Hi all,hope someone can point me in the right direction. My s2 is now finished and on the road but I am not at all happy about the way it starts. The battery and cables etc are 100%,I have rebuilt the startermotor and the engine cranks at a rate of knots.what I am not happy about is the way it constantly spins about four or five revolutions before starting and then only if you have not touched the throttle. I know the manual says that the car should be started without touching the throttle but I ran an early citreon volcane with pre cat bosche mp3.1 injection and never had any trouble starting,it would fire off of the first half turn. To make it worse I am worried about anyone else using the car as if the throttle is pressed when starting it will not start. Has anyone really got to the bottom of this,many thanks John.
Engine management problem or just the way it is
- Thread starter pegasus
- Start date
John,
They never start well. Cranking for a while before firing is a common trait, and I have yet to see one which didn't do this. (I didn't buy the first car I saw because it did this, and in retrospect I think I turned down a good'un. The seller's protestations that "they all do that" fell on deaf ears, alas!)
I think I heard that the ECU won't fire the plugs until it has spun at 30rpm for a certain length of time, to ensure that there is enough oil pressure to prevent damage before starting. I'm not sure how true this is tho'.
Oli.
They never start well. Cranking for a while before firing is a common trait, and I have yet to see one which didn't do this. (I didn't buy the first car I saw because it did this, and in retrospect I think I turned down a good'un. The seller's protestations that "they all do that" fell on deaf ears, alas!)
I think I heard that the ECU won't fire the plugs until it has spun at 30rpm for a certain length of time, to ensure that there is enough oil pressure to prevent damage before starting. I'm not sure how true this is tho'.
Oli.
hiya john, as i understand my s2 included they all seem to be "lazy starters",but always start, imy baby had been in my garage for 2wks with no use as i had a chest infection and she started more or less on the button, so hope its nothing too serious and its just normal 944 behaviour, regards jason p
Thanks for that lads,it would be nice to know exactly why the car has this slow starting thing, It is a fact when you jump from car to car and in the real wold where a car is a tin box to get you around the throttle is pressed when the key is turned as it fires your in gear and under way, when in the trade years ago you would drive cars with snapped clutch cables back to the garage by starting them in first gear and doing clutchless changes. Like I say my volcane started in half a turn and prior to the s2 my mazda v6 started in half a turn, strange thing is that sometimes you automatically stop cranking thinking it has fired only to find ithasn't,on cranking immediately it fires right away,strange?
I would like to know exactly what is going on when you crank the engine over,If you want to check for a spark you find that you have a spark as soon as the engine turns,not after it has achieved a prescribed rpm for a set time. If the designed delayed start idea is correct it is not done by the lack of spark and the fact that if you touch the throttle it only seems to flood the engine so delayed start can't be lack of injection,what is going on. I,m sure that the club has a technical guru that can explain this,many thanks all,John.
]Sorry but you did not explain anything, "I think I heard" is not an explanation and if this delayed starting is built into the system why do the plugs spark on the first turn and any use of the throttle flood the engine, I would really like this explained to me in technical facts many thanks John.
sawood12
New member
No engine as far as i'm aware fires up on the first turn, you'll always get a good few revolutions of the engine before it fires up, it's just a 944 turns quite slowly compared with smaller capacity engines so it appears it labours longer than smaller engines, but in actual fact it probaly fires up in the same number of engine revolutions. I don't think (am pretty certain) that there is any deliberate delay built into the starting 'sequence'.
But in anycase, an engines cyliners are not perfectly sealed therefore once the engine stops the pressure in each of the cylinders gradually equalises to atmospheric, even if one piston happens to stop at TDC of a compression stroke. Therefore it stands to reason it will take a few turns of the engine for the compression to build up in each cylinder before the conditions are right for large combustion to take place that is powerful enough to overcome the compression resistance of the other three cylinders and the overall friction of the engine. As soon as the enigne starts to turn both the ignition and fuel circuits are switched on so you have spark and fuel, unburned fuel will build up in the cylinders and help initial ignition - don't forget at the slow speeds of the engine turning over on the starter motor you are not getting a fast flow of induction air for the fuel to atomise into, so the fuel doesn't mix with the air and relys upon evaporation on the crown of the piston to create the vapour that will mix easily with air and will ignite by the spark. Go on, I know this isn't as an authoritarian answer as you'd like but though probably not 100% facutally correct is probably along the lines of what's going on during those first fiew turns of the enigne prior to ignition.
