lml@lancaironline.net Mailing List Archive

Bernie,

It is now becoming apparent that the preheating of the fuel is causing the problem. Van's and Spruce have a shield for the fuel pump with the blast tube. It works a lot better then the blast tube only. You should also make a shield with blast tube for the gasolator if you cannot buy one that's fits your model. Installing these covers increase's the blast tube effectiveness greatly along with shielding from radiant heat. You might also consider insulating them (covers) for more effectiveness. You might also do the same for the boost pump assuming it is on the firewall. I would consider all this an AD if it were my butt in it.

As some have mention fuel injection is subject to some surging. Some more then others depending on the prop you are spinning. The heavier the prop (metal) the less the surge. Lighter (wood) the more the surge.

I see no need for a check valve and I hope it was not a sniffle. Sniffle valves are to drain fuel out of the manifolds on horizonial intakes after shutdown.You have two pumps that I believe have check valves built in. You should eliminate as many restrictions as possible, Did you open up and clean the flow divider yet.?

steve alderman N25SA 360

-----Original Message-----
From: Berni Breen <bbreen@cableone.net>
To: lml <lml@lancaironline.net>
Sent: Thu, May 24, 2012 9:01 pm
Subject: [LML] 360 still surging

Today I made 2 changes to my airplane in an effort to remedy my surging issue. Both changes were made as per suggestions from LMLers.

Change #1 - I removed the in line fuel filter and in line fuel check valve formerly located in the cabin footwell of my airplane. I bought a 28" piece of rubber fuel line and clamped in on the void created by removing these items. I then took the airplane for a flight during which it performed flawlessly as it always does in a first start scenario. I taxied back to my hanger, shut down and let it sit for 20 minutes. I tried a restart but experienced difficulty for the first time. I was not able to restart utill I turned the electric fuel pump on and left it on during the start. I then taxied and still experienced my surge issue. I was able to turn the pump off and fast taxi.

My theory on why I experienced the start issue was that the removal do the check valve allows fuel to pass back though the system unimpeded creating the possibility of a loss of prime at the engine driven fuel pump. I believe that check valve (sniffle valve) needs to be in the fuel line. Comments?

Change #2 - I installed a blast tube and directed the airflow directly onto the engine mounted fuel pump. I started the engine (it was again cool from sitting idle for a couple of hours) and went for flight #2. Again the engine performed flawlessly. I landed, taxied back to my hanger, shut down and let the airplane sit for 20 minutes. I restarted (again had to keep the aux fuel pump on) and began to taxi but felt the surge right away but it was not as pronounced a before and seemed to be lessening. During run up I let the engine run a bit longer than usual at 1800 RPM. When I went back ti idle...no surge. I taxied to the active...no surge and took off. Flew great, landed and repeated the

Et sit for 20 minute thing. I restarted, taxied with a bit of a surge but was able to eliminate it during taxi and run up.

I am not ready to celebrate yet but I definitely see a marked reduction in the severity of the surge and the ability, at least today, to eliminate any surge by simply taxiing and or a bit of an extended run up. I believe the blast air is the reason for the improvement. I believe I should also add a second blast tube with the air directed at the gascolator.

Does this make sense? Any and all comments welcome!

Berni