Cavalier 1.6L - no spark to HT lead - P King
My 1992 Cavalier 1.6L wont start. The previous day, I had driven 70 miles in London through heavy stop start traffic, with about 20 starts in all. The engine behaved perfectly all the time even when the cooling fan was cutting in on high temperatures in traffic jams.
I called out the RAC and the patrolman checked that fuel, spark plugs, distributor cap, ignition leads, igniton coil are all OK. He thinks it is the "amplifier module" which sits under the ignition coil that is likely to be faulty. He did not have a matching spare but said I should get one from a authorised dealer and it would be "very expensive". I have taken the amplifier off the car and checked the resistances across the four terminals - and these range from 10 ohms to 120 ohms, i.e. there is no open circuit or shorted circuit.

I have spoken to a friend who suggests it could be the ECU or the distributor itself. If it is the distributor, how does it come off? It looks like it is one-piece/moulded to the cylinder head.

Any suggestions? Any ideas as to how much it is likely to cost to have this fixed at a Vaux dealer?. Thanks for your help.
Re: Cavalier 1.6L - no spark to HT lead - T lucas
Years ago we had a few cavs do what you described and found a problem with a earth strap from the bulkhead to the windscreen motor. Find this strap,clean the connections and you may well be lucky.
Re: Cavalier 1.6L - no spark to HT lead - Adam Going (Tune-Up Ltd)
Dear P,

From your despcription your engine does not, indeed, have a distributor as such, merely a cap and rotor fitted to the end of the cam housing. These have no bearing on ignition timing or spark creation, just the allocation of the spark to each cylinder. If no HT spark from coil the first thing to check is power to the coil - should be battery voltage present at both LT terminals with ign on. Next you need to check for a signal from the Crank Angle Sensor - for this you really need an oscilloscope, but an analogue voltmeter may do. If all this is OK then the module you have already been pointed to is very likely at fault - it can be tested off the vehicle if you have a module tester, but not just by looking at terminal resistances I am affraid. Sustitution is your best bet. Coil failure cannot be ruled out, but it is probably the most relaible component in the system. Wiring faults between any of these components are always possible.

The suggestion from T Lucas is a good one for very much earlier Cavaliers, but not applicable to anything as late as yours - sorry !

Unless you are determined to sort this yourself, I have to say that expert diagnosis may save you time and money in the long run, if you start fitting parts you don't really need.

Good Luck, Adam
Re: Cavalier 1.6L - no spark to HT lead - P King
I have checked for presence of battery voltage at both LT terminals on the coil, only one of them shows volts.
Also, there is battery voltage present on one of the four terminals at the ignition amplifier module.
The coil resistances are about 1 ohm across LT windings, and 50k ohm across HT.
It was suggested to me that I could put a 5W bulb across the LT side of the coil, crank the engine, and watch for flashing bulb. This I did, result; no flashing of bulb.
Are mobile tune-up technicians able to diagnose faults in these contactless systems, or is their capacity limited to fuel & timing adjustments on cars such as my C16NZ model Cavalier?
Re: Cavalier 1.6L - no spark to HT lead - Adam Going (Tune-Up Ltd)
Certainly sounds to me as though you have an amplifier problem, although you should have 12v at both side of coil LT. The primary resistance at about 1ohm is correct, and coil should therefore have continuity and give 12v at negative side as well as positive. It is possible that primary winding is breaking down when loaded, and hence no voltage despite continuity when ohms tested.

Can't speak for all mobile tuners/mechanics/technicians, but anyone suitably qualified and experienced and with the right equipment should be able to diagnose this problem. You can take it as read that anyone trading under the name "Tune-Up" and a member of the Association of Tune-Up Technicians is so qualified, but there are many mobile operators who are not associated with us who are perfectly competent. There are also people who advertise a tuning service who are not so hot !! "Tune-Up" is a trade name, the term tune-up is generic and can be used by anyone.

According to my data C16NZ means you DO in fact have a distributor, and this means there could be a problem with the Hall Effect Switch inside it, rather than the CAS I reffered to before. Again, you really need an oscilloscope to test this. Timing is set by turning the distributor with the pins 'A' and 'B' at the diagnostic socket bridged together.

Hope this helps. Adam
Re: Cavalier 1.6L - no spark to HT lead - P King
thank you, Adam.

I searched at two scrapyards for the parts - but could not get identical bits.

In the end, I paid £76+ at Vaux for a new ignition module, put that on, still no spark! Returned the part and got a refund.

Then I managed to get the Distributor off, cleaned up the hall sensor contacts, allowed the cylinders to dry out of flooded petrol overnight thru open spark plug holes.

Fired up this morning - hey presto, engine back to normal!

Thank you again.

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