Low-pressure fuel joints and compression fittings

[sdynes]

Hello -

We've a Perkins 4-108 from the mid-'80s in our sailboat. We are looking to replumb the low pressure side of the fuel system as the compression fittings are failing.

One piece of information we've been unable to obtain has to do with the tubing/device joints.

On both connections to the lift pump we have tubing with brass ferrules:


At the end of the tube from the lift pump to the on-engine secondary fuel filter we have this connection - a 'bubble' fashioned in the tubing and a length of rubber tube:


We think the connection to the secondary fuel filter is of the same type as for the brass ferrule compression fitting, and are thinking of using that when we remake the tube. It does seem that the rubber tube is the type of compression fitting used for the banjo nut/steel fuel line joint on the rear of the secondary fuel filter.

- Does anybody know if we can use the straight tube/brass ferrule in place of the bubbled tube/rubber tube? If not, why the bubble?

- Any idea of where to source the rubber tubing?

Thanks!

[DavidLGCrawford]

I can not answer your question unfortunately but do have an FYI about the brass ferule fitting. In the photo it is not on correctly. It needs to be slid on to the pipe more so that the pipe extends out the end. The pipe must bottom into the fitting on the engine/filter/whatever, and then the ferule is slid forward to make contact with the fitting. Lastly the threaded connector is threaded in.

[sdynes]

Thanks, David.

In the other example we have the tubing is protruding through the ferrule. I will be sure to bottom out the tube before tightening the nut around the ferrule. I do wonder if the bubble/rubber tubing is a substitute for spending the time to bend/trim the steel tube so it is centered and bottoms out in both connection locations.