IBob

Yes....but do we get to shout at each other???........................😬

Skippy, so after it began to play up, you flew level again at normal power, and it still played up? I ask because on my aircraft, the airflow around the cowl changes (as you would expect) with different aircraft attitudes. The result in my cases is that in a hard climb the naca scoop on the top no longer scoops. A long shot, I know, but I thought I would tip it into the mix....

Okay, just saw your above post, Dermot. Are they now using 577 all round?

Unless Rotax have changed it, the elbows into the water pump take Loctite 243, while the elbows into the heads take Loctite 480. I repositioned the elbows into the water pump using a dowel and a propane torch, as you describe. But I did it with that part of the water pump off the engine and held lightly in the soft jaws of the vice. It felt a bit amateurish, but it worked. Due to an error not of my making, I ended up having to replace one of the elbows on the underside of the heads......and that wasn't easy. As I recall, I ended up using acetone and one of those gun cleaning brushes to clean out the threads in the head. As noted, those elbow threads are very fine......and they are also 'soft as butter'.

Very nice!

bobcharl I posted more pics before this last post.

BTW, the hoses at the radiator ran quite close to my front exhaust pipes, so I inserted little aluminium shields. You can't see clearly here, but they are stepped out so that the shield stands away from the hose, with air passing both sides of the shield. My thought was to protect the hose from the radiated heat of the pipe. I did that on both sides:

Ah, okay. here you can just see it making it's way through the engine mount and up just to the rear of the engine mount (ignore the thinner corrugated pipe at top LH, that is oil). It then bends forward just under the top tube of the engine mount, where the 'rubber' connector hose is clamped on, then to the coolant reservoir.

Hi bobcharl, I don't recall the RH tube being difficult, but it's been 5 years since installation. Unfortunately I can't show you the rear of the motor, it's hidden by the airbox and associated scat tubes etc. Assuming you are referring to the big pipe from radiator to pump, the spigot/junction at the pump can be bolted on in various positions, I may have turned mine to better accept the pipe. This is the best pic I have from the RH side, but I don't think it offers any more info than the previous pics:

Well, Skippy, you're not short of advice and suggestions. Time now to actually troubleshoot the problem?

Thruster, I take your point, but I don't think it's that clear cut: what Skippy is reporting is intermittent apparent pressure drops. It seems to me that could be either pump or pressure sensing: if the sender is failing, it is possible that it does not respond reliably to the (lower) pressure of the mechanical pump, but does respond to the (higher) pressure of the booster. That's why I think it would help, if possible, to determine whether it is pump or sender/circuitry before shopping for a replacement.

Yes, that occurred to me too, Skippy. That's why I suggested borrowing a steam gauge if you can: identifies whether the problem is the fuel pressure or the sensing. And if it's any consolation regarding location, I see the Kavlico unit boasts 'Outstanding Shock & Vibration Performance' and an operating temperature range from -40 to 125'C (depending on seal material).

These are certainly considerations, Nev, but I don't entirely agree: our refrigeration ones were mounted into pipework on very big ammonia compressors, most of which run 24/7 until overhaul. Having said that, the 0 to 15PSI sender for the fuel is far more delicate than the oil pressure sender, by a factor of about 10. Personally, I would not be mounting it in the engine bay, for reasons not only of heat and vibration, but also because these are gauge pressure units that rely on also sensing a steady and accurate ambient pressure.

FWIW, I would say $300 is about the going rate for an economically priced transducer (sender). They come in: 2-wire, (loop powered), 3-wire, as this one is, 5v/0v/signal (output) 4 wire, power/0v power/Signal+/signal- (less used nowadays) This one has a 5V power in, and gives an output signal of 0.5v to 4.5V which is presumably 0 to 15PSI (though I note elsewhere that Dynon say you won't see anything below 0.5PSI.) So any sensor, suitable for use with petrol, with those operating parameters should be a direct swap-in. Depending on how far you want to dig, and on what adjustable parameters your Dynon offers, you could also swap in something with different parameters. For instance, the oil pressure transducer on the Rotax has an output signal of 4 to 20mA, (which is an industry standard) and it's quite possible the Dynon can be configured to accept that. All depends what Dynon setup you have. 0 to 15PSI is a good range for 912 fuel pressure unit. These senders are inclined to fail if the pressure exceeds their max rating. Typically we used to specify them as max pressure x 2, so for instance in a refrig setup where we might see 12 or 13 bar, we would fit 25bar transducers: that gave as a good degree of accuracy, with plenty of pressure safety margin and excellent reliability. One other note: some refrig enginerooms might have 20 to 30 pressure transducers over multiple compressors and the various vessels. Things may have improved now, but a few years back, of those 20 to 30 we would often get 1 or 2 that failed almost immediately. Of the rest, if they lasted a week, they gave no trouble after that.

I had a lot to do with pressure transducers over the years.....in industrial refrigeration and hot water systems, also in hydraulics etc. I note from the P255 data sheet: https://www.mouser.com/datasheet/2/657/sensata_p255_stainless_steel_pressure_transducer_d-1769810.pdf that it's principally for dry media, with Note 1 saying "For wet conductive media please contact us." It also notes that the internal seal needs to be compatible with the media. In short, I would be checking with the manufacturer that what you are looking at is compatible with petrol.