My first post here... on behalf of my sweet partner. He's had this beautiful old 68 volvo wagon (photo below) ever since we met (1990) and he is very fond of it. We have a problem with starting. History: This engine was just rebuilt. We put on a Weber carburetor as the SU's were worn out, which necessitated a change-out of the manifold. We have a new mechanical fuel pump, new filter, new gas lines from the pump to the carburetor.
We've adjusted and adjusted the carburetor. We timed it, checked that the valve clearances were in range. When it runs, it sounds quite good, doesn't smell rich.... purrs along nicely, however if we let it sit for more than a couple days, it doesn't want to start. He'll crank over 6 or 8 times, and repeat that about 3 times in a row, but no start. Sometimes if he just walks away from it for 10 minutes, it will then start. If he sprays in starting fluid, it starts right up. The no start condition happens even when fuel is visible in the clear filter chamber and in the float bowl.... though if it has been sitting quite some time, like weeks, those will be empty.
We've run a vacuum test, and that was good. We're stumped.... and wonder if any older mavericks can give a hand with long distance diagnostics, at this time or if someone can suggest a person or forum where this could be addressed. He's very sad that he can't count on this car running anymore, especially after doing everything we could do to get it a good second life. No one in our town has a clue how to work on old volvos.

 

I don't have what you're looking for, but I'll try to help by asking an expert about it.

 

I am almost certain it is a problem with your carburetor (considering it is the main component you changed out)

Assuming your weber carburetor is new, perhaps you should have the factory check it out, or perhaps someone with more knowledge about carburetors could perhaps guide you.

You say "however if we let it sit for more than a couple days, it doesn't want to start. He'll crank over 6 or 8 times, and repeat that about 3 times in a row, but no start. Sometimes if he just walks away from it for 10 minutes, it will then start."

My guess is something is clogging your carburetor. The fuel sits and something gums up, the new fuel pumped in when you try to start it dissolves that over the course of a few minutes or so and then it starts right up. You said it yourself that when starter fluid is sprayed, it starts right up, so it is most definitely an issue with your fuel system. Perhaps you are not using a fine enough micron of a fuel filter (although if it is an OE replacement it should be good enough), or that any metal lines that have not been cleaned may have residue that can gum up your fuel system.
Perhaps the new carburetor you are using is more picky about how clean the fuel is, and wants a more fine of a filter?

The people (or mechanics) you ask for help do not need Volvo specific information to diagnose a fuel system issue. Your fuel system is very generic, weber carb and mechanical cam driven fuel pump -- that's about as simple as it gets.

Man that car is pretty, I sure wish mine looked like that!