1995 Lexus SC400 back pressure
05-09-12, 07:48 PM
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1995 Lexus SC400 back pressure
I've always wondered everytime I put gas, I open the gas cap and pressure comes out. Is this bad or no? I was told to change the gas cap. Has anyone had this problem or know why it happens?
05-09-12, 08:02 PM
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thats a good thing that means ur evap system is woking properly and pressure isnt coming out its going in. your evap system is pulling a suction on your gas tank so no fumes do not release into the air..
05-09-12, 08:13 PM
#4
^^^What do you mean? I'm replacing my gas cap gasket tomorrow, cause I don't feel the pressure anymore this past month. Is there anything else I need to look into? I'm having problem with my MPG also, and I've replaced my fuel filter and coolant temp sensor.. Having problem checking readings from my MAF, but already adjusted TPS to spec, will clean ISC valve and will also check if my fuel pump ECU is functioning correctly tomorrow.
05-09-12, 11:41 PM
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05-10-12, 06:18 AM
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ok due to the federal gov compaines have been required to make there vehicles more environmently safe/better. so as we all kno that gas vapors fast even faster when its heated up from the engine. those fumes are pulled into a purge canister and are help there and not relased to the air. and those fuses are usually used by the vehicle at start up. after your car is started the emssions systems pulls a vac on the tank to catch all of the fumes. i havent had much time to play with lexus's and not 100% comfortable with all there systems yet but i can tell you 70% of most cars i have ever had to diag with pulls air in when cap is released due to the tank pulling a vac. i may b wrong on how lexus has there system set up since everything else on there cars is over enginnered.
how many miles does your car have..
how many miles does your car have..
05-10-12, 10:36 PM
#13
All SC's of this gen that I've seen create pressure differences in the gas tank that are noticed by a whooshing sound when the cap is removed.
This is normal, I've been told by a mechanic at the dealership I work at (Alderson Lexus) that this is normal. Nothing to be worried about. Fuel pump just creates pressure in the fuel tank. If you're gas cap was broken there would be no pressure difference between the gas tank and the outside air. Gas Cap creates a tight seal so the only time that you notice it is when you open it as the pressurized air and fuel vapors will rush to escape the fuel tank until the pressure in the fuel tank and the outside air equalize.
There is nothing wrong with the gas cap.
This is normal, I've been told by a mechanic at the dealership I work at (Alderson Lexus) that this is normal. Nothing to be worried about. Fuel pump just creates pressure in the fuel tank. If you're gas cap was broken there would be no pressure difference between the gas tank and the outside air. Gas Cap creates a tight seal so the only time that you notice it is when you open it as the pressurized air and fuel vapors will rush to escape the fuel tank until the pressure in the fuel tank and the outside air equalize.
There is nothing wrong with the gas cap.
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