Fuel pump failures

1975 Jensen Healey

What are possible reasons for fuel pump failures – other than old age and trash in the fuel?

Background: Have replaced fuel pump about five (5) times in past eight (8) years. It has started to behave erratically, again.

Added point of info (or possibly a red-herring): the clock (original, analog) starts to run after the car is jump-started and may continue to run through several shutdown/start-up cycles but frequently stops at the first shutdown.

Is there ethanol in the fuel you’re using?


Is this a low mileage, rarely driven car? Electric motors (as in fuel pumps) like having constant voltage. If the voltage gets too low, they can burn out and fail. Is the car stored on a battery tender to maintain good voltage to the battery when the car is run?

The erratic clock leads me to suspect a voltage problem.

AS far as we know, yes. That is, we believe all California gas has 10% ethanol. And yes, we do put premium gas in the car.

Yes. It is, indeed, a low mileage, rarely driven car. Largely because of its unreliable nature. We recently did install a maintainer. And we, too, suspect a voltage problem. We’d appreciate any suggestions you might make about possible sources of voltage problems.

BTW: Thanks for your participation!

When you go to start the car after a long period of non use the battery voltage can be below normal. The fuel pump is activated as soon as you turn the key, then you move the key further to activate the starter. This means voltage changes and surges hitting your fuel pump.

I’d suggest a battery tender to make sure the battery is at full charge when you want to run the car. Then I’d turn to key to on and pause for a few moments and let the fuel pump get up to speed and pressurize the system. Then I’d hit the starting motor. The delay from on to kicking the starter is about 30 seconds. It might not make any difference, but perhaps your fuel pumps will last a bit longer.

You might consider using a fuel stabilizer. It could extend the life of the fuel pumps and also many other fuel system components.

California has had ethanol gasoline since 1999. You might want to read this and find out what ethanol might be doing to your fuel system. http://fuelschool.blogspot.com/2009/02/phase-separation-in-ethanol-blended.html


Thanks to you, too! The fuel school link is VERY interesting. We happen to spend a lot of time on the water and understand some of the problems associated with ethanol. The fuel school provides alot more detail than encountered, previously.

Thanks to you all – we’re signing off and going for dinner, now. Will log-in again on Monday sometime to see if there are any further comments / suggestions.

If there is a fuel pump relay in the circuit make sure that there isn’t a voltage drop across the contacts while the pump is runnig. That would cause the pump motor to run slower than normal and an increase in motor current. Also check for any AC voltage across the battery coming from the alternator while the engine is running. It should be less than .5 volts.

It could very well be that ethanol is behind this problem. I had a conversation with a lifelong friend of mine today who now lives in Oregon. All of the gas where he lives has ethanol in it.

He has a 3 wheeled motorcycle with a Chevy 350 and Edelbrock carburetor. He said that recently the vehicle had started running badly and getting about 8 MPG. Inspection showed that ethanol was chewing up the rubber fuel lines and rubber parts in the carburetor.
He also said that a lot of people in his area were also experiencing a lot of major fuel-related problems with weedeaters, chainsaws, and boat motors due to this.

Around here anyway, stations for the most part avoid carrying ethanol gasoline at all for these very reasons even though corn growing has become a huge, and subsidy driven, business.