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Monday, January 31, 2011

Fuel System Update ...Update

Reader Michael took a good look at the pictures I posted for this previous post, and noted that the inserts for the hose flare fittings did not appear to be fully seated (excess threads were showing). We exchanged a few emails with me pointing out I had never used these fittings before and him forwarding some tips and tricks from his extensive experience with this sort of stuff. In the end, he was right. I did not have the fittings "completely" installed. So last weekend I went through each of the hoses to ensure a proper fitting install and performed a pressure test. Big thanks to Michael for his advice, otherwise, my discovery of this down the road may not have been very pleasant (read: leaks).

To spare frustration for any reader's future encounter with these fittings, I will go over what was done.

Here is an exploded view of the fitting. From left to right you have 1) collar 2) flare tightening nut 3) female flare insert.

While holding the hose end in a vise, take a sharp utility knife and bevel the edge of the inside rubber wall. This helps guide the female flare insert into the inside of the hose when it is tightened.

With the hose still in the vise, thread the collar onto the end. This has very coarse LEFT hand threads (tighten counter clockwise) and digs in to the outer plastic jacket of the hose. Tighten all the way till the hose butts up just under the inside top threads. Then back out the nut (clockwise) about a 1/4 or 1/2 turn.

Now place the collar in the vise, and begin threading the female flare insert, with the tapered end through the tightening nut, into the collar. This fitting does not have a hex around the neck of the insert, so there is nothing to wrench on. So, join the tightening nut/female flare end with a matching male end (like a plug or other male fitting, something that has a hex to wrench upon). Make sure the join is tight. Now wrench upon the male hex and drive the insert into the hose all the way till no more other threads are exposed.


Once fully seated, peer into the end of the fitting with a small flashlight to check for any rubber shavings that may have been created by the sharp tapered end digging into the inside rubber wall. Any of this risks creating fuel blockages. If you see any, back out and remove the insert and trim the shavings with an exacto knife. Another way to get it out is with a drill bit, slightly smaller than the inner diameter and a variable speed drill. CAREFULLY and SLOWLY burr out shavings by contacting the edge hose with the side of the drill bit. Re-seat the insert all the way, till no outer threads can be seen.


For pressure testing, I fashioned a hose barb joined with a male air fitting hose clamped on to the other end of the hose. Plug the flare fitting end with a male flare plug. Connect the air fitting to your compressed air source and dunk the flare fitting end into a bucket of water. If, after a few minutes, you do not see any bubbles from air leaking, you have a good indicator that all is well (I used 90 PSI of compressed air).

Remove the male flare plug and the air fitting. Blow out any rubber crumbs inside the hose with your compressed air source.


So there you have it. Here is how the fittings all look after the re-install.

I will say again, if you have access to the special crimping tool for the crimp style fittings, use that instead of these non-crimp fittings. Installation is likely much easier.

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