Turbo Double Relay Going Nuts

[M@tt 77]

I'm having a look at a Turbo loom for Nat which doesn't appear to be working.

 

It's an XM loom (the same as my turbo conversion) so you'd think it would be straight forward in sorting it out!!

 

Anyway with the loom plugged onto my turbo engine it will not fire at all.

 

It appears to be sparking intermitantly or not at all. I've pinned all the essential connectors out and they all appear to be fine ie no broken wires, and the correct wires from the XM loom are mated up to the correct 205 loom wires and the double relay has the correct permanent and switched lives at the correct pins on the double relay plug. When you turn the key to the Engine ON position the first relay in the double relay clicks once which is correct, but when you crank the engine to start it you can hear the other relay going nuts ie opening and closing repeatedly really fast. As a comparison, my working loom just clicks again once as you crank it and it then bursts into life. The relay closing when you crank it is the one which feeds the coils packs and the fuel pump hence the no starting issue.

 

The ECU, Double Relay, Ignition Amp, TDC sensor & Coils are all working perfectly.

 

The tricky thing is that this second relay is closed by the ECU pulling to ground once it detects that the engine is spinning so it's a bit of a black box interms of whats going on. The TDC works fines as my looms runs fine and i've pinned out the TDC connector and there aren't any broken wires.

 

Any suggestions??

[pug_ham 240 3 Cars]

Is the main ecu earth connected?

 

The switched feed in isn't connected to the wrong side of the relay is it? (ie fuel pump, coil pack etc output?

 

Graham.

[M@tt 77]

it defeinitely sounds like some sort of earth or reversed polaity issue doesn't it .

 

all the earths have been connected and i'm pretty certain the switched live (32/2a from the 205 plug) has been connected up to the double relay wire correctly although i'll be double checking that tonight. it's got to be somethign simple!!

[pug_ham 240 3 Cars]

Have you tried your ecu?

 

It does sound to be something simple.

 

You said you've tested all the connections to the D/R & found them right so my initial suggestion might be worthless.

 

Graham.

[M@tt 77]

ECU works spot on with my loom plugged in everything runs fine, as soon as my loom is replaced with Nat's is when it doesn't work, so its got to be somethign wrong with the wiring somewhere but it's eluded me so far

[pug_ham 240 3 Cars]

I tried looking through my Autodata for the wiring diagrams but they don't have them listed for the XM.

 

All the XM 2.0t's are on MP3.2 so its hopefully a simple mixed up wire connection.

 

Good luck.

 

Graham.

[sonofsam 5]

Right this sounds exactly like my age old problem that I had with my 2.0T engine.. No spark and no fuel pump!

IIRC I had to hook up a new earth to pin 10 injection double relay, my car had been off the road for months

while we figured out what the hell was wrong and it was a

very stressful time indeed so I hope this can solve it and she fires into life!

[M@tt 77]

nice one Sam

 

I'll give that a whirl, i can see that it should work but that would indicate that ECU pin 3 is not pulling to earth properly by the ECU, but it obvioulsy is when the ECU is connected to my loom which is weird.

 

It does mean though that the that realy is premanently closed then when the ignition is ON so the fuel pump will be running even when the engines not running though

 

I'll give it a whirl and see how i get on

Edited March 16, 2009 by M@tt

[M@tt 77]

well last night if i unplugged the CPS the relay was not clicking when you cranked it so it's definitely something to do with the ECU receiving a signal from the CPS. I've belled out the 3 wiers from the CPS connector back to the ECU and all appear to be ok and none of them appear to be shorted with each other. I wonder if maybe there's any interference in the wire which could be causing the problem?

 

looking on the Autodata CD i can see that the ECU should have the following pins earthed

14

19

24

54

47

so i'm going to double check these are indeed earthed

[All Praise The GTI 3]

hello mate. not sure if it makes any difference but i think i told you on my gti the fuel pump wiring has been bodged in the glove box so the pump is on all the time when the ignition is on. although with the loom in your car this wouldnt effect it.

keep up the hard work

cheers

[pug_ham 240 3 Cars]

IIRC I had to hook up a new earth to pin 10 injection double relay

Looking at the MP3.2 wiring for the XU10J4 & autodata pin 10 from the D/R goes to pin 3 on the ecu not a direct earth.

 

On my Autodata, pin 14, 19 & 24 appear to be ecu switched earths & not permanent although one of them must be the main ecu earth to the gearbox stud.(19 sounds familiar for this)

 

47 & 54 are optional, 47 for the auto version & or H2O sensor.

