Fuel pressure sensor install

So one question.

  Looks like the Rotax manual procedure call for installing a psi gauge to that port when you need to check for pump pressure.

  They don’t mention any possible anomalies with regards to what you said.

  Very likely that I’m not quite understanding what you mean. 

Wade, I only mention this because there are a couple of locations that the return line restrictor orifice can be located in that distribution block. There is one setup that  causes the potential problem I mentioned, probably not worth worrying about.

Ok sounds good….thanks again for the info

Hello all, I would like to discuss this a bit more...  Wade, are you suggesting that the fuel pressure sender (I have the one from Dynon) be screwed directly into the port on the engine?  I think I read a post from Roger elsewhere that the fuel pressure sender should not be mounted on the engine because vibration can cause the sender to fail?  I haven't checked yet, but I saw where one builder said that he needed an adapter for the fuel sender to thread into the fuel block (i.e. it is not 1/8 NPT?).  That builder mounted the fuel sender on the firewall and ran a fuel line to the port on the engine.  Also, I think Roger's post said the fuel sender location on the firewall should be "above" the engine so the fuel would not accumulate?  BTW, I have a 100HP Rotax 912 ULS manufactured in late 2022.

Oil and fuel pressure senders over the many years have had some issues with vibration. So many including aircraft MFG's have mounted these on the firewall to help dampen out some of the vibration. So many including aircraft MFG's mounted the fuel sender on the firewall hanging down and down around the lower part of the engine. This causes another problem especially if you use auto fuel. That fuel then sits in that hose that is upside down for months and years. This has the fuel in the hose going through many heating and cooling cycles and it just gets stale and starts to clog the tiny hole in the fuel pressure sender (i.e. like VDO sender) The stale fuel causes a build up over that long time which starts to clog up that tiny hole. When you take the sender off the bottom of the hose you can smell that stale turpentine odor of fuel. I use a can of carb spray with that little red nozzle on it and spray in that hole about 1 second 4-5 times and many times that will fix it. Of course sometimes not. The spray exorcises the mechanism inside the sender and cleans out the hole.

This all said I now mount the fuel pressure sender above the engine on the firewall. The sender now faces up and not down. Vibrations are still low, but when the engine is shut down for the day the fuel drains away from the sender. Now there is no clogging and old turpentine smelly fuel is not there and it's always replaced with fresh fuel.  All the ones I have done this to have never had another sender issue.