<VV> Fuel delivery problem - long

[Kent Sullivan]

Very often the rubber hose that connects the fuel line under the car to the
fuel line into the engine compartment can get hairline cracks which open
depending on the lines twisting a bit. If it opens just a little, in comes
air and then you have a nice fat bubble with no gas.

--Kent
-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org] On Behalf Of Doug Mackintosh
Sent: Sunday, August 20, 2006 7:34 PM
To: Virtual Vairs
Subject: <VV> Fuel delivery problem - long

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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