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Primer system...

comfortcat

comfortcat

Well Known Member
OK, I'm not talking about paint, but anything with the word "prime" in it seems to start a war.

I'm building my O-320 Carb engine primer and plan on two cylinders. I am using the electric valve and I bought a pair of AN4022-1 discharge nipples from Aircraft Spruce.

BUT

Instead of seeing a AN type male fitting, I'm seeing a cup in the top of the discharge nipples. OK, what do I need to attach that? I'd like to use as short a copper line as possible, and maybe a flex hose from the primer valve to a t-fitting on the top of the engine. Can I get flex hose with a 2d fitting?

Thoughts?

Dkb
 
Larry---I've had builders that wanted to plumb 1, or 2, or 3 cylinders. 2 and 3 are the most popular.
Tom
 
I know you didn't ask about using it or not, but in 12 years with an O-320 powered -8 I may have used it once or twice - on the first and second flight. Removed and never went back. Go simple, and go light.
 
Primer wars?

My Skyhawk always started with two pumps and two blades.

Of course, it was an O-300 Continental. I assume the O-320 will be the same.

Dancing with throttle while cranking the engine sounds like a worn out starter to me.

Van's system has two ports.

Thanx for the advice, but back to my question. I'm planning on a T fitting on top the engine, with copper or Stainless tubes to the ports. One of Tom's fuel lines from the gascolator to the T.

I still need to know what kind of fitting goes to the nozzles.

advTHANKSance

CC
 
Possible backfire

mike647m said:
If your carb has an accelerator pump, pump the throttle once or twice after starting to crank.
Click to expand...

I used to do this but read about a backfire when all that fuel was supposed to be sucked up into the intake but ended up around filter when the fire caught.

Picture having to climb out, get the fire extinguisher, pulling the cowling off or maybe lying on the ground and shooting it up into the cowling area.

I think the primer (whether manual or electric) eliminates this possibility.
 
grubbat said:
I used to do this but read about a backfire when all that fuel was supposed to be sucked up into the intake but ended up around filter when the fire caught.

Picture having to climb out, get the fire extinguisher, pulling the cowling off or maybe lying on the ground and shooting it up into the cowling area.

I think the primer (whether manual or electric) eliminates this possibility.
Click to expand...

Actually, you can overprime with just about any system and end up dripping fuel down into the airbox. Fires caused by pumping the throttle to prime are generally caused because people pump the throttle BEFORE cranking, not DURING. I have also seen the lien in to the primer solenoid break, casuign a fuel leak into the engine compartment.

I removed the primer from my RV-8 after having a cracked line (and there were relief loops). The only time it was ever used was to test it before first flight. I have never found a need, even when starting on winter trips up north - pumping the throttle WHILE CRANKING does just great - and there is one less thing to break.
 
Primer Wars

What you need is an AN800-2 "union cone" and an AN 805-2 union nut. You silver solder the copper line into the cone. I have been very happy with my 4 cylinder priming system for 1260 hours and 10 years, Really cold starts sometimes take as long as three blades.
 
Ok

10/4, using the right procedures is the key

Ironflight said:
Actually, you can overprime with just about any system and end up dripping fuel down into the airbox. Fires caused by pumping the throttle to prime are generally caused because people pump the throttle BEFORE cranking, not DURING. I have also seen the lien in to the primer solenoid break, casuign a fuel leak into the engine compartment.

I removed the primer from my RV-8 after having a cracked line (and there were relief loops). The only time it was ever used was to test it before first flight. I have never found a need, even when starting on winter trips up north - pumping the throttle WHILE CRANKING does just great - and there is one less thing to break.
Click to expand...
 
comfortcat said:
My Skyhawk always started with two pumps and two blades.

Of course, it was an O-300 Continental. I assume the O-320 will be the same.

Dancing with throttle while cranking the engine sounds like a worn out starter to me.

Van's system has two ports.

Thanx for the advice, but back to my question. I'm planning on a T fitting on top the engine, with copper or Stainless tubes to the ports. One of Tom's fuel lines from the gascolator to the T.

I still need to know what kind of fitting goes to the nozzles.

advTHANKSance

CC
Click to expand...

Spruce sells a nut and ferrule that go specifically with that discharge nozzle. These parts are made for 1/8" tubing. I will be using copper.

Larry
 
Low Pass said:
I know you didn't ask about using it or not, but in 12 years with an O-320 powered -8 I may have used it once or twice - on the first and second flight. Removed and never went back. Go simple, and go light.
Click to expand...

It depends. I agree with Bryan here; however, if you visit areas where it gets cold (below freezing) and you overnight, I would install the primer.
 
az_gila said:
The firing order is 1-3-2-4 so do you want two that fire next to each other, or two equally spaced in the firing sequence?

I think 1-2 or 3-4 might be better, and easier to plumb...:)
Click to expand...
I had mine originally on 1 and 3 and it worked just fine. Usually fired up within 2-3 blades. Having said that, I woke up one day to find a broken copper line going to my #3, got a very uncomfortable feeling, and pulled the whole system. I've found using the accelerator pump per Paul's instructions above worked just fine through the last winter and have no plans to reinstall the system. (However, I have a rule taken from Mike Busch against starting my engine if it's not preheated to at least 45-50 degrees. Maybe if I tried to start a colder engine the primer would be more beneficial, I don't know.)
 
Last edited:
az_gila said:
The firing order is 1-3-2-4 so do you want two that fire next to each other, or two equally spaced in the firing sequence?

I think 1-2 or 3-4 might be better, and easier to plumb...:)
Click to expand...

I have mine on 2 and 3. Also right next to one another in the firing order.
 
Primer wars

I wonder how many people without primers fly where it's cold? Sometimes preheat not available. Lycoming says preheat nessesary below 10 degrees Fahrenheit. My experience with Pipers is that a really cold soaked engine wouldn't start sans primer no matter how much the throttle was goosed. But that was in the the days of straight weight oil and no electronic ignition.

Mine is plumbed to all four and orfices sized to act as a poor mans fuel injection should the carb ever stop functioning for any reason. An alternate way to get fuel to the cylinders in an emergency. Probably will never use that function! I do know someone who made it to a runway in a c152 by pumping the primer to get enough power boosts to extend his glide after an engine failure. Should be much easier with a solenoid system.
 
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