petrol freezing in carb? Possible

Our man in Havana

I had a problem with my 91 micra where she was dying after 5-10 mins of driving. Complete loss of power and conking out. It would restart and continue without incident after a min or so of being stopped.

Anyways the mechanic put it down to the air filter being in summer mode and not in winter mode. Would this cause the petrol in the carb or pump to freeze?

mukki

the switch is to help the engine warm up faster in the winter,

i would presume having it in winter mode in the summer might cause overheating, but having the summer position on in winter would just make the car slow to warm up,so more likely to cut out a junctions and wolly hat needed for first 10mins





sounds more like your fuel filter is partially blocked


BTW-petrol freezes at about -50

peasant

On old type engines freezing carburettors were not entirely unheard of.

The petrol doesn't freeze because it's so very cold outside, but because during evaporation it loses heat and turns cold (see the working principle of a fridge) and cools down the carburettor and fuel lines with it.
Should the carburettor now be cold to start with, it is possible for the the whole shebang to freeze solid in places and bring everything to shutdown.

endplate

Single engine planes fitted with piston engines i.e. (2 seater cessnas) are prone to carb iceing espicially on warm humid days. As the air speeds up passing through the carb the temperature drops and the moisture can freeze restricting the flow of air to the engine. A serious problem for planes mainly when decending or landing i.e. engine loosing power but not for cars. The planes get around this by the pilot divirting warm air from around the exhausts into the carb when necessary. The mechanic was nearly right except it the moisture freezing and not the petrol

CJhaughey

I had this with a MKII golf make sure that there is a duct going from the exhaust manifold to a point within the intake system.
It may have corroded and fallen away.

MercMad

I used to have a 1.4 Corsa, years ago, with big Weber carb and K&N filters on it, and if driving in the fog the carb used to ice up. She'd drop off a cylinder or two and crawl along then because of the reduced airflow it would thaw out a bit and fly off for another few hundred yards !

Basically the above set up had no manifold heating effect but all standard cars would have this !

In this weather I doubt that is your problem.........but worth a shot !

crosstownk

Bond-007 wrote:

Anyways the mechanic put it down to the air filter being in summer mode and not in winter mode. Would this cause the petrol in the carb or pump to freeze?

In winter mode the air intake draws air in across the exhaust manifold which prevents freezing as the air speeds up as it passes the venturi in the carburettor.

If switching to 'Winter' makes no difference then check the warm air duct from the exhaust manifold as CJHaughey said.

Pigeon Reaper

Carb icing happens due to the venturi effect in the Carbs which causes the air temp to drop and any water vapour in it can freeze. It happens alot on motorbikes and some older cars. Cool damp days are perfect for it especially the type of weather this week as there is still alot of moisture in the air. I tend ot notice it after some high speed driving and then slowing down resulting in the revs dropping. The air temp doesn't need to be too low for carb icing but it does need some moisture. Most Carbs on vechicles imported to Ireland and England would have heaters built into them or use the exhaust heat to try and avoid this problem by keeping the temp in the carbs above freezing. It could be worth checking these out to ensure they're functioning.

Max_Damage

Bond-007 wrote:

I had a problem with my 91 micra where she was dying after 5-10 mins of driving. Complete loss of power and conking out. It would restart and continue without incident after a min or so of being stopped.

Anyways the mechanic put it down to the air filter being in summer mode and not in winter mode. Would this cause the petrol in the carb or pump to freeze?

I've got the same type of car as yourself, only mines a '90. Swtiching the summer/winter thing on the air filter housing makes no difference (I leave on the summer setting all year round).

My car starts and runs like a bag of nails in cold mornings, although it doesn't cut out, it takes about 15 minutes for it to get to normal, when the engine heats up.

It could be a probelm with your automatic choke (I think all post-'89 models had auto chokes). The chokes in those carbs are a wire coil sort of thing that expands when the engine gets hot, and thus opening the choke. Yours may be stuck opened, and hence letting too much air in when the engine is cold. Could be wrong though.