scottso

Haven't been running well lately - everything is suspect. So I don't know if I just never noticed or if I'm paranoid or what....

When you turn your key for a cold start and the pump primes - how healthy does it sound? Every time I do the pump gives off an unhealthy groan. It always sounds like it just barely making it to get the pressure up.

JakeRobb

I'm pretty sure the stock fuel pump on my Z28 (just over 100k miles) is not audible from inside the car under any conditions that I'm aware of. I'm about to leave work; I'll double check and post back later.

JakeRobb

Okay, so it's audible, but very quiet. I recorded the sound with my phone:

http://youtu.be/Bl9FJfwe9fA

rv93

mine sounds the same. so thats normal.

scottso

Hmm. Mine sounds nothing like that. Its a lower groaning pitch, sounds slower (like its running at a lower voltage), and like it is fighting against the pressure buildup.

So next question - would a failing fuel pump just ~fail~ or is it possible that my loss of performance could be related to a "sick" fuel pump unable to keep fuel pressure up?

And what's involved with changing it out?

JakeRobb

The fuel pump is, at it's core, an electric motor. There are a couple different failure modes, but yes -- one of them is essentially what you're describing. Other times you'll experience intermittent failure, where one time you turn the key you get nothing at all, and other times it works perfectly (I've witnessed this one personally on a '94). The last (and I believe rarest) possibility is that it just up and quits, never to work again.

There are two approaches to changing it out. The first is to pull the exhaust, drop the rear end, and remove the fuel tank, on top of which you'll find the fuel pump. The second is to cut an access panel from inside the car, allowing you access to the pump without removing anything else. Extreme care must be taken here, because you could accidentally cut into the fuel tank itself, but this option is generally considered to be the easier of the two.