Revmeter again.

grinder · April 10, 2009, 10:13:30 AM

i cant see why you would need the rev counter to work for the car to run - it just seems dead strange to me thats all

if the rev counter is linked to the ecu - can you not meter it out at the ecu - and see what voltage you get from it ??

if the rev counter is playing up - the meter would show the voltage changing aswell

then its a case of chasing wires

pdtaylor18 · April 10, 2009, 10:38:12 AM

Bang on mate, I think we need a little more info as to what the engine is doing in relation to the rev needle. You do not have to have a working rev meter for an engine to work, however if that rev/RPM wiring is faulty all the way from the coils then the imput into the ECU is also wrong and that will upset everything inside and also the outputs. I think Daves initial diagnostics for the cutting out is an AFM is highly likely the culprit but this could also be linked to a fuel pump. I had almost the same problem on the white FC and it was the pump. In this case he is seeing the needle go down or bouncing,engine juddering etc and thats because it is,his engine is probably on the brink of cutting out, so there is probably nothing wrong with the meter or rpm side of it as this is just the symptom and not the fault. His original post was about cutting out and similar fault as above and it looks like nothing has changed.
Apart from wiring lets look at a list of items that could cause this and hopefully he can check them one by one and get to the root cause.

Coils
Distributer
ECU
AFM
Fuel Pump(inc relays etc)
Fuel filter

The only way to check most of the above is to swop stuff over but you should be able to get resistance and voltage checks and most of the above to check correct. Coils rarely go wrong,same for ECU\'s as well unless they have got wet. I would focus on AFM/fuel and they are relatively simple things to test.

dthebuk · April 10, 2009, 01:11:01 PM

hokay, the cars completely dead now. Starter works fine but the spark plugs just arn\'t getting anything.

pete: thanks for the offer but i don\'t think its the distributor as the leads going into it arn\'t getting anything. Also when the rev counter fluctuates it doesn\'t affect the actual revs on the engine, though it will judder/misfire sometimes.

grinder: thanks for looking though all those threads, legend

prof: tried wiggling some wires and it did actually seem to help, but now the problems gone too far. As for the AFM, would that that really stop the spark plugs sparking? I shall give it a look anyway!

got a few days off work so i may just just taking everything apart and putting it back together:D got nothing to lose now.

edit: just read your last two posts, i shall have look. Im guessing checking all these things will be in the haynes manual, so i\'ll get on it, then start chasing wires. Just to clarify, sometimes the rev counter would drop off completely and i would be driving for up to 10 minutes without it. Also its good to know that that is likely to be a symptom more than the fault. cheers guys

pdtaylor18 · April 10, 2009, 01:41:17 PM

Theres also the main relay if the EGI\'s have it, TII\'s are by the charcoal canister area, theres also a relay under the steering colume,again I can only assume its roughly the same as TII\'s for the basic stuff in wiring and relays etc. The one under the steering cowling is black/yellow in colour. If you need any of those then send a pic of your old ones and I will gladly send any of that stuff as i do have quite a few.
If its completely dead then at least you have to start with the basics now:

Dead why? do you have fuel pressure? do you have spark and where at?
if you are not getting spark to the distributer then the problem lays at the coils or the power going to the coils. Something worth looking at is your main EGI fuse,make sure thats in and a snug fit. Good luck and keep us imformed as you go along. I will have a look at the diagram and see if there are a few pointers for you if you have no luck.

dthebuk · April 10, 2009, 01:45:09 PM

dead as in it just wont fire, its not getting any spark. Checked the fuses first thing and they wern\'t broken, could be different now that the problem has worsened

Prof · April 10, 2009, 01:54:47 PM

Just been looking at the wiring diagram for the EGI - the coils and injectors get there feed from the same power source, which comes from the main relay - the one tucked in the corner by trailing coils - it has 2 feeds coming from it - one feeds most of the 12v power in the car - ECU etc, the other one is only used for the coils and injectors.

On the passenger side shock tower, there is a small black capacitor - the wire leading to that is also connected to the same voltage source - if you can get a multimeter on that and check that you have 12V there.

