Slow Manifold pressure gauge on 67F

[chrisk]

I've got a friend with a 67F and we are planning a trip in 2 weeks.  Then he tells me his MP Gauge has an issue.  He has described the Manifold Gauge as being slow to react.  Basically you change the throttle setting, and it takes a while for gauge to settle and give a stable reading.   Any ideas?   His mechanic thinks it needs to be be rebuilt.  Where would one send the combination Manifold and Fuel pressure gauge for an overhaul / IRAN?

 

Anyway, I'm looking forward to flying a plane with a Johnson bar again.  It's the first Mooney I ever flew.

[Guest]

A build up of "goo" consisting of oil and fuel dye in the MAP line can be the cause and is easy to verify by opening the line at the gauge and the engine and blowing it clear.

If nothing in the line there is a very small orffice in the gauge which can also become clogged, this means gauge removal and repair.

Not sure what instrument shop to recommend.

Clarence

[KSMooniac]

I'd try Clarence's suggestions first, and if he wants to try another gauge I have one I removed from my '77 J that I believe is likely the same one.  Working fine when removed.

[BigTex]

I had a similar issue and my mechanic just disconnected the tube from both ends and blew it out. That resolved my issue. Just make sure that you securely reconnect it. My A&P just figure tighten it back and when it came loose, I had one very unhappy engine!

[sreid]

If the other options don't resolve the problem and the instrument needs to be repaired, Kings Avionics has an associated instrument shop that repaired my MP gauge several years ago with good results. 913-829-4606, and they are located on the New Century airport in the Kansas City area.

 

Steve

[chrisk]

Guys,

Thanks for the suggestions.  I'll ask him about the line.

[N201MKTurbo]

If you blow out the line and it is still slow, there is a screw looking thing inside the fitting of the instrument. Unscrew it and clean it, then screw it back in. If the instrument is too slow then screw it out some. If the needle is vibrating with the engine then screw it in some.

If you want the instrument rebuilt better then new by an instrument tech who has been doing it for over 50 years PM me. He will do it for less then half of anybody as long as you don't need an 8130. If you need the paperwork he can do that also, but it will cost about the same as most other shops. The repair job is the same either way.

[podair]

I seem to be experiencing a similar problem after a few months of inactivity (plane was stored in hangar). Gauge works OK , up and down, then after prolonged flight WOT it does not read under 24in if you reduce the throttle, however the gear warning horn sounds if you pull all the way back (needle stays stuck at 24) so the problem is definitely on the gauge side (where does the gear horn take its reading?). Could this be a bit of goo in the line or is my original gauge showing signs of age. How easy is it to disconnect and clean the tube for someone with two left hands (my mechanic is 600nm away and an oil change is all I have managed to do on my own so far)? I have a spare gauge (combined MAP/Fuel pressure) but if I can fix the MAP side first without fiddling with the fuel pressure line, I'd rather do that then start replacing it and having to play with fuel lines.

[carusoam]

Podair,

From my 65C experience...

1) MAP has a small 1/8" diameter aluminum line with a tiny calibrated vent hole drilled in it. If the line cracks you get readings that are closer to atmospheric pressure.

2) gear warning requires two inputs. Throttle switch, a micro switch that is engaged when the throttle is pulled most of the way out. And the gear switch, which is engaged when the gear is stowed.

Please update your avatar data you have been here for a really long time... Portugal? (Old memory)

Best regards,

-a-

[podair]

good memory! I was in Spain for a couple years, now back in the UK, and fly mostly UK<->France