Anybody had luck with fuel additives to free up a sticking in-tank fuel pump anti-drainback check valve?
Vehicle info:
I've been troubleshooting a long cranking time issue on our '05 Mercury Mariner (Ford Escape) 3.0L V6, and have it narrowed down to the fuel pump drainback check valve. The ECM reports several useful PIDs including fuel rail pressure, desired fuel rail pressure, and fuel pump duty cycle. It's a returnless system with no pressure regulator, using a pressure sensor on the fuel rail and pulsewidth modulated fuel pump in the tank. The fuel pump is a Delphi replacement assembly installed February 2016 when the factory pump failed.
Symptoms:
I noticed around June timeframe a long crank time of ~5 seconds, which only happens after the car has been sitting for ~1hr or so. ECM has been reflashed with updated firmware per an old TSB for this issue, no effect.
Troubleshooting:
Scan data shows the ECM runs the pump at 75% duty cycle continuously when the key is in the RUN position, engine not running. Desired fuel rail pressure is 80 inHg, and it reports 80 inHg actual. There is also an audible hiss from the pump for ~1sec on initial key turn to RUN, but I can't scan during that initial turn (no data acquisition)...the additional hiss suggests a 100% duty cycle initial priming run.
However, with the fuel pump fuse removed, I see rail pressure drop at a rate of ~20 inHg per 10 minutes. Very slow dropoff, and by 20 minutes it's reporting ~38 inHg. Haven't been able to let it sit for a full hour as yet.
Yesterday, I pinched off the rubber fuel line running from the tank to the filter canister with a plastic clamp. With the fuel pump fuse removed and key in RUN, the ECM reported the pressure held steady at 76 inHg for >30 mins testing time. This rules out the injectors as the leakage source, it's likely the fuel pump drainback valve.
So...before I open up the fuel tank and take Delphi up on their lifetime warranty, I figured I'd experiment with additives. TC-W3 at 640:1 was loaded on Monday and it'll be burned by the weekend. Any other recommendations appreciated.
Vehicle info:
I've been troubleshooting a long cranking time issue on our '05 Mercury Mariner (Ford Escape) 3.0L V6, and have it narrowed down to the fuel pump drainback check valve. The ECM reports several useful PIDs including fuel rail pressure, desired fuel rail pressure, and fuel pump duty cycle. It's a returnless system with no pressure regulator, using a pressure sensor on the fuel rail and pulsewidth modulated fuel pump in the tank. The fuel pump is a Delphi replacement assembly installed February 2016 when the factory pump failed.
Symptoms:
I noticed around June timeframe a long crank time of ~5 seconds, which only happens after the car has been sitting for ~1hr or so. ECM has been reflashed with updated firmware per an old TSB for this issue, no effect.
Troubleshooting:
Scan data shows the ECM runs the pump at 75% duty cycle continuously when the key is in the RUN position, engine not running. Desired fuel rail pressure is 80 inHg, and it reports 80 inHg actual. There is also an audible hiss from the pump for ~1sec on initial key turn to RUN, but I can't scan during that initial turn (no data acquisition)...the additional hiss suggests a 100% duty cycle initial priming run.
However, with the fuel pump fuse removed, I see rail pressure drop at a rate of ~20 inHg per 10 minutes. Very slow dropoff, and by 20 minutes it's reporting ~38 inHg. Haven't been able to let it sit for a full hour as yet.
Yesterday, I pinched off the rubber fuel line running from the tank to the filter canister with a plastic clamp. With the fuel pump fuse removed and key in RUN, the ECM reported the pressure held steady at 76 inHg for >30 mins testing time. This rules out the injectors as the leakage source, it's likely the fuel pump drainback valve.
So...before I open up the fuel tank and take Delphi up on their lifetime warranty, I figured I'd experiment with additives. TC-W3 at 640:1 was loaded on Monday and it'll be burned by the weekend. Any other recommendations appreciated.