The tach take off comes from the rear coil, but the coil gets the signals first from the ECU - and then it\'s passed to the other circuits (rev meter) etc.

grinder · April 11, 2009, 12:19:43 AM

if you get the full manual it will tell you what ohms / volts you should get on most components - so might be worth having a read of that - and then just checking everything has 12v

is you car making any funny noises ( clicking etc.. ) - i went thru a 14 page thread trying to get my cab to run - in the end it was the ecu

but i checked SOOOOOOOOOO much stuff it was unreal

its a pain now i know - but once its running again - you will have learnt soo much stuff

i think they main thing is to try and get one thing working , then move onto the next etc..

so start at the relay that dave said - or even the ECU and just starting tracing wires

dthebuk · April 11, 2009, 02:18:02 PM

ok havnt been able to get much done, been busy grrrr.

anyhu, coils are fine ive just checked them and im about to look at the crank angle sensor/distributor. anyhu, my dad looked through the wiring diagrams and seems to think that connector f39 could be a problem. Can anyone tell me where this is/how to locate it?

thanks

dthebuk · April 11, 2009, 02:26:43 PM

ok, having troubles checking the distributor. Its different to every manual i have!

dthebuk · April 11, 2009, 03:17:04 PM

right it seems the s4.5 ignition system is different to every other FC!!!
look

these are only ignition coils i have, all the other cars seem to have more.

Anyhu, ive managed to check the 2 cables going into the distributor and thats fine, as for checking the distributor itself im not too sure on how its done, as i don\'t seem to get any readings when checking it ??

also prof is this the place you were talking about with the relay and the cables?

not sure what i need to check and where tbh, my electrical skills are somewhat limited

thanks again

dthebuk · April 11, 2009, 05:46:14 PM

ok the car has decided to start working again now.... if its working how can i test for faults?

Prof · April 11, 2009, 06:08:58 PM

Quote from: dthebuk;598213ok the car has decided to start working again now.... if its working how can i test for faults?

Going to be difficult to do that

That pic is the Main relay - I was looking at your ignition circuit - and you kept talking about distributor - then it dawned on my that your car isn\'t wired up the same way as an N/A in the field service guide.

Your dizzy sits on the worm gear that would normally have the CAS sensor - and because you have a Dizzy - you only have 2 coils - not the normal Leading / Trailing coil setup that we have in the S5 Cars. The Service guide - and Haynes - show only the US setup - with fully electronic ignition.

Not sure what provides the signal to fire the coils - is there some low voltage take off that goes to the ECU off the Dizzy ? Likewise the injectors would need a similar (the same?) signal to fire also. I don\'t think I have a circuit for a dizzy setup with ECU.

pdtaylor18 · April 11, 2009, 07:05:03 PM

Well what did you touch to get it working again?
I have an S4 main relay mate,send me your address and i will pop one in the post for you, no good to me as the connectors are different for the S5 ones, at least you will have a spare.

dthebuk · April 11, 2009, 07:50:17 PM

Quote from: Prof;598218I don\'t think I have a circuit for a dizzy setup with ECU.

does such a diagram exist?

thanks for the offer pete, i might just take you up on that, ill send a pm in a min.

i had a play around with the wires/connectors in the second picture i posted. Is this where the relay you suggested is prof?

And another update, i just took the car out for a drive. Its not completly problem free but the problem is now different. Occasionally under acceleration at around 4 - 5.5 krpm the rev counter will start going crazy (inbetween the two readings) and will over read. Though has no effect whatso ever on the engine. The rev counter did not drop once and the engine was running smooth as...apart from the horrendously loud backfiring

Prof · April 11, 2009, 08:25:54 PM

Quote from: dthebuk;598252does such a diagram exist?

thanks for the offer pete, i might just take you up on that, ill send a pm in a min.

i had a play around with the wires/connectors in the second picture i posted. Is this where the relay you suggested is prof?

And another update, i just took the car out for a drive. Its not completly problem free but the problem is now different. Occasionally under acceleration at around 4 - 5.5 krpm the rev counter will start going crazy (inbetween the two readings) and will over read. Though has no effect whatso ever on the engine. The rev counter did not drop once and the engine was running smooth as...apart from the horrendously loud backfiring

Yep that metal can thing is the main relay.

The 2 smaller wires are the relay coil, the other wires make up the 2 main circuits. I\'m guessing the coils / injectors will still get their 12V feed through a fuse and that relay - so it should be possible to test that bit of the circuit and at least prove that part is working. Beyond that I\'m a little in the dark on this one.