74 Spider starting problem

[alfapop]

I have a 74 Spider with Weber 34 DMSA carbs. Car starts great and runs great. But if I turn it off and don't restart it within 5 minutes I have to wait 45 minutes. Otherwise is just spins and spins. I took off the air cleaner and pushed the throttle and do see gas going into one of the throats, and I can hear the fuel pump running, so I don't think it's a fuel problem. I also rebuilt the carb last year. I had also already opened the gas cap to relieve any suction and traced all fuel lines from tank to engine to ensure they weren't neat the exhaust. So good fuel, good battery, good starter, and as the car fires right up when cold it seems the electrical system should be working. What gives? Any recommendations would be greatly appreciated.

[18Fiatsandcounting]

Sounds like an ignition problem more than a fuel problem, namely, something causing a weak spark when the engine's hot. Could be the coil, bad plugs or plug wires, point dwell is way off, etc.

The first thing I'd do is put a timing light on one of the plug wires when the engine isn't starting, and crank the engine. Does it flash as it should? Even if it flashes, I usually pull one spark plug, reconnect the plug wire, and place the body of the plug on top of the engine somewhere so the casing of the spark plug is grounded. You should see a fat spark when you crank it, although you might have to do this when it's relatively dark outside. Or in a garage. The reason for the second test is that a sensitive timing light can flash even when the spark is very weak.

-Bryan

[alfapop]

You've given me a few things to check out. I will do so and let you know how it goes. Thanks.

[alfapop]

Hi Bryan,

I tried to use "Private Conversation" but couldn't figure it out. I hope you get this.

I did as you suggested. I took the car out for a spin to warm it up and
then came back and parked it for 30 minutes. Tried again and it wouldn't
start. So I hooked up the timing light and got a strong flash. Hm. So then
I went and checked the carburetor again to see if it was getting fuel and
it was. I tried to start it again and it STARTED. Hm. Then I figure this
out - it started after I had manually opened the butterfly valves to the fully
open position so I could see if fuel was going in. When I pull out the
choke the butterfly valves are fullly closed (how I start it when cold).
Then when I push the choke all the way back in the butterfly valves only
partially open. Are the supposed to flip fully open when I push in the
choke? If so, I would assume there is a spring that is supposed to flip the valves fully
open and it is not working. So the engine isn't getting enough air. The Carb was rebuilt last year
but maybe the spring is either too weak or not hooked up properly? I could
take it apart and inspect it but it is a lot of work if I am barking up the
wrong tree. I'd include pictures but I guess it is no allowed on this site.
Have I identified the problem?
Thanks,
Rob