cmaddox03

Just pulled the car from the garage after a gear swap. The car is leaking fuel from an Evap Filter? I'm not sure what the component is. It is the white plastic filter in the picture. What would cause fuel to leak from here?

cmaddox03

I did some searching and found out this is the fuel tank vent.


Here is how much it leaked after a 25 minute drive. I did a 25 minute drive for gear break-in.



I drove the car to take my son to baseball practice and it did not leak any fuel at the park. The drive home after practice was longer and it did leak fuel once I got home. It was less than the leak shown above. I don't know if it regularly does this because it's my father in-law's "play" car. He doesn't pay attention to things like this.

Injuneer

Tank overfilled?

cmaddox03

I wish it was this simple. It only had 1/4 of a tank.

Injuneer

The vent tube, on the sending assembly, only projects into the top of the tank about 3/4". And there is a metal baffle a 1/4" under the end of the open tube.

Does this happen mainly in warm weather? Do you have excessive pressure in the tank when you open the cap? The vent valve is designed to contain a small pressure, then open before pressure gets high enough to damage the tank. Ditto on vacuum. Excessive heat input into the system may cause the fuel to boil, particularly when the tank level is very low (could be as little as 2 gallons at 1/4 tank). As vapor vents, it may be condensing in the valve.

Not sure what else could explain the problem.

I would also be concerned that the pressure control valve to the EVAP canister is designed to open before the vent valve, and you may be saturating the canister with wet fuel. Or it may already be saturated with fuel, and preventing the tank from venting through the EVAP system.

cmaddox03

I think the problem is incorrect fuel pump hook-up. I replaced the fuel pump assembly. I copied how the previous one was arranged. The previous owner had bent down the tab under the vent tube and hooked up the hose with the 90deg bend. It should have been a red flag to me that I had to modify the brand new pump. I opened it up this afternoon, disconnected the hose with the 90deg bend, and re-bent the tab.

What is the purpose / function of the hose with the 90 deg bend?

Injuneer

All I have to work with is a complete (minus the level sensor) new, replacement sending unit. That was purchased about 15 years ago, when we needed a fuel level sensor, and the only way to get it at the time was to drop a huge amount of money on a new sending unit. I did not do the sensor replacement, a shop did when they were doing some other work on the fuel system. They didn't want to replace the original factory sending unit because is had already been modified to accept a high pressure Bosch fuel pump. So they drilled the rivets out of the old and new sensors, and swapped them.

I fitted the original stock fuel pump into the new sending unit. It has the main corrugated clear plastic fuel supply line, but does not have the two hoses that attach to the nipples on the fuel pump bucket.

The fuel return pipe is the first one on the left when looking straight down from above, lines pointing upward. That (according to not very clear diagrams in the factory manual) gets connected with one hose to the nipple on the centerline of the fuel bucket.

The second hose appears to connect the pump bucket vapor vent nipple, toward the right side to the vent connection with the baffle. Does the 90-deg connector fit easily onto the vent pipe's 3/4" projection into the tank, and then seems to be held there by what I described as the baffle? It's the only connection left for the vent hose. I don't know why they would sell the replacement sending unit with the "baffle" tab already bent up to the vent pipe, if it needed to be bent down to attach the vapor line, then bent back up to restrain it. The factory manual diagram shows there is a "vent hose retainer", but it is much lower than the "baffle" and appears to be notched so the hose fits in it. The view of the actual connection to the pipe is obscured by the white plastic roll-over valve.

But this leads to another possibility. The vent hose nipple and the fuel return line nipple on the bucket are both the same size. Internally, the vent nipple is at the very top of the bucket. The return line extends deeper into the bucket, and appears to have a small sock on it. Is it possible you have the two hoses at the bucket switched?

GaryDoug

The white valve is a two-way one. It opens with about 1psi in either direction.

GaryDoug

You still don't get it and we have stated it multiple times. I suggest that you study the difference between the abbreviations PSI and PSIA. PSI is relative to the atmospheric pressure, so when we say psi (not psia) it means in addition to that pressure. The valve opens under relative pressure or vacuum. Stop confusing PSI with PSIA. You are using the wrong term when you do that.

Wrong:
"If that valve opens at 1psi either direction then it is working as I thought, letting air in and not out, since on the outside of the tank ATM is 14.7 PSI"

I give up also.

94Z28LS1toLT1

Hope this helps buddy but my camaro did the same exact thing as far as the leaking through the fuel tank vent valve (white part).
My evap solenoid both of my lines were crossed n Rob on this site showed me the diagram of the hoses one for the throttle body n the other for one of the fuel lines

Injuneer

Amazing.... two degreed engineers trying to help him understand how a very simple device works, and he refuses to accept what we are saying. Since he's so offended by our lack of professionalism, hopefully he won't be back.

Injuneer

Total highjack of the OP's thread, and he calls us unprofessional!

Injuneer

Please stop interfering with this thread. If you want to discuss the differences between the B-Body and the F-Body fuel/EVAP systems, start a new thread. I'll even move all your posts to the new thread. You are not helping the OP by continuing this.

Thank you.