Triumph Repair: Triumph Spitfire 1972 - Not Starting, zenith stromberg, vacuum pipes

Question
Perfect!  Thanks, Jim.

It's running.  Next issue is the carb.  (Surprise!)

I'm running the Zenith Stromberg CD carb.  The issue (I think) is with the air valve.  It doesn't seem to be lifting, so the car will top-end at about 2,500 revs.  If I raise the valve manually & then accelerate, it will rev properly.

I have checked all the simpler aspects (gaskets, etc.) and they all seem fine.  I'm not 100% familiar with the Stromberg, though, so I don't know if I have all the vacuum pipes / settings correct, etc.

Thanks again, Jim,

Gavin.
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The text above is a follow-up to ...

-----Question-----
Hi Jim,
I just bouight a 72 Spitfire.  It is in pretty good condition, but it is just not starting.

The previous owner had the carb mounted badly.  It had two gaskets on one side.  One gasket was back to front and the other was up-side-down.
I sorted that out and also took the opportunity to clear out the jet and float chamber.

Also, the firing sequence was set to 1243 (assuming 1 is the plug nearest the front of the car.)  I switched it to 1-3-4-2 but still no joy.

It just won't fire, though there does appear to be fuel in the carb.

All plugs are sparking too.

Any thoughts?

Thanks,

Gavin.
-----Answer-----
Gavin,

Yes, #1 is the plug at the front of the engine.  Normally the distributor cap is set with #1 closest to the front, with 1 and 2 on the cap close to the engine.

The simplest way to test for fuel is to get a can of starting ether.  Give it a shot into the air filter... if the car pops and sputters then it's a fuel delivery problem.  If not, it's a timing/ignition problem.  The best way to clear up a timing issue is with a decent timing light to verify the firing setting.


Cheers,

Jim

Answer
Gavin,

I take it you're referring to the dashpot?  It has the mixture needle affixed to the bottom?

If so, it's most likely that the diaphram inside the top cover has failed.  They only seem to last a few years before giving up the ghost.

The Stromberg is of the type of carb referred to as a "constant depression" carb.  Sometimes it seems to refer to what it does to the owners, but it really is a technical description.  In reality it means that intake vacuum is used to raise the dashpot to keep the mixture in it's proper range.

Cheers,

Jim