Thread: Oil Pressure Sender Problems

I posted just a few days ago regarding an oil pressure problem I am having, however since the bulletin board change, it appears to have disappeared from the threads.
I received e-mail notification to advise some replies to the thread had been posted however was unable to read them as the thread is longer there, in fact everything in the Rotax 912 section prior to July 09 has gone, so I hope those who responded can re-post.

Just to reiterate, on start up the oil pressure is around 53 psi however as soon as I increase power on the engine to say 3200 rpm (having achieved 122F) the oil pressure drops to 36 psi. At cruise power (5000 rpm) the oil pressure will fluctuate between 36 psi and 53 psi. (I have the Dynon EMS.)
The oil pressure sender is mounted on the engine (by the factory) and I suspect it is starting to suffer the effects of vibration. (total 260 hours)

If anyone has had the same problem, can you advise whether remotely locating the oil press. sender has cured the low/fluctuating oil pressure indications.
Is there a kit available to facilitate remotely mounting the oil pressure sender? I bought something similar from CPS for the fuel pressure sender, however could not find an oil pressure sender on their website.

Thanks in advance.

Dave

Hi Dave,

I had exactly the same problem. There is nothing wrong with the position of the pressure sender, the problem lies within the design of the pressure REGULATOR:

The Oil pressure regulator consists of a metal ball valve that is forced to colsed position by a spring. The problem is that the ball which sits on top of the spring exerts a force onto the top coil of the spring which presses it sideways against the walls of the cylinder, so it generates much more friction than intended and the oil pressure is regulated in steps, the oil pressure gauge reads correctly!
Exchanging the spring and ball only helps for a short while, but Rotax is aware of this and should be able to provide You with a refined design as in my case: The ball is replaced with a valve that has a ball-like top, but a cylindrical bottom which does not exercise a sideways force on the spring and voila, the pressure is regulated as it should, linear with no "jumps" at all.

Hope You could understand my Austrian english and tell Rotax what they should send to You, in my case without any costs..

If they don't, keep me informed and I can ask the rep at the factory in Austria to fix it for You.

Regards,
Markus

Markus.....thank you for that information. Your comments tally with something else I saw on this forum (see below) so I might try replacing the regulator before replacing and relocating the sender.

"Rotax is now switching from a ball valve PN-432-680 to a cone shaped valve PN-857-230. According to the charts sent over with this info, the new valve will result in a higher average oil pressure across the entire range of RPMs. This product has been under development for the past two years and IS NOT A MANDATORY RETROFIT nor is it covered under warranty."

Regards,

Dave

Do you have the part number for that valve? I've been trying to get one for the past year but my local Rotax distributor cant find the part number.

Would be very curious to see how this works for everyone.

Doug

I have searched a lot of Rotax parts web site's and can find know referance to this part number PN-857-230 for oil pressure valve ?? does anyone know where you can get one ??

Rgs Mike

according to Eric Tucker it's the answer, just trying to get one is the problem

Just like WestCoast Oz I started having problems with fluctuating oil pressure within the past week (approx 150 hrs flight hrs). At times it was going to extremes... like no oil pressure to max oil pressure on the Dynon. This occurred after a flight of some 3 1/2 hrs following reduction of power on descent and happened on two consecutive flights. Initially I thought it was the sender, but from reading this forum and talking with WestCoast Oz I decided it was most likely something to do with the oil pressure regulator. Discussion at our field with other Rotax operators confirms the theory that it is the regulator and not the sender causing the oil pressure problems.

I took the part number mentioned on this forum to the Rotax Australian agent and I am told there is one in the mail to me as of yesterday. Apparently the agent has only just returned from the Rotax factory and had them in his bag. Hope to have it fitted in the next few days and will report back on success or otherwise.

Fitting is a very simple process I am told. Simply remove the bolt below the oil pump/filter housing, remove the shim, internal spring and "ball" (Part No: 432-680). Replace the ball with the "cone" shaped new part and re-assemble. If this takes more than 5 mins I will be very surprised.

I have one question however... if Rotax have determined the current "ball" is at times defective in maintaining the correct oil pressure within the system why hasn't a bulletin been issued on this? It becomes even more confusing when you read that Rotax took 2 years to design the replacement for the "ball" in the oil pressure regulating system.

Don't be willing to throw money at it until you rule out a few things so you can point a definitive finger at the right problem.

First tighten the ground wires whether you think they need it or not put a wrench on them behind the instruments on the back of the inside firewall.
Either put a mechanical gauge in line on the oil line and cross check the pressure or if you happen to have a know good pressure sender swap out your possible bad one. A mechanical gauge to double check your electronic one can be purchased at a local hardware store for about $15-$20 for the gauge and copper tubing. The oil pressure threads are 1/8" NPT. We are only checking pressure so make the tubing very small I.D.
It is extremely rare for the regulator to be bad.
If you don't confirm and identify the real problem you have fixed nothing, may cause other issues and cost your self more money.

I have checked many of these issues so do your check list first. It is usually the ground or a bad oil pressure sender.

If you feel like putting in the new regulator that's ok, but that won't fix the problem.

Thanks for your input Roger - your valued comments are appreciated and will be followed.

The first thing I checked was wiring integrity to the Dynon but will check again and fit a direct reading guage as well to check and verify the actual oil pressure readings.

The cost of this replacement part is extremely small (the Australian Rotax agent is actually supplying it to me gratis) and if it does the job it could save a lot of expense on not only for me but for others with the same problem as well. A replacement sender unit (if you use a genuine Rotax part) is not inconsiderable at approx US$250. The replacement part for the "ball" in the oil regulator cannot cost any more than 1/10th of that.

I received this reply from a query put to Flight Design Germany through the Australian FD agent 2 days ago re the new part that is available for the oil pressure regulator. I believe it is reproduced here exactly as written by Rotax in reply to the query from FD...

"This valve: PN-857-230, really offers a solution for engines with deviating oil pressure indication only– this part should improve stability of the readings.
Reason:
ROTAX has no influence what devices the customers mount, they can’t test all available Oil Pressure Gauges or EMS in the world. Therefore they have come up with this update for all other installations with deviating oil pressure other than the Rotax tested Flydat ."