Oh, one other thing: which end would the one-way valves go?

 

Ok, it's self-evident: obviously where the word "OUT" is clearly marked on the pump outlet itslef with a felt-tip pen...

Sorry!

 

Yago
You got that right. I am surprised that the "new" pumps should be leaking back but as I said the cheapest way to fix it is installing the valves.
Can't help with the size as I passed on the S2 to an acquaintance a couple of years ago. (Fleet number reduction)
Cheers

 

Bill Mac, I ordered these online (they'll get here on Tuesday, 26th Aug) but I don't know what to make of the clamps!


'Trusty' clamps–but are they really?

Also, I did not heed your advice on working on empty tanks, and I'm having trouble containing the continuous gas / petrol leak!

See, I wanted to make sure I was ordering the right-diameter-size valves BEFORE I purchased them–and now I have a split fuel line in my trunk till Tuesday, when the order comes in!

So far it's eaten up all sorts of plastic membranes, film, bags, the rubber bands holding them firmly onto the hoses... I've ended up opting for metal screws of the right diameter and I've managed to contain most of the leak, but not all: my guess is fuel is finding its way out following the 'path' between the thread and the interior side of the hoses, 'cuz I have driven the screws all the way in–and they're long too–but to no avail!

Significant other is already complaining about the strong gas smell in the house... and Tuesday's still a long way off!!

Also, I'm having trouble findind worm-drive clamps for such a small size (15 mm / 0.6 in outside diam.), but I'd prefer to use them over what they provide with the valves.

What's your take on it?

 

Yago
You are not dealing with very high pressure in this fuel system. At the most 4 PSI or .3AU.
Those spring clips should be able to do the job.
You could have used a bit of cloth on the screw threads which would make a better seal.
I have used wood plugs for the same problem. I also use miniature vice grip pliers to compress the fuel line.
Cheers

 

Yes, just use locking pliers to clamp off the hoses until done.

 

Bill Mac, Slofut: finally stopped the leaks by cutting away a bit of hose so that the head of the screws I was using as "leak-stoppers" would sit flat against the end of each hose end–and that worked!

Like so:


Tight fit achieved–leakage finally stopped!!


Anyway, job done! So much for originality looks...


One-way fuel valves finally installed–originality out the window, though...

 

Yago
Glad to see the valves installed. That should be the end of cross draining tanks.
Don't get too excited about originality.
In older cars like this which is roughly fifty years old you sometimes have to compromise to keep them going.
Furthermore, the fuel pumps and valves are installed in the boot with a hard cover over that area and will not normally be visible.
Cheers

 

Hi Bill Mac et alii,

After almost seven weeks of driving almost exclusively on divided-lane highways since I implemented the repair of adding two check (one-way) valves to the output line of each of the fuel pumps in the trunk (boot) and topping up both tanks, I've managed to put an extra 534 km (332 mi) on the car before the engine began to sputter due to fuel starvation.

I switched tanks and drove to the nearest gas (petrol) station to refill.

Well, I must say I'm a bit disappointed as to what I've accomplished after all the trouble I went into with all this.

One, the engine started sputtering after 496 km (308 mi) from my last refill, and there's simply no way I can do such a high mileage on the contents of just one tank (I wish!).

(Normal figures for one tank's mileage would have to be around 300 km–186 mi–nowhere close to the miles I managed to do! )

Two, I've in effect put 44.63 liters (11.8 Imperial gal, 9.8 UK) in the left tank and 39.94 (10.6 Imperial gal, 8.8 UK) in the right tank, and this was just a little AFTER I shifted between tanks!

Therefore, gas (petrol) is clearly STILL passing between the tanks.

The slight 4.7-liter (about one UK gal, or 1.24 Imperial) difference between the two might have to do with the fact that this transfer is probably slow, thus there being not enough time between stopping the engine and filling up the tanks for the level in the tanks to fully equalize.

I'm aferaid this has NOT work, then...

 

Honestly, like I said before, I've had iffy success with the aftermarket one way valves. On one of my bmw 635's, I have a brass one (after trying three different types) that is very much intermittent and has been since day one. I have a FP guage plumbed in before the fuel rail and sometimes it holds 45lbs forever, sometimes I can drive it and have fuel drip at the one way valve and pressure will leak down. But really, if you will, just blow through each end of the new valve a few times (the old fashioned way), bet you get different results.
Bill S

 

Is it possible instead that the valves I got on Amazon were of shoddy quality, Slofut? I mean, surely they'll need a clean-up every now and then after some usage, but I had just installed them!

 

Yep, I've install several different ones brand new with similar results. Again, do the blow test on them before you install them and see what results you get. They're pretty cheap on amazon, I'd buy a few different types and see if some look more promising than others. As for your immediate problem my money is on a leaky new valve, not much room for magic here. I'll ask again to be sure, but does your car have return lines?

 

Originally Posted by Slofut: "... does your car have return lines?"

Nope–'carbbed' (twin SU H8s, I believe it's got under the hood) engine, no fuel return.