1994 Q45a Failed Emissions

[GreenQ45a]

I took the Q in for a Quick test and I was gonna have them register the Q.She tested fine fro ALL test but one.

The GAS CAP! I replaced it and passed I asked the tech what would happen if the cap didn't vent.He said a lot of pressure could cause a fuel pump to wearout sooner than it should.

[DAEDALUS]

Say what? The gas cap doesn't vent outward...that would be an emissions problem. The gas cap holds pressure in and allows air to pass into the tank if necessary. The evaporative system routes gas fumes to the intake for combustion via the charcoal cannister under certain conditions.

[GreenQ45a]

Thats could be why he is working at an emissions stop

He didn't sound very sure of his statment thats why I posted it.

Could a bad gas cap cause a fuel pump to wear faster than it should?

Or would it just waste gas?
Modified by GreenQ45a at 12:04 PM 7/30/2005

[RobertsnewQ]

Yes, a bad gas cap can cause the pump to wear sooner than otherwise - fuel pumps aren't designed to pump against a vacuum. Daed is right - its vented IN not OUT.

It can also cause the fuel tank to collapse. Crazy.

[szh]

It can also cause the fuel tank to collapse. Crazy.

I guess this is because air pressure at 14 lbs/sq. in. can exert a lot of total force on a gas tank.

(Although, I suppose it would be a bit less actually, just the differential pressure between the outside and the inside as the fuel pump worked. Regardless, if you consider the total external area of the tank, it can get a lot of actual force on it!)

Z