Author Topic: Fuel Surge on new IO550 (Read 506 times)

Frank Woods · « **on:** May 23, 2011, 01:55:40 AM »

I have a strange problem with my fuel flow on my new IO550 upgrade on my N model 35. If any of you have any ideas I would very much like to hear from you. After takeoff an into cruise flight, my fuel flow will momentarily surge. If I am running 2400 RPM and 23" MP and a FF of 15 g/h it will surge to around 18 to 20 g/h then settle back to 15 g/h. It does not do this all the time. I had a flight to PNS on Saturday at 8k ft with no surge at all. On the flight back home to SFB it surged three time, about 3 to four minutes apart. The surge only last about 2 to 3 seconds. If I run lean of peek the surge is not as pronounced but still there. I've had my mechanic look at it and he has made some adjustments to the maximum fuel flow settings but it still persists.

Thanks,

Frank Woods

N4589P

Robert Martin · « **Reply #1 on:** July 21, 2011, 01:05:14 PM »

Call TMC technical. They will probably tell you to send the fuel control unit in for replacement without cost.Robert Martin2011-07-21 21:06:21

Tom Pelz · « **Reply #2 on:** July 21, 2011, 03:57:00 PM »

Frank,

I assume that you still are using the analog instruments. IE, you are not using a digital fuel flow device.

I would purge the line from your engine to the back of the fuel flow gauge.

This is done by removing the line to the back of the fuel flow instrument and then running the fuel pump for a few seconds. This will purge the air from the line between the instrument and the engine.

Tom

Tom Pelz · « **Reply #3 on:** July 21, 2011, 03:57:36 PM »

Quote from: Tom Pelz

Frank,

I assume that you still are using the analog instruments. IE, you are not using a digital fuel flow device.

I would purge the line from your engine to the back of the fuel flow gauge.

This is done by removing the line to the back of the fuel flow instrument and then running the fuel pump for a few seconds. This will purge the air from the line between the instrument and the engine.

That will fix your problem

Tom

Don Lawrenz · « **Reply #4 on:** July 21, 2011, 09:51:26 PM »

Frank

One other possibility is that you are passing fuel vapor/bubbles (due to the heat) through the system and that is throwing the flow meter off. You might want to try the boost pumps the next time it happens and see if things stabilize much quicker.