Technical refusing to start after stalling

[Bushboy]

Hello! First post and all that.

Quick question. Ive got an MK1 Fiat Uno 45 Fire (carb) as a run around but occasionally it will play up.

99% of the time it is sound as a pound and causes me no problems atall, starts on the button on full choke, wait 10 seconds and put the choke in and all is good... but once before and once today, it has refused to start after either false starting or stalling the engine.

Today, I went to start the car but my fingers slipped off the key, mid start, and it stalled. Went to start it again and it refused. Even with pedal pumping and full choke, it just refused to fire. Wasnt even trying. Eventually, after sitting there for around 15 mins, it started and drove away no problem.

Now, there was definatly fuel and i checked under the bonnet and there was definatly fuel in the filter too.

The previous time, I was very low on petrol and it wouldnt restart after being turned off, although there was fuel in the filter. I checked for a spark too and all was fine, just refused to start. again, 15 mins or so of waiting and it eventually fired.

Also, once or twice before, I have put the choke in too early and it has stalled, leaving me stranded for 15 mins again.

Ive owned a few unos in the past, mostly injection but I did have a carb model before and I had the same problem a few times. Even once or twice with an injection model. Stall the car and it refuses to start for around 15 mins, no matter what you do.

Anyone ever experienced this or have any ideas as to why this happens? is it a fault or just one of the woes of running a carb and choke?

 

[alexGS]

Hello and welcome to the forum :wave:

I think you summed it up well in the last sentence. I think it sounds like the engine is flooding easily - due to an over-active choke - the 15-minute cooling off period allows the excess petrol to dry out of the combustion chambers.

Note that one way to speed that up - avoid the-15 minute wait when it refuses to start - is to press the accelerator pedal slowly down to the floor, hold it there, and then try to start. Only release the pedal when the engine actually fires and gets up to 2000+ RPM (and before it gets to 6000+ RPM )

It's important not to pump the accelerator as that will aggravate a flooding problem.

I'm not sure if this completely explains why the engine should be difficult to restart after stalling, but I also suggest you check the ignition timing. Should be 5 degrees BTDC with the engine idling and vacuum advance disconnected. Connecting the vacuum advance should have a noticeable effect on the idle speed (advance becomes 15-20 degrees) - if not, it has a split diaphragm: common problem.

My experience of the carbed 999cc FIRE is that they are easy to start, in all conditions, but when the engine is cold, they bog down easily (as my father would have said, "couldn't pull the skin off a rice pudding"). Which is why FIAT provided an especially-enriching choke to overcome the bogging-down in cold weather. The problem is, in warmer weather, you have to avoid the full effect of the choke.

One way to do this is to turn up the fast-idle speed on the choke linkage, so that pulling out the choke increases the idle speed a lot but doesn't enrich the mixture so much. Actually they started off like this as standard - with the engine warm, pulling out the choke fully increased the idle speed to about 3000RPM and if you tried it when driving, you had 'cruise control'. That is of course bad practice, as the enrichment is bad for the engine when warm (and bad for your wallet).

Also check your spark plugs. Perhaps the difficult starting is due to carbon-fouled plugs from the over-active choke?

Hope that gives some ideas to start with

-Alex