But in anycase, an engines cyliners are not perfectly sealed therefore once the engine stops the pressure in each of the cylinders gradually equalises to atmospheric, even if one piston happens to stop at TDC of a compression stroke. Therefore it stands to reason it will take a few turns of the engine for the compression to build up in each cylinder before the conditions are right for large combustion to take place that is powerful enough to overcome the compression resistance of the other three cylinders and the overall friction of the engine. As soon as the enigne starts to turn both the ignition and fuel circuits are switched on so you have spark and fuel, unburned fuel will build up in the cylinders and help initial ignition - don't forget at the slow speeds of the engine turning over on the starter motor you are not getting a fast flow of induction air for the fuel to atomise into, so the fuel doesn't mix with the air and relys upon evaporation on the crown of the piston to create the vapour that will mix easily with air and will ignite by the spark. Go on, I know this isn't as an authoritarian answer as you'd like but though probably not 100% facutally correct is probably along the lines of what's going on during those first fiew turns of the enigne prior to ignition.
Sorry Scott the time to build up compression theory would mean that the engine would spin quicker at the turning of the key and then load ou prior to starting,I have a large single cyl motor cycle that fires up normally on the first kick,cars used to have starting handles and slack pistons compared to today and they would fire on pulling one cyl over ,It would be nice to explain the slow starting rather than excuse it,thanks for the input,all the best John.
There is a delay in spark until certain rpm's are reached its in the workshop manual or a Bosch book somewhere - I have definitely read it. If you are looking at the sparks with the plugs out it is going to get to that rotation speed significantly faster than with the plugs in.
If yours wont start when you touch the pedal I suspect there is an additional issue causing you weak sparks/rich fuel one or more of the following:- rotor arm / speed/position sensor / ISV fault / throttle position sensor / dirty air filter / faulty fuel pressure regulator / coil fault / earth fault. Clarkes garage has simple diagnostics for most of the above.
Tony
If yours wont start when you touch the pedal I suspect there is an additional issue causing you weak sparks/rich fuel one or more of the following:- rotor arm / speed/position sensor / ISV fault / throttle position sensor / dirty air filter / faulty fuel pressure regulator / coil fault / earth fault. Clarkes garage has simple diagnostics for most of the above.
Tony
Guest
New member
Mine cranks to some tune .. Maybe 5 - 6 seconds.. I discussed this very subject with Barry Smith recently and Barry suggested that it was a trait of the US cars that all the fuel returned to the tank and left the lines dry. The fuel pressure then has to build up at startup. Thomas (ikillcopiers) 944 Turbo starts up a hell of a lot quicker than my US Spec car...!
Funnily enough if my car sits for a week or so it starts up really well....! its the cars caracter . I never heard of a 944 as a getaway vehicle......!
DavidL
Active member
My turbo spins 4 times and starts every time, always has.
My old S did much the same. After a newly recon starter motor it did spin faster but still for a similar number of times.
Interestingly the S I am driving currently (courtesy car) starts almost instantly. I'll ask what they have changed as it has had a lot of work.
David
My old S did much the same. After a newly recon starter motor it did spin faster but still for a similar number of times.
Interestingly the S I am driving currently (courtesy car) starts almost instantly. I'll ask what they have changed as it has had a lot of work.
David
S2s and Turbos seem to crank longer than 2.5 N/As... of the S2s and Turbos, some are better than others, not surprisingly given all the possible variations in battery, starter, fuel, ignition system, and general engine health. There are also two different sized starter motors (perversely, I believe the smaller ones out-perform the larger ones). Another possible factor I recently learned is that many electric motors don't give their best performance when cold.
sawood12
New member
Good point on the speed thing. I reckon there are a number of things at play here - the engine turns more slowly than other cars for sure, I am convinced that the engines start in comparable number of engine turns though. No car i've ever owned starts on the first rev, unless you are starting the engine a short time after shutting it down. If you count the number of turns of the engine based on the noise the enigne makes as it turns I reckon my 944 starts in roughly the same number of turns as my 1.8ltr petrol Focus does, it just takes longer. 944 engines have large piston diameters and therefore large piston crown areas meaning the starter motor has to overcome quite a high force to push the pistons through the compression strokes.
Tony, are you sure about the spark delay thing? Does it apply to all 944 Motronic ECU's? When I had starting difficulties the RAC man explained that as soon as the engine turns the reference sensor pick up the rotation off the flywheel and the signal tells the ECU to energise the coil and deliver spark. In my case the ref sensor was loose and wasn't outputting the signal therefore the coil wasn't energised.
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