Why pump the throttle?

[Roger, Roger]

Because the mechanical fuel injection in most aircraft don't distribute the fuel that well.

Not so much that, more that it doesn't react fast enough to prevent a temporary lean mixture in all the cylinders as you open the throttle and let a bunch more air in.

 

[ryan1234]

Pumping the throttle if the engine isn't turning will just pool up a bunch of fuel on the carb and start a fire if it backfires. Use the primer instead.

+1
On the CJ-6, the fuel is pressurized with the manual wobble pump, and then primed by turning (by hand) one half blade for each cylinder with a shot of prime at each half turn. The throttle never really moves but 1/2-1 inch for start.

On another note.....not too long ago I was turning the blades through checking for hydraulic lock and this guy with 2 epaulets on his white shirt came over in the FBO to tell me that it's "unsafe" to ever move the prop through by hand.

 

[mshunter]

On another note.....not too long ago I was turning the blades through checking for hydraulic lock and this guy with 2 epaulets on his white shirt came over in the FBO to tell me that it's "unsafe" to ever move the prop through by hand.

"OMGZ! I need to tell that guy that he doesn't know what he is doing to his airplane! He's going to die checking a radial engine for a cyl. full of oil!!!! I have two stripes, so I otta' know! My instructor told me so"

That reminds me op people who put tow bars on from the side, as if the engine is going to magically start on its own.

 

[KSCessnaDriver]

On another note.....not too long ago I was turning the blades through checking for hydraulic lock and this guy with 2 epaulets on his white shirt came over in the FBO to tell me that it's "unsafe" to ever move the prop through by hand.

Hey well, you know, they get paid so much that they think that means they know everything. sarcasm I had one tell me that pulling the prop blades through some cycles on a Rotax was bad, because it could start. I laughed and told him to do some research on the engine and how the ignition system works. Also told him it was impossible to check the oil level without doing such a thing. Still couldn't change his mind.

 

[ryan1234]

Hey well, you know, they get paid so much that they think that means they know everything. sarcasm I had one tell me that pulling the prop blades through some cycles on a Rotax was bad, because it could start. I laughed and told him to do some research on the engine and how the ignition system works. Also told him it was impossible to check the oil level without doing such a thing. Still couldn't change his mind.

Ha - well if you were around XFL when that happened to you, it may have been the same dude... I think he was from one of the flight schools in the DAB area maybe....