Bypass fuel pressure regulator

Hi Terence,

Last question first - my last aircraft came with an adjustable fuel pressure regulator. The aircraft/engine predated the fixed bleed/return line manifold now installed in most, if not all, Rotax 912 fuel systems - Yes it worked. However the penalty is considerable extra weight & complexity. Hardly desirable.

My understanding of the fixed orifice manifold/ return line has more to do with vapour mitigation than pressure regulation.

Assuming the correct mechanical fuel pump had been fitted and all fuel lines are in good order (last 5 year rubber replacement?) - I cannot see how you can have "too high" pressure. The mechanical pump will only deliver at the specified fuel pressure & volume.

What fuel pressure readings have you seen?

Have you verified this pressure using a master gauge? or even a temporary replacement?

Pressure gauges using a "Bourdon Tube" usually have a restrictor in the pressure line/or gauge to smooth out the pulses - If this is the type of gauge you have, the restrictor may be missing.

Describe the fuel pressure gauge.

You are correct the 912 didn’t originally have the return line and the pressure was within limits.  I have a VDO sending unit going to a Grand Rapids Engine Information System. 

Thank you for you reply.  It gave me some ideas.  The VDO sending unit has a metered orifice to smooth out the pulses.  

Terence