engine won't run at high RPM
05-11-2003 | 02:15 AM
#1
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From: Oklahoma City,
OK
engine won't run at high RPM
I have an OS40LA engine that has about 20 flights on it. Yesterday I was flying my plane and it just died in the air. I landed it and now I cannot get the engine to run at high RPM. It will idle fine. I have
1. replaced all the fuel lines.
2. changed out the muffler.
3. tightened all the screws on the engine.
4. Put the engine on a different, working plane.
5. Put a working engine on the original plane and it works fine.
6. Changed out the fuel with new fuel.
When I hold my finger over the exhaust it will run up to high RPM but as soon as I take my finger off the exhaust it dies.
Has anyone experienced these symptoms and have any ideas what to try next. I have only been flying for 2 months now and can not think of anything else to check.
1. replaced all the fuel lines.
2. changed out the muffler.
3. tightened all the screws on the engine.
4. Put the engine on a different, working plane.
5. Put a working engine on the original plane and it works fine.
6. Changed out the fuel with new fuel.
When I hold my finger over the exhaust it will run up to high RPM but as soon as I take my finger off the exhaust it dies.
Has anyone experienced these symptoms and have any ideas what to try next. I have only been flying for 2 months now and can not think of anything else to check.
05-11-2003 | 02:43 AM
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From: Sterling , CO
engine won't run at high RPM
Check for Vaccum leak at base of carb, or plugged spray bar.Blocking muffler pressures fuel into carb, air leaking at base of carb. makes it lean.
05-11-2003 | 02:47 AM
#3
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From: Chesterfield, MO
engine won't run at high RPM
It is probably too lean.
Have you opened up the needle valve?
Or:
Disconnect the fuel line from the carburetor and connect about one foot of fuel line. hold this fuel line below the tank and watch the fuel flow. It should siphon out of the tank at the rate of 1 or 2 ounces per minute. If it does not, then something is clogging it - perhaps a kink in the line inside the tank.
If the fuel flow is fine from the tank, then it is clogged in the needle valve area. remove the needle valve and blow fuel thru this area. you can just pump fuel into the normal nipple that goes into the carb and fuel will spurt out from the hole where the NV used to be.
Also, get the engine started at idle, then begin to open the throttle watch carefully for bubbles in the fuel line. I know you said you changed the fuel lines, but this is an easy test to run. if there are bubbles in the fuel line the engines tend to go lean in the air and quit.
Finally, sometimes air can leak around the NV or where the carb is attached to the front intake. Try to check for air leaks in this area.
Have you opened up the needle valve?
Or:
Disconnect the fuel line from the carburetor and connect about one foot of fuel line. hold this fuel line below the tank and watch the fuel flow. It should siphon out of the tank at the rate of 1 or 2 ounces per minute. If it does not, then something is clogging it - perhaps a kink in the line inside the tank.
If the fuel flow is fine from the tank, then it is clogged in the needle valve area. remove the needle valve and blow fuel thru this area. you can just pump fuel into the normal nipple that goes into the carb and fuel will spurt out from the hole where the NV used to be.
Also, get the engine started at idle, then begin to open the throttle watch carefully for bubbles in the fuel line. I know you said you changed the fuel lines, but this is an easy test to run. if there are bubbles in the fuel line the engines tend to go lean in the air and quit.
Finally, sometimes air can leak around the NV or where the carb is attached to the front intake. Try to check for air leaks in this area.
05-11-2003 | 02:58 AM
#4
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From: Oklahoma City,
OK
engine won't run at high RPM
I have swapped the engines on two planes and the other engine ran fine on this plane but my 40LA still exhibits the same problems on the other plane. This leads me to believe it is definitely a problem with this engine. Thanks for the advice. I will try pumping fuel through the needle valve and checking for vacuum leak at base of carb or plugged spray bar.
05-11-2003 | 03:16 AM
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From: Oklahoma City,
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problem solved
I like to do one thing at a time so I went to the garage and pumped fuel through the needle valve both with the valve in and with it removed. I hooked everything back up set the needle valve and tried it. It works fine now. Thanks for your quick response.
ChrisC
ChrisC
