LANE A START UP QUESTION
in 912iS Technical Questions
8 years ago
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by JUSTIN » 8 years ago
First you need to find out why the fuel pressure is not rising, it could be you have a restriction or some other loss of flow.
Disconnect the fuel hose from the engine fuel RETURN fitting (at fuel regulator above cylinder #4). Connect a temporary hose to this fitting and place open end in a fuel container. Turn ON the main fuel pump for exactly 1 minute. Record amount in fuel container. It should be at least 6 liters.
Repeat for Aux pump.
Both pumps should provide at least 6 litres. (Max Take-0ff fuel consumption (26.8Lph) + 125%=60.3Lph)
We checked orifice first when there was the problem,then check the fuel return and fuel flow,finally changed fuel pump.You said the fuel flow we have checked, the main fuel pump and the auxiliary fuel pump are normal value.
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by JUSTIN » 8 years ago
We have five engines and the orifice size is 0.7 MM. The other four are normal, only this fuel pressure has a problem.
I checked all the spark plugs today and there was no mistake.And check the connection of the ignition coil but found no problem.Why is it that when I turn on LANE A the engine has obvious shake and RPM decrease?
Have you actually inspected the orifice on the suspect engine.
This is not a time to assume anything.
When operating on a single lane only 4 of the fuel injectors are used.
When both lanes are in service, the two injectors on each cylinder share the duty by injecting on alternate intake cycles.
If you have a bad injector, it may be one of the disabled ones when lane B is operating.
An Injector issue could also be related to the slow fuel pressure increase.
This is the new engine, what's the probability that the injector is broken?As far as know that new parts need to be replaced after the injector is removed.But we don't have any spare parts at present, we need to buy additional.Could there be other reasons?we get rid of the other possibilities,finally remove the injector after purchasing the parts.Thank you for your reply.
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by Rob Seaton » 8 years ago
I think you should look at the most likely cause: There is a very, very low probability of the injector being broken as all the engines are thoroughly test run at the factory. But the chance of introducing contamination from the newly constructed aircraft is very high.
Did you test the fuel flow?
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by JUSTIN » 8 years ago
Did you test the fuel flow?
Rob ,Thank you for your advice! We checked fuel flow at fuel regulator. Only turn on Main fuel pump is 0.9l/min. Turn on both pumps is 1.7l/min. We repeated it on another engine, is 1 litres when turn on Main fuel pump. Maybe the fuel flow is normal .The fuel pump capacity is approx.120l/h (912is installation manual).
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by JUSTIN » 8 years ago
Why is it that when I turn on LANE A the engine have obvious shake and RPM decrease?Only opened LANE B, the engine start and works very well.Have some relevancy between them(LANE A & FUEL PRESSURE)?
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