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  #1  
Old 08-17-2017, 06:57 PM
dbaflyer dbaflyer is offline
 
Join Date: Oct 2009
Location: Iowa USA
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Default Fuel Primer Installation for O-320

I have the kit from Vans, but am considering soldering the discharge end at the port or going completely SS. I know how much the SS route is going to cost and would like to first consider the solder method. I also think trying to get the length right on the SS lines is going to be difficult.

My engine came with two AN4022-1 discharge ports that would fit into the primer port on each cylinder. Looking at them the discharge hole is very tiny compared to the AN816 fittings that came with the Vans kit. Is that correct? Does't seem like much fuel would get through there.

My engine also came with a 3 way brass splitter, AN795-2.

This fittings are not the same thread as the blue fittings that Vans supplied in the kit. So those coupler nuts are not good here, but I would need AN805-2 intstead? And AN800-2 union cones which are soldered to the copper line? What do I need to purchase to perform that soldering?

Then how do I transition off the primer pump using the blue AN fitting sizes into the brass splitter? These are going to have different sizes on either end of that line which I would like to have as SS.

Finally I am struggling a bit how to route all this to my front two cylinders and keep it secured. I am considering attaching an adel clamp to the bottom screw on the #1 cylinder valve cover and securing the 3-way splitter to that. That would make a pretty short run of copper to the primer port on that cylinder. Then running down and across the engine (near the sump) and securing the line using another adel clamp attached to the case mounts next to my alternator and then up to the #2 cylinder.

I've managed to find one set of photos of other peoples routing but I figured there should be way more out there somewhere. Anyone have some sites or photos to share?

Denis.
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  #2  
Old 08-17-2017, 07:14 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Denis,
I have a O-320 D2A engine that came with a primer system. It is copper. I did have to get a couple weird fittings to make it work, but I think it is installed properly. I will be doing my first engine start next week, so I guess I will find out.

I can get a couple pictures if you want. Email me and I will get them tomorrow at the hangar.
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  #3  
Old 08-17-2017, 08:08 PM
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Dbro172 Dbro172 is offline
 
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You don't need a primer and could consider removing it. Especially with impulse mags or dual impulse mags. My -9A O-320 has no primer and haven't had any issues starting it down to 0 degrees. Same with my 0-360 Mooney. Just a few pumps of the throttle, let it vaporize and crank. 2 pumps, with 4-5 seconds in between on the RV is usually sufficient. Now with a pmag one pump would probably suffice. The mooney needed 3-5 pumps. My 182 with an O-470 continental had a primer and it was definitely needed to start that beast. I'd bet that most carb RV's dont have a primer.
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  #4  
Old 08-17-2017, 09:37 PM
bikes_and_planes bikes_and_planes is offline
 
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Location: Olathe, KS
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+1 for skipping the primer, at least if you are using an electronic ignition system. My airplane has a O-360 with dual PMags and no primer, and has always started immediately. I do preheat when it's cold, which may help. Having a good, strong starter also helps - I've got the PP starter from the Vans FWF kit.

On the other hand, I've flown a few spam cans with mags, really anemic starters, and probably somewhat fouled plugs from students flying and always running full rich. One in particular always needed several shots of primer to start.
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  #5  
Old 08-18-2017, 06:24 AM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by dbaflyer View Post
My engine came with two AN4022-1 discharge ports...
I have one of those installed in my #1 cylinder only and it works just fine. You'll save a lot of plumbing (and possible leaks) by only doing one cylinder. My plane won't start in cold weather by pumping the throttle because I have the accelerator pump linkage set to minimum (long story). Three or four pumps on my Essex primer and the plane starts right up on a cold day. (I do have an oil pan heater for really cold days.)

I used 1/8" copper tubing for my primer line from the firewall to the cylinder, with the "Union Cone" soldered to the line with standard silver-bearing plumber's solder. I did as you mentioned and supported the tubing with an Adel clamp mounted on the bottom rocker cover screw under the #3 cylinder. The firewall end of the tubing is flared to mate with a standard steel AN-2 fitting.

