Technical 45 Fire dies when decelerating

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Technical 45 Fire dies when decelerating

(CZ)enda

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The car is 45 Fire with Weber 32 TLF.

The symptoms are:
-Engine dies when throttle is eased and I shift to neutral,
-Car jerks when driving with, say, 1/4 throttle, same when decelerating with gear engaged.
-Idling while stationary is OK, car drives OK when throttle is pushed more than, say, 1/2.

Causes eliminated:
a) Ignition - spark plugs, HT cables, distributor cap
b) Fuel etc. - fuel filter, air filter, advance diaphragm and its hose, econometer hose and sender (it was leaking, but its removal and blinding off the hole on the brake servo hose did not change things too much).

I suspect the mixture is getting too weak somewhere between idle and full throttle and I did not disassemble the carburettor yet. I do not want to play with the mixture screw until 101 % sure it will fix things (well, after all, the screw cannot turn by itself, can it?).

I wonder if I missed something obvious...:confused:
Thanx for suggestions.

Edit: Jets and emulsion tube were blown clean.
 
Last edited:
I would have suggested blocked jets in the carburetor, but it seems you've already eliminated that. Might be worth double checking that nothing is blocked?

Other things to check. Advance weights inside the distributor? They can come off/ break with age. And what about the ignition amplifier on the side of the distributor?

Last thing I can think of is some kind of air leak, but that should raise the idle speed.

Sounds more like you need to go back over the parts you've replaced to double check all is ok.

One last thing, have you checked the valve clearances?
 
One last thing, have you checked the valve clearances?

No - but, should they be incorrect, is it possible for the fault to develop over, say, a week? Anyway, I think this was the last drop I needed to assign some time to this job - one should, indeed, check the clearances on the engine with 220+ kkm on the clock...

It seems I fixed the issue, at least temporarily, but I am not sure which of the actions brought the remedy. I changed the distributor for the one I had saved from my first 45 and played with the advance (the distributors are not the same, IIRC one is 101A, the other 101E, ignition modules look different - one is bigger - and Haynes BOL suggests that advance is 2° for one of them while 3° for the other), cut the end of the hose from inlet manifold to brake servo and reattached it, increased idle rpm using the screw on the carb (i.e. not the mixture screw) and disconnected the engine ventilation hose attached to the air filter.

I also noticed that the plastic piece attaching the hose to the brake servo drum is somewhat "wobbly" and that the rubber gasket under the piece seems perished, but when I tried for tightness by sucking, it seemed airtight.

I think I will double check the distributor as suggested, it spent 3+ years on the shelf.

Thanks for suggestions.
 
Quick update:
It seems it was the ignition coil. Although I checked primary/secondary resistance, which seemed more or less OK, I also noticed that the troubles were more frequent under damp conditions. The coil was also the last part of the ignition system I did not change/renew.
The problem did not reappear since I changed the original Ducellier coil for the Magneti Marelli one.
Bloody French parts :mad:.
 
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