924Board.org

Blas Costagli · Guest

Over the summer, I have noticed that my car's fuel pump has been getting louder and louder. Especially on warm days during a longer ride. I assumed that it was getting time for a replacement fuel pump, seeing that the car is a 1979 924 with the original fuel pump in it. But interestingly enough, when the car is pulled from the garage in the morning, the pump whine is barely noticeable. I replace both the fuel filters regularly, and can only note that after driving the car a good distance and parking it for 8 hours, it is hard starting, like the fuel is starving or flooding, but after a few moments running all is fine, and it runs great. The other day after a long ride, I pulled in the driveway, the pump was whining away, and I decided to open the fuel cap. The engine suddenly died. I restarted it and the fuel pump noise was almost gone. Should there be a vacuum or pressure in the fuel tank? How is it controlled? That is, how is the air in the tank let in or out as fuel is used? My fuel pump is mounted in the rear of the car, under the right side, external to the tank. It appears to be mounted correctly, as it is original.

Thanks,
Blas

[ This Message was edited by: Blas Costagli on 2001-08-23 10:26 ]

edd1em · Guest

Hey Blas, I hate this cars vacuum system, and I would bet you my spare tire, that there has to be vacuum in the tank. Well actually of course the has to be pressure, as the pump is outside, pulling rather than pushing. So that problem we know about, now how about the whining? I dont like the way the pump sounds, come to think of it I dont like a lot about this car. #1 Dislike, steering wheel position.

[ This Message was edited by: edd1em on 2001-08-23 06:15 ]

larso · Guest

i know theres one tube that goes from the carbon canister back to the fuel tank, and of course the fuel return line from the fuel distrib,

this car's steering wheel postion i liked, nice and low and horizontal...no need for telescopic adjusment, fits me perfect with out those seat raiser things that they had in the 924s (haven't been in one with the seat raiser things though, don't even know what they look like or how high it adjusts u)
Could use a slightly smaller steering wheel so your arms don't get tangled maybe but then u cant drive in parking lots....seats a crappy if they are soft...they are nice if they are in good shape, I absolutely hated my 931 seats because they were soft from a number of "big" previoius owners...but i sat in a newer 924 seat and they are excellent (still prefer a racing seat to hold u in more though, but compared to other seats NEW 924 seats fit niceeeeeee).

Blas Costagli · Guest

Well I'm glad we have covered the steering wheel and seat issues...? What's that about?

edd1em · Guest

I tried to get my car to stall by taking the gas cap off, it didnt. That could also be because I just took most of my emissions junk off, have you?

larso · Guest

sorry, won't post here again but i was talking to em1 on the second part of my message.

[ This Message was edited by: larso on 2001-08-24 03:26 ]

jcope · Guest

I have a similar problem on my 924S. The pump is brand new and sometimes it gets to be very loud. I have been wondering if it is working properly. I did open the fuel tank once while the pump was whining, and there was a big whoosh. But that didn't quiet the pump down. I didn't do it with the car running, though.

Is it a sign that something is not working properly if there is lots of pressure in the fuel tank? Like maybe a plugged line to the charcoal canister? The charcoal canister is supposed to clean the gas vapor out of the air in the tank so it doesn't escape to the atmosphere right? So what would be the point of that if the tank/canister was a closed system? But if it isn't closed, then there shouldn't be so much pressure in the tank. Am I right?

edd1em · Guest

why would you try it with the car off? Does you car stall when its off? I'm drunk and still, I dont understand what a plugged line to the charcoal canister has to do with a loud pump? It pumps to the engine, pumps as much as the gas pedal lets it... gas goes to the cylinders, not the canister. Now why does your car stall, and mine doesnt?

jcope · Guest

The pump was whining. I had the car turned off. Asked someone why they thought the pump might whine. They said "maybe it's the pressure in the fuel tank." So I opened the gas cap and let the pressure out. Then I started the car up. No change.

I freely admit I didn't know exactly how the canister works. Thanks for the enlightenment. Judging by how much other stuff I've had to fix, I'm sure I would have been figuring it out for myself at some point.

[ This Message was edited by: jcope on 2001-08-25 01:26 ]

AznDrgn · Guest

Is it pressure or is it a vaccume? beacause if it is pressure you should have no problems what so ever the pump should actually have to work less, but if it's the same as in my case there's a vaccume then you got issues. When your pump takes gas out of the tank if air does not go in to fill the space you end up with a vaccume and the pump has to work harder to get what's left of the gas out. Basically it's just like trying to collapse the tank instead of the fuel being free flowing and the pump just having to pressureize it.

jcope · Guest

It's probably vacuum, now that I think about it. There isn't much of a fuel odor after the pressure equalizes when the cap comes off. It's probably sucking air in.

That would explain the pump having to work extra hard and all the noise.

I really haven't given this much thought before. I don't really know how the tank is vented.

Blas Costagli · Guest

Ok...It's Vaccuum for sure.
The fuel is pulled out of the tank, and air must replace the volume. All polution equip. is in place.
I wonder if the cap is not allowing any venting? should it?
As I mentioned, the whining sound was cut dramatically when the cap was opened and the vaccum released. Could be that I'm overworking the pump. Much more noticable when the tank is less than half than when full...i.e. more vacuum..hmmm...
Oh ya..I had the fuel check valve replaced a few years back too.

[ This Message was edited by: Blas Costagli on 2001-08-25 06:34 ]

edd1em · Guest

jcope: you have the wrong start relay, fuel pump is not supposed to work with the car off.

As for others, if there is pressure on the fuel it will go easily, if there is no pressure but it vents, then it would still be easy since its still not vacuum. Now if we clog up the fuel line or fuel filter, then we have a problem. But I doubt that you fuel line is that clogged. Lets look farther down the line shall we... Where does the fuel go after the second fuel filter.

jcope · Guest

No, no, no! You misunderstood. My fuel pump doesn't come on with the car off. I only vented the tank with the car off. Then I started the car back up.

How could this be related to lines or other components that are downstream from the tank?

Does anyone know for sure how the tank is vented?

[ This Message was edited by: jcope on 2001-08-26 03:13 ]

kaffine krazed · Guest

For the pepole having problems with vacuum in the tank do you have an OEM gas cap or an aftermarket gas cap?