Manifold Pressure problem

[Jerry De Santis]

My plane is a P337G 1975 model with Riley A.C. and Intercoolers. Engines are TSIO-360 CB's

Problem: Rear engine manifold pressure does not go lower than 24 inches. We know it is not the gauge because we switch connections from rear engine gauge to front engine gauge and the problem stayed with the engine.

We disconnected the line from the gauge and the hoses on the rear fire wall and blew air through it to make sure nothing is impeding the line. It is clear.

Anyone have a suggest where I should look next to determine the problem?

Cheers
Jerry
N34EC

[Ed Coffman]

Jerry,

Is that on the ground and at altitude? If so what altitudes.

Ed
________
Dodge avenger

[Jerry De Santis]

That's on the ground. Once I spool up it is okay however, when I throller back on landing, the MP will not go below 25 to 24 inches, yet fuel flow reduces as it should.

Jerry

[Jerry De Santis]

Sorry, make that throttle back!

[Ed Coffman]

Jerry,

Sounds like an intake manifold leak. Have you checked for that?

Ed
________
The hills forums

[Ed Coffman]

Or a crack in the line to your gauge. We have had that happen before, it usually breaks where the guage line goes into the intake manifold at the front of the engine.

Ed
________
Fuck

[stackj]

Jerry,

I had a similar symptom on my front engine. The problem turned out to be a split nut on the tubing connecting to the pass through connector on the fire wall.

I flew the airplane about three years looking for that. It was just a hairline crack.

[Paul Sharp]

I had a somewhat similar problem. I say "somewhat" because mine was pretty much, although not exactly as you described. But after $3000 or work by Million Air here in SLC, I finally took it to my regular mechanics (had used M. Air because I wasn't sure it was safe and if it really was just a leak they should have found it right away. Anyway, my regular guys put a meter on it, pumped up some pressure, found it was in fact leaking, and in about 10 mins. found the section with the leak. They then pulled off the line at the back of the instrument panel, noted a cracked fitting, and rebuilt that little section in about 10 minutes more. (They could have replace it even if they hadn't found the crack as they knew the leak was in that section, but having the cracked piece was valuable to me.) In total 1 hour I was in the air back to SLC, where I showed the cracked line to the head of maintenance at Million Air. To their credit they reversed all of the charges except for the turbo controller overhaul which they had put me through as part of their previous work.

If soeone has a simple pressure meter setup, finding the leak should be child's play.

[Jerry De Santis]

Thanks guys. when I get an opportunity to get my plane over to where my mechanic is I will have him check the line.

Cheers
Jerry