Triumph Repair: Fuel, electric fuel pump, weber dgv

Question
Howard, I have a 1972 Spitfire with a Weber DGV carb.  When it sits for a week it doesn't want to start.  A shot of starting fluid and it hits right away.  There are no leaks to be seen anywhere, but it seems as if the carb is out of fuel.  Everything works well once it starts?  If I drive it several times per week it doesn't have a problem.  Any ideas?  Thanks, Alan

Answer
Hi Alan,

It sounds like either the choke is not on or it is as you suggest, no fuel in the carburetor.

If the choke is on before you try to start it you can run a couple of tests or just remove the top off the carburetor to see if there is any fuel in the float chamber.

No fuel in the carburetor in the morning is a common problem on many cars due to the problem of heat under the hood boiling all the fuel out of the float chamber when the car is shut off and left for some time.

The Spitfire has a mechanical fuel pump that only operates while the engine is running and it takes a long time spinning the engine to refill it. The problem is made worse when no fiber block is installed between the intake manifold and the carburetor thus transmitting heat from the engine directly to the carburetor. Also the lack of an insulated heat shield between the carburetor and manifold allows heat from the exhaust manifold to radiate up to the carburetor. Add in the fact that when the engine is shut off no air is circulated past the carburetor like there is when the engine is running.

A simple test to see if these are factors can be done by leaving the hood open and placing an electric fan blowing on the carburetor for a while after shutting the car off in the evening. Then see if it starts without the starter spray in the morning. If you don't have a garage or driveway and must park out on the curb this may not be an option.

Another option is to install a electric fuel pump (1.5 PSI to 3 PSI not higher) in place of the mechanical pump thus refilling the carburetor before starting.

Howard