Hello fellow SkodaMotorDoters.

I have a '96 pre-facelift 1.3 glxi Felicia stuck at the bottom of my road with no spark. It cut out completely whist driving.

I was looking for any clues as to the problem. I've scoured these pages for hours and I'm still not very much wiser...

So it's either a sensor, the ECU or the coil - the black lead to the coil has power... I'll go test the green one when the engine's turned over. I've also seen mention of imobilisers, is there one on this model?

The timing (Hall?) sensor is clean, I doubt the throttle body would affect the spark unless a sensor in there is dirty - is there one?

I will admit to it needing a service...

(I'm an old school mechanic, points & carbs).

I knew a Haynes would have come in useful sometime - why are there no wiring diagrams online???

Any more clues will be much appreciated.

Thanks,

Tone.

the first thing i would check is the hall effect switch, they can appear to be in good condition when they are actually stuffed

Is there a simple test that can be done with a test-lamp or is it a case of swapping it out for a new/good one? And is that the flywheel timing sensor?

Check the coil, remove it and visually check for signs of damage, for a burning smell and se if you can measure any resistances through it.

The ignition coils have testing points under a cover. The procedure using a multimeter is explained in the haynes manual.

Thanks: I have no multimeter nor a Haynes (I know, I know... I've got maybe 30 Haynes but none of them are injection/ECU cars). I've had two tool kits stolen and now rely on pound-shop specials lol! & I was last a mechanic in 1989...

I reckon that if I'm NOT getting a feed through the green ignition wire when the motor's cranked, then the fault lays before the coil and if there is a feed, then it's the coil.

I've also realised that it could well be the TB (throttle body) that needs cleaning as I just changed fuel supply and as previously mentioned, it does need a service. Roll on Friday, when I get paid!

If I could get it home I could tinker to my hearts content.

Right, off to play...

Right: Constant feed to both terminals under the cover & no feed from the green wire - might that be the ecu return circuit?

The coil has no external damage (burning etc.) & there's no spark when using a plug lead instead of the king-lead.

Had the air filter off, butterfly & venturi/TB are clean, no corrosion on any sensor terminals.

Does any of the ign. circuit have a fuse? I'll check the manual!

i'm assuming it's a single point injection model with the bosch motronic ecu right??

on the ignition coil the black wire should be a permanent live, the brown wire goes to earth, and the green wire is the signal wire from the ecu which tells the coil when to fire so it should pulse at half the engine speed when the engine is running

i'm assuming it's a single point injection model with the bosch motronic ecu right??

on the ignition coil the black wire should be a permanent live, the brown wire goes to earth, and the green wire is the signal wire from the ecu which tells the coil when to fire so it should pulse at half the engine speed when the engine is running

Yep, SPI with Bosch electrics. There's no feed at any time to the green ign. wire, so I guess the fault lays before the coil and whilst I may be wrong, I doubt any injection management sensors would cause the ecu to stop sending the pulse (two per rev., it's a 4 cyl. motor, two fire per complete rev. :P).

That brings us back to your original hypothesis of it being the Hall Sensor (about which I know a whole lot more now!). 5v magnetic induction sensor creates square wave pulse in close proximity to a magnet - basically replaces the points & lobes from a dizzy. Failure rates for Hall Sensors are approx 10 per million per year. Also used in abs sensing.

It's not an injection side sensor fault as I just remembered that I smelled fresh petrol when I removed the air filter, so that's working...

Now I'm awaiting email quotes for a replacement (edit) Hall Sensor/Sender.

Thanks Teflon - oh and I love your post concerning the Q-Car! I read it all with wonder & admiration.

On a slightly different track, but related: Would the dizzy from an MPI fit (if I extended the loom to use the hall sensor in there) and if so, would there be any advantages?

Oh, and it's home now.

OMG!!!

Your quote consists of 1 part(s):

----------------------------------------

Part Request Ref: 955867

PartType : Engine

Part(Details) : hall sender,  

Part Condition: USED

Price : £45

Part Warranty: 30days

----------------------------------------

Additional Information:

Delivery : £15

VAT : £10.50

Total price : £70.5 (inc VAT and Delivery)

Can anyone do better please???

Have you tried Butts of Bawtry?

Skoda Parts & Accessories

Might be worth a shout. Otherwise local scrappies?

Previous quote was a used one from a scrappy.

I just managed to get through to Farmers Skoda (after trying all day...) and a new one is £38 + VAT! And one in stock.

Bonus is that I live less than 2 miles from them. I could be back on the road by teatime WOOOOO!!!

S*** I haven't got cash til Weds... :(

It looks like the pushbike is going to be needed after all :eek:

OK. One £2 scrapyard replacement, albeit off a P reg 1.3 injection which is a slightly different unit with no wire coming off it, yet has the same connection, Hall sensor later and I have two Hall sensors and a flattening battery... (I've got a charger, it's all right ).

Any more suggestions please? (other than buy a NEW Hall sensor - or am I too trusting in scrappy replacements?)

Thank you in advance.

Oh, I'm off to get a Haynes now/soon.

immobilizer fault then!

I don't think it's got an imobilizer on it. The key head is empty (I checked) and if there were an imobilizer, it'd have a red flashing light wouldn't it? It would also usually be the battery in the key at fault & it doesn't work with the spare either. (That was actually the first thing I tried when I got it home.

Off to get a Haynes now. £17.99 and up a BIG hill on my pushbike. :eek:

At least I'll have a wiring diagram!

they dont have batteries in the keys because it is a passive transponder

Haynes is a big help isn't it???

