Triumph Repair: Carb or Fuel Problem, vacuum gauge, manifold vacuum

Question
Hi Howard, I recently pick up my first Spitfire it sat for three years outside.(i have replaced the starter,battery,and clutch salve cylinder) I am a Younger Guy and don't know much about older stuff other than Hondas.. well i have been having trouble getting my car to run more than a mile or two it just stalls out.  sometimes while still in motion ill try to kick start it acts like it wants to start and briefly runs but when i give it gas it just dies. when i come to a stop and turn the key it starts up but then shortly dies in idle or when i move like 100ft or so it happens all the time. I checked fuel from pump to carb and it squirts good so i was thinking it has to do with the carb.? another thing i notice is it always runs or idles while its cold but the problem seems to happen when the car tends to warm up or get to proper temp. is that because of the water choke ?

Answer
Hi Daniel,

Yes, it can be a heat soak problem but it also can be a lot of things so you need to run some tests.

You need to know what the fuel pressure is at the time of failure not after you stop. To do this you need to put a "T" in the fuel line at the carb and run a long hose out from under the hood and place a pressure gauge under a wiper arm so you can see what the pressure is at the time of failure not after you stop. You want to see from 1.5 to 3 PSI at the time of failure. This will ID or eliminate fuel supply as a fault. Be sure to put clamps at all of the hose joints.

Next you need to run a manifold vacuum test just as you did the fuel pressure test. (most vacuum gauges have a section for fuel pressure so one gauge will work for both tests)

In this case you connect the vacuum gauge to intake manifold vacuum and drive the car until you have the failure and watch the gauge. At no time no matter what throttle opening or load you put on the engine should the vacuum go below 5 in hg. The best way is to keep a steady throttle setting and watch the gauge. It should maintain a steady vacuum all the way to a stop. If the vacuum starts to go away before the engine dies you need to check for a stopped up exhaust system.

The water choke on the Stromberg carburetor is a constant problem and it either does not operate at all or it may be stuck on all the time which is easy to spot as the car will blow a lot of black smoke out the tail pipe. When they don't operate at all, it is very difficult to start cold.

Howard