Jump to content

Oil pressure intermitent on a M20J 1987


juanM20J

Recommended Posts

After installing a new GTN 750 last summer, oil pressure gauge indication works fine for a about 30 min of flight, then drops to almost zero, no oil or cylinder head temp increase.  After landing, checking, same symptom.  Avionics shop checked pressure  (OK) and grounding at gauges - Pressure test on ground are normal - After several short fligts, also found that if I turn Master OFF then ON, oil pressure signal is back.  Any suggestions?

 

Edited by juanM20J
clarification
Link to comment
Share on other sites

Did you check the ground at the sender? Some senders ground via the clamp that holds the sender in place. Mine got wonky once and was easily remedied by cleaning (sanding) the body/strap interface. And it doesn't hurt to apply a light coat of contact cleaner or dielectric silicone grease in the connection to prevent future corrosion.


Sent from my iPad using Tapatalk

  • Like 1
Link to comment
Share on other sites

Anyone want to describe the the oilP gauge that we are talking about?

The original ship's gauge probably brings the pressurized oil through the fire Wall to the mechanical gauge on the instrument panel.  The line is about 3' long with a small diameter and doesn't circulate much oil.  Temperature sensitivity of the gauge itself would not be very strong.

'Super dangerous' if the line breaks and starts filling the co-pilot's shoes with hot oil, and he is a smoker... :)

Updated oil pressure gauges (like a JPI) use electronic sensors that can be sensitive to grounding issues... check the ground straps that connect the engine to the plane and instrument panel...

It can be a challenge to double check an oilP reading without being a mechanic with tools. Some things are naturally easier to double check.

 

PP logic, not a mechanic...

Best regards,

-a-

Edited by carusoam
Link to comment
Share on other sites

30 minutes ago, carusoam said:

The original ship's gauge probably brings the pressurized oil through the fire Wall to the mechanical gauge on the instrument panel.

On my 86 J , an electronic oil pressure sensor is mounted on the engine side (by the factory). Your 87J should be the same.

I had faulty transducer amplifer (small electronic box between the sensor and the gauge). I had to send it to IAI for a rebuild.

  • Like 1
Link to comment
Share on other sites

Thank you guys for your prompt responses - FYI My Mooney has a pressure transmitter located in the engine compartment, a Transducer/amplifier located on top of the instrument cluster and the actual pressure display (by the way very similar arrangement to the fuel pressure system)  My shop did tighten  the grounding nut... but will ask them to remove it completely and see if there some corrosion there.

Guillaume,  in case grounding check is not effective and we need to send the  transducer for repair who is IAI (address) and cost od repair?

Link to comment
Share on other sites

8 hours ago, N201MKTurbo said:

I have the old super dangerous wet gauge. It is the most reliable gauge in the plane...

You probably have dangerous fuel lines running under the floor as well, I'd remove them.

Clarence

Link to comment
Share on other sites

8 hours ago, juanM20J said:

Guillaume,  in case grounding check is not effective and we need to send the  transducer for repair who is IAI (address) and cost od repair?

http://internationalavionics.com

I don't have the exact cost at hand right now, but I remember it was ~ $300 but I guess you may ask them for a quote.

The amplifier is manufactured by IAI. The gauge is manufactured by Rochester.

I'm not sure who makes the sensor.

I remember that my problem was "easy" to troubleshoot as tilting/touching the wire at the amplifier base would fix the problem.

Link to comment
Share on other sites

I own a 1987 205 as well.  I had the wire connection to the oil pressure sensor became frayed near the sensor (apparently due to years of vibration).  A simple repair was made to the connection and all's well.

I hope that this helps.  Intermittent connections can be a pain to troubleshoot. 

