Fuel pressure sensor line not getting pressure

Hi Matt,

"I turned the electric fuel pump on, expecting to get a stream of fuel out of the line that feeds the sender but all I got was a trickle."

There may be a restrictor jet in the fuel sensor line.😈

I've owned the plane for about 14 years now and I've never seen this behavior.

I spent some time this afternoon following the fuel lines around and, other than the tightly-packed spaghetti of the design, it seems pretty straightforward. I took a picture and annotated it, see below. The only question I have is which of the two lines goes down to the header tank and which goes to the sensor.

Questions: does it seem like a reasonable thing to disconnect the two lines going down to the header and sensor, then disconnect the line going to the sensor and attempt to blow through it to clear any blockage? Or perhaps use a large syringe?

Thanks in advance.

The chances of a blockage, after the fuel filter and the filter in the engine drive pump are slim, assuming that you have used good quality hoses and replaced them (all rubber) at the recommended 5 year interval.

If your fuel system uses barbed fuel connectors and you/your mechanic pull off/push on fuel lines, it is possible to damage the inside of the hose, thus liberating rubber particles into the fuel system, which may cause a blockage. If you are using multi barb push on hose connectors, I strongly recomend replacing them with modern automotive type connectors.

Problems with fuel pressure sensors have been discussed on this Forum before - in general it is best to locate the sensor as high on the firewall as possible and drain the fuel line, going to the sensor, at regular intervals (eg 100 hourly). The sensor should not be in contact with liquid fuel. The gas/air, in the hose leading to the sensor, will be pressurised by the fuel and the sensor will read/respond accordingly. It is not unusual, for pressure sensors, to have a restrictor jet located "downstream" to the sensor. The jet smooths /modulates any fuel pulses.😈

Yes, all fuel hoses have been replaced. I'm using ethanol-tolerant hoses, if it helps they're blue on the outside and black inside. There are no barbed connectors.

The SeaMax is unusual in that it doesn't have a firewall. The engine is a pusher configuration, mounted in a nacelle above the fuselage. This is why the fuel pressure sensor is behind the panel up front. The sensor is necessarily below the engine (behind the panel) as there's no other place for it. 

So it seems like, from the sensor side of things, everything is fine. The sensor itself appears to be electrically working correctly - blowing on it gives a positive fuel pressure reading on the EMS. If I understand things correctly, there should never be a strong flow of fuel out of the line that feeds it. It appears that the sensor is not in contact with fuel; there is an air gap.

What's not working fine is getting the pressure down from the fuel system to the sensor itself - it's reading zero. If there is a restrictor jet in place, should I just drain the line using gravity?