Two paragraphs describing what it does, then one wire & a big black arrow from the ECU saying "Immobiliser!"

I bet this isn't going to be pretty :(

Is the chip under the Skoda badge in the key? Because like I say, otherwise the key head is empty and I have no red flashing light.

You know what? I didn't actually check the 3 fuses that control all this stuff too

Oh well, it was worth a look anyway... Fuses all fine.

I've just been having a deeper look at what else may cause this problem. Might it be the temperature sensor on the back of the inlet manifold? If it can produce an ECU code would that be enough to disable the ign. circuit in the ECU?

I'm deffo going to change the Lambda sensor too! Poor fuel consumption, none of the other symptoms of it failing though.

Might it be the temperature sensor on the back of the inlet manifold?.

that wont stop you getting a spark

I've bypassed the imob, tried new(ish) Hall sender, swapped ECU, fully charged battery and STILL no spark :(:(:(

Utterly utterly frustrating!

Will a Skoda dealer be able to test Hall & ECU off the car?

The ECU should generally be fine unless the fuse has blown I think. I'd imagine skoda would be unable to test it on it's own as they may not have the wiring loom. I am assuming they are still able to use the diagnostic socket for the bosch monomotronic system near the charcoal cannister where the battery is. It would need to be checked in place anyway while it has the memory maintained by the car's battery to check for fault codes.

Just trying to think of more simple things than expensive things. If you have swapped out the ECU and Hall sender I'd say it's a good chance the problem lies with neither of those, or whatever the problem is killed those and has killed the replacements.

Just to check, is the starter motor turning? (If not I'd suspect something to do with the immobiliser bypass, or it could even be the ignition switch itself [but you can tell if it is switching correctly as the brake warning light etc should come on]).

Have you checked/swapped out the ignition coil itself? (There are two test points for a multimeter under a small cover that can be lifted off to test both the low tension and high tension coil resistance, but even if these test fine, a fault is still possible I would guess.)

Is petrol definitely being delivered? Lift off the air filter box top and look at the butterfly under the injector while the engine is cranked, there should be a visible flow over the throttle body.

That's probably the limits of my knowledge I'm afraid.

i thought there was an immobilizer built in to the ecu??? if you have swapped the immobilizer then surely you will need to get the keys coded to that ecu?

i thought there was an immobilizer built in to the ecu??? if you have swapped the immobilizer then surely you will need to get the keys coded to that ecu?

Yes. Thanks Jeffers, I sussed that one after I'd fitted it & it didn't work. Saying that, if the immob was immobilised (bypassed) then I'm sure it would work...

Question: Does the fuel feed pump in the tank have a pressure cut-off switch? When I turn ignition on, it will pump for a couple of seconds then stop, as if building pressure up - 2 or 2.5 bar I've read here somewhere - or is is a constant flow/ bypass return system? The Haynes does not state which it is, though logic (mine anyway ) says the former.

I ask this because if it were the immobiliser, surely it cuts fuel off as well? After attempting to start the engine, there is fresh fuel IN the throttle body - by smell.

The ECU should generally be fine unless the fuse has blown I think. I'd imagine skoda would be unable to test it on it's own as they may not have the wiring loom. I am assuming they are still able to use the diagnostic socket for the bosch monomotronic system near the charcoal cannister where the battery is. It would need to be checked in place anyway while it has the memory maintained by the car's battery to check for fault codes.

Just trying to think of more simple things than expensive things. If you have swapped out the ECU and Hall sender I'd say it's a good chance the problem lies with neither of those, or whatever the problem is killed those and has killed the replacements.

Just to check, is the starter motor turning? (If not I'd suspect something to do with the immobiliser bypass, or it could even be the ignition switch itself [but you can tell if it is switching correctly as the brake warning light etc should come on]).

Have you checked/swapped out the ignition coil itself? (There are two test points for a multimeter under a small cover that can be lifted off to test both the low tension and high tension coil resistance, but even if these test fine, a fault is still possible I would guess.)

Is petrol definitely being delivered? Lift off the air filter box top and look at the butterfly under the injector while the engine is cranked, there should be a visible flow over the throttle body.

That's probably the limits of my knowledge I'm afraid.

All lights come on; all fuses are fine; engine turns over fast enough that full oil pressure is attained (after re-charging the battery); the switched ignition feed (through fuse 20) also sends power to the black terminal on the coil which has power, the green lead to the coil from the ECU will, when operating correctly, have a 12v pulse at twice engine speed to charge the coil in readyness to discharge the HT circuit through the spark plugs, this does not have power.

The Hall sender has a constant 5v feed from the ECU to power it and this in turn sends a return pulse to the ECU at TDC & BDC to tell it when to send the coil pulse and to open the injector depending on load (throttle body sensor), engine temp (temp sensor on inlet manifold), combustion efficiency (Lambda sensor) and engine speed itself (Hall sender).

Actually, I've just had a thought: If the coil has a constant power feed then why? The coil does not have a switch in it & certainly not a timed switch (that's the ECU). The green lead can ONLY be an earth return through the coil to the ECU (you'd have to know how a coil works) and this is how the coil is charged & spark is timed. On an old points system, the earthing of the coil through the points is what discharges the coil. To test that, I would put the lamp across the black & green wires to the coil (disconnected) and if I get a pulse when the engine's turned, it's a faulty coil - which it almost certainly is now.

The only test equipment I have is a lead-lamp and both the test terminals under the cap have power & that's all I could say. I know that these are used to test resistance, so my tests were inadequate.

My only question now is: Why didn't I take the coil from the scrappies too? :lol:

Back on the pushbike

Thank you for allowing me to brain-storm :P