Kavlico, Fuel Pressure Sensor, PN 103755-000

[skippydiesel]

Hi All,

 

Rotax 912 ULS

 

My fuel pressure readings have become a bit weird, while in Cruise (all good on the ground). Random (increasing in frequency) drops to below 2 psi - instant recovery  to 5 .5 psi when Boost turned on.

 

Note: Engine continues to purr away without any hesitation.

 

Done the usual "fixes" :

• Draining fuel pipe to sensor.
• Relocated sensor to highest available location in engine compartment.
• Cleaning Gascolator filter screen (which looked nice and clean anyhow).
• Ensuring sensor has access to ambient air pressure.

 

Thinking sensor on the way out. Looking for replacement :

 

                                       OM is Kavlico PN 103755-000 V2, 1/8-27 NPT, 15 psi. Part Marking P255-15G-E4A. Pressure Range 0.6 -15 psi. About $300 AU delivered.

 

Looking for :

 

• Most Cost Effective Supplier (only found two in AU)
• Alternative part, same specifications, /compatible with Dynon system, that you can recomend.

 

My thanks for any constructive assistance.😈

[IBob]

Skippy, any chance of getting your hands (temporarily) on a steam gauge?
You could then identify whether you have a fuel pressure problem or a fuel pressure sensing problem.
 

[IBob]

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.
 

[IBob]

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.

 

 

[Blueadventures]

I have a UMA fuel pressure sensor, works good.  They don't like heat so mounted away from engine in the compartment in an air flow area to keep it as cool as possible.

[facthunter]

 Engine vibration is destructive also. All these senders are quite Unreliable. It's a harsh environment for them Nev

[Underwood]

10 minutes ago, Blueadventures said:

I have a UMA fuel pressure sensor, works good.  They don't like heat so mounted away from engine in the compartment in an air flow area to keep it as cool as possible.

Have a UMA fuels pressure sender also, it is working fine after 10 years service mounted on the cabin side of firewall but with the threaded portion going penetrating into the engine bay.

but they arent cheap (£295 in UK)

[IBob]

49 minutes ago, facthunter said:

 Engine vibration is destructive also. All these senders are quite Unreliable. It's a harsh environment for them Nev

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.