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Emissions Fuel pressure test questions

B

blu3fan

NAXJA Forum User
Location
Arizona
Hey guys.
So I went and got my new 92 xj from Texas. drove her home.
Went for smog and passed everything except for the fuel pressure test.
I passed the Evap pressure test.
so.... My prior jeep never failed fuel pressure before (I've failed the evap prior)

From my understanding of the XJ fuel system, Tank pump has one gasket and 2 hoses. Rail has regulator and fill/return line. so my guess would be the tank gasket or gas cap?

where is common for it to leak pressure from?
 
Pic of the new project. She's decently clean. Still needs full paint correction and a few dents pulled... I'll start on this in a few months
ee53c7cc042c3f102daa7b9ee0843b37.jpg


Sent from my Pixel 3 XL using Tapatalk
 
Fuel pressure test? How did they do that?
 
I guess I should say Fuel Tank pressure test*they hook a tube to the gas cap/gas tank.
I'm assuming they are pulling a vacuum on the fuel tank/cap to see if it holds?
 
Odd, here in CA that's part of the evap test. It's the Low Pressure Fuel Evaporative Test (LPFET). They put in a special gas cap with a hose connection and pressurize the tank. At the evap canister, they pinch off the hose that runs to the aircleaner (at least on my '88).

How much gas did you have in the tank?
 
Just went and looked. the only hose that appears to connect to the charcoal canister was broken/disconnected.
Gonna replace that and try again with a full tank.
 
Yep, broken hose would do it. I usually have about 1/2-3/4 tank when I test.
 
I didn't have line that fit both sides. I used ID1/4"(6mm) The side connecting to the metal hose is much smaller than the charcoal canister side. so I used silicone to seal it up.
When it dries i'll take it for re-test
 
ljobbins said:
The check valves/vents for tank could leak as well but that rare if they haven’t been messed with before.
Click to expand...

The fuel gauge on this jeep reads empty when full and full when empty, so it's possible someone wired up the sender unit wrong. (guessing someone has been in there)
 
It's a never ending journey of discovery with an old XJ. :)
 
Saudade said:
It's a never ending journey of discovery with an old XJ. :)
Click to expand...

It hopefully will end. when I rip the dash... all the electronics... engine and driveline. and put my XJ parts in it...

My Old XJ parts > new XJ. but the shell is decent. which is all that matters.
 
i avoid the gas cap and pressure test on two of my cars. The smog nazis waive the test for me as they dont have the correct adaptor for funky gas caps. one is an old vw with a odd mechanism to lock it, the other a triumph with a hinged flip cap
 
I fixed the hose up front.
I've been busy and havn't gone back for smog. I walked behind the car today and I smell gas.
Opened the cap. 0 pressure released. this means we have a problem still*

I'm still pretty messed up from my accident but I'm gonna stick my head under the car and look for melted hose/try to replace it this weekend. I suspect the other side of the hard line might be melted at the gas tank side*
 
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