Here?s a fuel pressure problem that seems a bit different than those documented in the site archives.
I have a new O-360-A2A (carbureted) engine on my RV-8, first flight was 10 days ago and now have just under 6 hours. In that time the fuel pressure has dropped to near zero 3 times. Details are:
? Each time the fuel pressure dropped to near zero the airplane was in level flight at ~75% power (2,450 RPM, 10.5 GPH with a Catto prop)
? Upon the fuel pressure dropping to 1 PSI the alarm sounded, I turned on the boost pump and the fuel pressure immediately returned to the normal range of ~ 5psi. At no time did the engine falter.
? After about one minute I turned off the boost pump, and the fuel pressure remained normal for the remainder of the flight using only the mechanical fuel pump. This included one flight where I circled over the airport for over 30 minutes to see if it would happen again, it did not.
? Environmental conditions were not stressful, OAT was between 60 and 70 degrees at 5,000 ft MSL.
I did manage to track the event one time. The fuel pressure fell in a linear fashion taking approximately 20 seconds to drop from the normal ~ 5 PSI to 1 PSI where upon I turned on the boost pump.
The mechanical fuel pump is a new Tempest AA15472, I did install a cooling shroud. The fuel sensor gauge is standard GRT LPS-02 low pressure sensor. After the second event I re-purged the fuel line to the sensor, it had no effect as the issue reoccurred the following flight.
Not sure where to go. It appears the fuel pressure sensor is working correctly since it reads normally when the boost pump is on. It also seems odd for a mechanical fuel pump to essentially fail completely and then run normally afterwards. I am hesitant to replace parts without a good reason to explain the events.
I have a message into the engine manufacturer but thought maybe someone in this group may have seen something similar. For now the airplane is grounded.
I have a new O-360-A2A (carbureted) engine on my RV-8, first flight was 10 days ago and now have just under 6 hours. In that time the fuel pressure has dropped to near zero 3 times. Details are:
? Each time the fuel pressure dropped to near zero the airplane was in level flight at ~75% power (2,450 RPM, 10.5 GPH with a Catto prop)
? Upon the fuel pressure dropping to 1 PSI the alarm sounded, I turned on the boost pump and the fuel pressure immediately returned to the normal range of ~ 5psi. At no time did the engine falter.
? After about one minute I turned off the boost pump, and the fuel pressure remained normal for the remainder of the flight using only the mechanical fuel pump. This included one flight where I circled over the airport for over 30 minutes to see if it would happen again, it did not.
? Environmental conditions were not stressful, OAT was between 60 and 70 degrees at 5,000 ft MSL.
I did manage to track the event one time. The fuel pressure fell in a linear fashion taking approximately 20 seconds to drop from the normal ~ 5 PSI to 1 PSI where upon I turned on the boost pump.
The mechanical fuel pump is a new Tempest AA15472, I did install a cooling shroud. The fuel sensor gauge is standard GRT LPS-02 low pressure sensor. After the second event I re-purged the fuel line to the sensor, it had no effect as the issue reoccurred the following flight.
Not sure where to go. It appears the fuel pressure sensor is working correctly since it reads normally when the boost pump is on. It also seems odd for a mechanical fuel pump to essentially fail completely and then run normally afterwards. I am hesitant to replace parts without a good reason to explain the events.
I have a message into the engine manufacturer but thought maybe someone in this group may have seen something similar. For now the airplane is grounded.