that allows you to replace the fuel pump without dropping the tank.
If you have to lower the tank to get access to the pump, you’ll first have to drain the tank before lowering it. You don’t want all that gas sloshing around while you lower the tank. Finally, people ask if they have to replace the entire fuel pump assembly just because the fuel level sending unit isn’t working. Well, you don’t have to, but you should. The fuel pump and pulse dampener are mounted to the sending unit frame. So you have to disassemble all of it to replace the sending unit. That involves disconnecting fuel lines from the pump and disturbing sealing rings that are almost impossible to find at the dealer. That’s why most shops won’t do it. They replace the entire assembly. Think about it from their point of view. If any of the seals leak or the 10 or 12 year old pump fails after replacing the sending unit, you’ll be standing at their front countering blaming them. Since the labor to do this job is almost 3 hours, no shop wants to take the chance of a fuel pump failure right after fixing a sending unit. And, ALWAYS replace the fuel filter when changing a pump.
Now let’s talk about the most common causes of fuel pump failure. Carmakers mount the fuel pump inside the gas tank for a reason. First off, these high-pressure pumps are powered by electric motors that get hot. They count on the gasoline to cool the motor and reduce wear. So the worst thing you can do is drive the vehicle at or near empty. You’re literally cooking your fuel pump by taking away its cooling source. And, if you ever run out of gas, you can destroy the pump by running it dry. If you ever had to replace a fuel pump, you know they cost about $800 installed. So it’s just plain stupid to drive around with an almost empty tank.
Clean the tank before performing a fuel pump replacement
The next most common mistake is replacing the fuel pump without flushing the tank. Recent service bulletins from pump manufacturers say that most new pumps that are returned as “defective” were actually damaged by crud that wasn’t cleaned out of the tank during replacement. Whether you’re a pro or a do it yourselfer, heed this warning—always get the tank professionally cleaned by a radiator shop prior to replacing the pump. Or, buy a new tank. In many cases you can buy a brand new tank for less than the cost of cleaning. See this video on how to clean a fuel tank before performing a fuel pump replacement.
Finally, here’s a tip on pumps. I’ve had terrible luck with aftermarket pumps. Now I only buy genuine manufacturer pumps. But the good news is that you don’t always have to pay dealer prices. For example, if you own a Ford product, go to fordparts.com and enter your vehicle information. The site will pull up a Motorcraft part number. Then scroll through the listings to find a genuine dealer. Compare prices across online dealers. Some offer better discounts than others.
For a full step-by-step post on how to perform a fuel pump replacement, click here.
© 2012 Rick Muscoplat
Posted on by Rick Muscoplat