Frequency Valve fuel line replacement options

[DMC-81]

Hi there,

The frequency valve fuel line is the last one that I want to replace. What are the options to buy this single line? I am looking for braided stainless steel, with the black cover to match my other lines:

41977

I wouldn't want the one that incorporates a short rubber hose and 4 connections within 6 inches of line.

What other options do you all recommend?

[Chris 16409]

I believe Hervey sells them individually. In order to avoid having that short bit of rubber hose, you would need to send in your frequency valve. Then the braided line could be properly crimped on.

[DMC-81]

Thanks Chris.

A few more questions for the community:

- I see that Hervey's hose looks like it has the same bit of rubber? hose, although without the clamps. I wonder how he makes that work?

- Has anyone bought this? If so, how do you like it?

- I see that it requires a core charge. Is that for the FV, or does he reuse the banjo fittings?

- I suppose that little bit of rubber hose would make it easier in case you have to replace the frequency valve. Is this correct or is the FV a NLA part?

Thanks all. I'm just trying to make an informed choice and have it match my other hoses.

[81dmc]

DPI sells them here (http://www.deloreanindustries.com/6-frequency-valve-feed-line/). I would trust Josh's stuff more than Hervey's...

As for the black cover, just buy heat shrink from Ace and cut to fit.

[axh174]

Thanks Chris.

A few more questions for the community:

- I see that Hervey's hose looks like it has the same bit of rubber? hose, although without the clamps. I wonder how he makes that work?

- Has anyone bought this? If so, how do you like it?

- I see that it requires a core charge. Is that for the FV, or does he reuse the banjo fittings?

- I suppose that little bit of rubber hose would make it easier in case you have to replace the frequency valve. Is this correct or is the FV a NLA part?

Thanks all. I'm just trying to make an informed choice and have it match my other hoses.


I have a set of Hervey's lines. They do indeed have the short bit of rubber between the Frequency valve and the line.

1) What's not shown in the pictures on his website is that it does actually come with clamps. They don't do the best job in the world of keeping the rubber on the FV, so I replaced them with a different clamp that does a slightly better job. The problem is there's really no "nub" on the FV around which the rubber hose can be clamped. It makes me wary of the hose somehow slipping off, but if I understand correctly, this is the low pressure side of the fuel system and the likelihood of that happening is somewhat nonexistent.

2) How do I like his lines? I love them! The fact that I'm off the old lines and now have braided lines that are smaller in diameter so I can get at things like spark plugs more easily is the driving point for my love of them. With that said, I believe some of Josh's lines have shaped solid line ends to better match the original lines, which is a nice touch. Hervey's are all straight flexible lines (at least the set I got).

How do I like the FV line and setup? Jury is still out. It's nice to have the option of easily replacing the FV if needed, but I would feel more at ease with a crimped connection. I didn't even know this was a option until Chris mentioned it above.

3) The core charge is because he refurbishes the banjo fittings.

4) It most definitely makes it easier in case you have to replace the FV. I'm not sure of the FV's availability, though. Up until a about a month ago, I was still seeing it in the DMCH store (out of stock at the moment).

Hope that helps!

-Kevin

[DMC-81]

Thanks all for the information. I have learned a lot.

So, I wonder how the FV helps regulate the pressure if it is on the return side? Is the pressure higher on the top, and lower on the bottom (where the vendors use the rubber hose)? What kind of PSI is on the line?

I see that the rubber hose clamps are not fuel injection style, rather a regular worm style, so that tells me that at least one side is lower pressure.

Cheers,

[Jonathan]

Thanks all for the information. I have learned a lot.

So, I wonder how the FV helps regulate the pressure if it is on the return side? Is the pressure higher on the top, and lower on the bottom (where the vendors use the rubber hose)? What kind of PSI is on the line?

I see that the rubber hose clamps are not fuel injection style, rather a regular worm style, so that tells me that at least one side is lower pressure.

Cheers,

Dana, have a look at the fuel, emissions and exhaust section of the workshop manual. Section D for that one. It explains how each component work, and the frequency valve specifically is on around page D:04:07.

It's not the easiest thing to understand how all the lines interact or what is balancing what, but when the frequency valve lets some of that higher pressure side fuel go back to the tank, it causes the system to need to rebalance itself and then adjust how much fuel is going to the cylinders. So the frequency valve affects the control pressure directly and the injector pressure indirectly.

The return line to the tank, the one off the end of the frequency valve not closest to the electrical connector, is at near atmospheric pressure. That is the end that loops around and connects with a second return line at the fuel distributor and then the fuel actually travels within that fuel line back to the tank. It would be that same very low pressure as you would find if you pulled off the hose up at the tank coming off the hardline where it connects to the flexible hose with the fuel pump. That return hose can still leak, but it won't be the one spraying all over the place if it were. That one would just drip.

[DMC-81]

Thanks Jonathan. I sometimes forget to consult the Workshop Manual. I'll read up on it...