Can anybody tell me where the pressure sensor is located on the 1997 Corvette C5. Is it on the top or side of the gas tank and can it be replaced without removing the tank? Thanks.

 

I think a fuel tank pressure sensor didn’t appear until the 1999 model year…97 and 98 use a “EVAP Purge Switch” which you can see the location and description below… on 1999 you can see the FTP sensor which is located behind a small access panel in the left rear wheelhouse area…are you having some EVAP issue ??

 

Hi and thanks for all the information and diagrams. Yes, I believe I am having evap issues because when I go the the gas station to fill up and take off the fuel inlet cap, a significant amount of pressure is released and a noise from my fuel pump get's louder. I suspected that the FTP sensor was not telling the Evap Purge solenoid or the Evap Cannister pressure relief valve to open and significant pressure is building up in the tank. This causes my fuel pump to make quite a bit of noise during a long drive. The fuel pump get's louder and louder as I drive but it doesn't make any noise at all until I have driven 20 to 30 miles in hot weather. Then it howls like a Banchee (whatever a Banchee is). I think if I could just determine what is allowing so much pressure to build up in the gas tank, the fuel pump wouldn't be so loud.

 

You may have a faulty vent valve which is supposed to relieve the pressure in the tank.

 

Thank you for the quick reply and instructions. I was wondering though if there is a way to check if the valve is functioning or if replacing it and test driving the car for fuel pump noise is the only way to know?

 

If you think the excess pressure is causing the fuel pump noise just remove the gas cap and see what happens.

 

With the pump making noise, I removed the gas cap. When I did, a significant amount of air pressure pushed out of the gas inlet passed the gas cap and the fuel pump noise got louder. Nest moring, it was quiet as a church mouse until I drive 32 miles, then it started to whine and by the time I drove fifty miles, it was howling loudly. When I put on my turn signal, the tone of the howl goes down and up to the beat of the turn signal flasher. Go figure. It's become a real mystery and nobody seems to have had experience with this issue. I took it to the dealer and they want to replace the fuel pump for the fourth time and take down the gas tank to see if any gas lines are kinked or there is some sort of blockage in the lines causing the fuel pump to work too hard. I have replaced the original fuel pump (the pump that first started making noise) three times with different fuel pumps and they all make that loud noise after fifty miles of driving. What a dilemma.

 

I would find a diagnostic shop in your area and take it there...dealerships as well as general repair shops only replace parts...a diagnostic shop will 'current ramp' the pump to see how many amps the pump is drawing...the C5 fuel pump draws about 4-5 amps and if they see 9 or 10 amps the pump is struggling...I would ask them if they can do that.

 

Thanks. You are right about the dealer. The shop foreman at the Chevy dealer in my area didn't know what the valve with the electrical connection to it was called or what it was for. He wanted to start removing the gas tank assembly and replace my fuel pump but I'm on my fourth pump so I doubt the pump is the problem. Something is causing these pumps to make noise. Incidentally, in the diagram you sent, there is a diagram of the vapor canister purge line with some sort of valve connected to that line. That is the valve that the dealer could not identify and has a rubber hose coming out of it that is exposed to the air (not connected to anything). Can you tell me what the valve is and how it functions as it comes before the purge valve and has an electrical connection to it. He are photos of the valve in question with my pointing to the mystery valve.on my 1997 C5. The third photo is a snip of the diagram you sent with the valve I'm taking about. What is this valve and what does it do? Can you tell me?

 

 

Again….info below !!…may be best to seek out an auto diagnostic shop !!

 

Thank you. I think you have provided a comprehensive explanation and amount of information about the evaporative emission system and I greatly appreciate it. Because I am a bit dense, I want to make sure I am perfectly clear on your identification of the part I was pointing to in the photos and cut out I sent. That part in the line that runs from the evap canister to the purge solenoid and is placed in the line before the line reaches the purge solenoid...that part is called the evap system "PURGE VACUUM SWITCH." And, that switch monitors the function of the PURGE SOLENOID. Is that correct? Did I get that right? If I got that right, it seems to me that the PCM signals the Purge Vacuum Switch to open if there is a certain amount of VACUUM in the evap canister line and the PCM signals the Purge solenoid to open when there is the appropriate amount of evaporative PRESSURE in the evap canister line, sending gas vapors into the engine. So the Purge Vacuum Switch releases vacuum and the Purge solenoid releases pressure. Am I thinking about that correctly or do I have it all wrong? As a side note, I am NOT getting ANY PCM, ECM, BCM fault codes.

Here's another scenario I thought of: If all the Purge Vacuum Switch does is monitor the purge valve solenoid, then perhaps all it is there for is to tell the PCM that the Purge Valve Solenoid is working or not working properly and in that case send a signal to the PCM and in turn present an evap fault code. Perhaps reducing vacuum has nothing to do with the Purge Vacuum Switch at all.