dougknight
Well Known Member
I have a friend with a RV 6-A. We took off the other day headed for lunch and the engine quit on us during climb out. Since then we have been trying to isolate the problem without much success, thus I address the community for added input and suggestions. We are pretty sure the problem is with fuel delivery.
Ever since he purchased the plane he has noticed an INTERMITTANT fluctuation in the fuel pressure gauge between zero and seven psi. He has kept a very close eye on it and anytime psi has dropped near .5psi he turns the electric boost pump (facet) on and it quickley returns to 6-7psi and no problems. The day the engine quit on us we had just taken off with the electric boost pump on and once reaching 800-1000 feet he turned it off, we were talking and he became somewhat distracted and did not monitor the fuel flow gauge for the next minuet or two whence it ran out of fuel and got quiet very quickley. He has been very aware of the low pressure problem since he bought the plane and immediatley re-energized the electric boost pump within two seconds and the engine surged back to life. We immediatly turned 180 degrees and landed at our home field, de-cowled and started investigating.
Approximatly two weeks prior to this incident he bought and installed a factory new fuel pump thinking the old one was the culprit of the intemittant low pressure readings and was trying to get away from flying the airplane with his eyes glued to the fuel pressure gauge all the time. I doubt the problem is in the engine driven fuel pump simply due to the odds of two of them in a row being bad with the same intermittant symptoms.
The engine is an O-360 Lycoming carburated with a fixed pitch prop and dual slick mags. He bought the plane complete and flying some 50 hours of flight time ago. Total time on aircraft I am not sure of, however total time on this factory new certified engine is approx. 750 hrs (2nd engine since the build) my friend is the third owner. The fuel system looks pretty standard RV (I have a 9A and I am the builder) as tubing comes from each tank to a selector in front of and between the seats then to a facet electric pump which is located just below the pilots left leg midway between the knee and ankle. Once it leaves the facet pump it goes through the firewall and does an abrupt 90 degrees for about 3 inches into the gascolator which is mounted on the firewall, exits the gascolator via a straight fitting and enters the starboard side of the engine driven fuel pump via a 90 degree fitting. It then exits the port side of the fuel pump via vans supplied fitting which allows for two tubes to exit, the main fuel line to turn 90 degrees and dump directly into a 45 degree fitting into the carburator, the second smaller line goes to the firewall mounted transducer for the fuel pressure gauge. All lines are flexable factory made hoses and are firesleve protected engine side of the firewall. Each tank has air vents routed and located per plans, however there are no fuel return lines as would be for an injected engine as this is carburated. All firewall forward pipe to tube fittings are AN type Aluminium except the 45 degree fitting into the carburator which is steel (we just replaced the aluminum). Both the fuel pump and the gascolator have shrouds around them with blast tubes originating from the baffles to aid them in cooling. We originally thought it may be vaporization of fuel in the line just inches from the carburator as it passed within an inch of the exhaust pipe but we have since installed a heat shield, double firesleeved the line and moved it up and away (3") from the exhaust pipe. Test flew it and the fuel pressure was still dropping intermittantly when the electric fuel pump was off.
This low pressure drop occures most frequently after first engine start of the day or after the plane has been sitting for more than an hour. It seems to be fine during taxi and run up even with the electric pump off. Turn boost pump on and take off it is still fine but as soon as you turn the electric pump off at 1000 ft agl we see an immediate slow drop in fuel pressure from 7psi to .5psi. Turn the electric pump on and the pressure builds back up to 7psi... turn it off and it again starts a steady drop to .5psi. After about the third time of boosting pressure back up with the electric fuel pump then turning it back off after pressure builds back up it seems to hold pressure just fine for the duration of the flight with just the engine driven pump running.
We are stumped and wonder if anybody else has encounterd anything like this or has any ideas.
Sorry for the long post but I wanted to provide as much information as possible.
Thanks in advance
doug
Ever since he purchased the plane he has noticed an INTERMITTANT fluctuation in the fuel pressure gauge between zero and seven psi. He has kept a very close eye on it and anytime psi has dropped near .5psi he turns the electric boost pump (facet) on and it quickley returns to 6-7psi and no problems. The day the engine quit on us we had just taken off with the electric boost pump on and once reaching 800-1000 feet he turned it off, we were talking and he became somewhat distracted and did not monitor the fuel flow gauge for the next minuet or two whence it ran out of fuel and got quiet very quickley. He has been very aware of the low pressure problem since he bought the plane and immediatley re-energized the electric boost pump within two seconds and the engine surged back to life. We immediatly turned 180 degrees and landed at our home field, de-cowled and started investigating.
Approximatly two weeks prior to this incident he bought and installed a factory new fuel pump thinking the old one was the culprit of the intemittant low pressure readings and was trying to get away from flying the airplane with his eyes glued to the fuel pressure gauge all the time. I doubt the problem is in the engine driven fuel pump simply due to the odds of two of them in a row being bad with the same intermittant symptoms.
The engine is an O-360 Lycoming carburated with a fixed pitch prop and dual slick mags. He bought the plane complete and flying some 50 hours of flight time ago. Total time on aircraft I am not sure of, however total time on this factory new certified engine is approx. 750 hrs (2nd engine since the build) my friend is the third owner. The fuel system looks pretty standard RV (I have a 9A and I am the builder) as tubing comes from each tank to a selector in front of and between the seats then to a facet electric pump which is located just below the pilots left leg midway between the knee and ankle. Once it leaves the facet pump it goes through the firewall and does an abrupt 90 degrees for about 3 inches into the gascolator which is mounted on the firewall, exits the gascolator via a straight fitting and enters the starboard side of the engine driven fuel pump via a 90 degree fitting. It then exits the port side of the fuel pump via vans supplied fitting which allows for two tubes to exit, the main fuel line to turn 90 degrees and dump directly into a 45 degree fitting into the carburator, the second smaller line goes to the firewall mounted transducer for the fuel pressure gauge. All lines are flexable factory made hoses and are firesleve protected engine side of the firewall. Each tank has air vents routed and located per plans, however there are no fuel return lines as would be for an injected engine as this is carburated. All firewall forward pipe to tube fittings are AN type Aluminium except the 45 degree fitting into the carburator which is steel (we just replaced the aluminum). Both the fuel pump and the gascolator have shrouds around them with blast tubes originating from the baffles to aid them in cooling. We originally thought it may be vaporization of fuel in the line just inches from the carburator as it passed within an inch of the exhaust pipe but we have since installed a heat shield, double firesleeved the line and moved it up and away (3") from the exhaust pipe. Test flew it and the fuel pressure was still dropping intermittantly when the electric fuel pump was off.
This low pressure drop occures most frequently after first engine start of the day or after the plane has been sitting for more than an hour. It seems to be fine during taxi and run up even with the electric pump off. Turn boost pump on and take off it is still fine but as soon as you turn the electric pump off at 1000 ft agl we see an immediate slow drop in fuel pressure from 7psi to .5psi. Turn the electric pump on and the pressure builds back up to 7psi... turn it off and it again starts a steady drop to .5psi. After about the third time of boosting pressure back up with the electric fuel pump then turning it back off after pressure builds back up it seems to hold pressure just fine for the duration of the flight with just the engine driven pump running.
We are stumped and wonder if anybody else has encounterd anything like this or has any ideas.
Sorry for the long post but I wanted to provide as much information as possible.
Thanks in advance
doug