912 loses 500 rpm during climb

Re: 912 loses 500 rpm during climb

by Eric Greenwell » 8 years ago

Eric Greenwell

5 16 5

Hi Roger - the electric pump was running.

The vent tubes are vented to the atmosphere - are you saying put a pressure gauge on them to measure the pressure in the float bowl? I'll see if I can find someone locally that's competent to check the floats; unfortunately, my usual mechanic is on the other side of the Cascade Mountains near Seattle, so it might be while before he can check them.

Re: 912 loses 500 rpm during climb

by Dennis Richardson » 8 years ago

Dennis Richardson

1 153 174

If you are having a fuel supply problem your egt's should increase. If you are having an ignition breakdown your egt's should decrease. You indicated that your egt's remained stable. I would be looking at the exhaust, perhaps a loose baffle that is moving around.
Dennis

Re: 912 loses 500 rpm during climb

by Dennis Richardson » 8 years ago

Dennis Richardson

1 153 174

I hate it when I make a mistake. I missed your post with the egt readout. I will go back to reading the posts and predicting the solution.
Dennis

Re: 912 loses 500 rpm during climb

by Eric Greenwell » 8 years ago

Eric Greenwell

5 16 5

I can create the problem on the ground by running the engine at WOT for longer than two minutes. The data logs show the EGTs are nearly identical until the rough-running starts, and then they are about 30 degF apart; the fuel flow is erratic during the rough period, and varies from 5 to 7 gph (4.9 gph is the flow when it's running properly); and an ignition check at 4400 rpm (and running roughly) has the same drop (about 150 rpm) for Left and Right. The electric fuel pump was not running during this ground test.

I've weighed the floats, and all four weigh 3.1 grams.

My mechanic is perplexed, but still thinks it's fuel problem, and likely a carburetor problem, but he'll have to visit the plane next week to pursue a solution.

Re: 912 loses 500 rpm during climb

by David Glosser » 8 years ago

David Glosser

1 1 1

Eric, I had similar problem with my Phoenix upon original delivery and training. We went to Lockwood and had fuel pressure gauge installed for diagnostic purposes. No help. Subsequently one of the carbs was replaced; with instant and durable cure. No subsequent issues.