It's a bit bizarre but I wonder if the ignition timing is too far advanced. That causes the spark plug to fire against the rising piston, which stops the cranking of the engine with a 'cough'. Perhaps when you removed that plug, the engine spun over just fast enough for the other spark plugs to fire at an appropriate time.
Ideally you should set the timing with a timing light (the thing that you clip onto a spark plug lead, connect to the battery as well, and then shine on some marks when the engine's running) but this is fast becoming an obsolete piece of workshop equipment as modern engines don't have adjustable timing. The FIRE does, so here's what I suggest:
- Mark the position of the distributor - scratch a line across the join between the cylinder head and the distributor body
- Slacken the two nuts that hold the distributor in place (one top, one bottom)
- Rotate the distributor anticlockwise (i.e. roll towards the front of the car) to about halfway along the slotted holes (of the two threaded studs that hold the distributor in place). As in, adjust it to the middle of its adjustment range.
- Try to start the engine again
- If it all goes pear-shaped, at least you can return the distributor to its original position and try something else...
You'll notice that the more clockwise the distributor is (advanced timing) the faster the engine will run, but the harder it may be to start, and the exhaust will have an uneven, popping noise. The more anticlockwise (retarded), the slower the engine will idle and the exhaust will have more of a chugging noise. Obviously, you want some happy medium in between.
Often the vacuum advance capsule fails (do a search for that term on this forum if you want to know more) and people set the timing too far advanced to compensate for the lack of the vacuum advance.
If you do get the engine to run, then perhaps drive to someone who can set the timing accurately with a timing light, but make sure that vacuum advance is working properly first. Take off the pipe from the capsule on the side of the distributor and cover the end (to prevent air getting in). The engine will be idling at a certain speed. If you put the pipe on and the speed increases, that probably means it's working correctly. If you put the pipe on and the effect is the same as if you leave the end of the pipe open, that probably means the diaphragm inside the capsule has split. It can't be easily repaired - get a replacement (from Italian Autos in Otahuhu, etc.)
Cold start procedure - the FIRE usually requires choke to start and run (otherwise they have an odd habit of starting, then immediately stopping). In the winter particularly, the choke needs to be left on while you drive away and for the first few blocks. It's a good idea to have a working thermostat, so the engine warms up nicely and then the choke can be pushed in sooner (plus, the heater will work better).
So - vacuum advance capsule and thermostat... in my experience, the two things most likely to require attention on an Uno FIRE...
Neither of which explain why yours won't run, but if the timing is wrong it could be a result of someone tinkering with it after the vacuum advance stopped working (as I mentioned above).
-Alex
