How would you know that you are getting the right gas cap.So far I have put two new ones on and the both fail CA SMOG.Ford does not go back that far so it is a after market thing.
Don

 

What is your truck ?
Specifics !

1977 F250 Right ?

Evap system ?
In Cab Tank?
Rear Tank ?
Mid ship tank ?

I can look it up in the motorcraft book from 1979.

 

It is a 77 f250 351 It is a rear tank and sorry,But I don't know what system it is.How would I find this out

 

i have had trouble finding on to fit my 73 f250 back of seat tank. the ones they give me are not long enough to catch. i also would like a nice billet one or something nice.

 

Being California with a CC It is an Evaporative system.

Evaporative Family L-5
http://www.clubfte.com/users/mil1ion...tivesystem.jpg


1977 F100-F350 aft tank w/evap system is Motorcraft # FC-793

Is it auto trans or manual ?

 

It is a manual 4 speed WITH OUT A CC

 

77 Mid & Aft Tank w/o evap = Motorcraft # FC-807

 

Is this a vehicle equipped with California, or Federal "49 state" smog? If it's california, it should have a CC, unless the vehicle is over a certain GVWR.

My 73 F-100 302-V8 had a CC.

Why are the new caps failing? Is it because of the pressure release or is it because of it not sealing right?

I'll make a few suppositions, and say that it's possible that you have the right gas cap for your vehicle, and the computer tester is failing it because it's testing it as if it was a cap for a vehicle equipped with a CC.

Or, you are getting a cap for a vehicle with a CC and the computer is failing it because the caps are different, for a non CC equipped vehicle.

or... I have had brand new gas caps, that were the right ones, fail the smog test, because they are not built quite right, and they dont seal properly.

Good Luck.

 

I have a cross reference list if you find another make of cap.

 

I couldn't find the box that it came in, But the numbers on the
CARQUEST INVOICE ARE CCA 34070 part number
In looking at the cap I can't see brand name.It has "vented" at the top and on the botton it has"ant-surge" remove slowly

 

Went to the Auto parts and they have "Stant" or "Fram" GAS CAPS

 

No cross-reference for FC-807.

Let me share another resource with you.

http://www.rockauto.com/catalog/cata...&parttype=5900

 

Thanks. This is great
Don

 

Now you see what I was up against without a motorcraft cap being available

I especially like the *more info* hyperlink that shows a pic of the cap

This is the one I picked.

STANT Part # 10749
Styleside; W/O Evaporative Emission System; W/Aft, Mid Tank {Regular Fuel Cap}

 

I hope they will have this.Going in tomorrow for engine Dignostic