I recently picked up a 2000 Chevy blazer. The truck seems to fall on its face when you go anywhere above like 1/2 or 3/4 of the way on the gas pedal. Today it threw two codes, P0171 and P0174, Lean Bank 1 and Lean Bank 2.

So I figured Id start simple and replace the fuel filter, no change. Then I cleaned the MAF sensor, no change. I looked inside the throttle body and it looks evenly black on both sides, no leaking Fuel Pressure Regulator. So now im led to the fuel pump, which was my first suspicion.

I bought a fuel pressure gauge and did some readings
-Key on when pump runs engine off - 60 psi
-Key on after pump is off - 53 psi
-Engine on - about 51 psi

Those readings don't seem too bad but is it enough to replace the pump? Thanks

 

Did you do a leak down test ?

 

NO! I forgot to do the leakdown when I was doing it all! darn!

 

60psi key on, is borderline and 53psi key off, is too low. Best to check maximum output of the pump at the fuel filter. It will require modifying the fuel pressure tester so all fuel pressure and flow ends at the tester. Should be 73psi to 108psi on your 2000, and it must remain above 55psi for 10 minutes after the pump shuts off.

 

i did a leak down test today. Pump started at 53, and in 10 minutes it was 48. I changed the MAF sensor from my totaled truck and it seems to be running a little better

 

Fuel pressure is too low. Key ON, engine OFF, fuel pump running: pressure must be 60psi to 66psi and must remain above 55psi for at least 10 minutes after the pump shuts off. See post #4 to check maximum pump output pressure. Post your results.