QuestionAnother specialist had me check the fuel pressure on my 89 Sentra which seems to be running rich and flooding under load (on hills). Even though a new fuel pressure regulator was installed in May to get the car operational (it wouldn't run at all prior to this); the pressure showing is 45 PSI. Shop manuals indicate 32-34 is normal for the GA16i engine with TBI for an 89 Sentra with 5 speed tranny. It was suggested by "Von Sudderath" that I should adjust the regulator. How is this done? I cannot seem to make out any mechanism or valve, screw, lever, etc. to try. Is the pressure controlled by vacuum line?
Thanks for any and all insight,
Be
AnswerThe fuel pressure regulator is mounted on the side of the throttle body. It maintains the fuel pressure at 34 psi (235 Kpa) above engine vacuum. It utilizes vacuum acting upon a diaphragm to control the amount of fuel pressure allowed to the injectors. To obtain an accurate fuel pressure reading the engine must by running. Basic fuel pump operation can be verified in a no start condition by observing gauge reading while cranking engine. Fuel pressure should be approximately 34 psi (235 kPa).
Remove fuel pump fuse from underhood fuse box.
Start engine.
When engine stalls, crank or attempt to restart engine 2 or 3 times to release pressure.
Turn ignition switch off and reinstall fuel pump fuse.
NOTE: Steps 1 through 4 are provided to release fuel system pressure to eliminate fuel spray.
Disconnect fuel inlet line from throttle body and install fuel pressure gauge.
Start engine and idle.
Fuel pressure should be approx. 34 psi (235 kPa). If pressure is correct, test is complete.
If pressure was high inspect fuel return line for restriction before replacing fuel pressure regulator.
If fuel pressure was low, gently pinch fuel return line at throttle body. If fuel pressure rose to normal, fuel pressure regulator is defective. If pressure still is lower than desired, inspect fuel filter before replacing fuel pump.
Hope this gets you on the right track...
