MAP and oil pressure failed, crossed out

[PH-LRV]

1. Since five weeks during the start-up procedure, I realized that some engine parameters like MAP and oil pressure were crossed out in the first 15 seconds. Then, they were steady. Since a couple of days, these crossed out parameters increased in their numbers. When I taxied out yesterday, I saw fuel amount and oil temperature in addition. Shortly after applying take-off power, it disappeared again. No issues until I reduced power and started to descend. Then, MAP and oil pressure were displayed with a red cross again. That continued until I shut off the engine.

2. When this happened the first time, I immediately ordered a new EMS 220 from the local Dynon dealer and replaced it. I thought, the fault is within the EMS. In fact, it didn't last very long.
I checked the wiring and the sensors, no issues at all.
Additional info. When I discussed this issue in my hangar, some guys mentioned that it could be a problem with the power supply. In my plane, the VPX is installed.

Thanks for the help and advice.
Best regards from Bavaria
Stephan
PH-LRV

 

[airguy]

Have you ever seen those problems without the engine running?

Try shutting off the alternator field after engine start, and see if that affects the problem.

All those components, if mounted on the engine, are relying on a good ground from the engine back to the battery. If that ground is not good, then when the alternator is trying to charge the battery, the entire engine, and everything connected to it, will actually rise in voltage slightly above the rest of the aircraft as the alternator tries to drive electrons across that less-than-perfect grounding between the engine and the airframe. That results in an "out-of-range" indication for that sensor to the EMS, which Dynon then displays as the "Red X". In order to avoid that, you need to make sure the engine (and everything mounted to it) is at exactly the same electrical potential as the rest of the airframe and the negative side of the battery, with very good wiring connections.

If the problem seems tied to engine operations (speed/rpm), that could be indicating that the alternator is causing the issue through a bad ground connection. If you don't see the problem at all when the engine is off, or the problem goes away when you turn off the alternator field with the engine running, that is your confirmation.

 

[PH-LRV]

Thank you very much for the explanation airgiy. That sounds very logical to me. This is a new option for me and I will try this tomorrow. I’ll check all ground connections according your description and keep you updated as soon as possible. Thanks for your help and the time to describe this issue.
Best regards from Bavaria.
Stephan

 

[jakej]

Do you have a plane power alternator fitted ?

 

[chriscalandro]

Those sensors do NOT rely on the engine ground. They have a dedicated ground wire that goes back to the EMS.

Sounds like you have a wiring issue somewhere.

 

[PH-LRV]

Do you have a plane power alternator fitted ?

Yes I do.

 

[jakej]

Yes I do.

Ok, what I'd do is unplug the Alternator & ground run the engine to see if the 'issue' is still there -IF yes, then "bite the bullet" & install a B&C Alternator & regulator.

 

[Stevec]

Jake can you explain why removing the alternator and seeing the problem remains points to an alternator fault. Just interested as I would have thought if it was an alternator fault and you removed the alternator the problem would disappear.
just interested to know the logic here.
Thanks

 

[airguy]

Jake can you explain why removing the alternator and seeing the problem remains points to an alternator fault. Just interested as I would have thought if it was an alternator fault and you removed the alternator the problem would disappear.
just interested to know the logic here.
Thanks

Agreed. I don't like Plane Power alternators either - but this is not a guaranteed Plane Power problem.

 

[chriscalandro]

It’s not an alternator issue.

That doesn’t make any sense.

It’s not an engine ground issue. That doesn’t make any sense either.

It has to be wiring or the EMS.

 

[GKC Aviation]

I have had a Plane Power alternator cause all sorts of dramas due to stator wiring connections cracking off internally. (it is a big problem with PP alternators)
It still worked, but obviously the output voltage was something other than clean DC. Also the amps were jumping around, but so fast that the EMS wouldn't reliably catch it.
I replaced it with a much cheaper and reliable B&C L40 with the external voltage regulator.
For a simple test like disconnecting the alternator for a run, it would at least discount this as a cause.

 

[jakej]

Guys the reason WHY I made the suggestion is exactly what GKC said.
I did not want to give reasons when a simple unplug of the alternator would/could give the outcome I expected. Sometimes a simple action can give instant results - it’s called experience

 

[chriscalandro]

Well I have what’s called a formal education AND experience, not only in electrical engineering, but in pressure transducers.

An alternator would not cause this issue. An unstable alternator output MIGHT show up as unstable readings (I’m not sure if the 12v out from Dynon is filtered in any way or not) but it would not show the sensor as no connection at all.

This is a wiring or a EMS issue.

 

[GKC Aviation]

You are probably right, but it's a nice quick check to eliminate one possibility. Take literally two minutes. That is all we are suggesting.
Both Jake and I do this for a living, we have seen a lot of weird faults, and it's best to start with the easy stuff first.

 

[chriscalandro]

You can test exactly the same thing by having the field turned off.

This is an intermittent problem. It’s not easily tested by just unplugging the alternator.

Good luck finding your wiring issue - Chris out.

 

[jakej]

Well I have what’s called a formal education AND experience, not only in electrical engineering, but in pressure transducers.

An alternator would not cause this issue. An unstable alternator output MIGHT show up as unstable readings (I’m not sure if the 12v out from Dynon is filtered in any way or not) but it would not show the sensor as no connection at all.

This is a wiring or a EMS issue.

"Well I have what’s called a formal education AND experience, not only in electrical engineering, but in pressure transducers"

Sometimes I'm wrong, hopefully not too often, & other times I'm good - hopefully between us WE can help others find a solution to their issues.
I certainly don't have your engineering quals, I just have "street smart" skills & 'in field' experience which can be useful .
Ps - a lot of times, too many, the "Experimental" Plane Power alternators cause problems more than they should.

 

[Stevec]

Sorry I just don’t get it.
1. Remove the alternator.
2. Run engine.
3. PROBLEM REMAINS.
4 . Must be a faulty alternator.
5. Replace alternator.

if line three said problem goes away that would make sense.

 

[jakej]

All I indicated was to disconnect (the field wire plug) the alternator.
Run engine.
Nothing about ”Problem remains”, however if it does remain, after the above, then the “issue” obviously must be elsewhere .
Never thought I’d say this, &mean no ill will, but ‘Stop acting like a troll’ you can do better

 

[Rhino]

I don't think he's intentionally trolling. He just didn't get the logic. If you disconnect the alternator, and the problem is still there, the alternator seemingly isn't causing it. But in post #7, you said replace the alternator anyway. That does sound strange.

 

[Stevec]

Thanks Rhino I have no intention of trolling anybody. I am here to learn as much about the system as possible so I can help the people I support. I don’t think I deserved that comment.