Technical Engine loses power momentarily

[Berlinette]

Hi,

Our Fiat 500 ran great all last year following initial problems of dying at the side of the road, traced to a faulty distributor cap and rotor.

Recently, on the way to its annual MoT appointment it ran fine for most of the trip but the engine lost power momentarily (didn't cut out) but was struggling for revs. Power was then restored and it managed to complete its journey. This has happened two or three times now. It's running electronic ignition and idles ok. Plugs have been out, cleaned and re-gapped and their colour looks spot on.

Any ideas what could be causing this please?

Got back two nights ago and noticed the Dynamo drive belt was a bit slack. Now sorted that but not been out again since.

 

[AndrewHarvey]

First thought is voltage of charging system / battery
Second is to reset tappet clearances

Electronic ignition will not tolerate low supply voltage

This engine also seems fussy about valve clearances

 

[Paolo66]

Valve clearances is my guess

 

[fiat500]

....and it might be a loose cable, eg. battery main cables at either end, main lead into or out of ignition switch or even a the switch itself dodgy, especially if it's the one on the dashboard.

 

[Toshi 975]

Just to compound the possibilities it could be a momentary loss of fuel for some reason

 

[Berlinette]

Thanks guys will check all these suggestions. Have checked tappers and all ok bar one.

 

[Berlinette]

Tried everyone's suggestions but problem persists.

The engine will idle ok but when trying to rev it using the carburettor link bar, it will not respond to quick revs. It will build slowly and then power returns.

Is this a carburettor or ignition problem does anyone think?

 

[Paolo66]

Sounds like an air leak from the carb. Squirt some easy start around base of carb, run it and look for leaks

 

[Luxe]

If you want to check if there is an air leak at the carb base.do this.

1. Start the car and let it idle.
2. Get a can of carb cleaner and spray it at the base of the carb.

If the revs pick up it is an air leak at the base.

Be careful not to douse the engine with carb cleaner as it is flammable.

 

[Berlinette]

Thanks to you all for your further advice.

Have tried some thicker gasket material today under the carburettor and base plate, which can take greater tightening pressure and higher temperatures, together with some decent quality gasket jointing compound. Seems to have cured the problem for the moment. Car ran well this afternoon, if anything slightly better than usual.