How to Diagnose a Failing Fuel Pump on Your Car
by Allen Teal on Feb 27, 2009 with 4 Comments
The primary symptoms caused by a failing fuel pump and other problems that can produce the same or similar symptoms.
When the fuel pump is working right, you will not even know that you have one. However, if it fails, you will be left stuck on the side of the road about to have your wallet emptied for a repair bill. Years ago, mechanical fuel pumps would cost you about $20 for the part and $30 to $50 to have it put on the car. Today, electric fuel pumps that reside inside the gas tank will cost you $200 for the pump and about the same to have it installed.
If you can learn the warning signs that the fuel pump is starting to fail, you may be able to spare yourself the part about being stranded. In fact, if you are handy with tools, you may be able to save the labor bill, too. Weak fuel pumps are not always easy to diagnose in by a mechanic. The reason for this is that when they are first starting to fail, fuel pumps falter intermittently. They also tend to manifest the problem at highway speeds rather than at idle.
The warning signs of a failing fuel pump are not hard to identify. The problem is that they can mimic other problems in the early stages. It is common for people to makes serveral lesser repairs before tackling the fuel pump. The expense of this big ticket repair scares most people away until there is no other choice.
Your engine will seem to miss at highway speeds.
A engine that misfires will cause the car to jerk occasionally while going along the highway. Frequently, the fuel pump will falter for a mile or so two or three times and then run fine for the next 50 or more miles. This type of problem can be misdiagnosed as a bad spark plug or plug wire. In some cases, you will just be told that you probably had a little moisture in your tank that caused your fuel filter to act up. A mechanic may even persuade you to change the filter or get a tune up.
Your car will lose power as you pull away from a standing stop.
You push down on the accelerator, and the car starts to go and suddenly seems like it is going to die. Immediately, it seems to restart and off you go. This type of problem can be thought to be an oxygen sensor failing. Since this is a quick but not always cheap fix, you may opt to give it a try. This same type of symptom can be caused by your smog control devices on the car. A final possibility is that the distributor or coil is not working properly. About 75% of the time, this will turn out to be the fuel pump.
You lose power at highway speeds especially when the car is climbing a hill or under a strain.
This problem is almost 100% of the time caused by a fuel system failure. The fuel filter is the first culprit. Once this is ruled out, the fuel pump is the next best bet. The difficulty here is that this type of failure can be intermittent, too.
Your car cranks when trying to start it, but it does not hit or start.
Two issues cause this problem. The first is the timing belt or chain has broken. Without a timing belt, your car will turn over, but will not start. Almost any mechanic will not have a problem figuring out which one it is. Most cars have an inspection plate to view the timing belt or chain. By taking a look inside, the mechanic can determine if the belt is alright. If it is, the problem is the fuel pump.
When several of these symptoms occur over a short period of time, you should seriously consider that it is the fuel pump. Taking early steps to have it replaced or replace it yourself will save you frustration and possibly some cash.
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Published in: Do-It-Yourself
Ron Kramer | Mar 16, 2009 | Reply
I have an 81 Triumph TR-7 with symptoms above. The fuel pump is very noisy (whiney). Since this model of TR is utilizes Boch L-Jetronic FI and almost 30 yr old, I plan to replace both the filter and pump at the same time… approx $100. I will let you know the results!
dominic | Jun 21, 2009 | Reply
i have a fuel pump stop woking on a friend and it didnt make no nosie and had no problims with it but it just quit for no reason and nothing above on here was helpful bc it wasnt right
Don | Aug 11, 2009 | Reply
Dominic: There are a couple senarios to this. One: If it’s an electric fuel pump, I’d check to see if a ground wire or coupler wire became disconnected. Check to see if you have voltage to the pump. Check the fuel pump fuse. Second: If mechanical, Check to see if a vacuum hose came off or if the diaphram is leaking. Then I would check the actuator arm.
It sounds more like a electrical problem though since it just stopped suddenly.
Good luck!
Jeremy Thomson | Oct 31, 2009 | Reply
I have a 2000 Chevy Silverado Z-71 4×4 with the 5.3L And when its cold the engine has no throttle power if you step it down from a stop, after it warms up about 3 to 4 minutes it seems just fine. Could this be caused by the fuel pump being weak? O2 Sensor? Air intake temp sensor? Im kinda at a confused point now about this.