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Gas cap

O

OKinNC

NAXJA Forum User
Location
Clayton, NC
Hi all,
First off I did a search and only found one thread about this and the question wasn't answered. I have a 89 XJ and my girlfriend left my gas cap at a gas station. I went back and couldn't find it. Anyway I went to get a replacement and there are two choices vented and nonvented, does anyone know which my XJ uses?
 
Just get the vented one. The non-vented was for california emmissions.
I take that back, the term is Pre-vented or standard, you don't want the pre-vented one. The term pre-vented cap is used for a cap that's not vented because the tank is vented "pre" or before the cap.
 
Last edited:
May want to look into a locking cap while you are at it. With the price of gas, more MFs are going to be stealing it. My brother had about 15 gallons siphoned from his Suburban a few months ago. I keep meaning to look into a locking cap for my 89, I just haven't gotten around to it.
 
I second the locking cap idea- twice in the last month I've had a full tank of gas magically lose about five gallons overnight when parked on the street. - can't wait to catch the MF who's doing it. hasta :hang:

20 gal ~$60+ protect the investment.
 
BCParker said:
I second the locking cap idea- twice in the last month I've had a full tank of gas magically lose about five gallons overnight when parked on the street. - can't wait to catch the MF who's doing it. hasta :hang:

20 gal ~$60+ protect the investment.
Click to expand...

That's not stolen gas, just the 4.0's magical way of sucking back the expensive juice... :wierd:
 
All the locking caps I found let vapors escape from the tank. I think they were venting though. Anyway, if I could find one that didnt vent I would for sure go with a locking one.
 
I don't think you can go wrong with the venting type. If you need the vented type and you use a non-vented one you could draw a vacuum in the tank. But the vented one will work fine in older xj's
 
BCParker said:
then I'm getting about 0.2 MPG on those first five gallons :wierd:
Click to expand...

Hehe. That sounds about right.... :laugh3:
 
langer is more or less correct.

The "vented" cap has a one-way vent - letting air INTO the tank. Any escaping vapours are sent forward to the carbon cannister, and are thence sucked into the intake with the engine running.

I don't recall as it's a problem for us, but some fuel injection systems will NOT work unless they have a vented cap, as the loss of pressure over the fuel can impede pump function.

The safe way to go is just get the regular vented cap and forget about it.

5-90
 
langer1 said:
Just get the vented one. The non-vented was for california emmissions.
I take that back, the term is Pre-vented or standard, you don't want the pre-vented one. The term pre-vented cap is used for a cap that's not vented because the tank is vented "pre" or before the cap.
Click to expand...

A vented cap has a HOLE in it.Air and fumes or raw fuel can come out any time under the right conditions.
A NON-vented cap has no hole,the " hole" is thru the charcoal canister that is why there is a vacumn when you open the gas cap.
Not sure what year the non-vented caps came into use ,but on a 1972 Duster I had to drill a 1/4 " hole in the cap to flow enough fuel to drag race it.
Looking at the factory caps as far back as 72 on a CJ they were all Non-Vented.
Wayne
 
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