cold start problem

[kensmith]

If I let my Fiat sit outside in the cold and don't start it for a couple of weeks it won't start unless I remove the air cleaner lid. It has a new filter. It just cranks but as soon as I remove the lid it fires right up and idles just fine. I put the lid back on and it continues to idle just fine. Ideas? Need more air to fire and once fired up, no problem? 1978 1800cc 5 speed. All stock.

[ORFORD2004]

If it's carburator, it's possible that the choke goes in only when you remove the air cleaner (Bent rod?)

[kensmith]

If it's carburator, it's possible that the choke goes in only when you remove the air cleaner (Bent rod?)

No, can't be that because I only remove the top of the air cleaner leaving the base in tact.

[majicwrench]

So it is carbed??? Factory air cleaner??

[kensmith]

So it is carbed??? Factory air cleaner??

Yes, stock 1978 124 Spider 1800cc carbed with stock air cleaner and new filter.

[RoyBatty]

This problem kind of defies logic.
On a cold start, cold day, more fuel is needed than air due to the fuel not going to vapor as easily as on a hot day.
So we have the choke to restrict the amount of air until the engine warms up.
Removal of the air cleaner top really shouldn't make that much difference in air flow at start up speeds.
Is there a thermostatic butterfly valve in the air cleaner cold air inlet that could be closing off air flow improperly?

Also when you say it won't start. Do you mean that the engine does not fire at all until the top is removed?
Or does it fire but wont keep running?

Can you elaborate?

[kensmith]

This problem kind of defies logic.
On a cold start, cold day, more fuel is needed than air due to the fuel not going to vapor as easily as on a hot day.
So we have the choke to restrict the amount of air until the engine warms up.
Removal of the air cleaner top really shouldn't make that much difference in air flow at start up speeds.
Is there a thermostatic butterfly valve in the air cleaner cold air inlet that could be closing off air flow improperly?

Also when you say it won't start. Do you mean that the engine does not fire at all until the top is removed?
Or does it fire but wont keep running?

Can you elaborate?

Won't fire with the lid on, take the lid off, fires right up. Runs fine with the lid on or off after fired up. Choke is closed on it's own, opened as engine warms up. Makes no sense to me either.

[2ndwind]

Odd problem. This might sound crazy but maybe it is just the opening of your hood that allows it to start and the lid on the air cleaner has nothing to do with it. The hood might be pressing on something.

[majicwrench]

In the end, it always makes sense. Perhaps the choke plate is not shutting, till the lid is taken off the air cleaner. Perhaps, as was mentioned, lifting the hood relieves pressure on something.
Does this happen repeated?? Twice, fifteen times??
Test test. Does it have spark when it won't start?? Then pull brake vac hose at booster without removing air cleaner lid, piss some fuel in hose. Does it now start??

[kensmith]

Tomorrow morning I will lift the hood and leave the air cleaner lid on and see if it starts. I can't see any other problem with the air cleaner. Choke looks fine. If I didn't know better I would think the new filter is the problem. But then, I have not had the car during the winter when it's cold out. Low 30s to low 40s.

[azruss]

does your filter housing have a snout on it. maybe you've got a mouse that is holed up in there.

[kensmith]

A friend told me to loosen the air cleaner lid nuts and try it. Started right up. I also had it in my garage which is a little warmer than outside and also had my hood up. I will try again tomorrow with hood down and lose lid. He said maybe if the lid is tight it would possibly cause displacement with the carb base causing a problem? We will continue testing.

[meman124]

Has anyone figuered this one out? I have exactly the same problem.
Airfilters on - engine cranks, but no ignition
Airfilters off - it starts
then it runs without any trouble with the airfilters on... have driven it for ca. 50 km without any trouble.
Meman124
1800 cc with dual IDF 40 Webers and K&N airfilters

[jctucker]

So, you loosened the nuts and it started? Could there be a crack in the carb causing some kind of vacuum leak or something? Removing the top un-stresses the carb?

[kensmith]

So, you loosened the nuts and it started? Could there be a crack in the carb causing some kind of vacuum leak or something? Removing the top un-stresses the carb?

That is my mechanics thoughts without looking at the car. Think I will loosen the base nuts from the air cleaner base also. Maybe use nylock nuts to make sure they don't come off.