Make sure you check the brass piece in the vapor return line from
the gas tank. This line goes up to the charcoal canisters. There
is a small brass piece, as I remember about 1/2 inch long, right
in the line. This should have a needle size hole through it's
center. If that hole is plugged, you will get vapor lock symptoms
after driving for an hour or two.
The purpose of the piece is to prevent gas tank overfill - as the
gas reaches the throat of the tank, there is still air above the
tank from the level of the bottom of the throat to the top of the
tank. If the air could exhaust freely, you could continue to fill
the tank (pushing the air out the vent hose) until you also push
gas out the vent hose. So the small hole allows air to vent under
normal driving, but not fast enough to let you overfill your tank.
If that hole is plugged, as you drive you create a vacuum in your
tank that increases as you drive until your fuel pump can't overcome
the vacuum at which point you get no more gas in the fuel line.
So how do I know this? Well, I spent about a year and a half
trying to figure it out. I learned that when the car died,
and the fuel line was then dry, I could disconnect the fuel
line from the pump and blow back into the tank (thus relieving
the vacuum, although at the time, I didn't realize that) and
viola, gas would flow again. I replaced filters, and did
alot of head scratching until one day I was paging through
my Bently manual and just came across the answer.
On 4/16/99 12:24 AM Space Aliens made Mark Milotay say...
>
>Hi list,
>
>This has probably been hashed out before, but I haven't been able to find a
>slution to this problem yet. Ever since I converted my Spit to twin SU's,
>I've had terrible problems with vapour lock like symptoms. The only
>difference, between this setup and my previous was that I used to have a
>shield between the exhaust manifold & the carb. The one I had wouldn't fit
>with the new assembly and was tossed by my friend who installed them. I've
>been experimenting with home made shields (aluminum foil & fiberglass
>insulation), but I have not been able to get the right setup. Has anyone
>else been down this path, and how did you fix it. If this keeps up I may
>just have to replace the LBJ with a Jeep.
>
>Thanks,
>
>Mark
>Mark Milotay, Principal
>On the Mark Software & Consulting
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