Comment

Comment by Ralph Sanson on November 12, 2011 at 9:51pm

Or swap the sender down lower to the next plugged port, off the engine oil feed gallery which will measure the pressure of the oil after the filter, couplings and cooler smoothed it out.

Mitchel senders from ACS are same as VDO and better than some of the others originally installed.

Ralph 

Comment by Stephen R. Smith on November 4, 2011 at 10:54am

Well there is something happening here; but what it is isn’t exactly clear…

First of all, for more information on oil system issues on Jabiru motors, spend some time on the Yahoo groups Jabiru engine form where this issue has been discussed at length in the past.

Oil pressure senders ALWAYS go bad on Jabiru motors.  Generally this occurs gradually over a few hundred hours.  The cause is one of the following: 1) Engine vibration or 2) internal damage from pressure pulses from the oil pump.

Keep in mind that the pressure sender is mounted directly adjacent to the oil pump and is first-in-line to receive the thousands of pulses the pump produces as it delivers oil.

Also keep in mind that oil is non-compressible so the pulses are “hard”.  Also realize the pressure that registers on your panel is some sort of average.  This is especially true when using a remote panel-mounted mechanical gauge.  The actual instant-to-instant pressure in the oil system can only be known by using a high-speed sensor which costs many hundreds of dollars.

Also realize that the mechanical components in the pressure sender can not keep up with the pump pulses and gets played like a musical instrument at times which is probably where the wild readings come from, depending on various conditions, like current oil viscosity, engine RPM etc, the pressure sender’s diaphragm and other internal components are “bouncing” off the pulse and producing erroneous readings.

And then there is the issue of the oil lines and fittings running to the cooler being too small and creating restriction and back-pressure, especially when using straight 50 weight oil.  And don’t forget the oil pressure sender is before the cooler circuit and oil filter – a bad (deadly) design if ever there was one…

Many Jabiru engine owners have moved the pressure sender off the engine to the firewall and supply the pressure sender via high-quality line from the opening on the main oil galley (not the current location).  This improves the life of the sender and gives a more accurate reading of the oil pressure actually delivered to the engine’s internal parts.

The moral of the story: the oil pressure reading on your panel may or may not be telling you what you think it is telling you.

Steve

Comment by Paul Hammond on October 31, 2011 at 3:43pm

I put a new vdo sender inbought from a major aussie part store ,but it runs at a higher pressure first one failed at,150 hours this one has 30 hours .I guess as long as the pressure is higher not lower it wont be so bad

Comment by David Gallagher on October 31, 2011 at 11:27am

I had one fail in a similar manner at around 170 hours.  I put in a new one from NAPA auto parts and it has run for about 30 hours without a problem.

 

Dave