How to plumb a mechancal fuel pump?

[ArVeeNiner]

How do you plumb the mechanical fuel pump on an O-320 with a carb? There are three ports on the pump. Two larger ports are on the ends with a smaller one in the middle. Obviously there is an IN and an OUT but I don't know which is which and have no idea what the middle one is for.

Thanks

[aerhed]

The little one is for a drain hose in case the diaphragm ruptures, should be routed out your bottom (preferably not over an exhaust pipe). There's usually an arrow symbol cast into the housing to show flow direction.

[OneCharlieKilo]

Kelly - assuming the connections are the same for O-360 and O-320, and I think they are, maybe this picture will help:




At least on mine, the fuel pump discharge is towards left side of plane (fuel pressure sense line taps off the discharge line fitting), fuel pump suction is towards right side of plane, and the vent overboard line is the small fitting.

Other pictures of my fwf fuel system installation are at:

http://rv6aproject.ckhand.com/Firewa...ngine_pg_5.htm

Good luck!

[ArVeeNiner]

Originally Posted by OneCharlieKilo

Kelly - assuming the connections are the same for O-360 and O-320, and I think they are, maybe this picture will help:




At least on mine, the fuel pump discharge is towards left side of plane (fuel pressure sense line taps off the discharge line fitting), fuel pump suction is towards right side of plane, and the vent overboard line is the small fitting.

Other pictures of my fwf fuel system installation are at:

http://rv6aproject.ckhand.com/Firewa...ngine_pg_5.htm

Good luck!

Thanks Chris:

It looks like you have some sort of brass fitting for the vent, is that right? I'm looking at the AS catalog right now and I don't see that fitting. Where did you get the plastic line from the vent? Is that from Orchard Aircraft Supply?

[OneCharlieKilo]

It looks like you have some sort of brass fitting for the vent, is that right? I'm looking at the AS catalog right now and I don't see that fitting. Where did you get the plastic line from the vent? Is that from Orchard Aircraft Supply?

Hi Kelly,
Actually, I think that fitting was in the finishing kit from Van's. When I ordered the finishing kit I got a listing of the parts from Van's before ordering and left off what I already had but I believe that vent fitting was in the kit and I just used that rather than a standard AN fitting.
Van's site says the fitting is for the RV-4 setup since a standard AN fitting won't clear the firewall; but it works fine in my 6A too....

Looks like the p/n is F OVERFLOW PLUG 1/8" and it sells for $9 on Van's site at:

http://www.vansaircraft.com/cgi-bin/...erflow-fitting

You could probably make a similar fitting or use one of the standard AN fittings that works for your setup.

In my RV, the installation and routing of the vent line plastic tubing into aluminum tube that passes through the lower firewall flange is per the drawing that came with the finishing kit. There was a short length of aluminum tubing for the end piece and I think some plastic tubing too in what I got from Van's, but I had to make a couple of the aluminum tube pieces before I got it right so I used what I had left over from my brake line installation for both the plastic tube and the aluminum tube at the bottom.

Edited comment to above: in looking at my pictures closer, I think the aluminum tube at the bottom is smaller than the aluminum brake lines as it fit into the 1/4" plastic tubing....I'll have to check the drawing and look at the line when I'm at the hangar next but you should be able to verify on your drawings.

Along with all the critical hoses fwf, I check that line everytime I pull the cowl (fairly often as I'm still in Phase I testing) just because the plastic line and tie wrap setup seemed a little "less robust" than everything else I put in, but it's holding up fine so far and is per Van's design...