fuel pumps

Hi Steven

Perhaps switch the wires on your toggles from 1 and 2 pumps.  Designate 1 as 2 and 2 as 1.  If it is indeed a check valve that may give you an answer.  When off,  the inline vane type pump does not pass fuel, the check valve lets it then flow around it.  Since the pumps are in series, in line, then it depends on which pump is running and flow to keep the check valve open.  It would be good to isolate if it is power related, switch or wire connection, or a pump issue itself.  If you can switch the connectors on the pumps themselves i would try that also. 

The fuel type and ethanol should have nothing to do with this problem.  

Cheers

I have a similar problem.

When the 915is is hot after an hour or so of flight, it can stop when turning off pump 2 (with pump 1 switch still on).  On a shorter flight, on shut down of pump 2, it stutters as the original poster described (see videos).  Initially I thought it was the check valves so I replaced the complete fuel pump assembly, which did not improve the issue.

I believe this is an electrical problem more than a fuel flow issue.  I am also having some other electrical issues with the Garmin avionics rebooting un-commanded.  I’ve had good interaction with Rotax and sent the BUD’s data files to them, they are still analyzing.  It has been suggested that the stators could be an issue, which appear to be good.  As this seems to be related to heat as well, I’m suspecting one of the rectifier-regulators or something with the Fuse Box.  I have checked all the grounds I could find.    

I have replaced the:

  - fuel pumps

  - fine fuel filter

  - battery  

   - radio

The following video links illustrate the issues

  A – Engine Stops When Pump 2 is Turned Off (when engine is warm after a 1-hour flight)

https://drive.google.com/file/d/1-9R2G3hW8Gzvtn2payDuER6oA9MJOuk9/view?usp=sharing

B – Engine Stutters when Pump 2 is Turned Off (usually after a shorter flight, notice the Amperage Draw)

https://drive.google.com/file/d/1-FzTKfVEVs8KtZXTLF3sMHTQzJjMY7xu/view?usp=sharing

The aircraft is a 2022 AutoGyro Cavalon 915is with 460 hours.

Mark

The injected engines have 3 phase charging to the regulators.  Be sure that each leg is working correctly.  Normally the B side of the charging is what fails and can lead to failure of the regulator.  

A quick check of the stator can be done by disconnecting your regulator, with engine off.  Take a good multimeter and bridge between wire 1 and wire 2, then wire 1 to wire 3.  Last check between wire 2 and wire 3.  This should show all 3 legs with equal resistance.  You can also check each wire end at the connector to ground, they should not any connection.  If you have a connection to ground on any of the 3 wire ends the stator has failed.  

Cheers

Hello Steven and Rotax Wizard

I still am having the same fuel pump problem.  I have determined its not an electrical issue.  I purchased and installed a new pump assembly with no change in behavior, it would still starve the engine when turning off the aux pump after a flight.  I made a test jig and ran mineral spirits through the old original pumps for 24 hours, hoping after I reinstalled it my problem would be solved, which didn’t help.

I’m flying an AutoGyro Cavalon and in September 24 they came out with a service bulletin describing this same problem with the solution of replacing the outlet of the fuel tank with slightly larger hardware.  I have yet to do that.

The good news is I can make the problem disappear TOTALLY be swapping the wiring as described by Rotex Wizard above (main pump power goes to the aux pump and aux pump power goes to the main pump).  Where the flow of the pumps are in series, I’m not sure I see a down side to leaving it that way other than that’s not how Rotax designed their product.

Food for thought,

I've seen similar situations like this on other things and it ended up being the wiring was too small to handle the proper electrical load. Once the wires were replaced with a larger wire the problems went away.