Fuel Pumps

[Leeky]

Whatcha!

Anyone else feel that their car is more agressive when you top it right up?

I know obviously a full tank of petrol makes the car heavier but i feel that the engine rev's a lot better when it full.

Is this my pump dying?

Or do you start to get some fuel starvation as the tank empty's?

Im going to upgrade to a 255ltr/h fuel pump eventually but just wanted to see if this is going to remedy this problem.

[Karma Supra]

Can't say I'm noticed it mate... But it is possible I guess that you could get a teeny bit more preasure under a full tank??? or (now this is really scraping the barrel) a full tank will have and gunk in there more diluted = pure-er (sp?) fuel..

One other possibility.. when you fill your car up do you always fill it up to the brim??? if so how long does a tank last on average? We know fuel gradually goes off..., maybe the "fresher" fuel has more poke???

Another thought hitting me I often notice when I take off the fuel cap (I always fill up to the brim, about twice a week on average) a huge whooshing noise as the air preasure equalises... the tank is negative preasure, maybe that preasure makes it harder for the pump to draw fuel out at a fast rate???

thinking out loud really

[Jimlad]

the whooshing noise.. ar eyou on about when you take your petrol cap off ?? I get that.

[Karma Supra]

Thats the one!!!!! most cars do it.. its the air rushing in the tank to replace the low preasure left by the fuel that WAS there...

In THEORY I'm sure fuel tanks are meant to have a breather (anyone???) .. but hey all my cars have done it!!

[DazH]

I agree with Karma on that one, reckon it's cos of the lower pressure in the tank when it's empty. If your pump was on its way out you'd know for sure

Citroen had a problem last year with the in tank high pressure pumps on their 2.0HDi (we run the Berlingo vans at work) They were cutting out on roundabouts and coming up to junctions cos of lack of pressure. The only way to solve the problem was to keep the tank at least 1/4 full till the pump got replaced.

[GIDDLEPIN]

Fuel tanks must have some sort of breather, otherwise they would suck themselves in, try running for a short distance with the cap off to eliminate this possibility (not with a full tank of course!)

[Leeky]

Yeah the pressure thing makes sence, i guess you could fix this by making a small hole in your fuel cap?

Tell you what i could do to test this theory, work your way down to half a tank then take off your fuel cap to let air back in and then put the fuel cap back.

May make a diffrence.