94 Mustang GT running too rich

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  • Witsend
    Banned
    • Nov 2012
    • 2942

    94 Mustang GT running too rich

    Had RICH Codes BAnk 1 and 2 , negative fuel trims, and both O2 sensors not switching and stuck rich. Checked no gas leaking past fuel pressure regulator diaphragm into vacuum hose. hooked up a fuel pressure gauge and I was seeing way too much fuel pressure at 70 psi. Couldn't tell if Fuel pressure regulator looked original or not . I disconnected the Return line at the rail and attached a hose to the end of the rail and put other hose in a container and fuel pressure dropped to normal . and showed good volume in container. I inspected the return line front to back except what I could not see on very top of tank. Nothing appeared crushed or kinked anywhere. I disconnected the section of return line beneath car at rear of vehicle from the main return line section and it was very difficult for me to blow through any air through the return line that attaches to the fuel rail by mouth and with line attached at fuel rail and disconnected at rear bypassing the tank and hose ran into container the fuel pressure again was 70 psi and very little flow into container, so that ruled out a restricted or kinked line at top of tank I could not see.
    I disconnected the return line from the rail again and attached a hose to the line at front and into a container and took shop air and blew through the return line at the rear of vehicle and blew out the line in reverse of flow and saw a small chunk of white colored silicone rubber from God knows where inside container , possibly chunk of diaphragm from the original fuel pressure regulator , but whatever was lodged in there came out and fuel pressure is now normal, O2 sensors working again , and short trims went from way negative way back up as car was re adapting to normal fuel pressure again
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