 

54 just says some models but no designation what purpose.

 

Just a thought, was this loom out of a Keypad or auto XM? Maybe there is an wire or two extra that need to be wired in (or removed) to make it work?

 

Graham.

[M@tt 77]

it looks identical to my loom and both had a keypad as far as i can tell that has been cut out. The wires athat have been cut are the same as mine and my loom works.

 

ECU Pin 3 acts as a switched earth hence why connecting it to a permananet earth will work, but obvioulsy its not as intended and will mean the fuel pump, coil will get power even if the engine isn't detected as running.

 

ECU Pin 3 is supposed to be pulled to earth once the ECU detect the engine is spinning but the TDC sensor thus allowing fuel and spark, but on this loom it doesn't seem to want to keep it held to earth.

Edited March 17, 2009 by M@tt

[pug_ham 240 3 Cars]

Yeah, I figured from the diagrams I have that its a switched earth.

 

Maybe try giving it a permanent earth & see if that fixes it then.

 

Does seem odd that its lost the switched earth which is controlled through the ecu though, must be something in the wiring imo.

 

Graham.

[M@tt 77]

right putting permanent earth to pin 10 of Double Relay instantly brought the fuel pump on and put 12v to the coil plug. So i was confident it would start. Wrong!!!!!

 

took a sparkplug out and cranked the engine over again and i was getting no spark! I'm pretty confident its got to be some dodgy wiring from the TDC sensor to the ECU as its obviosly not knowing where the engine is in the cycle and so not sparking. The ignition amp and coil are both working perfectly as they run my car. So i'm tempted to run a new cable between the sensor and the ecu

[sonofsam 5]

Looking at the MP3.2 wiring for the XU10J4 & autodata pin 10 from the D/R goes to pin 3 on the ecu not a direct earth.

 

 

 

Graham.

 

Yes Im well aware of what the wiring diagrams dictates, however alot of these looms are different.

Like for instance 406 V's XM having different pin numbers on the double relay for its switched live connection

and inclusion of inertia switches and engine fuseboxes found on the later 406.

 

 

 

 

Getting closer though M@tt !

[All Praise The GTI 3]

the engine was from an auto xm with keypad. altho when i went to remove the engine i didnt have to enter a code as the guy said it was in safe mode???

not sure if any of that makes any difference

[maxi 36 1 Cars]

I really feel for you Matt! Those poxy 2.0 turbo looms can be a bastard to say the least! Ive had identical problems to these in the past. I spent a month of weekends trying to get one started in the past, going over and over the wiring diagram, belling out every connection in the whole loom and still no joy. In the end with that one I changed the loom and it went first time. I think it all breaks down to the fact that there are around 5 variations of the loom.

 

Good luck with it, poxy things!

 

Maxi

[M@tt 77]

well i've spent another fruitless evening on the sodding thing.

 

I made a new lead from the TDC sensor to the ecu plug from a shielded mic cable, but it made sod all difference. I also discovered that earth wire for the other relay that powers the injectors also wasn't pulling to ground so i had another stroke of genius to earth that wire aswell thinking right, fuel pump is running, injectors will have 12v to them, the coil and ignition amp have power to them so it must start!

 

Wrong!!!

 

still no spark

 

It's got to be TDC related though surely as the i'm sure the ecu should pull these 2 none working earths to ground once it detects the engine is spinning and also controll the spark. The TDC sensor and ECU definitely works as it runs the car with my loom in place

 

can anyone confirm exactly what needs to be plugged in for the car to be able to start just incase i've missed something obvious (but i'm sure the other loom i've tested for Nat worked with only these things plugged in as well)

 

I've got the

3 throttle body sensors

ignition amp

coil

TDC sensor

ecu temp sensor

double relay

ECU plug

[Miles 331 1 Cars]

What amp is it? MTR 04 I guess

[M@tt 77]

yeah its the proper xm amp.

 

I've got nat's which worked with the first of his looms and also mine again which works fine

[Miles 331 1 Cars]

BFOH?

[M@tt 77]

gettig close to it or a large pair of wire cutters

[All Praise The GTI 3]

its stil being a pig i see then

after i filled it up with petrol and then it stopped working again i nearly got my box of matches out

[M@tt 77]

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

[Goliath 94]

What sort of clicking noise is it making Matt? Normal relay clicking noise? Mine is making a very quiet 'hissing' type noise, its the sort of noise you get when a wire is shorting out and is about to catch fire which is a bit worrying!