88irocz28

I think there's a bad leak in my 1994 LT1's EVAP system allowing fuel vapors to enter the car. Driving down the road with the windows down, the smell of gas drifting into the car is overwhelming. The odor also accumulates in the car when left parked, especially just after having been driven. The odor is unbearable in hot weather, especially when there's any less than 1/2 a tank of gas left. I also noticed that as the smell got worse, the old fuel pump would get louder and louder until it coudn't even deliver enough fuel to let the engine idle. I would then have to remove the gas cap (venting some serious pressure!) and let cool air into the fuel tank for a while before it would start again. I recently replaced the OEM style pump with a Walbro 255 lph pump, which has had no problems maintaining fuel pressure, but it too sounds slightly labored whenever the fuel gets hot and vapor starts leaking out.

I did a search and the closest I could get is this https://www.camaroz28.com/forums/sho...ight=fuel+odor except that mine's not throwing any codes. I have also previously checked the EVAP purge solenoid valve and lines attached to it and didn't find any signs of leaks or fuel vapor at that end.

I've had the vapor canister out once before to inspect the hoses, and though they felt crumbly and old, I didn't see obvious tears or rips. All the connections were intact too as shown in the this diagram http://shbox.com/1/evap_system.jpg .

I will go ahead and replace all the rubber hoses as precaution anyway, but assuming that doesn't fix the problem, could somebody explain to me the purpose for the evaporative emission pressure control valve (#2 in the diagram) and how it works. Is there any way to test it or any benefit to bypassing it? Also, I noticed a 2nd vent line that goes from the sending unit assembly to the front of the tank, where it terminates in some sort of white valve looking plastic piece by the fuel pump weatherpak connector right behind the back seat bulkhead. What is this thing and what does it do?

88irocz28

Nobody has any idea?? Seriously?

Injuneer

First, verfiy that the EVAP purge system is working. First check that you have the connections on the right nipples on the solenoid. Pull a vacuum on the line normally attached to the throttle body. Activate the solenoid by applying a ground. Solenoid should open, and you should smell fuel vapor at the vacuum pump.

Then check all the vapor lines at the canister and at the tank. They are very likely to be dry rotted after 16 years. The "extra" hose with the valve at the end it probably the vacuum/pressure relief valve. That prevents the tank from over pressuring, or pulling excessive vacuum if the pressure control valve in the line to the canister is not working.

Make sure there is nothing causing the fuel to overheat. Does your exhaust run too close to any of the fuel lines - either the supply or return? Are all the heat shields at the tank still in place? Sounds like the fuel in the tank is heating up, and heat generates more vapor, possible more than the canister vent system can handle. With the old pump, the signs of fuel vaporization, possibly in the pump suction, were evident. The pump itself may have been overheating and contributing to the problem. The new pump shouldn't be having that problem though.

88irocz28

Thanks Injuneer!

The connections at the motor checked out fine, so I pulled the vapor canister. Lo and behold, the vent line from the tank to the canister was completely disconnected and the pressure control valve was busted open. I went ahead and replaced all the dry rotted rubber hoses and reassembled the pressure valve, and voila, no more gas fumes inside or outside the car. I got to drive it around with less than a 1/4 tank of gas on the one of the hottest days here so far, allowing it to build up plenty of fuel vapor. Still no leaks

Injuneer

Glad I could help, and thank you for......

.... taking the time to read and follow the advice. You'd be surprised how many people get all kinds of help, but never bother to follow through on it.

.... providing feedback on the advice, letting us know it worked.