I have an interesting problem with my car. Over the winter, or perhaps only then because she wasn't being driven regularly, I've noticed that over the course of a day or so the fuel tank will lose about 1/16th to 1/8th of it's volume according to the gauge. I've checked for leaks on the underside, and though there are a couple 'dark spots' in the undergunk, rubbing firmly and smelling shows not a hint of fuel.

Thus I have concluded that my evap system is at fault. I've checked the PCV and at 2000rpm it opens and starts sucking. I believe that either a line is clogged or the charcoal canister needs replacement. The latter seems more likely. And so I have two questions:

1). Is there another potential problem with the fuel system causing the loss of gasoline? I doubt it's in the filler neck as there's nowhere near enough rust on the car to warrant suspicion of the filler neck leaking.

2). Does anyone manufacture a universal charcoal canister? I can't find it on Mazdatrix and O'Reilly's doesn't list even the category.

Thanks for the time.

 

No way any fault with the evap system would cause a loss of 1/8 a tank of fuel per day.

Are you sure the fuel is missing? Maybe the gauge is wrong?

In the cold weather, irregular and short trips are murder on fuel economy.

It could be a leak in the fuel lines, only leaking when pressurized.

Check your pulsation damper!

 

The gauge is wonky, I should try to drop the tank and at least look at the fuel level sender* while she's down with a cracked rad, but I've been averaging 10mpg (*normal driving*) this winter back and forth to class (when I did drive her), last winter it was around 12-13mpg. And it isn't necessarily per day, 1/8 down would be sitting over the weekend. And the PD is fine, there aren't any leaks there (I've had one before, I could smell it).

*fuel gauge will 'inflate' while car is sitting, then return to normal after the vehicle is warmed-up. Will read as high as 200% more than what is actually in there. If there is a way of refurbishing these senders I need to know, because I already have the radiator and clutch, not to mention exhaust manifold, tires, ect to replace, on top of getting the AC converted to R134.

 

1/8 of a tank per day just sitting would mean a fairly LARGE leak under the car. Gasoline just doesn't evaporate that fast unless it's very hot out. And you'd definitely smell it.

 

Someone must make a universal charcoal can. Sounds like a good idea.

 

Ide go with what Aaron said. Probly the fuel lines

 

yup i agree too. maybe a leak

 

Maybe you have a neighbor with a 5 liter jug and a little suck hose .

 

LOL. Fuel is really expensive right now.

 

Also, what is the year of your RX7 ? Sometimes age of a car does have an effect, you know ?

 

Ya know, that's a pretty good possibility. Locking gas caps were common for a reason...