Hi Frans
The "air" bubbles were indeed vaporizing 100LL. I did introduce
air, by ever so slightly pushing on the quick drains mounted on the
bottom of either Andair 375, WOW foam city, that was air introduction. I
am very concerned when I see drain valves seeping on Europas, especially
914s.
The pre-pump you are talking about would help the bubbling a little, but
don't think it's needed. I tested the ability to prime with
various heads and also introducing intake restriction, and was very
satisfied with the results.
If you are hell bent on a pre-pump, I actually have one that would work.
I was planning on using it to transfer fuel. I had a fleet of 3 Volvo 740
Turbo Station Wagons (two 1992 and one 1990), I finally switched them out
a few years ago. The main Bosch fuel pump would consistently fail between
~ 85 and 125K. I always stocked one. I also stocked a pre-pump that lives
in the fuel tank. It's a small thing about the size of the 914 pump
(I just weighed it and it's 242 grams) that is very low pressure and
lots of volume taking a 12 volt input. I always checked the output of
this pump when changing the main pump or filter and never had a failure.
I'm not complaining because it meant dropping the fuel tank.
Anyway if you look up 1992 Volvo 740 turbo with a 2.5 liter turbo engine,
then the in fuel tank pre-pump (not exactly sure what they call it) it
could be a good choice. It has a slight necked down area on the OD of the
the intake side of the outer case with an OD of 1.430" x .675"
long, nice and smooth and looks to be very robust. If you wanted to use
it inline, that would be a good area to put a piece of rubber coupler
over with a clamp, then the other side could have an adapter. The output
side has a.312" (5/16") hose barb. The main pump although I
have tried aftermarket once when I was in a pinch, it did not fit
perfectly and the wiring connections were not the same, so I stuck with
the Bosch. I saw the pre-pump on special once so I bought one just in
case. I suspect the one I have is aftermarket? It's in a clear
plastic bag that's staples closed, on the bag (Bosch always comes in
a nice graphics box and it says Bosch everywhere):
3517845
F/Pump in tank
700 Turbo 85 - 95
You may be able to cross the numbers on the pump (no Mfg. name I can
see):
6443270(V3517845) then under that number : C3435-2
Just a quick note, both pumps ran off of a fuel pump relay, after
between
~ 85K and ~ 125K they too would fail. What would happen is because solder
is such a bad conductor (solder is between ~ 4 and 5% the conductivity of
annealed copper 110 that has 100% conductivity) the joint that carried
the high current would fracture fail from the long period cycling between
cold and hot. You would get the tell tale ring that many suspect is a
"cold solder joint" but in fact a fractured solder joint.
Anyway the relays were cheap enough, but not cheap enough for my liking,
so I kept a spare in every car (only takes a few minutes to change)
and would re-solder them every few years (all 3 at once). They came apart
really easily and the contacts still looked fine so I just kept on
re-soldering. I actually solder sucked out the solder that fractured, and
re-flowed with model aeroplane racing solder, what racing solder is,
it's a fairly low temp solder with some silver in it, so I would
re-solder and suck a few times to get as much new in the joint, it holds
up a little better than 63-37 or 60-40. Again getting off track, it was
not possible on this joint, but if there is enough tail on whatever it is
you are re-soldering to a board that failed from fracturing, if you can
make a wrap of wire around the tail and solder the two ends of that wire
to another part of the copper land, you will greatly reduce the chance of
failure later on. On many an occasion if I had a troublesome joint, I
would purchase a new component, not because the component failed, but for
it's longer tail and do whatever to make more solder surface area of
solder that is conducting that would prevent a lot of heating and cure
the malady, or at least greatly increase the time between failures.
Anyway if you do go to two pre-pumps (or even one) be cognizant that two
pumps in parallel draws enough amps that over time any solder joint that
may flow electrons to the two pumps could in fact be a failure point. The
first time it happened to me it was a drive you crazy malady to figure.
First time, didn't hear the pump working with a stuck car. Come back
and it runs fine? OK replace the pump and all is well, for a week or two,
then the same thing, get stuck, come back and all is well. Depending on
heating and cooling the fool joint would make or break. Hard to
troubleshoot, easy to fix once you know.
Ron P.
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