[urq] Fuel Pump surge - still having problems

[urq]

Man, it sucks to hear that your problem remains ... (pun intended)

A couple things come to mind ... 

 * A low pressure system should be less prone to cavitate.

 * It seems to me in the CIS situation that the pump supplies the same
amount of fuel at all times, if you don't need as much as the pump provides
the rest goes back to the tank.  This would tend to speak against
demand-based cavitation.

 * I think many of the in tank pumps were added because the tank sits low
... a full tank in an urq should have plenty of gravity behind it.  I am
assuming that there's at least a half a tank of fuel during the testing ...

 * Have you let the pump run without impediment into an empty fuel
container?  It seems to me you would hear the most cavitation with the pump
running open loop.  

You might want to try using a fuel container to feed the system for a test
... maybe even better to get a fuel cell that you can sit in the trunk for a
test.  

Steve B
San José, CA (USA)

-----Original Message-----

I am still having problems with fuel pump surge/cavitation after converting
to
EFI(Megasquirt).  For those who may recall some details, I have completely
removed the
tank and cleaned a few times. Have replaced pump and experienced
improvements, but
always seems to get back to the problem - fuel flow is exceeding the
capability for
gravity to feed the line into the pump.   This car wants to be fast - very
fast, but
this fuel delivery problem is preventing it from being tuned properly.

Damn filter sock is near impossible to get out without cutting bottom of
tank out and I
don't know if I want to go and modify my tank unless no external solution is
available -
I also don't really think this is the problem since the tank appeared to be
clean and
clear as new..  I have new uncrimped/clear open lines and using a
pre-filter.   There
seems to be no real difference with the pre-filter removal using  a straight
line.
Basically seems with the lower pressure of the EFI or for whatever reason,
the fuel pump
will start cavitating - sucking air and under load, engine will cut out as
it is
literally sucking the line dry - we'll more like soda pop bubbles.

I'm thinking that some sort of surge tank may work.  This is where I could
use some
ideas and sources.  Unless I modify the tank inside with huge outlet, it
seems I need
some sort of high volume-low pressure pre- pump into a  small tank, then
back out to the
main pump.

The later cars all seem to use some sort of dual-pump system, and it makes
sense.  Would
be nice if there is a nice cylindrical tank I could mount below the main
tank. I don't
know - just looking for ideas.  Just seems the stock UrQ tank is not
conducive to EFI.
Maybe I have a clog/bog somewhere, but I simply have not found anything
obviously wrong
other than the original design not ideal for the higher flow.  

I'm wondering if as a workaround, I can raise the system pressure closer to
the stock -
that would slow the return flow down, keeping the line "charged".  I'd have
to retune my
EFI system, but that is fairly straightforward.

Really looking for ideas here and if I need to would be open to having the
tank
modified, but that seems extreme and finding someone who can do this -
draining the
tank, transporting, welding, etc. - well there has got to be something "less
risky" to
try first.

Ben
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