MP gauge needle "jumping"
Thread Starter
Joined: Sep 2002
Posts: 778
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From: London, UK
MP gauge needle "jumping"
What might be causing the needle on my MP gauge to jump after seemingly sticking? In particular, when decreasing throttle setting I've noticed it stick at a particular point for perhaps 1 second and then jump down about 2 or 3" worth of MP. It doesn't appear to be carb-ice related in that application of carb heat doesn't seem to make any difference, plus it happens in circumstances not conducive to carb ice.
Joined: Oct 1999
Posts: 568
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From: Swindon, Wilts,UK
Drauk,
Could be many things but usually two main contenders.
1) Mechanical I'm presuming that the gauge will be a Bourdon type. So the gauge could actually be sticking due to wear, lack of lubrication or dirt.
2) A slug of moisture in the line. This has more inertia than the air that should be there so either causes lag or if positioned in a certain place will cause an air lock until it moves then allows a rush of air through.
Either way I'd suggest you get it looked at before you blow the engine due to faulty reading.
Could be many things but usually two main contenders.
1) Mechanical I'm presuming that the gauge will be a Bourdon type. So the gauge could actually be sticking due to wear, lack of lubrication or dirt.
2) A slug of moisture in the line. This has more inertia than the air that should be there so either causes lag or if positioned in a certain place will cause an air lock until it moves then allows a rush of air through.
Either way I'd suggest you get it looked at before you blow the engine due to faulty reading.
