Full Throttle Pressure Check

With vehicle on jackstands, disconnect vacuum line from carburetor and place selector lever in Neutral and in Reverse. Operate engine at fast idle (700 - 1000 RPM) in each position. Neutral pressure should be 145 psi, and Reverse pressure 230 psi. Connect vacuum line.

If either pressure check was low, check vacuum modulator for loose attaching bolt, collapsed bellows, or stuck modulator valve. Also check pressure regulator valve and spring for sticking, plugged orifice, or collapsed spring. Check regulator boost valve for sticking.

If either pressure check was too high, check vacuum line and vacuum modulator for leaks or sticking valve. Also check pressure regulator valve and boost valve for sticking.