Hello, I'm new here so hi to all!

I bought a imported 1976 127 900cc this time last year. Bought off ebay unseen (madness I know - won't be doing that again).

Anyway, drove the car back from Birmingham to Newcastle at 50 mph and it seemed ok, if a bit gutless, until it blew a spark plug clean out of the head! Close to home by then so got back on 3 cylinders ok. So head off, plug liner in (in fact two as another was about to go), head back on and back up and running. Seemed ok but still gutless and running hot. There was no thermostat when I bought it so have put one in but concerned as to why someone would remove it!?

Sorry for the long story!

Drove it each weekend over the summer but just before the cold weather hibernation she started to stall at junctions. Having woken her up again, the problem is still there but slightly worse - she just won't idle unless the choke is full on, even after warm up. In the garage, the engine sounds rough as though misfiring (still with choke on).

Have changed plugs, leads and condenser as a matter of course and coil because the resistances were way off spec. No difference. Have checked the timing and fuel pump (by using gravity feed) and they seem ok. Haven't changed the dizzy cap yet but am getting good regular sparks from each lead so don't think it's that. Have cleaned the carb and fitted new needle valve and accel pump diaphragm from standard refurb kit etc. No change. Compression readings are a bit all over the place: 145/100/137/117 psi but they were like that after the head went back on well before the problem started. Have seen blogs talking about air leaks but don't really see where they could be, gaskets are all new and no vacuum advance on the carb.

So that's me stuck. Any help or advice would be great.

Many thanks to all who lasted this far!

David

Hi David,

Welcome to Fiat Forum.

I ran a '77 127 for 9 years in the 1980's, so here's a few thoughts that occur to me having read your post above :-

Needing to use the choke to get engine to idle when warm suggests a weak mixture at idle. You seem to have checked the usual suspects.

Have you checked for wear on the throttle/butterfly spindle in the carb?

Another area where an air leak can occur on the 127 is the engine breather rotary valve in the carb. This should only allow crankcase fumes to be drawn into the engine at above idle speed, not at idle speed!. This rotary valve is to found inside the carb body, it surrounds the throttle/butterfly spindle just behind the accelerator linkage and is hidden by a large washer. This rotary valve (iirc, approx. 13mm dia. and 4?mm thick) is made from plastic? and is easily damaged/have a piece broken off or even iirc be fitted the wrong way round on the throttle/butterfly spindle - either of which can cause a large air leak at idle. Also, if the engine is worn and has a lot of blowby past the pistons/rings, the oil fumes, if drawn in at idle, will tend to strangle the engine to the point of cutting-out! To check this, simply block off the pipe stub where the small breather pipe from the carb is attached to the carb (close to the throttle spindle).

You might need to clean the idle jet more than once, despite having already cleaned the carb. The idle jet holder is the one on the outside of the carb body (screwdriver slot head) so no need to remove the carb!. After you remove it, also pull the actual idle jet from the holder (it's just a push fit) and blow clean. It's not unusual to find a little piece of debris lodged inside - the inlet to the jet is the large cross drilling whereas the outlet from the jet is the tiny drilling in the conical end).

Re:- your compression readings? Obviously 2 cyls are low. Did you try a wet compression test (where you inject a little oil into each cyl before testing). This would help to ascertain if worn bores/pistons rings or valves are the problem. Did you happen to check for valve leakage while the cyl. head was off (e.g. by inverting the head and filing the combustion chambers with petrol/paraffin/diesel to check for poor valve sealing) ?
If 2 cylinders are low in compression, then, of course, the performance will seem flat.

Some other things to check re. poor performance -
Set points gap to 16 thou (0.40mm).
Set timing to 10 degrees btdc (this is the left hand mark of the 3 marks on the timing cover).
Check the mechanical ignition advance mechanism isn't seized (it's under the rotor arm).
Set valve clearances to 6 thou (0.15mm)inlet and 8 thou (0.20mm) exhaust, cold.
If timing chain is very rattly, it would be worth checking the valve timing as if the chain is badly worn, it can jump a tooth and badly affect performance.
A worn timing chain will also cause timing scatter.

Re:- Engine running hot.?

Did you try flushing the cooling system? (best remove the thermostat for this).

Have you checked the coolant flow through the radiator? When the engine heats up and the thermostat opens, does the bottom 1/2 of the rad get hot? BE CAREFUL when doing this check as the rad. cooling fan can start up suddenly.

Have you checked the bypass pipes on the cylinder head - these and their fittings can become blocked. These are important for preventing airlocks when bleeding the system.

Also check the hose from the coolant expansion tank. There's a metal pipe in the bottom of the exp. tank which can become blocked.

Bleed the cooling system with the heater valve open and radiator cap removed. Run engine until the thermostat opens and the cooling fan kicks in, then top up via the expansion tank until the rad is full, refit the rad. cap and top up the exp. bottle to the full mark (approx. 1/2 way up). Once the system has been bled successfully, the rad cap should not need to be removed, and any topping up can be done via the expansion tank.

Hth,

AL.

Hello AL, Many thanks for your ideas and for your time to write them all down! Some more good stuff to check there, I'll keep you posted.

Unfortunately I didn't do those checks when the head was off but will try the pressure readings again with the oil trick. Not sure what the pressures should be but I'm guessing maybe 150?

What are you driving now?

Thanks again.
David