[alfa] Minimum Flow Rate

["John S." <roadtrip999@xxxxxxxxxxx>]

Andy - I've never seen the factory spec on the SPICA alfa's supply pumps. 
Wes Ingram says that the minimum flow rate (as measured exiting the forward 
fuel fitting on the injection pump) should be .6 gpm. That is also with 
fresh filters.

I think you're concerns about fuel picking up too much heat via too-fast of 
cycling is unwarranted. There's a restrictor in the outlet fitting of the FI 
pump that is there to maintain pressure. By it's nature it slows down flow. 
As long as the restrictor is the correct size for the pump being used (3/32" 
for stock supply pumps, and 1/16" for L-Jet supply pump replacments) you 
should have problems. On the early SPICA cars without in-tank fuel boost 
pumps (3.5 psi) to supply fuel under positive pressure to the main supply 
pump, there was a problem occassionally with vapor lock caviation of the 
main supply pump when the fuel level got very low (less fuel to soak up the 
heat from recirculated fuel), high ambient temperatures, and reflected heat 
off a hot road surface. The standard cure for that was to not let the fuel 
level go too low on long hot weather trips.

As far as pressure goes, my experience has been that the injection pump can 
perform poorly under heavy throttle long uphill climbs with lower fuel 
pressure. Although the fuel low pressure warning light is triggered at 7 
psi, I think the injection pump is MUCH happier with 15 psi under any load 
condtion. Weak/failing supply pumps (or dirty filters) can put out much 
lower than that or even give  intermittent low pressure warning lights. If 
you EVER get a fuel low pressure warning light except for a few seconds when 
you first turn the key to "on", you need to find out why. Change the filters 
first, check voltage to the fuel pump, then suspect a weak/failing pump. 
With some of these supply pumps approaching 30 years old, there's a lot of 
failure ready to happen. If I had an original supply pump in my car, I'd 
change it to a new model L-Jet supply pump as a matter of reliability 
improvement.  Over on AlfaBB.com, there's several theads that address this 
stuff in detail.

Cheers. John

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