View Full Version : Manifold pressure guage

04-19-2009, 10:01 AM
My Pacer (0290-D2) has a manifold pressure guage in it. However, since we bought the plane it's never appeared to read correctly and it has now dropped to 11-12 and stays there. We've had no decrease in engine performance in any way.

My questions are:

Do I need a manifold pressure guage? In other words, should I bother to trouble-shoot it or simply pull it out of the panel.

If the answer to that is "Keep it" then how do I trouble-shoot what's wrong with it. Somebody mentioned they can get oil in them and you need to clean it out.:confused:


04-19-2009, 11:31 AM
Rip and tear. You don't need a MAP gauge unless you have a Constant Speed prop. It is of [very, very] little value in verifying carb ice, but if it's toast anyway then an EGT/CHT dual gauge is a MUCH better investment to put into the blank hole. Because there is such a premium in panel space in this Type, even a perfect MAP gauge is the first thing to go if you wanted to install, say... a VOR/LOC head (or ANYTHING else of any "value"). Don't forget to plug the tapping in number three cylinder when you yank it all out. There is more value in having the "fourth" primer nozzle than a MAP gauge, if you need another "excuse" to remove it. You can only find the "original" type primer nozzle if you have the Luck O' the Irish and HAPPEN to step on one at a Fly Market, but the new style (oh...1954 or so???) works just fine, even mixed with the "old" type.

If your MAP gauge filled up with oil, then the airplane was "maintained" by somebody with a relatively poor work ethic. There was a Piper S.B. the better part of a hundred years ago to add a .060" hole in the line where it comes out of the cylinder fitting. This eliminated the "oil in the MAP gauge" problem (in all fairness, it COULD HAVE been "plugged" with some spooge. But its moot).