[alfa] RE: Low Spica Fuel Pressure - Followup

["Mitch" <wolberg5@xxxxxxx>]

<Snipped some good advice from roadtrip>

The battery and alternator are putting out normal voltages, though they
haven't been checked when the low pressure light was on. I've started
carrying a voltmeter in the car so I do this the next time it occurs.

1. Failing supply pump (most likely)  - Nope, its new.

2. Leaking pressure relief valve in the front fuel filter - Possible, any way
to check.

3. Someone installed an L-Jet supply pump as a substitute and didn't narrow
the FI pump outlet restriction - No but I've never fully understood this one.
I can see how narrowing the outlet orifice would increase pressure and fuel
speed (Venturi Effect) but it would also reduce the flow rate. Wouldn't a
higher flow rate create more system pressure regardless of the pump pressure?

4. Clogged fuel filter(s) . . . . checked already.

5. Plugged up fuel tank vent creating a vacuum in the fuel tank - Forgot to
check that one but not likely, the cap gasket is pretty old and hard.

6. Excessive fuel temperatures causing supply pump to cavitate - This is a
possibility, it only occurs on a hot day after getting off the highway. OTOH
the tank was half full and the coolant temperature was 175 the whole time,
not
that the underhood temperatures couldn't be a lot higher.

Cold weather has finally arrived in Colorado, so I might not get another low
pressure symptom until spring.

Mitch Wolberg,
Denver, CO
69 Berlina
69 Spider Jr.
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