It seems that the VDO resistor-type oil pressure sensors commonly installed on the Jab 3300 routinely wear out every couple of hundred hours - or less!  I'm at 550+ hrs and noticed my 3rd VDO sensor was starting to show signs of failing - usually evidenced by sudden spikes of high pressure.

Some have tried to avoid this problem by either mounting the sensor on the lower oil gallery port (which gives lower oil pressure readings and has to be taken into account) or remotely mounting it via an oil line with the theory the oil line will absorb some of the oil pump's pulsations and extend the life of the sensor.  I tried the lower oil gallery mount and saw no difference in the sensor's life.

It occurred to me to try one of the newer, solid-state oil pressure sensors.  Aircraft Spruce sells a "Swift" 0-5v/100 psi sensor that they say is "similar to the Falcon" and "with no moving parts ... which does not allow the sender to become worn out mechanically." It costs no more (maybe even a little less!) than a VDO sender.

Since it is supposedly resistant to wear, I installed it in the original location that Jabiru uses and plugged the lower galley port.  I display my pressure on the MGL XTreme EMS with the RDAC XF interface, so on the RDAC, I connected the red power wire to the +5v, the black ground wire to ground, and the signal wire to the OIL P connector.  Someone had told me I would need to install a resistor in the signal wire, so I connected a 1/4w, 1 KOhm in series to the signal wire. I set the XTreme menu to "0-5v" sensor and chose the "UMA TIEU100" since both are 0-5v, 100 psi sensors.

Initially, the sensor did not work correctly!  I double-checked and found the  pull-up resistor dip switch was "ON" on the RDAC, so I switched it off and it worked great after that.  Hmmm - makes me wonder if that in-line resistor was really necessary and could I have deleted it and just left the pull-up resistor switch "ON" on the RDAC board? I suspect that's the case but since it is working fine, I just left it as-is.

I had also been advised I might need a capacitor to filter the signal and prevent erratic or jumpy readings. Again, however, it did not seem to be necessary and the oil pressure readings are quite stable.  The person advising this had used a cheap Ebay Chinese sender, making me suspicious that's why he had to modify the installation - perhaps the "Swift" sender is a little better design/quality?

Anyway, now I just need to put a couple hundred more hours on the STOL 750 and see if durability is there!  ;>)

John

N750A

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Hi John,

I just noticed the solid state sensor is 1/8 NPT and the hole is 10mm.  Did you use an adapter?

Pete Krotje who was at Jabiru USA told me the oil gallery port was actually tapped to 1/8 npt but the factory uses a VDO sender with a M10 x 1K thread. There are adapters available, but the threads are virtually identical.   I've used Permatex high temp sealant and have never had a hint of leakage with senders of either thread. I really don't think an adapter is necessary, especially since the factory doesn't think so, either.

John

Think Pete is correct.  The VDO does have M10 x 1K threads and a copper washer.  However, when I put new one on it got pretty tight before it ever got to the shoulder and washer indicating the hole was getting narrower the further in it was screwed.  I ran engine a while and got no leaks.  Guess I will watch carefully for leaks and unusual oil consumption.  The original was installed on engine when I bought it and I had not removed until today.  However, I took it out by hand after about an eighth of a turn with wrench.  I am sure I am tighter than that so not worried about too little torque.

Next to figure out how to interface the solid state sender with Skyview.  Guess I will ask if anyone has done that.

Thanks again John!

It's a tapered thread so you just tighten it until it's good and snug, just as you would any pipe fitting.  I had the same experience - it tightens up well before the threads bottom-out, so the provided copper washer is not necessary - and as I mentioned, I used Permatex high temp sealant, too.

John

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