Auto choke and poor sparks

cacaolat · Post by **cacaolat** » Sat Aug 18, 2007 10:40 am

Thank you ellevie that sounds right. When I removed the hood from the carburator the choke flap was in the right position, nearly closed.
A few months ago when the same thing happened the recovery guy used a spark tester just like yours and said that there is no spark, but just like this time after a while it all worked again. I will clean that plug, that goes into the amplifier (sorry I thought this was the ignition module)....I did not even know cars have amplifiers ..thought that was something for audio.
I will read the thread you recommended..

cacaolat · Post by **cacaolat** » Sat Aug 18, 2007 10:59 am

just bought the spark tester from ebay....

ellevie · Post by **ellevie** » Sat Aug 18, 2007 12:19 pm

cacaolat wrote:just bought the spark tester from ebay....

You won't regret it. Make sure to always keep it in the car. Of course the problem will never come back now and you will never get a chance to use it in earnest, but I expect you can live with that disappointment.

Sorry --- I use the term ignition amplifier and ignition module interchangeably. The module amplifies a weak signal from the magnetic sensor just underneath it in the distributor, and reshapes the signal to make it suitable to drive the coil which generates the spark.

These types of "intermittent" electrical problem can be a real curse to diagnose simply because the problem often does not show itself when you bring it in to your garage. I suspect that a lot of perfectly good amplifiers have been replaced over the years to fix ignition problems; the very act of replacing the amplifier will clean the contacts with the result that the ignition will then work ok. Just disturbing the wiring can sometimes be enough to make the problem go away temporarily. I had an ignition problem for years where it sometimes would not start after about 20 or 30 minutes of cooling down. Fortunately for me, it would invariably start if I opened the bonnet for 2 or 3 minutes. The change in temperature brought about by the rush of cool air into the engine must have caused a metal joint in one of the connectors to contract just enough to make a sufficiently better connection to enable it to work. You could well be experiencing this cooling effect.

You say the choke flap was "nearly" closed --- this might be because the engine had not cooled down sufficiently. It would probably be worth it to convince yourself that it "fully" closes, perhaps first thing in the morning when you can be sure that the engine is completely cooled down. You should be able to confirm that the flap is touching the wall of the chamber. Poke it with your finger to confirm that it returns freely to the "fully" closed position --- a gap of just 3 or 4 mm could be enough to cause cold start refusal.

Don't forget also that for some petrol models the Citroen Users manual tells you to start a hot engine by first pressing the accelerator to the floor and then turning the ignition. This is not needed if you just switch the engine off for a few minutes but I sometimes find that it is necessary after I come out from shopping or something like that. Needless to say you have to take your foot off the pedal quickly once it fires.

cacaolat · Post by **cacaolat** » Sat Aug 18, 2007 5:11 pm

Done the cleaning of the plug and checked if the choke flap was closed. I would call that closed ? there is a gap of about 1mm left.
I think it says on a sticker on the windscreen that the accellerator must be fully depressed when the starting with a hot engine.

ellevie · Post by **ellevie** » Sat Aug 18, 2007 5:50 pm

1 mm is probably ok --- the flap is not a perfect fit in the chamber. Did you manage to confirm that it springs back to the closed position nice and freely when you push it open with your finger ?

With a bit of luck by cleaning the plug you might have cured the problem. Fingers crossed.

cacaolat · Post by **cacaolat** » Sat Aug 18, 2007 6:19 pm

yes the flap springs back nicely, I still gave it some WD40