Vacuum or Vapor Lock Issue?

[gr8scott]

I used a fabric material that looked like the old finger grabber stuff you played with when you were a kid.

Chinese finger trap...haha ;D

https://www.youtube.com/watch?v=bovLQSkAxXU

 

[SteveL]

Thanks Steve L. How do you check for leaks?

With it running spray some carb cleaner around the adapter. If the rpm goes up theres a leak.

 

[DirtDonk]

Or if it goes down there's a leak.
Or if it smooths out there's a leak.
Or if it gets even rougher there's a leak.

In other words, if you spray around something and the idle changes at all, there is a leak.
How much it changes will let you know how big or small the leak is, in the relative scheme of things.

Paul

 

[Broncobowsher]

And you want to get the flammable version of carb cleaner. It acts as fuel going into the engine, mixing with the air leaking in. That is why the idle will change, you are adding fuel to an air leak. But non-flammable cleaner isn't fuel.

 

[ntsqd]

I get wanting to keep it stock, but the solution is to make the system return fuel to the tank. To do that you need an electric pump back at the tank. Most will say that pump needs to be below the fuel level, not always true. The line between the tank and the pump is still in jeopardy of vapor-locking so keep it as short as possible and use the emissions barrier type EFI hose for at least this section if not all of the hoses in the system. The reason for this is that the inner liner is somewhat stiff and will be more resistant to collapsing under vacuum. That liner is resistant to newer fuel so even though it is expensive it will last a lot longer than the cheap stuff.

Add a returning type regulator as close to the carb as you can get it.

If your tank has no return fitting can drill and tap the fill-neck to add a return fitting there.