1994 LT1 EVAP system questions, strong fuel odor!!
07-14-2010, 12:17 AM
#1
1994 LT1 EVAP system questions, strong fuel odor!! 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 couldn'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.
Last summer when I was having the same problem, I checked the EVAP purge solenoid valve and lines attached to it and didn't find any signs of leaks or fuel vapor at the motor. I also pulled the vapor canister out 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 a 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?
Last summer when I was having the same problem, I checked the EVAP purge solenoid valve and lines attached to it and didn't find any signs of leaks or fuel vapor at the motor. I also pulled the vapor canister out 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 a 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?
07-16-2010, 11:08 PM
#2
Oh well, problem fixed. Vent line from tank to vapor close was hanging loose and the pressure control valve was busted open. Popped the control valve back together and all the dry rotted rubber hoses with new ones. No more leaking fuel vapor!
