Fuel Pump surge - still having problems

Ben Swann benswann at verizon.net
Tue Apr 15 14:43:46 PDT 2008

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.


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