Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Hi

I'm near the completion stages of restoring my M plate 1.8ls, you can see on projects and restorations. Today I decided to throw some fuel down the carb and see if it would kick over. I noticed when turning ignition on that there was a spark sound from engine but it wasn't something that made me concerned, sounded more like a relay snap on.

Proceeded to turn it over and no joy so got screwdriver out and checked for spark from no 1 plug lead, nothing. Then tried the coil. As I watched the coil lead and turned on ignition I noticed a spark fly out from the lead but not when I started cranking it.

Granted I've not done much electrical work on the car so I can't think of anything I could have wired up wrong, and I think it would take a bit of electrical wizardry to actually achieve this so I'm looking for thoughts and opinions on anything I can check. I've so far checked the usual culprits including the coil multiplug.

The only other thing I can thing of perhaps is could it be something wrong with ignition switch? The turn of the key is quite stiff after lack of use. No idea if this is mechanical side of ignition barrel or the switch is stiff. Thinking maybe it has dried out or shorted out maybe?

I also noticed on one occasion when I went to turn on ignition it sounded like either the starter solenoid or the starter itself kicked on and off for a split second. I can't verify what it was but it sounded like something moving or activating for a split second. It wasn't like a relay sound it was definitely mechanical hence suspect either starter or solenoid was somehow activated by only having ignition on.

The only electrics I've touched in this restoration is:

Plugs and wires around head/starter/alternator
Wiper motor and heater fan motor plug, both of which are unplugged currently
Tank electrics and ABS.
Battery connection.

Any thoughts would be most welcome.

Andrew

Something sounds like it is shorting to earth...

Allowing the first spark from the coil.

as you know the coil needs to have a continous on / off / on / off situation to operate.

sounds like the coil is not being turned off again.

faulty coil windings or wiring short?

Do you have access to another coil which is a known good'un?

Ignition switches tend to smoke before they go belly up.

Hmm - which 1800 is it?

The C18NZ has an amplifier unit sat under the coil on the inner wing.

We have just had a bout of wet weather, and this location is ideal for stuff getting damp.

Hmm - shorting to earth due to damp, trapped wire or damaged wire insulation?

Quick check, pull the plug off the dizzy and poke a wire in the centre pin of the harness. Flash it to earth briefly, each time you hit earth with it you should get a spark from the king lead. If you do then the hall sensor in the dizzy has likely died, or it's not going round (check cambelt and dizzy drive). If you get no spark when doing this then you are looking at the coil or the amplifier. It vaguely rings a bell that you get a spark on ignition switch on when the amplifier goes down but in all honesty it's been so many years since I did one I can't be sure.

Robsey wrote:Something sounds like it is shorting to earth...

Allowing the first spark from the coil.

as you know the coil needs to have a continous on / off / on / off situation to operate.

sounds like the coil is not being turned off again.

faulty coil windings or wiring short?

Hmm got me thinking about low and high tension circuits,. Would I be right in saying that I will get a spark from the high tension side with only turning ignition on? Thinking on it I would if I am shorting it with a screwdriver to engine metal, but if plugged into dizzy it won't earth out through a spark plug until the rotor starts turning and passing the dizzy points. If that is correct then it seems like that part of it, the ignition turn on part, is working correctly.

colin1 wrote:Do you have access to another coil which is a known good'un?

No don't have other coil.

Robsey wrote:Ignition switches tend to smoke before they go belly up.

Hmm - which 1800 is it?

The C18NZ has an amplifier unit sat under the coil on the inner wing.

We have just had a bout of wet weather, and this location is ideal for stuff getting damp.

Hmm - shorting to earth due to damp, trapped wire or damaged wire insulation?

C18NZ....I never actually suffered any bad weather robsey, I'm in Scotland, where for once it's been good weather for last few weeks! I wonder though, maybe just maybe, that my removal of the water scoosher bottle has soaked the coil plug or coil? Looking at it today though it looked dry enough.

Had a haunting feeling there that tensioner had not been tightened or something and belt had slipped off, meaning no spark! Thankfully not, everything still turning; I tightened that thing up good.

Do the centre pin thing, you can check the entire system in one hit doing that. First thing I always do with the 3 wire distributor setup.

planetc wrote:Do the centre pin thing, you can check the entire system in one hit doing that. First thing I always do with the 3 wire distributor setup.

Quick check, pull the plug off the dizzy and poke a wire in the centre pin of the harness. Flash it to earth briefly, each time you hit earth with it you should get a spark from the king lead. If you do then the hall sensor in the dizzy has likely died, or it's not going round (check cambelt and dizzy drive). If you get no spark when doing this then you are looking at the coil or the amplifier. It vaguely rings a bell that you get a spark on ignition switch on when the amplifier goes down but in all honesty it's been so many years since I did one I can't be sure.

Hi planetc can you explain that a bit more, what harness are you taliknig about? Are you saying to short the coil lead to earth while ignition is on? Do you hold the plug lead with plastic pliers I'm assuming so you don't get a bang from the lead?

I don't think I have a hall sensor ignition is all electronic.

Cheers

Andrew

Correct - on the C18NZ, the distributor only provides distribution of the high tension circuit to the plugs.

The switching effect is controlled by the ecu, which senses crankshaft angle from the 58 toothed ring.

Ok we now seem to be getting a spark. Had a look at the plug on the coil and the pins looked a bit corroded. Gave them a clean and some petrol jelly for good measure. I had my assistant jeeves crank over the engine while checking one plug lead for spark, and away it went, accompanied by a big pop from the carb and a little wisp of vapourish looking smoke stuff. That'll be the gas I dumped down it's throat yesterday having a pop at me!

Squirted some WD40 done it's throat to try again and it made that 'catching almost there' sound so next step is tank filler neck on, gas it up and churn it over and hopefully lift off.

I'm a numpty, didn't read properly and thought I'd seen the mention of a carb. The centre pin trick works with the old distributor type ignition systems.

planetc wrote:I'm a numpty, didn't read properly and thought I'd seen the mention of a carb. The centre pin trick works with the old distributor type ignition systems.

I kind of thought that's what you were driving at, the older version. Carb - should have been clearer - the SPI unit I was meaning.

That relay noise you heard as you turned the ignition on could be the safety system for the fuel pump which only provides power to the pump when engine is turning. However to get it started it pulls in for a very short period when ignition switch turned on. This is standard on injection, may apply to carb models also. No-one wants a fuel pump running after a bump.

If this is fitted then its possible that the fuel line has not purged. On some Cavs there is a return line from the engine compartment to the tank so that hot fuel is moved out of the way before it can cause a vapour lock. There is a restrictor in the return pipe, if this blocks purging can be a slow process.