Link to comment
Share on other sites

I'll add the same thing here I have posted elsewhere.  When I had an MG B roadster when I was a young guy back in the Cretaceous period, I went through every electrical connection and made sure that they all had good connectivity by disconnecting, cleaning and reconnecting   At 14/28v the amps driving current isn't that much and if it has to overcome corrosion as well, you will get problems.  So as an "ongoing" maintenance project and where regs allow, you would not do any harm by disconnecting a connection, cleaning it, re greasing it if required, and re connecting it. 
You will be amazed by the difference, for example when I did it with the starter circuit on my MG, the engine nearly jumped out of the bonnet when I turned it over to start it.  It is definitely worth doing.  
Andrew


"Bonnet".

It's such a pleasure having you on MS.


Sent from my iPad using Tapatalk
  • Like 2
Link to comment
Share on other sites

13 hours ago, Hyett6420 said:

I'll add the same thing here I have posted elsewhere.  When I had an MG B roadster when I was a young guy back in the Cretaceous period, I went through every electrical connection and made sure that they all had good connectivity by disconnecting, cleaning and reconnecting   At 14/28v the amps driving current isn't that much and if it has to overcome corrosion as well, you will get problems.  So as an "ongoing" maintenance project and where regs allow, you would not do any harm by disconnecting a connection, cleaning it, re greasing it if required, and re connecting it. 

You will be amazed by the difference, for example when I did it with the starter circuit on my MG, the engine nearly jumped out of the bonnet when I turned it over to start it.  It is definitely worth doing.  

Andrew

Ah...reminds me of my young gotta have a British Leyland sports car....MGB,triumph gt6....all with Lucas electrical components.Standing joke was LUCAS...prince of darkness!!

Edited by thinwing
  • Like 2
Link to comment
Share on other sites

Ah...reminds me of my young gotta have a British Leyland sports car....MGB,triumph gt6....all with Lucus electrical components.Standing joke was LUCUS...prince of darkness!!

Amen to that having owned several MGs and Triumphs (and even two Fiat 124s) with Lucas electrics.





Sent from my iPhone using Tapatalk
Link to comment
Share on other sites

Not British but my '66 Karmann Ghia had a 6V generator/electrical system. As mentioned in previous posts gremlins tend to rear their ugly heads in low-voltage systems such as 6 volt cars and 12 volt planes. Good grounds are imperative.


Sent from my iPad using Tapatalk

  • Like 1
Link to comment
Share on other sites

1 hour ago, thinwing said:

Ah...reminds me of my young gotta have a British Leyland sports car....MGB,triumph gt6....all with Lucus electrical components.Standing joke was LUCUS...prince of darkness!!

I kind of liked Lucas. They knew their stuff failed often, so they made them easy to work on. They recognized that their starter gear would frequently "stick" engaged in the ring gear, so they extended a square end of the shaft out the rear of the starter. You could disengage it with the proper size wrench. With practice you could unstick one in less than 30 seconds. MG-TDs, MG-TF, Austin Healey and several Lotuses.

  • Like 1
Link to comment
Share on other sites

3 hours ago, DonMuncy said:

I kind of liked Lucas. They knew their stuff failed often, so they made them easy to work on. They recognized that their starter gear would frequently "stick" engaged in the ring gear, so they extended a square end of the shaft out the rear of the starter. You could disengage it with the proper size wrench. With practice you could unstick one in less than 30 seconds. MG-TDs, MG-TF, Austin Healey and several Lotuses.

I used help my brother replace broken rear axels on his mg-td ...the hard part was retrieving fractured spline end of axel engaged in differential...what fun...cool car though..I always wanted a Morgen..

Link to comment
Share on other sites

I have the EI electronic oil pressure gauge in my plane and started to get some weird reading and fluctuations.  Changed the sensor and fixed tha problem.  It will make you hear skip a beat when the voice comes over the headsets saying check oil pressure and temperature.

 

 

Link to comment
Share on other sites

Many thanks Guillaume, cnoe, jsimmons619, hyette6420, 1964-M20E for your suggestions and shared experiences.  Also thanks to all those vintage british cars drivers for sharing the issues related to grounding corrosion... I also once upon a time owned an MG for 4 years... but luckily had no issues with that then.

I will post the solution... once we find it - Juan

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.