the number of times I come on here to piss and moan about my car I should probably

a) give it a name out of courtesy
b) get the mods to stiky it!!

Anyway, for the last few months its been a none starter, well sometimes anyway. Turn key ignition light comes on (i.e. everything working, but alternator not spinning yet), turn one notch further, light goes out, but nothing else happens 🙁

Assume that it's a dodgy solenoid (it's only intermittent), so I check it this morning, starts first time, "ahh well" says I, I've got the part now, I'll be done in time to get to the shops to buy some bacon for a lunchtime sarnie.

Does it work now, does it f***!!! Ignition light now comes on, and stays on through the entire process. Checked all the connections, checked there's a voltage getting to the solenoid, there's a voltage through the solenoid, there's even a voltage at the coil where (AFAIK) the starter solenoid earth's itself (oddly, onto the +ve terminal, presumably this is +ve when the engine is running and as a results makes sure the solenoid is firmly shut).

Grrrrrrrrrrrrrrrrrrr, can't figure it out. Must have nudged something with my elbow while fitting the new solenoid, most likely somewhere between the solenoid and its earth, but can for the life of me figure out what.

Have you tired this?

I used to have a fiat X19 Bertone which gave me constant electrical grief,including the headlights opening and closing at random and a dodgy starter motor.

When I contacted the owners club to try and get a plausible wiring diagram, they pissed themselves laughing and suggested that I start all over again as the diagrams they have only actually apply to the cars it was taken from, as they tended to be wired with whatever was lying around the Bertone bit of Fiat's factory.

Mind you, at least it didn't have electrics by Joe "Prince of Darkness" Lucas.

I always used to smack the solenoid with a shifting spanner before turning the key.:)

This earthing through other things is rubbish.

I have progressively given everything it's own earth. It makes fault tracing a lot easier next time round. If coil needs feed, give it a new feed from the ignition.

It could be the ignition switch on it's way out, used to be a very common problem with old Vauxhalls, and I've recently had similar problems on my campervan. What makes it hard to diagnose is that when you turn the key to ignition voltage passes, so a multimeter on the solenoid terminal shows 12v, but the contacts are worn so there isn't enough current to engage it. Try pulling the plug off the switch and hotwiring it.

I had a similar issue on a Triumph Herald and it was an earthing issue – there was corrosion around one of the engine earth points.

I ran an earth lead straight fromt he engine to the battery in the end and never had another issue.

where (AFAIK) the starter solenoid earth's itself (oddly, onto the +ve terminal,

if the solenoid is erathing to +ve that's a problem

yep i had an imp that did that.

major things to check, batter lead to solenoid, solenoid (test direct to battery), battery earth lead starter motor and engine to chassis earthing

Intermittant faults are always a PITA. You must eliminate the switch
– by pass it – dirty contacts within the sw.can do this + ensure that the starter motor is properly earthed & as rootes1 says check the battery to chassis earth ;-take the leads off the battery and check that they are clean internally + clean the batt. terminals

after a bit of digging (why don't lucas have a clear explanation about what terminal does what?) the solenoid is supposed to be earthing itself through its body, the second lead is just a cold start lead to the coil, gives it a big juicy 12v while the engine startsrather than the ~7v it normaly runs on.

Still no idea whats going on, cleaned off the solenoids mounting screws and still no joy.

Missus is picking up a new multimeter from maplins at lunchtime so will be doing some conductivity testing to try and find the problem.

What's odd is the problem was fairly definately a solenoid problem before, so that only realy leaves the new solenoid to be faulty as well? Lucas prince of darkenss is on the rampage!

everything works appart form the engine (lights, wipers, horn, etc etc) so the battery connections are obvioulsy ok. Or should at least be ok enough to click th esolenoid.

What gets me is the old problem resulted in the ignition light going out when switch was turned, the new problem means it stays on. It worked sunday morning, grrrrrrrr, realy need a car for wednesday morning, not good.

Not always I've had lights etc work but not a good enough contact for the starter motor to turn. Can you bypass the starter switch?

I am going to say ignition switch again, AFAIKR most switches disconnect one of the circuits while cranking, hence the ign lights going off, the light staying on would seem to indicate thats not happening. If you can get to the back of it with a multimeter work out which wires need to be connected to live and bridge the starter circuit. When I ran a motor factors I'd say 90% of the starters that were returned as faulty but bench tested ok were fixed with a new ignition switch, the other 10% were earth/power problems.
What car is it?

1975 MG midget,

the problem was a second duff solenoid, the new one was even more duff than the original!