Frequency valve hose fittings disassembly

[Jonathan]

Anyone know how the frequency valve hose fittings work? Or how they come apart more specifically?

I have a small leak on mine and I believe it is coming from the low pressure/return side hose fitting. I'd like to disassemble it and clean it as best I can before putting it back together.

The thing is, while the pressure side hose fitting looks straight forward enough (just a threaded connection from the looks of things), I'm not sure what is going on with the low pressure side.

Looking at the brand new one online (NLA), it almost looks like a quick connect of some kind to me, like one you would pinch in one direction and then pull it apart in the opposite direction. I'm not so sure this is how the one I have is though. It being filthy doesn't help (kind of why I want to clean it up) and I'd just as soon not destroy it accidentally taking it apart the wrong way.

I also don't see just that low pressure return side hose on the parts store pages, as I'd like to zoom in on what that fitting looks like when not connected to the frequency valve.

Any ideas or pictures of your own frequency valve and hoses after they've been disassembled? (I did take the bracket clamp off the valve, but don't have a photo showing it this way at the moment). Thx.

388303883138832

[opethmike]

The stock hose is heat shrunk on. I don't think it can be disassembled; you'll likely have to replace the hose.

[Mike F]

+1

I had to cut mine off when changing over to stainless fuel lines. Couldn't see any way of being able to remove and reinstall it.

[Jonathan]

Ok, the bigger picture is getting clearer.

I had Dave M. recently help explain to me how the inside of any of these fuel lines is really a smaller "tube" running down the length of the external rubber protective layer. Then on each of the ends, where this tube connects to the looped fuel fitting, that fitting is heat shrunk to the tube. That helped remind me that the outside component is more for protecting the inside tube from getting bumped or damaged rather than providing additional fuel pressure containment.

I also saw that since this particular return line is at basically no pressure, you could replace it with regular fuel hose and hose clamps. What I don't get is how you would deal with the fittings on the ends when doing this?

If this line has an inside run of tubing that is actually carrying the fuel in it, how would you splice in a new fuel line to somehow connect with the existing fittings? Would you splice in to the old hose in such a way that you peel back the outer layer of the existing hose and fuel clamp down on this tubing to make the joint? I'm not sure how that would play out right at the frequency valve itself.

My leak seems to be right at the point where the frequency valve would combine with the hose, like at this heat shrunk point, so I thought that it would be this that would need to come right apart to let me redo the joint somehow. If it was a regular threaded fitting, it would be easy and straight forward. With this heat shrunk end, I'm having a hard time visualizing what part I would cut into or remove and what I would replace. Even if I had a brand new hose at my disposal, I don't get how you combine the two (hose attached to frequency valve)?

I see now why on the parts diagram, it shows the frequency valve with a hose attached to one end and that hose isn't listed separately elsewhere. It sounds like it wasn't meant to be separate.

[Bitsyncmaster]

That hard plastic inside line (hose) would be cut completely off the fitting. There should be a steel or brass pipe then exposed that you would clamp on a standard rubber hose with a hose clamp.

I would carefully use a knife like an Xacto running down the plastic line for about an inch long at the end. Then it should pull off. The banjo fittings are constructed the same way but for the high pressure lines you need 100 PSI rated hose or greater.

[Jonathan]

That hard plastic inside line (hose) would be cut completely off the fitting. There should be a steel or brass pipe then exposed that you would clamp on a standard rubber hose with a hose clamp.

I would carefully use a knife like an Xacto running down the plastic line for about an inch long at the end. Then it should pull off. The banjo fittings are constructed the same way but for the high pressure lines you need 100 PSI rated hose or greater.

That makes sense.

And then for the opposite end, that has the "looped"/banjo fitting that connects to the fuel distributor, would you do the same there, and then have basically all new hose in the middle and only reusing the two fittings at the ends?

The fuel distributor connection for the return line(s) is the larger, double hollow bolt one.

[TheMaverick]

Hi Jonathan,
Did you ever complete this repair, any advice? I'm the process of replacing this hose also but I want to make sure I pick the best/correct method for this...

[David T]

While you can assume under normal operating conditions the return hose is under low pressure, during a malfunction that hose could see line pressure and should be able to handle it.

[Bitsyncmaster]

While you can assume under normal operating conditions the return hose is under low pressure, during a malfunction that hose could see line pressure and should be able to handle it.

Only malfunction would be an accident crushing the return line or it plugging up with 10 year or more old fuel. There is only tank pressure which should be zero.

[Jonathan]

Hi Jonathan,
Did you ever complete this repair, any advice? I'm the process of replacing this hose also but I want to make sure I pick the best/correct method for this...

No, I didn't. Too many question marks on how to do it and never saw a clear enough answer to feel it was worth the risk mucking with parts you can't replace right now (the frequency valve namely that is being NLA). Everything went back together well after my VoD work and nothing was leaking, including at these frequency valve hoses. Not something I'm going to work on proactively until a little more certain of how to do it.