I got my first "Low Fuel Pressure" warning today upon takeoff. Of course I'll be checking all suspects but so far it looks like what many others have experienced. How many have upgraded to the higher pressure fuel pump? I note that its a an optional change. So..how many are just living with it?
Van's Air Force
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Higher Pressure Fuel Pump
- Thread starter Tacco
- Start date
Me too
I too saw this low fuel pressure after months of it not being an issue yesterday. Odd we are both in Washington. I thought I solved the issue by drilling a slightly larger hole in my fuel cap. This seemingly solved the problem for the last 6 months. After yesterday (it always seems to happen when I take my wife for a flight) I ordered the upgraded pump after reading this link.
http://www.vansairforce.com/community/showthread.php?t=167151&highlight=low+fuel+pressure
I hope the $54 solves this issue for ever.
I too saw this low fuel pressure after months of it not being an issue yesterday. Odd we are both in Washington. I thought I solved the issue by drilling a slightly larger hole in my fuel cap. This seemingly solved the problem for the last 6 months. After yesterday (it always seems to happen when I take my wife for a flight) I ordered the upgraded pump after reading this link.
http://www.vansairforce.com/community/showthread.php?t=167151&highlight=low+fuel+pressure
I hope the $54 solves this issue for ever.
Jim,
Haven't looked at my pressure without the electrical pump on.
This was a stop and go takeoff after about a 20 minute flight. Looking at the Dynon data, the pressure was normal on approach, about 5.1 PSI. After stopping and applying full throttle for the takeoff, 5200 RPM, the pressure dropped immediately to 2.1 (hence the alarm) for a about 4 seconds then began a slow climb to about 2.5. As soon as I reduced the throttle, it climbed rapidly back up to 5.1 PSI.
OAT was about 60F.
Haven't looked at my pressure without the electrical pump on.
This was a stop and go takeoff after about a 20 minute flight. Looking at the Dynon data, the pressure was normal on approach, about 5.1 PSI. After stopping and applying full throttle for the takeoff, 5200 RPM, the pressure dropped immediately to 2.1 (hence the alarm) for a about 4 seconds then began a slow climb to about 2.5. As soon as I reduced the throttle, it climbed rapidly back up to 5.1 PSI.
OAT was about 60F.
RFSchaller
Well Known Member
Try running with 50% AVGAS on the really hot days. I have found it makes a big difference in eliminating vapor lock.
PilotBrent
Well Known Member
n=1
I experienced occasional low fuel pressure issues both at takeoff for a few minutes and also during my descents from higher altitudes. Been off and on for several years, with no measurable effect on engine performance. Always transitory, but disturbing nonetheless.
At my 5 year annual in the spring, I replaced both the engine and facet pumps (obtained it from Van's so I'm not sure if was of a higher pressure spec or not). In over 40 hours of flight since them, while I may see a "higher" pressure warning on the ground - often in the yellow range on Dynon, I have not experienced a single instance of low fuel pressure during flight. Whether its 100% mogas or 100LL, hot day or cool, doesn't matter.
I'm convinced these low pressure issues are the result of under performing (possibly failing?) pump(s). Can't be sure whether its the facet or engine driven pump, but it appears to be independent from instrumentation or fuel mixtures. Maybe the long fuel line design of the RV-12 exacerbates it, but with "new" well functioning pumps, the problem was eliminated.
Just my own experience.
I experienced occasional low fuel pressure issues both at takeoff for a few minutes and also during my descents from higher altitudes. Been off and on for several years, with no measurable effect on engine performance. Always transitory, but disturbing nonetheless.
At my 5 year annual in the spring, I replaced both the engine and facet pumps (obtained it from Van's so I'm not sure if was of a higher pressure spec or not). In over 40 hours of flight since them, while I may see a "higher" pressure warning on the ground - often in the yellow range on Dynon, I have not experienced a single instance of low fuel pressure during flight. Whether its 100% mogas or 100LL, hot day or cool, doesn't matter.
I'm convinced these low pressure issues are the result of under performing (possibly failing?) pump(s). Can't be sure whether its the facet or engine driven pump, but it appears to be independent from instrumentation or fuel mixtures. Maybe the long fuel line design of the RV-12 exacerbates it, but with "new" well functioning pumps, the problem was eliminated.
Just my own experience.
I tend to agree.
Today I did eight stop-and-goes and the fuel pressure never dropped below 2.6 at its lowest. Cool 60F day. The only difference between today and yesterday was that the stop-and-go occurred after a straight in and decent from 4000 ft.
I've ordered the higher rated pump but don't think I'll put it in for while. I also removed the seal on the pressure sensor as some folks think it might help if an altitude change is a contributing factor to a low measurement.
Reading other posts here and thinking through it, I think the issue is that the fuel system design causes the pressure to be on the hairy edge of tripping the Dynon alarm under some circumstances. The electronic pump (constant output) is pushing fuel to the engine driven pump (RPM variable output) and as the RPM increases the fuel pressure naturally drops. If the output of the electronic pump is reduced for any reason (its failing, takeoff acceleration, or just pump-to-pump variability) the the engine driven pump has to pull more. Throw in hot fuel (low vapor pressure) and my guess is that the engine driven pump cavitates a bit. That's why pulling back the throttle shoots the fuel pressure back up.
I'm not a fluids guy but there's my two cents.
Today I did eight stop-and-goes and the fuel pressure never dropped below 2.6 at its lowest. Cool 60F day. The only difference between today and yesterday was that the stop-and-go occurred after a straight in and decent from 4000 ft.
I've ordered the higher rated pump but don't think I'll put it in for while. I also removed the seal on the pressure sensor as some folks think it might help if an altitude change is a contributing factor to a low measurement.
Reading other posts here and thinking through it, I think the issue is that the fuel system design causes the pressure to be on the hairy edge of tripping the Dynon alarm under some circumstances. The electronic pump (constant output) is pushing fuel to the engine driven pump (RPM variable output) and as the RPM increases the fuel pressure naturally drops. If the output of the electronic pump is reduced for any reason (its failing, takeoff acceleration, or just pump-to-pump variability) the the engine driven pump has to pull more. Throw in hot fuel (low vapor pressure) and my guess is that the engine driven pump cavitates a bit. That's why pulling back the throttle shoots the fuel pressure back up.
I'm not a fluids guy but there's my two cents.
