Yesterday we (David Tallerico and I) attended a Seat Time session at Summit
Point track after a too-long hiatus. The weather temp wasn't hot but
pretty warm - mid to upper 80's or so. It is 1.5 hour drive from my house
there and we stopped in Charles Town for gas. at around 7:50 am. At the
station the car would not restart and we discovered that it was getting any
gas for the plugs were dry. The fuel pressure light went out but it took
longer than usual for it to go out; usually after running for a bit, it
only takes 1 second for it to wink out. I removed the return hose from the
SPICA pump and gas was pumped out with the fuel pump on. We 'fixed' the
non-starting problem with starter fluid sprayed down the throats. Off to
the track!
Barely into my first session of the day, I started getting a whiff of
gasoline but I attributed it to all the other cars whizzing past me. But
then it got stronger and stronger which lead me to pull into the pits
before I caught on fire. On the false grid, I stopped and opened the hood
- no smell there. But in the trunk, there was a light layer of gas in the
fuel gauge sender and a light coating over portions of the tank. When I
loosened the filler cap, I could hear air escaping at more than normal
pressure. And the car would not restart. I removed the air cleaner but
this time it started without the need of the starter fluid. And replacing
the air cleaner did not kill the engine. Gas supply related, perhaps?
On the next session I withstood the fumes until they started bothering my
eyes, so I exited the track and drove the car to our spot. This time gas
was dripping from the front of the tank as well as being on the fuel gauge
sender. The drip was not coming the lower exit to the fuel pump but up top
where the SPICA fuel return hose is connecterd to the tank. My flashlight
turned out to be dead so I couldn't see if it was really coming from that
connection. Once again the tank was pressurized far more than normal. I
removed the fuel vapor recovery container and found it to contain a
considerable amount of fuel - so much so that it when held level it poured
out the two lower outlets (one drains condensed fuel back into the tank,
the other allows vapor into the container). I drained the fuel back into
the tank. The return fuel line did not show any evidence of cracks at the
end and I tightened the clamp a bit more than normal when I put it back on.
I reasoned that the fuel in the vapor container was blocking the outlets
and thus leading to over pressurizing the tank; and the fuel was
an accumulation over many years. The two hose connections to the tank were
clear as well as the vacuum line back to the engine. And the air breather
on the vacuum line allowed in and out - I don't think that it is designed
like the later models that had a check valve to allow air in but not out.
On the next session (tank was about 1/2 full by now - should have started
with 1/2 tank), I ran the full 20 minutes and didn't smell gas (well, at
least not nearly as much as previous session). Back at our spot, I checked
the trunk and I could hear air loudly hissing from the filler cap (tightly
screwed on) and from the vapor container's air breather. I could hear
gurgling sounds from inside the tank. And when I started to pull the
filler cap from the tank neck, fuel & air spurted out of the filler all the
way up my arm and partially on my face - fortunately I was standing to the
side and didn't get sprayed full on. I screwed the cap partially back on
to let the pressure escape. After the tank was depressurized, I discovered
that the vapor container remained pressurized. There was even more gas in
the container than previous which I drained back into the tank once the
pressure was released.
We left before the last session. At the end of the 1.5 hour trip back
home, I cracked open the filler cap and found no pressurization. Tank had
about 2-3 gallons left in it. The temps in the DC area where much warmer
than at Summit Point and the traffic much slower.
So just how is the tank getting so over pressurized?? Outside source?? My
rear muffler is not too close to the tank for there is the standard 3"-4"
gap between them. The gas tank was warm to the touch when over pressurized
but not frying pan hot. I did replace the front resonator with a straight
pipe but that shouldn't heat up the rest of the system that much. And how
could it heat up almost 11 gallons of fuel so quickly on the track to cause
the pressurization?
And how could the normal operation of the fuel pump system lead to
producing this much pressure ? It is a closed system but with a vent to
the outside via the vapor recovery container's air breather. If the system
is in working order on the car, the pressure built up so rapidly as to
overwhelm the air breather's venting capacity and then the high pressure in
the tank forced gas up into the canister which in turn covered the two
lower outlets aggravating the problem in the tank.
All in all, very odd and disconcerting. It will be hard to replicate the
problem in the driveway since it only seems to happen the car is driven
hard on the track.
Any ideas where I should look ??
Thanks,
Bruce
'73 GTV
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