Can someone please tell an electrical/electronics numpty how an immobiliser works? 

Does it stop the engine turning over? 

1999 Felicia 

Thanks 

 

Thanks Ricado, that's helpful. I still don't know what the fault is but I think I can eliminate the immobiliser. 

If the engine isn't turning over, check the wire/connection to the starter solenoid. This is the thinnest wire going to the starter/solenoid assembly.

If it's anything like a mk2 Golf this connection isn't weatherproofed, but should've been, so corrosion can cause loss of action.

Thanks Wino, the engine is turning over but not starting.

Last Saturday it suddenly died as I was driving. The battery was red hot and flat so probably the alternator over charging. Fitted new battery so it now turns over but will not start.

Was told it could be immobiliser prob hence the question. I've been told I need to get an auto electrician to test it but can't afford their high charges. 

Not sure what to do next. 

18 minutes ago, LEricG said:

it now turns over but will not start.

Well, you clearly have volts, but not one or other (or both) of fuel and sparks.

 

So does the exhaust tailpipe smell of petrol?

Fuel and sparks are what I was going to try to have a look at soon. 

No noticeable smell of petrol at the tail pipe a few minutes ago. Tried turning engine over for a minute but still no smell. 

@LEricG

The most efficient method to diagnose the no start problem is to use a so called VAG-COM interface and associated software running on a laptop and connected to the OBD socket of the car. Since you mentioned you are a newbie in electrics/electronics the best viable alternative is to ask the closest owner of said interface to help you diagnose the fault and gather evidence. Have a look at this topic to see the map of UK owners and ask for help.

 

Meanwhile give us more details about the sudden engine stall you experienced while driving. Then tell us what did you do after that. How did you get the car home? Can you relate it to other event? The problem may be as simple as a blown fuse or corrosion in a connector. Other times it is the crankshaft position sensor. The overvoltage you talked about is based on any evidence? Because we could make a long list of potential faults, it is important to tell us everything you remember about that incident. Otherwise we shoot in the dark.

The engine just stopped and I had to coast into a nearby lay-by. I don't remember any noises or anything. I tried to restart it but the battery was flat - just enough power for the instrument lights to be on. When I looked under the bonnet I found that the battery was very hot.

For most of the previous week, there had been a weird smell every time I drove the car but could not figure out what it was. It was at this point that I realised it must have been the battery overheating.

I got someone to take me to a nearby garage and bought a new battery. The salesman said it is probably the alternator overcharging the battery and said if I took the car straight back after fitting the new battery they would test the alternator.

Having fitted the new battery the engine was turning over well but would not start - no sign of it firing, so left it in the lay-by.

Phoned the garage who said it could be an immobiliser issue, as already explained, and he said to lock, then unlock the car and if it is the immobiliser that should fix it. Unfortunately, my driver's side lock hadn't worked for a long time -  had to lock and unlock from the other side.

 I went and bought a tow-pole and my wife towed me back home. I ordered a pair of new locks and fitted one when they arrived. Of course, it is an uncoded key - not sure if that makes any difference.

I'm not sure if there is anything else that  I can add but will post again if I think of anything.

Thanks

1 hour ago, LEricG said:

Phoned the garage who said it could be an immobiliser issue, as already explained, and he said to lock, then unlock the car and if it is the immobiliser that should fix it.

 

Apparently your garage don't know Felicia. Central locking is primitive and has nothing to do with immobilizer at all. 

If you had Immo issue, you'd be able to start for few seconds, before immobiliser cuts off fuel supply.

Did you check fuses? When you switch ignition to light instrument lights, can you hear fuel pump running?

Can't say I've ever really noticed the sound of the fuel pump running. Had a listen just now but difficult to hear anything here beside a busy road but couldn't hear it. When the missus gets home I'll get her to turn the key while I stick my head under the bonnet.

As to the fuses, I just checked and the number 20 (ignition module, engine control unit or carb) had blown so put a new one in. That one blew (unless it was already blown - forgot to check before putting it in) Put another in but still not starting.

One thing I meant to say in my last post, but forgot, is that I've been having a bit of trouble for quite a while now and that is that, when starting the car, if I am too hasty and release the ignition key as soon as the engine fires up but before it is properly running, when I try again it just keeps turning but not starting, but if I leave it for 15 to 20 minutes it will then start.

I've just had a thought; the fuel pump is close to the battery - the battery got really hot - maybe it melted the internal insulation on the wiring.

Crazy! I checked the fuses again and found that the fuel pump fuse had blown, so changed it. Still wouldn't start. Left it. After dinner checked fuses again and all OK, so turned on ignition just to listen for the fuel pump. From inside the car, I could hear a faint click coming from the direction on the pump. Got the missus to turn the key while I stuck my head under the bonnet - she accidentally turned the key too far a couple of times and (would you believe it) the second time the darn thing started up.

I've now got myself some breakdown cover but going nowhere till it kicks in tomorrow.

Many thanks to you all for your help: much appreciated. 

4 hours ago, LEricG said:

Can't say I've ever really noticed the sound of the fuel pump running. Had a listen just now but difficult to hear anything here beside a busy road but couldn't hear it. When the missus gets home I'll get her to turn the key while I stick my head under the bonnet.

Listening under the bonnet will not help. The fuel pump is inside fuel tank, which is under the rear seats. Remove the fuel filler cap and listen inside while somebody else turns ignition key on without trying to start the engine. You'll have to hear the pump buzzing for 3-5 seconds.

Now, from your description (which lacks the mileage of the car) I'd say the fuel pump is on its last leg. I'd be very reluctant to drive too far from home.

About the battery being hot: it could mean many things, one of which being voltage regulator faulty. You don't have evidence for that but if that is the case your new battery will cook soon.

When I bought the car, about 2 years ago, it had about 35k (genuine) on the clock. It now has about 50.5k. The previous owner had it for 14 years and hardly ever used it. 

Thanks for the info/advice. 

Ok, guys, I'm learning, thanks to all your help.

In case you missed it - the engine is now running but I now need to establish why the battery was overheating.

Having taken in all your advice (plus looking at the Haynes manual etc)  I've just checked the charging system with my multi-meter. Starting the engine and revving it way up (with headlights and heater fan on) the meter reads over 18 volts, with the meter probes on the battery terminals (as per the instructions in the Haynes manual). Way too high. That tells me that I probably need to buy a new voltage regulator (rather than buying a complete new alternator).

Before I go ahead with that I just wanted to check that I'm on the right track, or is there anything else I need to consider first.

Cheers

1 hour ago, LEricG said:

I probably need to buy a new voltage regulator

No "probably" about it!

4 hours ago, LEricG said:

In case you missed it - the engine is now running

Well, yeah, but let's hope the fuses blew up only because of overvoltage and nothing else had time to cook. Replace the voltage regulator with an identical one.

Yep, it's failed voltage regulatir. It's common fault on Magneton alternators.

 Just checking before I buy - Does this look like the right one?

https://www.ebay.co.uk/itm/GENUINE-SKODA-FAVORIT-FELICIA-ALTERNATOR-VOLTAGE-REGULATOR-115901253B/143147795846?fits=Model%3AFelicia&hash=item2154460586:g:FzEAAOSwbX5cc~~M

This is mine.

 

That is a Chinese overpriced part. Nothing OEM about it.

I am using HUCO 130954, made in Germany.

This one?

 

https://www.trodo.eu/alternator-regulator-huco-130954

 

Yes. Or here

Thanks Ricado. Got one on order. Do you think it might be possible to change it without removing the alternator? 

Normally yes.