Focus Fanatics Forum banner

1 - 5 of 5 Posts

·
Premium Member
Joined
·
21,235 Posts
Discussion Starter #1 (Edited)
This one might be difficult to answer correctly, but I'm going to give our knowledge base a go at it before I take it to Ford.

The fuel tank is supposed to be a sealed system in modern vehicles, which is why we have a "check fuel cap" light. Unless my knowledge is off, the tank is vented through the evaporative cannister, and engine vacuum draws vapors from the tank through a filter where the vapors condensate and are returned to the tank.

My problem is that my "check fuel cap" light is not coming on when it should. I drove around for 20 minutes from one station to another last night with the fuel cap off, and this is the second time it's happened. I don't think this would cause a noticable drop in fuel economy, but I do think it's something I'd like to resolve so that I don't drive around like an idiot with my fuel door open and the cap swinging in the breeze.

Does anyone know anything about this system, or is my understanding of how the tank fits into evaporative emissions incorrect?
 

·
Registered
Joined
·
3,737 Posts
I believe the test for the "check fuel cap" only takes place at certain times, such as starting, and to avoid false alarms it may require a couple of occurances or test cycles the show the light.

Leave the fuel cap loose (not off) for a couple of days and you might see the light.

That said, my Z4 shows a check gas cap light within five minutes of driving with it off.
 

·
Registered
Joined
·
2,803 Posts
I can't really imagine it making a difference with your fuel economy, but it will make a difference with the emissions...
And of course, keeping your from looking silly with your gas cap dangling.
Just don't start driving around with the fuel pump hose that you neglected to remove [:D]
 

·
Registered
Joined
·
534 Posts
When I had an incorrectly sealing locking gas cap, it took a couple of days/trips for the light to come on. After I replaced the cap, it also took a couple of days for the light to go off.
 

·
Registered
Joined
·
4,805 Posts
mvhudson said:

Just don't start driving around with the fuel pump hose that you neglected to remove [:D]
I seen that happen before. Kinda funny, guy took off, then hit the brakes.
Good thing those got a safety release.

To answer the question... there's no problem. Although the gas cap is off, Ford has done many things to eliminate vapors from escaping the fuel cell... at least to my knowledge, and newer restrictions...
 
1 - 5 of 5 Posts
Top