316i M40 does not start.

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e30cbe
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Tue Dec 08, 2009 4:56 am

My 1990 316i M40 refuses to start.The engine turns over fine but does not fire.Have had the car for around 2 months now and was running fine until a week ago.
Put in a new battery last week and all was good.Thought it might be the fuel pump relay or fuse cause the pump does not come on when the ignition is switched on.Cant figure out which the fuel pum,p relay is but direct connection from the fuse box to the pump makes the pump run but the car still wont start.
Checked the spark in one of the plug leads and there is no spark either.
Could this be a blown Crank Position Sensor?
Also if someone could throw some light on the relays in the fuse box it would be great.Dont know the function of each of them as i dont have a repair manual.
Cleaned out the crank sensor yesterday and still the same.Is there anythjing i should look at before removing the crank sensor.Any help would be greatly appreciated.Thanks
mrLEE30
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Tue Dec 08, 2009 6:08 am

Checked the spark in one of the plug leads and there is no spark either.
clearely you first port of call!!

check you have voltage at the coil first with the ignition on.
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e30cbe
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Tue Dec 08, 2009 6:12 am

mrLEE30 wrote:
Checked the spark in one of the plug leads and there is no spark either.
clearely you first port of call!!

check you have voltage at the coil first with the ignition on.
there is voltage at the coil.
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Brianmoooore
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Tue Dec 08, 2009 9:22 am

Fuel pump only runs when the engine sees pulses from the crank sensor.
Unplug the CPS under the inlet manifold, and measure its resistance. Check that its wire hasn't come loose where it passes the water pump pulley, and been savaged by it.
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e30cbe
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Tue Dec 08, 2009 9:45 am

Brianmoooore wrote:Fuel pump only runs when the engine sees pulses from the crank sensor.
Unplug the CPS under the inlet manifold, and measure its resistance. Check that its wire hasn't come loose where it passes the water pump pulley, and been savaged by it.
thanks a ton for that.Will check.Also there seems to be a wire running from near the crank to one of the plug leads,can you tell me what this is.
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Brianmoooore
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Tue Dec 08, 2009 9:56 am

e30cbe wrote:Also there seems to be a wire running from near the crank to one of the plug leads,can you tell me what this is.
This is the M40's equivalent of a cam position sensor.
Car will run OK without it, but run slightly better with it.
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e30cbe
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Wed Dec 09, 2009 4:35 am

Brianmoooore wrote:
e30cbe wrote:Also there seems to be a wire running from near the crank to one of the plug leads,can you tell me what this is.
This is the M40's equivalent of a cam position sensor.
Car will run OK without it, but run slightly better with it.
thanks.fixed it yesterday.it was a faulty crank position sensor.There was some moisture in the connector under the inlet manifold but cleaning it made no difference.Swapped the crank position sensor from my cousins car and it fired up right away.thanks for the help.cheers!
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