It's really a PITA to get a tool in there to tighten the fitting. As you can see, I had to nibble away the baffle for access:

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  #6  
Old 08-18-2017, 07:06 AM
TS Flightlines TS Flightlines is online now
 
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Denis---we make both SS primer lines, and teflon hoses to do a primer system.

Tom
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  #7  
Old 08-18-2017, 07:36 AM
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Raymo Raymo is online now
 
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If using the "pump the throttle" method, please have someone nearby with a fire extinguisher. A back-fire will light the fuel and they'll be busy. If a fire does start, keep cranking until it goes out (hopefully).
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  #8  
Old 08-18-2017, 01:41 PM
jbDC9 jbDC9 is offline
 
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Quote:
Originally Posted by Dbro172 View Post
Just a few pumps of the throttle, let it vaporize and crank. 2 pumps, with 4-5 seconds in between on the RV is usually sufficient. Now with a pmag one pump would probably suffice. The mooney needed 3-5 pumps.
As Raymo stated above, pumping, waiting, then cranking is not a great idea due to the fire hazard; a perhaps better technique is to pump the throttle while cranking as the atomized fuel is sucked into the engine as opposed to pooling in the airbox.

A few years ago I watched a hangar neighbor start a cowl fire in a carbed 150hp Cardinal using the pump/wait technique. Oops!
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  #9  
Old 08-18-2017, 05:04 PM
dbaflyer dbaflyer is offline
 
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Location: Iowa USA
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I was also wondering whether there is any reasoning to which cylinders you use. It would certainly be easier to do #1 and #3 for example as there would be no need to route over to the other side and the gascolator and primer pump are mounted to the right side of the FW. It's also going to be easier for me to use #4 for my manifold pressure.

Thanks all for your suggestions and good photos.
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  #10  
Old 08-19-2017, 08:02 AM
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Bob Martin Bob Martin is offline
 
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Location: Richmond, Virginia
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Default Primers

Quote:
Originally Posted by dbaflyer View Post
I was also wondering whether there is any reasoning to which cylinders you use. It would certainly be easier to do #1 and #3 for example as there would be no need to route over to the other side and the gascolator and primer pump are mounted to the right side of the FW. It's also going to be easier for me to use #4 for my manifold pressure.

Thanks all for your suggestions and good photos.
Glad to see you are moving forward with a real primer system over using the accelerator pump as a makeshift one.
As far as which cylinder goes if you are doing less than all of them, it doesn't matter to the engine that I know of. Do understand how it works. The primer system puts fuel into the intake manifold just outside the intake valve. If the valve happens to be closed, which in the 4 stroke cycle it is 75% of the time. The fuel coats the area behind the valve and excess, if there is any, runs down the intake tube and vaporizes while waiting for the intake stroke. If you hapen to catch the valve open, well , you hit the jackpot and you get some fuel in the cylinder.
So clearly the more cylinders are primed, the better the primer system will work. You mentioned the MP line on the #4 cylinder, this is why most systems use 3 or less cylinders for priming. You also mentioned the complexity of dividing the lines and taking one or more to the other side. These are all good points to consider. Also every fitting is a possible fuel leak while priming and intake air leak while flying, and yet, the normal seems to be to use copper or believe or or not aluminum. Another point to mention is all this tiny tubing is routed around the bottom of the engine, along with electrical wires and cht and egt wires and next to exhaust pipes which makes it harder to install and inspect.
Do understand your system, if you are using the Van's primer system,you do not actually have a primer pump. The larger heavy metal part is a solenoid valve, not a pump. When energizerd, it opens to allow fuel to flow. The pressure to deliver the fuel comes from the engine system boost pump. That is right, you first turn on the boost pump, then switch open the solenoid valve to allow fuel to flow to the primer lines and squirt or spray out the terminations in the intake manifold. That is why you count....1,2,3.
Sorry for the long post. This journey is all about learning. It is your airplane, do what you think is best for you.
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