ophelious

I'm hoping to get some advice on how to proceed with this issue. Thanks in advance!

It started when I began hearing a whining noise from the back of the car which I took to be the fuel pump going out. I replaced the fuel pump and it actually made the whining noise far worse. I suspect the new fuel pump must be creating more pressure than the old one was.

Here's what I can tell about the noise. High, constant tone. Happens most often when the tank is less than half full, and gets worse toward empty. Happens more on warm days, or when turning corners. Sustains for about 5 seconds after turning the car off.

I began to suspect it has something to do with venting tank pressure because if it is making the noise and I remove the gas-cap (to a big burst of pressurized air coming out at my hand) the noise stops. It seems the pressure is building up and is not being equalized like it is supposed to be.

I began to investigate possible cures/causes:
#1-- Check/Cut valve replacement
#2--Vented gas cap
#3--checking the line to the charcoal canister for blockage
#4--removing charcoal canister

If anyone has an idea about which of these (or any other) solutions would be a good place to start I'd appreciate the advice.

thanks,
matt

j9fd3s

iTrader: (3)

i'd start with #3 and or a blocked charcoal canister could do it too

ophelious

I'm putting this in just in case anyone else has had a similar problem...I was checking some old RX-7 service bulletins and one mentioned the check/cut valve. It said that there was a defect in some valves that resulted in a high pitched noise coming from it. The bulletin suggested that if it was annoying it could be replaced with an updated valve from Mazda that had a different design. The bulletin confirmed that it happens mostly when the tank is not full and when the outside temperature is very hot.

TOFUDRIFTER

I've got the same problem with my fb, I just pop the gas cap whenever I park it. Nothing of concern to me, I just be sure not to run it hard when I've got less than half a tank. As far as I.can tell there's been no damage or anything to worry about.

flight_of_pain

Disconnect the vent line from the top of the tank, if the problem disappears then the blockage is after the tank. If the problem persists then reconnect the tank line and disconnect the valve next to the tank that terminates that vent line, if it works normally, then move to the next line forward, etc.

Isaac