Seeking to track down problem described as follows.
RV9a with YO-320-D1A, with carb and about 60 hours TT. Do not have fuel flow monitor, yet.
Engine not running, mixture set to "cut off". Fuel pressure = 0.4 psi. Turn on electric fuel pump and fuel pressure increases to 2.2 psi. Turn off electric electric pump, fuel pressure remains at 2.2 psi. Open mixture, and pressure drops.
Engine running, at idle, mixture rich, engine running smooth, then switch on electric fuel pump, engine stumbles and black smoke out exhaust. Switch off electric fuel pump, engine runs smooth, exhaust clears. At idle, fuel pressure without electric boost = 1.9 psi, pressure with electric boost switch on = 2.3 psi.
Engine at run up @ 1800 rpm. Fuel pressure without electric boost = 1.9 psi. Fuel pressure with electric boost = 2.2 psi. No noticeable change in engine operation or rpm.
Engine running at cruise, during flight. Fuel pressure without electric boost = 2.2 psi. Fuel pressure with electric boost = 2.2 psi. No noticeable change in engine performance or rpm.
Presume electric fuel pump is causing engine to run rich at idle.
Some potential causes of rich conditions at idle with electric fuel pump on:
1. with electric fuel pump on, fuel pressure is sufficient to overcome the resisting float pressure on the needle, thereby pumping excess fuel into the carb, and flooding the engine. Weak float?
2. with electric fuel pump on, air bubbles are being "sucked into the fuel on suction side of pump" and bubbles entrained in the fuel enter the carb bowl, cause the float to sink, and therefore allow excess fuel to enter the carb. Seems ths would impact all phases of operation.
3. electric solenoid type of primer, and possible leak in the primer system that allows excess fuel to enter cylinders when electric fuel pump is switched on.
4. Other?
Are there any other ideas? Suggestions on the most efficient way to track down the cause?
Thanks,
Wayne
Dues paid 2017.
RV9a with YO-320-D1A, with carb and about 60 hours TT. Do not have fuel flow monitor, yet.
Engine not running, mixture set to "cut off". Fuel pressure = 0.4 psi. Turn on electric fuel pump and fuel pressure increases to 2.2 psi. Turn off electric electric pump, fuel pressure remains at 2.2 psi. Open mixture, and pressure drops.
Engine running, at idle, mixture rich, engine running smooth, then switch on electric fuel pump, engine stumbles and black smoke out exhaust. Switch off electric fuel pump, engine runs smooth, exhaust clears. At idle, fuel pressure without electric boost = 1.9 psi, pressure with electric boost switch on = 2.3 psi.
Engine at run up @ 1800 rpm. Fuel pressure without electric boost = 1.9 psi. Fuel pressure with electric boost = 2.2 psi. No noticeable change in engine operation or rpm.
Engine running at cruise, during flight. Fuel pressure without electric boost = 2.2 psi. Fuel pressure with electric boost = 2.2 psi. No noticeable change in engine performance or rpm.
Presume electric fuel pump is causing engine to run rich at idle.
Some potential causes of rich conditions at idle with electric fuel pump on:
1. with electric fuel pump on, fuel pressure is sufficient to overcome the resisting float pressure on the needle, thereby pumping excess fuel into the carb, and flooding the engine. Weak float?
2. with electric fuel pump on, air bubbles are being "sucked into the fuel on suction side of pump" and bubbles entrained in the fuel enter the carb bowl, cause the float to sink, and therefore allow excess fuel to enter the carb. Seems ths would impact all phases of operation.
3. electric solenoid type of primer, and possible leak in the primer system that allows excess fuel to enter cylinders when electric fuel pump is switched on.
4. Other?
Are there any other ideas? Suggestions on the most efficient way to track down the cause?
Thanks,
Wayne
Dues paid 2017.