How much will a hole in the top of your gas tank affect milage? I think theres one because when i open the tank after going through a whole tank it dosent suck any air in at all? and my milage isnt that great at all?

 

Hi,

I had 2 cars with holes in gas tank.

At first, you must confirmates your suposition with:

1.- A big gas odor.

2.- Seing gas in the floor when tank is full full full

3.- No vacuum @ gas cap (confirmate).


For affecting mileage you must have a big hole with vissible leak.



Denis V.

 

There might be a hole, but more likely is that it is somewhere other than the tank top. Have you checked the lines to the return vapor cannister or the gas cap itself? Do you smell gas around the car? You might want to check some of these simpler places before yanking the tank out.

 

Mine pushes air/pressure out when i remove the cap. There is also a check valve around your gas tank. It is a small white cylinder looking thing. Make sure it is good. Do you smell gas? I would imagine you would if you had a hole.

 

Aside from the tank pressure control valve that ninetyone mentioned, there is a pressure relief valve in the cap itself. It's an emergency pressure release in case the tank pressure control valve fails. Check both for holding pressure. It's unlikely your car is actually leaking fuel. If it were you would know it. Gasoline has very low surface tension so even a tiny hole will gush fuel. It's far more likely that your engine is simply guzzling gas.

The 3rd gen V8s weren't terribly efficient to begin with. 16mpg average is doing fairly well on these cars. Since the tank is only 16 gallons, it will go through a tank of fuel pretty quick. With a thorough tune, including verification of engine health, and new O2 sensor, you may see 18mpg. Check brakes for dragging, verify that the TCC is locking up at 45 mph and that OD is holding in cruise mode. Driving style has a big effect as well.

 

Hell, try some fuel injector cleaner too. Couldn't hurt really. I use Lucas. Also, remember most of your fuel inj. sensors contribute to your air/fuel mixture. I just replaced my IAT sensor under my plenum and i am now getting better mileage. Timing will also greatly effect fuel mileage. Check your timing. When was the last time you did a full tune-up?