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RE: Fuel pump flow

The mechanical pressure regulator in the K-lambda (84-88 turbos) is
simply a spring that pushes against a o-ring and orfice.  I think the
system pressure is a function of the flow rate against this spring.  If
the FP flow rate should fall off then the system pressure should also
decrease.  This was precisely the problem I had with my car.  I had too
low of a flow rate due to a check valve to damper restriction.  The
pressure would fluctuate between 55-70psi. The press. reg. would start
to open at 70psi and then there was not enough flow rate to maintain
this press. so it would drop off to 55psi and back and forth.

I think you are going to have to measure the actual flow rate and match
this to any new pump. Otherwise the system pressure will be too high or
too low. If you are close you can adjust the press. reg. but I would
guess you would have to be +/- 10-15psi otherwise it would take major
adjustment to the press. reg.

You could do this right on the car without removing the FP.  Just remove
the return fuel line and adapt a hose and measure away.


> ----------
> From: 	Sachelle Babbar[SMTP:sbabbar@iris.nyit.edu]
> Sent: 	Friday, January 30, 1998 9:03 AM
> To: 	Russell Southerlin
> Cc: 	quattro@coimbra.ans.net
> Subject: 	Re:Fuel pump flow
> I was reading a manual once and it said that the fp's flow is more
> than
> necessary to support the engine and it is highly unlikely that it's
> flow
> will fall off to a point that it would need to be replaced. One thing:
> I
> need flow to compare it to other types of fuel pumps, not to check
> wether
> it's bad or not.
> Steve
> '84  5ksT 1.6-2.0 bar
> Disclaimer:"Any information contained herein is based purely on my own
> personal experience and may not necessarily reflect yours. Use caution
> as
> your results may vary from mine."