Prime the carburator or the Cylinders? (65-8F)

[7ACDriver]

I have to redo my primer line that goes to the carburator at this time. Just like alot of guys, I send 2 shots of primer, pull through about 6 blades, switch the mags on and the engine starts at the firts blade .

This works fine but if the primer went to each cylinder, wouldn't this avoid pulling those 6 blades hence going to a direct start

[joea]

I have thought about this a bit as the engine in the Sedan is primed to the cylinders and not the carb.

I do like you do with a couple of shots and pull it through 2-3 blades. Like yours it hits on the first blade.

Would think that if its primed through the carb that it would take more turning over and less if direct to the cylinders. Good topic for discussion.

BTW. am moving this to the "engines" catagory as this is not only a "Champ" question.

[Nathan K. Hammond]

Pulling the prop through several blades does more than pull fuel into the cylinder; it allows you to preflight the motor. As the blades are pulled though, you can feel the compression of each cylinder, listen for any un-natural sounds like a deflated lifter, and probably most important pre-oil the engine.

There are some other concerns with changing the priming location. If you spray directly into the cylinder (like a lycoming,) as the fuel condenses on the cylinder wall, it can wash away oil intended to lubricate the piston/rings/cylinder. Same reason why you should not to run the fuel pump for extended amount of time on an injected engine (when not running.)

Personally, I like the primer to run into the spider, or the intake tubes. The only concern with those locations is over-priming that can pool fuel and create a nasty backfire; or at worse, an intake fire. Luckily these rarely happen, especially with good education and understanding.

nkh

[pablo]

To start my 7AC (A65 Cont) during hot weather (Apr to Nov) I used to pull the prop about eight times (twelve times cold weather -Dec to Mar-) for the first start of the day, turn switch to both, and most of time the engine started at the first blade. The temperamental engine has changed within the last 3 months, demanding 2 squirts of priming, regardless of the ambient temperature. AP has checked everything he could think off, with no success.
Once the airplane is flown, all succesive starts are at the first pull.
Any interesting theories or explanations?

Pablo

[Captgrumps]

How is the compression? Have you checked it--is it the same as before? You know these are 4 cycle suck, squeeze, bang and blow engines. Any wheezing like it has mechanical asthma? Where rather than using an inhaler you use the primer to get it its breathing in sync.

Doug

[7ACDriver]

Nate,

Thanks for your reply, hadn't seen it that way before. I guess I'll keep primig that spider!

[pablo]

Doug:
The compressions are quite good and unchanged (average 76/80).
When pulling the prop I do not hear the strong "suck" sound that it used to make, but there are no leaks found by my mechanic.

Thank you for your input.
Pablo