Manifold Pressure Gauge

[Jimmy Hayes]

I own a Super Decathlon, that has about 100 hours on it. I am having continuous problems with the manifold pressure gauge. Apparently oil (blow by) is travelling through the line and seeping into the gauge. I have had the MP gauge cleaned (rebuilt) twice. The loop has been checked for proper positioning and it still reverts back to same conditions. Engine runs great. Uses only a couple of quarts between changes every 25 hours. American Champion suggested a 3 inch loop and a tiny hole in the bottom of the loop. My mechanic did that and the MP is erratic. He covered the hole and it was back steady.

Any thoughts on how to attack. We did see a Mooney with the hold in the bottom of the loop. However, the line on the Mooney was much larger and therefore the hole did not cause erratic MP.

Thanks.

 

[stuhoffman]

Hi. I have a 2001 Super Decathlon. My MP gauge kept sticking so I had it inspected. I was told that fuel had gotten into the gauge, possibly from operating the electric fuel pump for too long during the start up. The repairman said that this was common and that a filter can be installed into the line if it were an ongoing problem. He purged and recalibrated the gauge and it's worked fine since. I limit my electric fuel pump operation now to a second or two. Hope this helps. Stu