Cracked (vent?) line on mechanical fuel pump?

[mbuehler]

While chasing some oil leaks, I came across a copper line coming out of the top of the mechanical fuel pump (O-320-E2A in an RV4). It looks like the previous owner attempted a JBWeld fix that has since failed (looks like removing it is some work). It just runs into those blue fittings then out the bottom of the aircraft and vents near the breather hose.

Can somebody tell me what that is? Same diameter copper tubing that the old priming system used. He mentioned that had broken somewhere and they had capped it rather than fix it.

[noelf]

It is a fuel discharge line that comes into play if the mechanical fuel pump internal diaphragm develops a leak. Fuel is then ported through the tubing and out into the airstream.

Van list this item (or at least they used to) in their accessory parts catalogue.

[Steve Melton]

I vote to eliminate copper lines and check for chaffing for the big white electrical cable against the mount in your picture.

[mbuehler]

**EDIT** You guys are fast, I was still typing

Finally found a diagram Looks like it is the vent port, which wouldn't do much unless the diaphragm ruptures, then you want that line dumping the fuel overboard.

Not sure why all the elaborate fittings if it is just a tube to space. Any need for a one way valve or something similar on the vent port?

[mbuehler]

Noelf,

Thanks, I'll see if I can find it in the catalog.

Steve,

I like that idea, not sure why something more flexible wasn't used. I'll check out those cables too, thanks!

[N941WR]

The newer drawings show a clear flex line running down to a small piece of aluminum tubing that exits through a small hole next to the firewall, outboard to he left side of the exhaust.

No fittings are used. You simply use safety wire to secure the tubing to the brass fitting on the fuel pump and the aluminum tubing down by the bottom of the firewall.

Maybe someone can post a picture from the plans.

[cajunwings]

The extra weight of the blue fittings and lower copper line will probably continue to fail the solder joint on the pump fitting. All it needs is a short length of copper tube coming off the pump fitting and some light rubber tubing (like Tygon) down to the firewall flange.

Don Broussard

RV-9 Rebuild in Progress
57 Pacer

[sblack]

I broke that solder joint on the weekend installing that fitting. That's when I discovered that it is only plumbing solder, the kind that you can melt with a propane torch or a soldering iron. I was able to re-melt it with a butane pencil torch. You probably could too if you could get the JBweld cleaned off.


Silver solder would be a much better choice. And I second that view that all of those fittings on the end is probably what cracked the joint. A bit of clear tube would not put such a load on the joint and it's all that is required.

[mbuehler]

I wasn't sure if those had some sort of one way valve in them, seems not. I agree all that weight hanging is not helping. I'll remove it all but an inch or so to attach a tube, and will clean up / re-do that connection. Thanks!

[Dean Pichon]

I noticed your pump installation puts the vent fitting very close to the firewall (touching?). I have the same issue in my -4. The other day, a mechanic suggested I could remove the pump, disassemble it, and "clock" the spacer that includes the vent to put it in a better location. In my case, that would be to clock it such that the vent moved to the space in the firewall cut-out that provides clearance for the prop governor.

Has anyone done (or considered) this?

Thanks,