Fuel pressure Question

I have a 92 s10 Blazer with CPI. I hooked a fuel pressure gauge to check the pressure and when I turn the key ( on position only) the pump brings it to around 55psi, once the pump turns off the pressure drops back to around 10psi. Should the pressure remain around 55psi? not drop off. Or is the pressure regulator shot on the CPI?. I already changed the CPI around 30K miles ago so I am hoping its not bad. Any ideas?
ps: When the car is running the fuel pressure is at around 55-60 but the gauge is NOT steady also car would not pass emission test I was told it was running lean . Help ! :banghead:

I have a 92 s10 Blazer with CPI. I hooked a fuel pressure gauge to check the pressure and when I turn the key ( on position only) the pump brings it to around 55psi, once the pump turns off the pressure drops back to around 10psi. Should the pressure remain around 55psi? not drop off. Or is the pressure regulator shot on the CPI?. I already changed the CPI around 30K miles ago so I am hoping its not bad. Any ideas?
ps: When the car is running the fuel pressure is at around 55-60 but the gauge is NOT steady also car would not pass emission test I was told it was running lean . Help ! :banghead:


When you pressurize the system, pinch off the return fuel line. If the pressure drops it's your CPI or nut kit leaking. If it doesn't drop, then most likely it's the check valve in the sending unit. Not something that really needs to be worried about... Just means you'll have an extra crank or 2 to start the engine...(This is directly from my dealer when mine was checked)

with the return line blocked off pressure should hold for at least 2 mins especially on the cpi vehicles.

Should hold for at least 15

Ok will give it a try this weekend if its not to cold here. Thanks