New fuel pump

by Roger Lee in 912 / 914 Technical Questions 12 years ago

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Re: New fuel pump

by Roger Lee » 12 years ago

Roger Lee

126 5.13k 4.56k

Hi Glenn,

Sounds like you need a restricter in the fuel pressure sending line. This is easy to do and can be done with a Bing idle jet in the fuel line. Same for the map and oil pressure. It will steady both of them right down. You need to reduce the hose ID to a small hole to keep the pulsation down. I have both Dynons and have no problems with them in flows, temps or pressure. The cover is not a problem and can be fixed with a light sanding on a very flat surface to finish the cover face a little for high spots. I little sealant can also be used on the cover "O" ring if necessary. I don't know why the carbs wouldn't hold a sync. It is usually something in the throttle linkage and if it was determined to be the carbs after only 3 months I don't know why it wouldn't be covered unless it was written up poorly for the warranty claim. The engine is covered for 200 hrs or 18 months so long as you do what Rotax prescribes in that time period.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: New fuel pump

by Ivor Floyd » 12 years ago

Ivor Floyd

0 11 0

I fitted a new BCP fuel pump to the 912ULS on my low wing SportCruiser. The BCP pump was a replacement of the previous AC pump, and was installed because of low fuel pressure readings. The BCP pump is installed in-line after an electric pump.
The fuel pressure readings are now approximately 0.3 bar and rises to 0.4 bar when the electric pump is switched on. What concerns me is the build up of fuel pressure when the engine is switched off, including the electric pump. Fuel pressure then increases gradually to over 0.55bar. Can someone please assist with advice why this should happen.

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Re: New fuel pump

by Michele Riccobono » 12 years ago

Michele Riccobono

2 16 17

This has nothing to do with the fuel pump but it's a consequence of the fact that the Sportcruiser fuel system does not have the return line to the fuel tank.
To avoid the pressure build up after engine shutdown, you can use the following procedure:

On the ground, close the fuel valve and let the engine run at IDLE (around 2000RPM) until you see that the fuel pressure starts to decrease then shut down the engine and reopen the fuel valve (just to avoid forgetting it closed at the next flight ;) ).
You should see that the pressure build up does not occur again as the fuel vapours are now free to discharge into the carb sumps due to the float valve being open as a result of the engine running some minutes withbthe fuel tank valve closed.

To solve the problem without using this procedure would require the addition of a fuel return line towards one ofnthe two wing tanks but this is not a mod authorized by CZAW and it also has some other disadvantages.

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Re: New fuel pump

by Ivor Floyd » 12 years ago

Ivor Floyd

0 11 0

Thanks Michele, according to the SportCruiser a return line to the fuel tank is fitted. I have not personally checked to see if the return line, which is visible in the engine compartment, actually does return to the left tank.
Regards,

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Re: New fuel pump

by Michele Riccobono » 12 years ago

Michele Riccobono

2 16 17

If the return line is there, may be you can check if it is clogged. Anyway, if you run the test I recommended and the post-shutdown high pressure goes away, you have a return line problem.

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Title	Category	Replies
Fuel pump	General Tech Discussion	11
Max takeoff fuel consumption	915iS Technical Questions	2
RPM issue, first start, new engine	912 / 914 Technical Questions	8
New vs Old - Oil Pressure Sender	912 / 914 Technical Questions	1
Fuel pump	912 / 914 Technical Questions	1

New fuel pump

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