Erratic Low Oil Pressure

[aerhed]

Guys, Jerry says he put a MECHANICAL gage inline and it still did it. I'm thinking obstructed flow or something wrong in the oil tank. Jerry, is that correct that your mechanical gage also showed pressure drop?

[JBPILOT]

be sure suction hose is tight and not letting a little air in at the tank or pump. A better description of what fluctuations are being seen would help.

John Bender

[Catbird]

Dave,

That's right. When running both gauges simultaneously, I noticed a short duration of erratic readings on both of the gauges at the same time. Problem is that the erratic readings were so short and slight that I wasn't 100% certain that it was real. This leads me to believe that the low oil pressure readings from last weekend were, in fact, real and not just erroneous reading due to sensor failure, bad grounding, or loose crimping.

That being said, I'll still go back this weekend and inspect/rework the wire crimp terminations behind the engine where the sensor wires connect to the panel wires. If I remember correctly, the sensor wires are solid conductor - not stranded. If so, then I can see how crimping could be problematic.

Of course, a close inspection of the oil hoses will also be performed to see if there is any possibility of air being pulled into the suction line. If this were the case, then it seems to me that the return line to the tank would returning an oil/air foam.

The pressure relief spring and related parts will also be inspected for premature wear.

[todehnal]

JFYI - Not sure if everyone knows, but Rotax offers a special spade connector for the three sensors on the engine. They look like the ones that Van supplied with the kits, but they are not, and they have a Rotax part number. You can really tell the difference when you make the connection. I bought 3 from Lockwood for about a buck. Lockwood discouraged soldering to the sensors. Too expensive of a part to destroy. Anyway, Rotax is well aware of the vibration that these connections are exposed to, and is comfortable with these connectors on their engine.


Tom

[Catbird]

Tom,

I believe you are referring to crimp fittings or special spade connectors that connect directly to the sensors. In the case of my oil pressure sensor, the wires are factory terminated inside the sensor cover. The crimp connectors to which I am referring are located at the opposite ends of the wires where they connect to the instrument panel wiring behind the engine.

Jerry

[Dave12]

Originally Posted by aerhed

Guys, Jerry says he put a MECHANICAL gage inline and it still did it. I'm thinking obstructed flow or something wrong in the oil tank. Jerry, is that correct that your mechanical gage also showed pressure drop?

Dave(the other dave), you need to humor us -12 guys a little. This oil pressure sender has been so bad, we will blame anything we possibly can on it!

[Catbird]

Yeah, yeah, that's it. About a month ago I was having a little trouble dialing in the autopilot servos. Kept wanting to climb and bank to the left. I was convinced that the oil pressure sensor had something to do with that.

[aerofurb]

At work we were the UK dealer for Tecnams for two plus years. In that time, we changed many Honeywell oil pressure senders which had failed in various modes - full oil pressure, low oil pressure and no oil pressure.

The Tecnam singles behaved themselves but all 3 twins we sold/operated had them fail, hours between 50-400 - one had both engine sensors fail (at different times). Not so bad on a twin that shows no oil pressure but on a single, that is an attention getter.

As a result, on the 12, we have installed a (Tecnam) T-piece on the oil pressure port on the engine and have two sensors. The twin used the T-piece for the Honeywell sensor and a Hobbs switch for the Hobbs meter and door lock.

The Honeywell sender is still there on the 12 (until it fails...) driving the main SkyView oil pressure 'gauge'. We now also have a Kavlico sender on the T-piece displayed as a 'widget' next to the SV oil pressure gauge. If there is a discrepancy, I will believe the Kavlico sensor.

I kept telling the hierarchy at the Rotax and Tecnam factories that the Honeywell sender needed ditching - it is expensive and unreliable and gets both companies a bad name....

[MartySantic]

Jerry,

Everyone seems to be pointing to the sensor even though the mechanical gauge showed the same.

Suggest removing the oil pressure regulator components and examining. Simple to do.

Try posting your issue on CTFlyer, Engine/Rotax forum. Potential assistance there also.

[Catbird]

All,

I'll be diving back into it this afternoon and tomorrow (Saturday), and will provide detailed information regarding the findings. Four areas will be inspected:

1. Electrical connectors behind the engine; specifically the crimp connectors on the solid conductor wires coming from the oil pressure sensor

2. Pressure regulator spring , cone, ball and other assiciated parts for premature wear and adherence most recent parts upgrade

3. Oil hose crimp connections and fittings from tank to heat exchanger to engine for possible air leakage of into pump suction

4. More detailed comparison of oil pressure readings between mechanical gauge and Dynon display

I think the most important thing here is to accurately diagnose the problem and then provide an effective solution. All of the discussion here has been helpful. Will advise.

Jerry