I'm working through my list of things causing crummy fuel mileage in my 83. So far, I've replaced the O2 sensor, located and replaced a broken vacuum hose (big improvement), and am now contemplating replacing the fuel pressure regulator, since I believe it's the original unit on this car.

Which brings me to the question of whether the fuel pressure regulator has any bearing on the amount of pressure that builds up inside the fuel tank? I've noticed that my 83 "lets out vapor" when I refuel but not consistently. Sometimes it does, and sometimes it doesn't.

Could this possibly be related to the fuel pressure regulator being worn out?

TIA

 

My little nissan truck does that but the 944 doesn't. The nissan sounds like when they depressurize a cabin or something on a sci-fi movie.
Something a little more helpful... the 84na, 86na and 86T do not do that.

 

mine does it on and off too. but mine only seems to do it when its been running for a long time/ is warm outside. i used to work at 2 different full service stations and the cars coming in would do it all the time....mine was the only 944 i put gas in though. but it just seems the heat in the tank will make it happen. thats all i know.

 

When I open the gas cap, my 83 usually hisses. I've never paid attention to it. But I'm sure its normal.

 

I believe it is suppost to hiss.

Mine sometimes does and sometimes doesn't..

My last smog test my cap failed the pressure test 3 times, but the previous smog test it passed ( 1 week prior )

So, I'm gonna be gettin me a new cap.

you may want to take it to a shop to get it pressure tested.

 

Luis, I think it's pretty normal. Especially seems to do it with the warmer weather.

 

Mine does it all the time. Get some weird looks at gas stations.

 

It depends on if I've been to White Castle..
Nevermind- That's me!

My surround seal is cracked at the fuel filler tube- I used to get the "vapor release" on every other car I've owned , but not this one.

My mileage has been crapo lately too- but I suspect it's dur to my cheap *** not wanting to spend 2.29 a gallon for premium.
Good point tho Luis.. I need to check some things out as well.

 

Mine does it also. My putt around car (93 Mercury tracer w/200k), does it really bad. Sometimes it seems like it will blow the cap off. The red car does it pretty much all the time, and the silver car does it also.

 

Interesting....

My 944NA does the vapor thingy, but not my 951...and both use the same type of gas cap.

 

Talking about gas caps (semi-hijack), when I bought a new cap for my S2, they guy gave me one with a lock and key that locks automatically--every time. Very annoying (and unnecessary, unless gas goes to $5 a gallon)!

Is there another cap I can use, that doesn't have a lock?? My OE cap (which I assume wouldn't pass inspection) has a lock, but you can leave it unlocked if you want.

Anyone know?

 

if the cap is good, the car will make a hissing sound. i find the vapors going in the tank instead of out - think about it.... between the emissions control and the fuel that is used out of the tank, there should be a relative vacuum in the tank. when you open it after a drive, it should hiss - this indicates a good seal at the fuel cap. other cars may or may not do it depending on their emissions controls setup.

-Mike-

 

I dont think ive ever noticed my 86 951 do it, hiss or vapors.

 

My '83 does. Startled me that first time - none of my other cars do.

Emanuel

 

my 951 doesn't do it. My civic did it badly when i had it.
~Eyal