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78 Spifire ignition problem

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EEjay:

All MK4's have breather tubes going to the tank from the carb. In later models, I've noticed the charcoal canister system was more complex.
In my case, I have a very early 1500 MK4, made in '72, sold in '73. It had the charcoal canister, but I removed it and directly connected the return line to the carb.
This is easy to see if you have the Stromberg - in your case your Weber may not have a return outlet on the carb.

Adam H.
____________________________________________________________
1972 Triumph Spitfire.
 
Thanks for all the supurb feedback.I meant a zip tie not a ziplock. The hose is folded over and the ziptie keeps it pinched. Tommorrow I'll try making it fail and opening the filler cap anbd see if it starts. There is no heat shield but it has a Cannon manifold that sticks out quite a ways to the side so the carb isn't real close to the exhaust manifold. Where the fuel line comes in to the carb there is another capped line inlet. Would that be the place to hook it? I thought about just cutting the line after it comes out the bottom of the trunk but hooking it into the carb sounds more sensible. When I open the filler cap after I've been driving, air rushes in.
 
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Where the fuel line comes in to the carb there is another capped line inlet. Would that be the place to hook it?

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No I don't think so. Just above the fuel line that goes into the carb (i.e. from the fuel pump) is another fitting, which is actually an outlet, not an inlet. It is the vent pipe from the carb bowl. Normally there would be a hose from that outlet to the cannister also, to allow the bowl to vent to the cannister when the engine is not running. When the engine is running, the bowl vents internally.

On the front side of the carb (i.e. the side towards the radiator) there is a connection for purging the cannister. See the attached. This is a purge port for both the valve cover and the cannister. Maybe you're still venting the valve cover to this port. I don't think I would want to tie the tank vent into this, though, since it would essentially vent gas fumes into the valve cover when the engine is not running.

[ QUOTE ]
When I open the filler cap after I've been driving, air rushes in.

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If the tank sucks air when you open the cap, you have a venting problem. It may or may not be the cause of your stalling, though. If it is, then once you open the cap and let air in the tank the car should start again, allowing for a little bit of cranking to refill the carb bowl.
 

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Re: 78 Spifire ignition problem [FIXED]

I thought I'd post my results. It turned out to be the vent tube. I tested it by running until it failed, popping the gas cap and it started every time. It probably only occurred in cold weather when the gas tends to contract whether than expand, so PO may not have known since he bought the car in early spring and sold it in Nov.
 
Re: 78 Spifire ignition problem [FIXED]

Wow. Thanks for posting. Its great to know you were able to solve this.

(I still think you need to replace that ignition switch though....hah)
 
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