Manifold Pressure Oddity

[AaronDC8402]

Had an odd issue come up today with our 1989 201. Fired the plane up and noticed that the manifold pressure seemed to be "stuck" higher than it should have been while idling (about 25"). Being a naturally aspirated engine, I knew the manifold pressure reading was not the actual manifold pressure. Also, the engine didn't sound loaded up like it would have if there was actually that much manifold pressure.

 

We have a JPI 830 and the original manifold pressure gage. Both were showing the same values. On full throttle, manifold pressure raised to an expected value. After pulling the throttle back, it never dropped below 20". 

 

My guess is that there is some kind of blockage in the line that connects the intake manifold to both the JPI sensor and original gage. Any common issue that would cause this?

 

Thanks!

[takair]

Cracked or chaffed MAP line.  Popular failure.

[Gagarin]

1 hour ago, AaronDC8402 said:

Had an odd issue come up today with our 1989 201. Fired the plane up and noticed that the manifold pressure seemed to be "stuck" higher than it should have been while idling (about 25"). Being a naturally aspirated engine, I knew the manifold pressure reading was not the actual manifold pressure. Also, the engine didn't sound loaded up like it would have if there was actually that much manifold pressure.

 

We have a JPI 830 and the original manifold pressure gage. Both were showing the same values. On full throttle, manifold pressure raised to an expected value. After pulling the throttle back, it never dropped below 20". 

 

My guess is that there is some kind of blockage in the line that connects the intake manifold to both the JPI sensor and original gage. Any common issue that would cause this?

 

Thanks!

Check for a leak on the manifold pressure line like a loose connection

[AaronDC8402]

Thanks for the replies. A crack or leak makes way more sense than a blockage. I'll be looking it over some this morning, and report back what I find.

[AaronDC8402]

For anyone interested, we found that flare on a line had broken off of the line. The line was still in the nut enough to give a little dynamic seal action. It'll hopefully be back together this afternoon, and we'll confirm it's fixed sometime this weekend.

Thanks again for all the help. You guys are great.

[AaronDC8402]

Problem solved. A new line fixed the issue. Thanks all.

[carusoam]

@AaronDC8402

make sure the new line has the calibrated weep hole in it already...

Older Mooneys, the mechanic put the new hole in a stock piece of aluminum tubing....

Newer Mooneys came with a more special part from Mooney...   a more special tube with fittings....   

old line was about a 1/8” tube....

Newer line is about 1/4” tube... probably has the weep hole in it...

really new is a wire... the sensor is closer to the engine.... no weep hole at all...

It would be a really cool engine... idling at 29” of MP....   max MP of 60” or so...   expect a huge fuel bill to go with that...

PP thoughts only not a mechanic...

Best regards,

-a-