Mechanical fuel pump LOST PRESSURE IN FLIGHT

[soarer20]

Our mechical fuel pump Fuel pump was just replaced as part of the 5 year rubber.

Less than 10 hrs on the new pump. Fuel pressure warning light has been flickering on and off since I got it back from annual.

On take off at about 700 agl I turned off the boost pump, and almost immideatly the fuel pressure warning light went on and the engine started to sputer and lost power. I turned the boost pump back on and the engine started to run normally again.

The mecahnic that did the work thought it was a fuel pulsation issue (SB OSB20-069).

Rotech believes its the pump but can't be sure until we check the entire fuel system.

Has anyone experienced a similar issue?

We want to make sure we properly diagnose the problem but it sure seems to be the pump.

Any thoughts would be helpful!

[Kesk]

What was the outcome? Haven't ever worked on the Rotax Diamonds, so I don't know the system. Certainly sounds like the mechanical pump is the problem.

[Da20Marin]

I'm having a similar issue. Normal run up without the electric fuel pump on. Electric pump on for take off and climb out, level off, switch off the electric pump and I now sometimes get the low fuel pressure warning light on for ~5 seconds before the light turns off again. The A&P took the whole fuel system apart and inspected it, cleaned the sensor, and inspected the inside of the mechanical pump. He could not find an issue.

Here is a link to SB 20-069 which describes the fuel pulsation issue. I'm going to see if we've had this performed this weekend.

If anyone else has ideas before I spend 1k replacing the mechanical fuel pump?

http://support.diamond-air.at/fileadmin ... I-AMMS.pdf

[Tavit]

I've had something similar happen with my own setup. I had a flickering fuel pressure light after a pump replacement, and it turned out to be a loose connection that wasn’t providing consistent pressure. It caused the engine to sputter, especially when I turned off the boost pump. I’d suggest checking all the connections, especially the grounding, and maybe do a full pressure check under load. If the pump’s acting up, you’ll likely see some fluctuation when the boost pump's off. Definitely worth checking the entire fuel system, but it sounds like it could be related to the pump.