car won't start

[dn808e2]

Hi,my M3 is playing up, fuel pump is working, spark good, but it will not start from battery,(just bought another battery yesturday) 68 amp hours from Uniparts
but car starts only with jump leads, don't know what to do,

[siddiqi1]

im a bit scared to advise you on anything tbh; its an M3! what a car! anyhooo drooling over!

I assume youve checked your EARTHS? Logic says to me; that if the jump leads are starting the car, and you have a new battery; it means the NEG JUMP LEAD is earthing the car correctly; and hence why its starting.

Now; when you mean its not starting; is the starter turning but the engine isnt firing? Or is the starter not even engaging?

First thing; i know its obvious; but assuming that some of the wiring is similar; checked the battery earth; which youve already prob done; then you may have an EARTH in the engine bay; on the suspension turret on the drivers side; check its all well.

All i can think is that its an earthing problem! What i suggest laso is that you connect the BLACK JUMP lead to another CARS EARTH and EARTH YOURS TOO; do not jump the car; but what this willdo is ENSURE you have a good earth; then try and start it with your own battery!!!!

hope i havent said anything wrong!

Saboor

[E30Mark]

Check earth's as already mentioned, you sure the new battery is charged???

[dn808e2]

yeap, its charghed, and the weirdest thing is when it does start , and works about 3- 4 min till engine is hot anough, than the car will start NO PROBLEM, It's only when it cold it won't start . (can it be one of the reley's ECU that playing up, but on the other hand as i've mentioned before it starts ok when its hot, but not wnen cold, so ECU is OK
i give up,
i've checked the earth on the engine, took fuel pipe of , and fuel gettin' in, took distributor cup off, cleaned it , spark plugs are ok,
one thing i haven't done is to GET TO airflow drossel and clean it , but i will do it tomorrow,
starter motor is working ok, i took plenum off , undone wires connected to the salenoid, put WD40 inside
just don't know what to think.
please help

[siddiqi1]

you know it could be your IGNITION SWITCH!

my ign swtch used to fail randomnly; when the car was hot; it wouldnt start, as soon as i attached a jump lead it would fire up!

youve seemed to have done everything; but one thing you havent mentioned yet is: what does it fail to do when it doesnt start; as in is the starter kicking in, or is it that the car is spinning over but just not firing?

[dn808e2]

The engine is spinning over but just not firing

[Brianmoooore]

Connect a 12 volt bulb between the + terminal of the ignition coil and body earth, and check that it lights when the ignition is turned on, and stays lit while attempting to start the car.

[dn808e2]

ok i'll do it tomorrow, but i still can't understand why car starts from the first turn of the key when the engine is worm, and it won't start when it's cold

[siddiqi1]

ok i'll do it tomorrow, but i still can't understand why car starts from the first turn of the key when the engine is worm, and it won't start when it's cold

thats one not even Brian has prob heard of! what a weird one that is!

[dn808e2]

can the idle valve be the reason why it hard to start when cold? or it effects the idle speed only

[siddiqi1]

i dont see why it cant; if its not operating correctly; it wont allow enough air into the engine! can you smell fuel on a cold day i.e. signs oif engine flosing before it starts?

Give the ICV a good clean with carb cleaner; the S14 engine is far to complex me to comment on; so my knowledge stops there!

[dn808e2]

[dn808e2]

still no luck, i give up. for now.
can some one drop the wireing diagram for me please (or the fuel pump diagram)

[Martinaston]

Does the oil light work ?

[Bobbydoughnut]

If it was the ICV then that wouldn't explain why it does start with a jump, would it?
The only 2 things it is getting when being jumped by another car is more amperage and another earth so that should be where to look methinks. It turns over ok on it's own battery, gets a spark, fuel and everything else it needs to start but won't.... but will with only a jump. So...is it getting a powerful enough spark with the right duration perhaps, you say it's good but TBH I wouldn't be able to judge a good or bad spark just by looking at it. Have you tested with an arc tester? Like a pair of plastic compasses that you can widen....? Brian's suggestion on testing the coil is where I'd go first, make sure the bulb is bright and doesn't dull badly when turning over. It sure does sound like the extra amperage from the jump is boosting your system, that can then overcome a failing electrical ignition component that doesn't need to be so good when warm. Worth checking every earth strap from the battery and engine to the body for corrosion at the contact point.

[dn808e2]

well we tested the sensors that go into bell housing,
2 identical sensors, but one shows smaller voltage than another, so hopefully tomorrow,, another sensor will be here and fingers cross it will start

[dn808e2]

it's ok now, car runs well,
it was one of the sensors responsible for "timing" stoped working (one that goes into bell housing),
today sensor was changed and car starts ok and fingers cross it'll stay this way
thanks everyone who tried to help