I have been working on my 88 cherokee for a few weeks now desperatly trying to make it pass SMOG evap test (I live in CA) I have replaced all fuel lines, vapor lines, the gas cap, sealed the rollover valves, and finally the replaced the fuel pump. When I start it up the engine sounds fine, but there is a noticable hissing sound comming from the rear of the vehicle around the fuel tank region. I've been googling for an hour or so and keep see that this means your fuel pump is bad and needs to be replaced or will fail soon. Any ideas seeing as this is a brand new fuel pump that I installed? I don't want to take the jeep back to take the evap test again if it's just going to fail... again. Any ideas would be great!

 

Maybe the hissing sound is the sound of a vacuum leak? Are all the evap return lines hooked up at the tank?

 

They are all hooked up at the tank, I am thinkin I am going to have to get back under it today. Just figured I'd see if I could get any ideas before I start fiddlin' around with it! Thanks for the hint.

 

I had the fuel pump replaced in my Jeep at a local dealer...When I went to pick it up I was told they needed to reinstall it.....It was throwing a large evap leak code....Said they found that the gasket hadn't been seated right the first time?...I dunno...I don't trust any of them...but maybe that's your problem..

 

I will have to check that its my next option i guess.

 

Been checking all out and still cant get it if any body gots something else out that might help please do this is my 5th XJ and this ones gots me stumped with the leak and the evap and also the hisss sound at the fuel pump.

 

Here's what I did. First go buy another gas cap, unless you have an old one laying around. Then get some vacuum hose and drill a hole all the way through the center of the cap that is just smaller than the hose. Push the hose through the cap and silicone both sides. Now you should have a cap with a sealed line going through it. Now you need an air compressor with a air nozzle. Slide the hose over the end of the air nozzle and secure with a hose clamp. Now THIS is the really really really freakin important part. The air compressor MUST have a regulator of some sort. If you pump 120 PSI into the tank you will have bigger problems then a tiny leak. Do not put more than 1-2 psi into the gas tank. After you have pressureized it get a spray bottle with a soap solution in it and spray every inch of every vacuum line and the tank. The leak is where the bubbles are. It's a bit of a pain I know but after pulling my hair out for weeks on my 2001 Durango with seemingly miles of vacuum lines it worked for me.

 

you sure the sound inst just your pump,some pumps make all sorts of noise when your close to the tank listening for it

 

im sure its not the pump to loud to be but im going to try the gas cap trick tomorrow sounds good and it wil help with the evap problem also

 

Started the go through the garage and got all the parts to make the test pump made will see how it works i also added a pressure gauge to mine to see what pressure my tank holds and find out if the shop is trying to get over on me will post all the parts to my gauge and test pump if it works as planned