M40 Not starting

[El_Fishe]

I have a late 91 318i M40 that won't start.

The car had been lying for around 6-8 weeks. It had a fuel leak from underneath the inlet manifold from one of the short rubber hoses which connects to the injectors. I replaced this hose and refitted everything as it was, including all plugs and hoses. I also replaced the battery. I tried to start the engine and it would turn and turn without any sign of starting. I removed one of the spark plugs to see if i was getting a spark, which i wasn't, i then replaced the spark plugs and HT leads, which has made no difference whatsoever.

Please Help!

[baptie0]

check for 12v across the terminals of the ignition coil using a test lamp.

[asmith88]

is it getting fuel? if so,try checking the distributor and rotor arm for wear

[daimlerman]

Oh dear.
Mr Moore suggested to me that a test bulb wired across the fuel pump would tell me if the ECU was instructing the pump to pump fuel and therefore the ECU to issue instructions to the coil to give a spark..
So in plain speak,lift the rear seat base to access the hatch for the fuel pump,remove the electrical connector,wire a bulb across the terminals and replace the plug,spin the engine over and see if the bulb lights.If it does,then you should also get a spark,if it does not,check fuse 11,then the fuel pump relay.

[El_Fishe]

next chance ill get a look is sunday but thanks for the quick replies so far!

[Brianmoooore]

check for 12v across the terminals of the ignition coil using a test lamp.

Not across the coil terminals! From the coil + terminal to earth.

[baptie0]

check for 12v across the terminals of the ignition coil using a test lamp.

Not across the coil terminals! From the coil + terminal to earth.

Sorry, i should have said check for 12v between the coil positive and earth. I am not the best at explaining.

[Arjun75]

is the king lead from the coil into the distributor getting a spark?

[El_Fishe]

i checked the resistance of the coil, and it was fine, however i checked the voltage between live and earth and was only getting 3v, any ideas?

[Brianmoooore]

The 12 volts you are switching on with the ignition switch isn't reaching where it should.
The green wire which leaves the ignition switch is the same one that arrives at the coil + terminal, with a few joints and connections in between, and commonly including the odd immobiliser or two in line, whether or not you are aware of their presence.
If all the warning lights in the instrument cluster come on as they should with the ignition switch, then we can assume that the switch is OK, so now you have to find where the break is!
I suggest the first place you try is the 20 pin C101 engine loom plug and socket, right next to the fusebox. Unclip it from the bulkhead, screw it apart, pull back the rubber boot on the fusebox side, and connect the bulb between the green wire here and earth (rear bonnet bracket), with the ignition on.
P.S: Put the meter back in the cupboard, and use a 12 volt 5W or 21W bulb for your testing.

[El_Fishe]

so now you have to find where the break is!.

Assuming there is a break, i would get a reading of 0V at the coil and not 3V surely?

[El_Fishe]

is the king lead from the coil into the distributor getting a spark?

No.

[Brianmoooore]

so now you have to find where the break is!.

Assuming there is a break, i would get a reading of 0V at the coil and not 3V surely?

I very much doubt that you have 3 volts there.
That's why I wrote "Put the meter back in the cupboard, and use a 12 volt 5W or 21W bulb for your testing." Meters give misleading readings in the hands of people who don't understand their limitations!

[El_Fishe]

so now you have to find where the break is!.

Assuming there is a break, i would get a reading of 0V at the coil and not 3V surely?

I very much doubt that you have 3 volts there.
That's why I wrote "Put the meter back in the cupboard, and use a 12 volt 5W or 21W bulb for your testing." Meters give misleading readings in the hands of people who don't understand their limitations!

I'm an apprentice electrician, so I'm fully aware of the correct use and limitations of a multimeter.

However, having knowledge of normal domestic and industrial electrics doesn't automatically give me knowledge of car electrical systems, although it does help.

The battery is definitely OK as it read 12V, the voltage at the coil when starting was definitely 3V. If you say there must be a break in the positive to the coil, then no voltage whatsoever would come down the line. I am getting a reading here though.

Saying this, I'll connect a bulb in the line tomorrow and see where this gets me. The fuel pump seems to be working also, as i can see and smell it on the new plugs.

[Arjun75]

i had a prob recently of no spark into the distributor from the coil.voltage at the coil being fine.Also fuel pump would not work.Ended up being the crank position sensor that had failed.but i hear this is very rare.

[El_Fishe]

i had a prob recently of no spark into the distributor from the coil.voltage at the coil being fine.Also fuel pump would not work.Ended up being the crank position sensor that had failed.but i hear this is very rare.

is this the plug underneath the air intake from the throttle?

[jbh]

where about are you? if your local to me id be willing to pop over and have a look over it.

[El_Fishe]

The battery can read 12v but have no amps behind it, that is the reason one load tests a battery, a multimeter will only give you an indication of what voltage it is carrying, not its capacity (amps=POWER!!)

The only case in which a battery would read 12V but have no current flow would be if there was an open circuit.

If there is no draw from the battery then no current will flow.



But I'm sure you know this...

[Arjun75]

i had a prob recently of no spark into the distributor from the coil.voltage at the coil being fine.Also fuel pump would not work.Ended up being the crank position sensor that had failed.but i hear this is very rare.

is this the plug underneath the air intake from the throttle?

yes.sometimes moisture in the contacts creates the problem and a good clean sorts it out.in my case the sensor was faulty.

[El_Fishe]

The battery can read 12v but have no amps behind it, that is the reason one load tests a battery, a multimeter will only give you an indication of what voltage it is carrying, not its capacity (amps=POWER!!)

The only case in which a battery would read 12V but have no current flow would be if there was an open circuit.

If there is no draw from the battery then no current will flow.



But I'm sure you know this...

I'm afraid you have no idea what I am talking about, suggest you read it again and think carefully......

I've read it and read it and obviously have no idea.... please explain what you mean in leyman's terms

[El_Fishe]

i had a prob recently of no spark into the distributor from the coil.voltage at the coil being fine.Also fuel pump would not work.Ended up being the crank position sensor that had failed.but i hear this is very rare.

is this the plug underneath the air intake from the throttle?

yes.sometimes moisture in the contacts creates the problem and a good clean sorts it out.in my case the sensor was faulty.

i'll have a look at that properly today, the connection is quite loose. This doesn't have anything to do with what i think is the pulse sensor on number 4 HT lead does it?

[Brianmoooore]

If you start playing around with other stuff that has no relevance to this particular fault, you will end up with multiple faults!
BULB BETWEEN COIL + AND EARTH.

[harry_p]

The only case in which a battery would read 12V but have no current flow would be if there was an open circuit.

If there is no draw from the battery then no current will flow.



But I'm sure you know this...

I'm afraid you have no idea what I am talking about, suggest you read it again and think carefully......

I've read it and read it and obviously have no idea.... please
explain what you mean in leyman's terms

it's possible for a battery to show 12v on a meter, but have no power. If you linked 8 1.5v aa batteries together you'd get 12v on a meter, but there's no way on earth you'd be able to start a car with them. Similarly a cat battery can show 12v on a meter, but die as soon as you ask it to deliver a wodge of current.

[El_Fishe]

thanks harry i understand now.

@ Brian:

Ok, thanks