HELP - YET ANOTHER STARTING PROBLEM!!

[trickster]

I last drove my S1 a couple of weeks ago and it was fine – this weekend I went to start it up and all it will do is turn over. When the key is released from the starter position it sounds as if momentarily it is just trying to fire.

I have checked for spark at the plugs and get nothing when the engine is being turned over, but get one when the key is released. Obviously this is not enough to start the engine. Except for the distributor, nearly everything in the ignition system is only 6 months old – plugs, leads, rotor arm, cap and coil.

I have tried a substitute ignition module with no luck and checked all the fuses and connections under the bonnet – so far nothing obviously wrong. I cannot understand how the car could be running fine and now be dead!

Looking through previous threads and on the Internet I have discovered that the ballast resistor can cause problems. I’ve taken it out and cleaned the connections but the resistor should be bypassed on startup. To check this I connected + on the battery directly to the + coil but still no luck.

After wasting a weekend trying to get it to start I am beginning to pull my hair out so if anybody has had a similar problem or can offer any advice, please let me know!!

Thanks

[tvrgit]

yes you're right the resistor is bypassed on startup - so it's unlikely the fault is in the resistor - more likely to be the resistor bypass circuit.

have you tried swtching on the ignition and working the starter manually (ie with a wire directly to the solenoid from the battery)? If that works, then the fault is in the startup circuit. What about the connector block at the ignition switch?

If the engine still doesn't start when the startup circuit is effectively bypassed (as above) then it's a fault in the coil or ignition wiring and only patient diagnostics with a multimeter will pinpoint the cause.

[trickster]

Thanks for the advice - I had checked the voltage going to the coil on startup and it seemed to be OK, but I have not checked that the actual ignition system (distributor, ignition module) was gettig power at the same time. It may be that in the ignition run position power is supplied to these bits, but when it is turned to start, power is taken away for some reason. This would explain the spark when realeasing the key.

Bypassing the startup circuit like you suggest would prove if it was working or not - job for tomorrow!

[Le TVR]

trickster said:

To check this I connected + on the battery directly to the + coil but still no luck.

That would definately run if the problem was the ballast resistor or the bypass from the starter solenoid.

Check if you have supply volts to the ignition amplifier (red)and start sense volts (white) IIRC these are the correct colours - the TVR cct diagram is wrong. The coil is supplied via the tacho.

And dont forget to check the ignition cct earthing (via distributor).

[trickster]

Thanks for your help so far - but still no luck.

I checked for supply voltage and sense volts at the ignition module and both seemed OK.

The only strange reading I have had so far is a voltage reading from -ve battery to +ve supply to coil (with lead disconnected from coil). With the ignition on there is roughly 0.6V which jumps to around 10 when cranking (ballast resistor bypassed).

The primary resistance of the coil also seems a little high at 4 ohms. The coil is only a few months old and the previous one had a simailar value.

Not sure what to do next!!??!!

[Le TVR]

trickster said:

Not sure what to do next!!??!!

You're not alone there

The symptoms are classic ballast/bypass fault. And you say you have tried a substitute amplifier module too

With the Duraspark amplifier module you should see +volts on the Red wire in 'run'and 'start' and +volts on the White wire in 'start' (IIRC it modifies the timing slightly).
If the coil is directly connected to +volts you should see sparks when cranking as well as when you release the key.... What if you disconnect the white start sense wire while cranking??

For checking some of these voltages try pushing a pin through the wire insulation and measure there. That way you check either side of connectors without breaking them.