After many attempts to rectify a cross leaking Fuel change-over valve, including buying a new one that leaked from day one and later taking my old one apart and fabricating a new plunger seal only to last for about a year (http://www.jag-lovers.org/snaps/snap_view.php3?id=1352922910) I had to think of an alternative solution.
The Pollak valve was one alternative but the hose ID is 3/8" and the hoses in our cars are 1/2".
The fuel pump will not work happily with that small hose inlet, I have tested it, it cavitates and the system started to do all kinds of weird noises.
After much research I found this one on Aliexpress. (no affiliation)
Code: CWX-25S DN25 G1
It’s a 3 Way, Two Position L Motorized Valve, 12v, brass with Teflon seals (compatible with E10), and Manual Override (a knob on the top with which you can switch the valve in case of an electrical failure).
It comes in two versions NPT or BSP.
The CR5 01 control unit (integrated in the valve motor) works by reversing polarity and stops automatically at the end of it’s travel.
It has a mechanical position indicator plus outputs for 2 LED indicator lights, a very cool feature.
I had to get the hose fittings separately, so I got both 10mm and 12mm to experiment.
I first fitted the 10mm and 10MM hoses but as I stated before the pump was not very happy, so I finally installed the 12mm fittings and the original 12mm hoses.
I have used the six port Pollak valves on two fuel injected Jaguars with zero problems. Drive mine daily with my '71 XJ. Half inch is only for the gravity feed lines and the smaller sized lines work well on SBC Lump conversions.
Does this valve come with six ports for the return lines? Having only the one valve that does both functions is simpler to maintain and then uses all non Jaguar parts and modern stuff.
Carl: You are lucky… at shut off my tanks show about 3/4+ full.
No, it’s either two or three.
I guess one could use 2 Two port, ore an other Three port for the return lines.
As mine where working OK I didn’t bother…
Aristides
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As the return is designed to be delivered to the top of the tanks - I cannot see any advantage of grouping the return and changeover at the latter’s position, Roger…?
There is a big advantage. If the valve breaks, everything flows where it’s supposed to. If the RH return valve failed while the tank is selected, or even worse: if the LH return failed open, your tank would overflow.
At least, I’d like to have a l/r return valve.
Guess I could have worded my reply better…the Pollak valve has the feed and changeover - plus the returns all in the one valve. Nothing under the car and all is in the trunk/boot.
I think you were always talking about the same thing, frank doesn’t want to have the returns in the same spot (by the way, as the return line runs under the floor anyways there is no need to be worried about the location of the return entry to the tank). It is an advantage in terms of reliability. No need to change as long as it works.
I have two fuel pumps with non-return valves that go into a T. A relay does the switching, it works well so far. At times there is a split-second delay when switching, that’s fine.
Is there a lot of effort involved in re-routing the return lines, Roger?
No problem at all, my S1 has S3 tanks, you can see the return and feed lines from the RH tank easily in the photo. Plus, how they all connect to the Pollak valve…note the tin can in line fuel filters between the tanks and the valve… plus there is a high pressure filter between the fuel pump and the high pressure feed line to the front of the car on the left hand side.
There is no delay in switching tanks and no loss of fuel pressure while doing it… this modern switch is used in lots of dual tank installations and is very reliable… Six port has return lines and three port is good for carbed vehicles.
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With the original FI set-up the transition is seamless, David, as the changeover valve feeds from both tanks during the transition. Which is why it may crossleak, maybe stuck half-way…
With two pumps there may be a minute delay due to start-up, but should cause no engine hesitation whether with EFI or carbs…
No, it means that the return valve is incorporated in the unit with the same drive. Otherwise the fuel would get too hot… and not make much sense for pressure regulation?
Thank you Roger, I see them. That would require rerouting the line that comes down to the old switching valves, that can’t be too hard. I like it.
No doubt it’s better, easy to troubleshoot and to repair, having all in one valve.
On the other hand, 99% it’s the switch-over valve that misbehaves, the return valves rarely cause a problem, and if they leak a tiny amount, a few grams of fuel returning to the wrong tank is not a huge deal.
And t’s so much more work involved, bringing the return lines from under the car into the trunk and then back out and into the tank…
So, as my return valves worked fine, I let them be.
As I said before, my biggest issue with the Pollak valve was the fuel line size for the pump feed (stock pump).
I had experimented before, with the same results, but I thought I would try again as I wanted to use Gates Barricade low permutation hoses everywhere, so I first installed the system with 10mm (3/8") hoses, and even though the engine was working fine, there were all sorts of noises, probably cavitation, that were even audible inside the cabin…
Maybe it was the combination of the 10mm hose plus the 10mm inline filters, I don’t know, but when I reverted back to the original 12mm (1/2") hoses with 12mm inline filters all the noises disappeared.
A particularity of my car maybe?
An easy way to rectify your switching problem would be to ad a delay on the relays, so both pumps work for a second or two while switching tanks.
Very easy to make one, or there are ready made adjustable delay relays for a couple of bucks.
The one one the diagram has a delay of 3 sec, but you can shorten the delay with a smaller condenser (220 or 100 uF).
That is a very good idea. For now, I only use one relay though, the n/c position for the left pump, the n/o for the right one. I didn’t have my coffee yet, but your setup should need two delay-relays and one of them must be open, the other closed normally.
Another solution is to only switch tanks while the engine is in overrun, then there’s no fuel consumption, and no hiccup. But such a delay can be fitted to a lot of things, so the drawing should be useful in the future. Thank you, Aristides!
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So the return goes to the valve, then to the tank(s), David…?
I was more considering that if the return valves were redundant their line connection should be blocked - to prevent tanks venting out through them. Fuel heating would of course be a point, but tank supply would still be required - not enough fuel is returned for the engine’s requirements…
The pressure regulator is perfectly happy, keeping rail pressure to specs, as long as there is no obstruction in the return lines. I ‘thought’ that the valve with 6 connection would be ingenious enough to prevent that…
