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New 912 Engine Starting Problem

Matronics Email Lists Forum Index -> RotaxEngines-List

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hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Tue Sep 12, 2006 1:02 pm Post subject: New 912 Engine Starting Problem

Gentlemen:  

<![if !supportEmptyParas]> <![endif]>  

After running my new Rotax 912UL in my Allegro 2000 for four successful trial runs, I decided to drain the main tank and refill it with new fuel. I drained the tank completely through the low point drain and refilled the tank about half full. When I tried to re-start the engine, it would not hit. It just turns over and over. Ignition is on, choke is on, and I am operating the electric fuel pump during the start sequence. I have tried three times to start the engine with the same result. I have done nothing different from the initial four runs other than draining the tank and refilling. Could I have a vapor lock or trapped air somewhere? I would think that the electric fuel pump would take care of air or a vapor lock in the lines between the pump and the carbs. Fuel bowls have stayed dry. Any suggestions how to find the problem, and correct it?  

<![if !supportEmptyParas]> <![endif]>  

Hugh McKay  

Allegro 2000  

N661WW  

        [quote][b]

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thilo.kind(at)gmx.net
Guest

Posted: Tue Sep 12, 2006 1:18 pm Post subject: New 912 Engine Starting Problem

Hi Hugh,

  

 suggest to check the fuel lines to the carburetors  with the electrical fuerl pumps running. Could be, that you are sucking fuel  from the tanks to the electrical fuel pump. With the tank now half full (less  pressure) you might create vapour lock in the suction line from tank to  electrical pump. 

  

 Good luck

  

 Thilo

 [quote]   ---

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lostpilot28

Joined: 26 Jul 2006
Posts: 7
Location: Southern California

Posted: Tue Sep 12, 2006 1:34 pm Post subject: New 912 Engine Starting Problem

Hi Hugh,

 I typically run my electric fuel pump until my 2 psi fuel pressure light goes out plus about 5 seconds.  This puts fuel in the float bowls and pressurizes the fuel lines.  I've never had a starting problem.  My guess is that you not only drained fuel from the tanks, but the lines as well (gravity fed back to the tanks).

  

 Regards,

 Sonny W.  

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jkuehn(at)mountaintime.my
Guest

Posted: Tue Sep 12, 2006 2:37 pm Post subject: New 912 Engine Starting Problem

Try disconnecting the fuel lines at the carburetors, one at a time, and 

turning on the electric pump briefly to clear the line.  Make sure fuel 

is flowing.  I have had slow starting after draining things out, and I 

do not think you have a real problem here, just no fuel getting to the 

engine.



Jack 



Hugh McKay III wrote:



 	  Quote: 	
		   Gentlemen:



  



 After running my new Rotax 912UL in my Allegro 2000 for four 

 successful trial runs, I decided to drain the main tank and refill it 

 with new fuel. I drained the tank completely through the low point 

 drain and refilled the tank about half full. When I tried to re-start 

 the engine, it would not hit. It just turns over and over. Ignition is 

 on, choke is on, and I am operating the electric fuel pump during the 

 start sequence. I have tried three times to start the engine with the 

 same result. I have done nothing different from the initial four runs 

 other than draining the tank and refilling. Could I have a vapor lock 

 or trapped air somewhere? I would think that the electric fuel pump 

 would take care of air or a vapor lock in the lines between the pump 

 and the carbs. Fuel bowls have stayed dry. Any suggestions how to find 

 the problem, and correct it?



  



 Hugh McKay



 Allegro 2000



 N661WW



*

*

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Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Wed Sep 13, 2006 4:28 am Post subject: New 912 Engine Starting Problem

Hugh,



1)	Is the fuel tank valve turned on? I know this is obvious but 

sometimes we forget. I have

2)	Are both mags on? I've forgotten this one too.

3)	Does the fuel pressure gauge read in normal range with just the 

electric boost pump  on? It should with just the master on and the fuel 

pump switch/cb on, and not cranking.

4)	When you crank, does the fuel pressure change? With the engine 

mechanical pump also doing its job, the fuel pressure reading should be 

a little higher than with just the electric pump on.



If 3 & 4 are good, then you know you are getting fuel to the engine, 

and the carbs, if there is no leak in the fuel system in the engine 

compartment, which would be visually obvious with the upper cowl off. 

This also means you are not getting vapor lock anywhere.



If the engine is cold, make sure that the choke is full on and the 

throttle is completely closed. When cold the engine will not start if 

the throttle is open even a little.



If it still won't start, remove the drip tray under one carb and then 

the float bowl to see if the bowl has fuel at the proper level and the 

float valve moves up and down okay. While you have the float bowl off, 

check to see if the starting circuit jet is loose. The starting jet is 

in the bottom of the little vertical cylindrical area in one corner of 

the bowl. If it is loose it could affect starting mixture and if it 

does start cause rough idling. Do this same thing for the other carb. 

and then reassemble carefully making sure you get the bowl gaskets 

seated properly.



If after trying all of this it does not crank, let us know and we'll 

proceed from there.



Thom in Buffalo

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_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
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