75ZT Community

Car wouldn't start this morning - totally dead (not the battery, it's fully charged). Anyway, a little later it would start and drove fine. Then, once again it wouldn't and now it will!!

So my ever helpful son-in-law is taking it to his families car/van hire business where the mechanic has a code reader.

So, what do you reckon the problem is ?

I always get 'totally dead' clarified. Did the central locking / remote work to open the car? Did any lights at all come on the dashboard when you switched on the ignition? Any clicks or whirrs? Did the engine go round but just not actually start? I've been caught out by descriptions of 'totally dead' before where actually there was a lot of life.

Crank sensor

...but I concur with Duncan..

First guess is starter solenoid. But I need to have the answers above or it's a stab in the dark.

everything works as it should except it won't start because it doesn't turn over on the starter.

Diagnosis is Camshaft sensor.

If it won't turn over (that is the engine doesn't go round at all) then it's not cam sensor. It will be the starter motor or wiring. I refer back to my guess of starter solenoid as the most likely given the intermittent nature and symptoms. Other possibilities are worn out starter brushes, immobiliser relay (inside the immobiliser) or a dodgy wiring connection.

Kind of underlines the reason for clarification of the symptoms as I'd have understood completely dead to include no lights on the dash.

Good luck with the fix, but don't change the cam sensor just yet!.

Duncan wrote:If it won't turn over (that is the engine doesn't go round at all) then it's not cam sensor. It will be the starter motor or wiring. I refer back to my guess of starter solenoid as the most likely given the intermittent nature and symptoms. Other possibilities are worn out starter brushes, immobiliser relay (inside the immobiliser) or a dodgy wiring connection.

Kind of underlines the reason for clarification of the symptoms as I'd have understood completely dead to include no lights on the dash.

Good luck with the fix, but don't change the cam sensor just yet!.

If the camshaft sensor isn't working and it fails to send a signal to the ECU (Engine Control Unit) doesn't that prohibit the starter from turning the engine over?

There can be a problem with the started solenoid - you should find a repair kit on eBay

The engine ECU can't tell if the camshaft sensor is working until the engine is going round, so no it doesn't stop it. It doesn't send a signal until the engine is moving, so it has to turn over first.

I can say for sure that is true with the V6 (from when my cam sensor failed and it would turn over but not start) and it's the same with the diesels from reports I've seen. I'm 99% sure it's the same with the K1.8.

Duncan wrote:The engine ECU can't tell if the camshaft sensor is working until the engine is going round, so no it doesn't stop it. It doesn't send a signal until the engine is moving, so it has to turn over first.

I can say for sure that is true with the V6 (from when my cam sensor failed and it would turn over but not start) and it's the same with the diesels from reports I've seen. I'm 99% sure it's the same with the K1.8.

That would seem to negate the need for a camshaft sensor! If it's not there to stop the engine turning over if the timing is out I don't see the point in having it - ie. if the engine has to turn over for it to work any possible damage would already be done.

Oh. I see you don't understand how engines work, then.

It's there so the engine ECU knows whether the engine is on the intake or power stroke, so it knows whether to inject petrol or fire the spark plug. In a four stroke engine the crankshaft goes round twice for every once the camshaft goes round, so the camshaft sensor tells the engine ECU where it all is.

So I can assure you it's needed. And not to stop the engine going round. After all, cam belt failures happen while the engine is running and it's too late to avoid the damage when it fails, a sensor is no help at all.

My understanding of the K series is that the ECU takes only an initial message from the Camshaft sensor prior to starting - the Crankshaft sensor providing the information to the ECU when the engine is turning.

That's OK.

But please read my explanation again and then you may understand why your understanding is incorrect, as that's completely impossible since the explanation explains why any signal prior to starting wouldbe irrelevant.

Duncan wrote:That's OK.

But please read my explanation again and then you may understand why your understanding is incorrect, as that's completely impossible since the explanation explains why any signal prior to starting wouldbe irrelevant.

Duncan.

Yes, I do understand what you are saying - and I can assure you that I am fully versed in the principals of a 4 stroke engine I will however admit to not being an expert in Engine Management systems (i am a 'fogey', after all ). I'm from the carb, points, coil and plug era, which is why the numerous magazine features I have written and had published have appeared in magazines aimed at the classic market.

However, I wouldn't dream of talking down to people who do not know about such things

[quote="TourerfogeyI'm from the carb, points, coil and plug era[/quote]

Ah yes, a completely different era...

Wont start so stick a new set of points in, then a new set of HT leads, then a condensor, then a coil, clean out the carb and it should start.

Then to EMS. Connect the ECU to the right readers it will tell you what is wrong but there is so much to go wrong.