Turbo Double Relay Going Nuts

[M@tt 77]

Relays just click normally with me shorting them to ground, no hissing i'm afraid.

[All Praise The GTI 3]

sure thats fine mate. just glad you are helping

hope it doesnt cause you too much greif tho

[maxi 36 1 Cars]

yeah it's not making much sense mate. i'm planning on stripping it right back and going throuhg it a wire at a time. i'm away till sunday you ok to hang on till next week before i send them back?

 

i'm determined to get to the bottom of it

 

 

This is exactly what I did on one and still couldnt get the c*nt working!! Matt, I will put money on it not being the right wiring diagram for the car even though Autodata says it is. I dont care what anyone says, I have counted 5 versions of the loom in the past. Good luck with it.

 

Maxi

[M@tt 77]

ah ha!! we have success!!!!

 

I told you i would not be beaten by a poxy french wiring loom!

 

After a couple of weekends and evenings I finally traced the problem to one of the 12v feeds to the ECU.

 

Basically if you look at this diagram below from Autodata (same as haynes as well) you can see that Pin 27 of the ECU gets a 12v switched feed via pin 3 of the Double Relay(red line). However on this XM loom there was no pin 3 on the double relay connector at all. Instead someone had cut and joined the wire from ECU pin 27 to the wire from pin 10 Double Relay to ECU pin 3 but they had done this inside the ECU plug itself so made finding it really difficult! (blue dotted line)

 

Now on first inspection it looks like this should work and infact if you put a multimeter to the ECU plug pins you would register a switched 12v on these pins which is what you would expect with the ignition on.

 

However the way the engine works is that when the ec receives a signal from the CPS that the engine is spinning, pin 3 of ecu is pulled to ground so completing the primary circuit of one of the relays in the double relay and therfore opening the secondary circuit which provides power to the fuel pump and the coils.

 

Because the ECU switched feed to pin 27 was also being pulled to ground everytime the flywheel rotated that is why the double relay was constantly opening and closing.

 

So what i did was run a new dedicated switched live to pin 27 (dotted green line) and she burst into life first go!

 

 

any way just thought i'd share

[Goliath 94]

Nice going! I still havent got mine to fire up

[M@tt 77]

if you get really stuck box it up send it to me and i'll take a look for you

[Goliath 94]

I think all I need to get it going is a new ignition amp, but I cant find anywhere that sells them and there are none in the scrappy

 

Don't have a spare one do you?

[M@tt 77]

i haven't mate i'm afraid just got the one for my turbo

[pug_ham 240 3 Cars]

Nice one Matt, not the most obvious problem but at least its sorted now.

 

Graham.

[Henry Yorke 269 3 Cars]

Always the worst trying to sort out someone elses bodges in amongst old wiring. Been there before so that is why it took the plunge and had a new bespoke loom built for my skip, as I would have run out of weekends and patience (and probably ability!)!