<VV> Fuel delivery problem - long

[Doug Mackintosh]

I am trying to diagnose a fuel starvation problem. If possible I want to find a "smoking gun" so when I fix it I know it's dead.
  The car is my daughter's 1964 Spyder. 5 times over the summer it has bucked then (most times) stalled. Up until now I have been too far away to lay hands on it during the incident. Note that during this period the car has made two trips of several hours duration with no apparent problem. The first incident occurred after about 7 hours of travel. 
  Yesterday she took the car for a test run after we replaced the oil cooler seals, to confirm the leak was stopped. She drove about 8 minutes at mostly highway speeds (60-70 MPH) at which point the car started bucking as if running out of gas. She turned around and came back home, bucking all the way. When she arrived, she pushed in the clutch and the car died in front of the house. We removed the air cleaner and pumped the gas while looking for the accelerator pump squirt - no squirt.
  This morning I loosened the fuel pipe from the fuel filter to the carb. There was no fuel in the pipe. I removed the carb bowl top with the float. I measured the fuel in the bottom of the bowl with my 6 inch scale - it measured 1.1 inches deep. I removed the inlet filter nut and used a small plastic straw on top of the needle tip to detect movement. When I set the bowl cover down there was no float movement, indicating that the float was fully dropped (needle open) when the bowl cover was in place. Based on all this, I have concluded that the bowl had "run dry" causing the car to stall. 
  I then reconnected the fuel pipe to the filter and ran a hose from the other end of the fuel pipe to a coffee can. Leigh then operated the starter to measure fuel flow. For a few revolutions there was no flow, but once flow started, it pumped about 1 pint in 40 seconds (which meets the spec). From this I concluded that whatever caused the starvation had corrected itself now. As this has been an intermittant problem, this is not a major surprise.
  I then reinstalled the bowl cover and connected the fuel line to it. We could then start the car and took it for a test drive along the same route as yesterday. At the point where it had stalled yesterday, we turned around and headed back. It then bucked as if out of gas, but then it returned to normal operation for the return trip. When we stopped I carefully removed the fuel cap (a simple vented cap - not "non-surge") to see if there was any whoose from built up vacuum. There was no evidence. From this I concluded that the cap vent was not plugged. 
  We then filled the car with gas. 
  I assume there must be some intermittant problem either restricting flow upstream of the the pump inlet, or that the pump itself intermittantly stops pumping, possibly due to debris blocking a valve open.  The list of possible suspects I can think of are: 
  - Gas cap vent plugged - Now ruled out
- Inline filter (at the tank) partially clogged
- AC fuel filter (in the engine compartment) partially clogged
- Inlet fuel lines blocked/restricted
- Air leak in fuel inlet lines (unlikely as these were recently replaced)
- Fuel pump intermittant valve problem (except it had to clear itself by sitting overnight since nothing else changed before it pumped at an acceptable rate)
  My plan is to next check the filter near the tank and replace it and disconnect the line from the pump and from the tank and blow it out from the engine end. 
  Have I missed any possibilities?
  Any diagnostic advice to help us find the problem and not "destroy the evidence" before we find the "smoking gun"?
  Thanks


-- Doug Mackintosh
  Corsa member since 1996
  Corsa/NC member since 1996,  Virtual Vairs member
  Corvair owner 1969-1971 and 1996-on
 		
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