billthe3

Just sort of confused as hell about this. Whenever my fuel tank gets low the car starts running a lot hotter (averages around the second bar up instead of the first bar when the tank is not low) and the car also seems a lot peppier in acceleration and whatnot.

Now I realize that 20gallons of gas adds up to a lot of weight, so is that the difference in acceleration? Or is there some fancier reason like the car is running leaner and making more power?

And then theres the temp issue, which I have no clue about. Running at higher speeds on the freeway will at first lower the temp down to midway between the two lines, but it eventually goes back up to a little under the second line. Even running the a/c to start the second cooling fan doesn't make a noticable difference. But then once I fill the car up the temps go right back down.

While I'm asking about temp stuff, my temp gauge seems to go crazy at times and will start jumping up and down. Its almost like its the electrical charge meter and its going up and down with the blinkers turning on and off (the temp gauge was actually jumping with them earlier today, but it was the first time i had seen that). Its happened in all driving conditions, but only seems to happen when the temps are above 1/2 way between the lines. Is this a faulty temp sensor or thermostat or something? Or could it be an actual issue with the coolant? I remember reading the european car 951 did a coolant flush and it got rid of its cooling issues.

Anyway, thanks for any knowlege.

Camaro_Muncher

I dont know for sure but here is some ideas:
The reason for running hotter is that because there is less gas circulating, so that gas gets heated up a lot, whereas lots of gas would be much cooler, and cool your engine. Some track cars have smaller tanks because they ddont need that much gas, as for performance i guess it could work, but your engine would run hotter.

Rock

That gas is probally hotter.

When there is less gass, the gas that comes off the return line gets really hot from being around the engine. It is then returned into the fuel tank, where it warms the gas in the tank. If there is less gas, there is less to disperse the heat.

Thats the only reason I can think of.

Camaro_Muncher

Copy cat.

Campeck

or maybe theres a little short somewhere and its messing with your temp gauge when your gas gauge goes down?

Dal Heger

Electrical problem. Check your grounding points. The gauges will start to act "strange" when there is a corroded ground, or a bad negative battery cable.

There is absolutely no reason a low fuel level would cause any car to run hotter.

Dal.

Rock

Welll damn. Shut us down. Waaah lol

billthe3

Poo, I hate electrical gremlins. Any idea where the grounds for any implicated systems are? I just had the battery connections off a couple of weeks ago and they were fine.

Operator

my car runs faster/smoother when my tank is full. i think my fuel pump is like.. messed up.. or something is gunked up somewhere? hmph.

johnny1423

i always heard that the lower the fuel level, the greater % of dirt and contaminants.
there fore it will run hotter burning "less pure" fuel...also explains why it will run smooother with a full tank...in addition you get better gas mileage on the 1st half of the tank of gas and less mileage on the last half tank
my0.2c

M758

less fuel = less weight = better acceleration

I typically run 1/3 to 1/4 tank in my 944 spec car. Car simply runs fast with less fuel due to weight and balance. I have not notice and change in water temps however.

billthe3

Yeah, thats what I was thinking, I just didn't realize it was that much of a noticable difference. I'm so used to driving a car without a working low gas light that I'm always watching the fuel and mileage and whatnot, so I'm fine with running the tank low.

Dal Heger

That would make sense if the fuel pickup floated. . . The pick-up is on the bottom/lowest part of the tank, it will always be at the lowest part, it will suck in whatever settles.

The fuel filter will always catch anything in the tank. The only way to clean out the filter is to replace it. Just adding fuel will do nothing.

Dal.

rberry951

Here's a thought...

When a car runs a little lean, it runs better, it also runs hotter. So is it possible the fuel pump is ailing and when there is a full tank of gas it doesn't have to work as hard to push the fuel to keep the pressure up, and when the tank is low it isn't capable of pushing hard enough to keep the pressure up and the fuel pressure drops and is causing a lean condition?

Regards,
Russell

Dal Heger

Nope. No way, no how. The fuel needs to be pressurized to at least 2.5 bar pressure (normal fuel pressure of the 2.5l cars ~37 psi) anything less than that would play havoc on the fuel atomization when the injectors open and the car would basically run like crap, with absolutely NO power. You wouldn't even be able to rev it because of low fuel delivery.

Dal.