Fuel Pressure Check
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Intermediate
Joined: Mar 2002
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From: Pearl Harbor HI
Fuel Pressure Check
Seems I'm losing fuel mileage...I want to check the pressure at the rail. Any suggestion on how to do this and what's the normal pressure for an '89 automatic coupe?
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From: SE NY
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Re: Fuel Pressure Check (akisana)
To check fuel pressure, attach the gauge to the Schraeder valve on the right fuel rail, disconnect and plug the vacuum line to the pressure regulator at the rear of the fuel rail, start the engine and record the pressure reading at idle. Stock value is around 44psi.
You may have a bad O2 sensor causing lower mileage; use the ECM's diagnostic mode to check for a bad O2 sensor or bad coolant temp sensor (see details on my site, link in sig. below).
You may have a bad O2 sensor causing lower mileage; use the ECM's diagnostic mode to check for a bad O2 sensor or bad coolant temp sensor (see details on my site, link in sig. below).
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Re: Fuel Pressure Check (akisana)
You might want to check fuel pressure under operating conditions...to do this, purchase and install fuel pressure guage as mentioned above.
Don't disconnect vacuum line to pressure regulator!
At first turn of the key, before starting engine, fuel pressure should be 40/42lbs
After starting engine and letting idle into closed loop, fuel pressure should drop to around 34 to 39 psi...39 being on the high side.
Now drive the car with the fuel prssure guage taped or otherwise fixed and visible through the indshield.
Cruising along, fuel pressure should be in 34 to 39 range, though I think it should be more toward the 34 than the 39.
Step on the gas to accelerate smartly and pressure should increase to 40+ as long as car is accelerating. It will drop back into the 30's as you let off the throttle
As far as mileage, I guess to much pressure can force too much fuel through the injectors, but I would check condition of ignition system including plugs, wires, roter, cap and timing
:seeya
Don't disconnect vacuum line to pressure regulator!
At first turn of the key, before starting engine, fuel pressure should be 40/42lbs
After starting engine and letting idle into closed loop, fuel pressure should drop to around 34 to 39 psi...39 being on the high side.
Now drive the car with the fuel prssure guage taped or otherwise fixed and visible through the indshield.
Cruising along, fuel pressure should be in 34 to 39 range, though I think it should be more toward the 34 than the 39.
Step on the gas to accelerate smartly and pressure should increase to 40+ as long as car is accelerating. It will drop back into the 30's as you let off the throttle
As far as mileage, I guess to much pressure can force too much fuel through the injectors, but I would check condition of ignition system including plugs, wires, roter, cap and timing
:seeya
