uses too much gas
 

My father-in-law has a 1985 Chevy with the 305 and 350 trans. The carb is a four barrel. My question is: When the truck is just sitting with the engine at an idle you can watch the gas gage needel slowly move towards empty. The truck is out of gear and just sitting there. What could cause this? I am at a lost. I want to help him but have no clue as to why he is useing so much gas. Anyone?

Re: uses too much gas
 

First off you need to actually determine if it is "using" gas or if there may be a problem with the gauge or the sending unit, or both.

Re: uses too much gas
 

Is it a dual tank truck? If so it maybe returning fuel to the other tank. I think 86 had a return line from the fuel pump or filter. A friend said his over filled and cam out the cap of the other tank.

Re: uses too much gas
 

Yes, it is a dual tank and he does use both tanks. The left tank is showing full and the right tank is the one now being used. When the right tank gets low he fills it back up and goes to the left tank. Back and fourth between the two tanks. I found out it is not a 85 but is a 1986 truck.

Re: uses too much gas
 

Check for leaks?