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Car is faster when gas tank is full![850/1995] posted by Rob Abel on
Tuesday, 31 March 1998, at 7:38 p.m.
My '87 740 B230F is somewhat sluggish on 1/4 or less gas in tank, and noticably
quicker on acceleration with full tank. I listened with stethoscope placed
on the top of gas tank (in trunk)with car running, and hear a faint hum which
disappears when I remove the fuse for the in-tank pump. The main pump sounds
the same almost all of the time (always noisy). Has new fuel filter. Do I have
a problem or is this normal?
Re: Car is faster when gas tank is full![850/1995] posted by Don Willson on
Tuesday, 31 March 1998, at 11:18 p.m.
There is a rubber tube connecting the intank pump to the outlet tube. In my '85 this was deteriorated and not connected to the outlet tube. When the fuel is low it has to suck out of the tank and may pull some air. If you get down to 1/4 tank it may quit altogether.
Re: Car is faster when gas tank is full![850/1995] posted by Gary Roberts on
Tuesday, 31 March 1998, at 11:33 p.m.
I've got an 86 760T B230FT- have seen the same. Sounds like fuel pressure, if you don't smell any gas leaks anywhere. Have you checked the O rings across the top of the fuel injectors? Possibly just re-vaselined them?
I've replaced in-tank filter, fuel filter, hose from fuel filter to fuel pump, fuel pressure regulator, and gas tank cap. Found poor to no seal at the top 2 electrical connections going into the tank pump. Applied Seal-All to mine and this did the trick. Did same to all joints up to fuel pressure regulator. Crude but effective.
The only thing I am not sure about is that there appears to be some kind of a valve between the under car fuel pump and the hose to the fuel filter.
Re: Car is faster when gas tank is full![850/1995] posted by tOPI on
Thursday, 2 April 1998, at 8:21 p.m.
Switch to Mobil gas....It's evenly watered down. Texaco has good stuff at the top and pure water down.
Re: Mobil gas![850/1995] posted by Rob Abel on
Sunday, 5 April 1998, at 9:02 a.m.
Touche' Topi.
Re: Car is faster when gas tank is full![850/1995] posted by Michael on
Friday, 3 April 1998, at 10:13 p.m.
If your in-tank pump is indeed operative, it may be a ruptured hose inside the tank to the fuel pump or a clogged in tank filter.
Hope this helps
Mike
Re: Car is faster when gas tank is full![850/1995] posted by Bill Bradley on
Saturday, 4 April 1998, at 11:04 a.m.
I think that it's probably the hose from the in take pump to the fuel
line, but there's one other thing worth checking. You may have a sticking
valve on the gas cap. If you hear a hissing noise when you open your gas
cap after driving for a while your gas cap valve is stuck and your in tank
pump is trying to pull against a vacuum (well, low pressure) This gets
worse as the tank gets lower since you're losing the pressure from the
weight of the gas.
Bill
'84 245Ti