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In Tank pressure!

M

midnightrunxj

NAXJA Forum User
Location
Willow Springs NC
Not fuel pressure. 89 4.0 auto 4x4. After a couple of miles my gas tank builds up a lot of pressure. So much pressure that it makes my fuel rail o-rings leak. When i take the gas cap loose it lets pressure out for at least 8 seconds! Ive replaced the cap. How does the rennix tank vent? If its through the charcol cannister im assuming that it is prpbally clogged. 242k on the jeep. Thanks in advance.
 
midnightrunxj said:
Not fuel pressure. 89 4.0 auto 4x4. After a couple of miles my gas tank builds up a lot of pressure. So much pressure that it makes my fuel rail o-rings leak. When i take the gas cap loose it lets pressure out for at least 8 seconds! Ive replaced the cap. How does the rennix tank vent? If its through the charcol cannister im assuming that it is prpbally clogged. 242k on the jeep. Thanks in advance.
Click to expand...
That can't be fuel pressure is 31# to 39# your tank has 5oz of pressure on it. You need new 0-Rings.
 
midnightrunxj said:
Not fuel pressure. it lets pressure out for at least 8 seconds!.
Click to expand...

yah but still needs to vent, vapor does build up and its handled by the evaporator, I know its there but im not positive wherre.
Its a can with a bunch of vacuum hoses on it, its inder the hood i think somewhere.

follow lines and stuff

play with the charcoal can
 
I don't have a drawing handy, but the vent for the gas tank goes through the charcoal canister. You can blow through the line back to the tank and find a small piece of hose and blow through into the canister. The opening into the canister is pretty small and seems like a likely place to clog. I've had fuel lines clog and had to blow them out with compressed air, seems plausible the vent line is clogged or the "line in" opening (orifice) for the canister.
But like Langer said, I doubt the pressure is what's making your injectors leak.
 
midnightrunxj said:
trust me that is what is making it leak
Click to expand...
Good o-rings are good for 300# or more. The cap on a 89 is a vented type I think you have the wrong cap. Now it could raise the pressure and cause bad 0-Rings to leak but good ones would never leak.
Your canister is just below the radiator bottle.
 
Last edited:
I didn't see where midnightrunxj mentioned the pressure on his rig? That's why I asked the question...what did he measure?
 
midnightrunxj said:
trust me that is what is making it leak
Click to expand...

You know...when langer1 1st got here, I thought he was a know it all jerk....but this guy knows his sh%t, listen to him. Respect is earned...he has earned mine.

Rev
 
Rev Den said:
You know...when langer1 1st got here, I thought he was a know it all jerk....but this guy knows his sh%t, listen to him. Respect is earned...he has earned mine.

Rev
Click to expand...
Ditto
 
I have not put a guage on the rail.I have noticed a lot of pressure in the gas tank since i bought it. I replaced all 6 injectors and related o-rings about 2 weeks ago. So last week i get home from work and smell gas again, I was like wtf. So i pop the hood and its the feed side o-ring leaking. So i go inside and eat some dinner. 30 min later i disconect the quick connect on the fuel feed side. Gas blows out of the fuel rail and just keeps coming. So i rush to the gas cap and take it loose. SWOOSH all this pressure comes out. The gas quit coming out of the rail too. HMM bad gas cap so i rob the one off of my girls 90' and go for a spin. Come back loosen the cap and SWOOSH! Problem is still there? IM guessin its the evap. Canister. Ill have to swap one out after i pick up my new comanche tomorrow. What do you guys think?
 
The canister is about all thats left. I have no press. on mine. Have changed caps, no diff. The only pressure I get is what the fuel pump puts out to the fuel rail.
 
midnightrunxj said:
I have not put a guage on the rail.I have noticed a lot of pressure in the gas tank since i bought it. I replaced all 6 injectors and related o-rings about 2 weeks ago. So last week i get home from work and smell gas again, I was like wtf. So i pop the hood and its the feed side o-ring leaking. So i go inside and eat some dinner. 30 min later i disconect the quick connect on the fuel feed side. Gas blows out of the fuel rail and just keeps coming. So i rush to the gas cap and take it loose. SWOOSH all this pressure comes out. The gas quit coming out of the rail too. HMM bad gas cap so i rob the one off of my girls 90' and go for a spin. Come back loosen the cap and SWOOSH! Problem is still there? IM guessin its the evap. Canister. Ill have to swap one out after i pick up my new comanche tomorrow. What do you guys think?
Click to expand...
Your on the right track, the line is mashed or the canister pressure valve is bad, but your o-rings still should not leak.n Read the warning on the cap once.
 
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