A Class no spark on no 4?

[glyn]

I have a 2000 A160 with no spark at cylinder no 4, could it be the coils?

 

[Dieselman]

Don't these use a twin coil pack utilising "wasted spark". If so the coil must be Ok and it must be the lead or plug thats faulty.

 

[glyn]

Yes it does use the twin coil,but the plug is OK and there are only 3 LT leads ,any ideas?

 

[Dieselman]

Three LT leads will be a common feed and one for return each coil.

With wasted spark coil the two HT leads should be joined at the coil end. One fires on the compression stroke and one as the exhaust valve is open so no mixture or compression.
Cylinders 1&4 and 2&3 will be the setup as they operate opposite each other.

You can test a coil with a multimeter or by applying 12v to the common and quickly shorting the return to ground. Expect a spark at the HT end as the LT spark makes and breaks.
If you rub the return lead over the main battery terminal that will create the rapid make and break required.

Make sure the coil is not connected to the ECU during live testing.

Are you sure it's the spark missing.

 

[glyn]

no 4 definately is not sparking, could it be anything else?

 

[Ian B Walker]

Have you tried another Spark Plug? Just maybe the plug is caput.

 

[glyn]

yes I have tried another plug,that is why I think it must be the coils.Do you know anybody in Kent who does used spares for Mercedes?