[urq] Fuel Pump surge - still having problems

[Ben Swann]

Cody,

Did not really want to get into the trouble-shooting aspect all over again, but to
answer your question below, the tank is neither vacuum nor pressure.  There is basically
an open line that was carbon can and pressure remains even with atmospheric.  I have
checked and rechecked for vacuum in tank along with restrictions, etc.

The system is similar to M90 and is in fact presently using the same pump Model 90 uses
- idoes not make much difference, as Wallbro worked pretty much the same..  If I recall
the model 90 setup is just more conducive to flow whereas the UrQ seems to have a number
of bends to go through.  I may be able to reduce the intake pipe complexity, but in the
end, don't foresee resolving this problem without some sort of dual-pump/surge tank or
cutting the tank open and installing an internal pump.

Interesting point about the voltage reduction - presently the pump is jumpered on all
the time and full current available through relay.  That may be contributing factor, but
don't understand why if pump is on continuously even with fuel pump relay - unless the
engine cuts.  I don't think going down this path is working toward a fix.

Basically was hoping someone knew of off-the-shelf surge tank available similar to the
one here: http://www.sdsefi.com/techsurge.htm
I can probably build one, but just one more 2 hour project that turns into 2 days.

Ben

[Date: Wed, 16 Apr 2008 23:47:29 -0400
From: "Cody Forbes" <cody at 5000tq.com>
Subject: Re: [urq] Fuel Pump surge - still having problems
To: <quattro at audifans.com>
Message-ID: <018801c8a03d$c30038c0$6401a8c0 at nuvolari>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
	reply-type=original

Louis-Alain Richard wrote:
> Ben,
>
> Maybe you can install a restriction on the return hose so the all the 
> circuit will be pressurized from the pump to the restriction but with 
> less flow overall ?

You mean like the fuel pressure regulator? ;-) The only way to really decrease flow
without incresing pressure in this case is reduce the voltage to the pump. BTW Ben....
you could reduce the voltage to the pump to slow it down and stop the caviation, maybe
install a switch to bypass the voltage reduction circuit in any case you need full
volume. For a matter of consistency I'd recomend a voltage regulating circuit instead of
just a resistance circuit.

How simmilar is a 80 or 90 fuel system (in the tank to pump area)? I know they are
gravity feed to an external pump like the urQ, and I know that Jim Green in his 1989 90
used his stock pump and such with both his 10v and 20v setups and power levels from
QLCC-ish to well over 500hp at the wheels. At a certain point he added a second stock 90
pump in paralel to add volume.

Ben are you certain that your tank isn't being drawn to a vacuum? Maybe just for a quick
test try with the fuel cap removed to just completely eliminate that possibility.

-Cody Forbes
http://www.5000tq.com
'87 5ktq - Fast.
'87 5ktq QLCC'd plus some
'86 5ktqCD
'86 5k
'86 5k 
]