remove wiring loom

[mike 850]

not sure if its obvious yet as i haven't looked but how do you get all the wiring off to the ecu box?

thanks

[Jamest5r]

You mean the engine bay loom?, if so it splits under the ecu case.

[Nealevo]

^^^^^ just borrow a James, he did mine lol^^^^^

[mike 850]

cool, got it. thanks just need to do some testing tomorrow :B_thumb:

[Jamest5r]

cool, got it. thanks just need to do some testing tomorrow :B_thumb:

What's your problem?

[mike 850]

starting issue mate, done pretty much everything now so going through the loom and making sure there are no shorts or open curcuits

[Jamest5r]

starting issue mate, done pretty much everything now so going through the loom and making sure there are no shorts or open curcuits

Ahh my favorite topic lol, been through a year or so of that one.

[mike 850]

yeah its a bit of a pain, im glad its not my daily driver! basically no spark, plenty of fuel. checked cam sensor and getting a nice fluctuation of 0-5volts by the sensor so now moving onto the wires by the ecu. did you solve yours?

[Jamest5r]

yeah its a bit of a pain, im glad its not my daily driver! basically no spark, plenty of fuel. checked cam sensor and getting a nice fluctuation of 0-5volts by the sensor so now moving onto the wires by the ecu. did you solve yours?

Mine was....god know's lol, problems with mapping i think after changing everything in the bay including the loom lol, but still would only start when it felt like it, changed the clutch about 6 months ago and now it starts everytime.....dont ask i have no idea.

[mike 850]

yeah mine makes no sense, only causes problems on the first start of the day, after that its fine, even when i start work at 7:30 and its left till 5 it still starts fine, only when left over night. and you can bump start it and it works straight away

[merc85]

The ecu box comes apart, then you are lift with just the base, take the rubber mate bit out, leaving a alloy floor exposed, this is in 2 halves, theres around 6 locking tabs that you need to prize the ally out of then the alloy floor comes apart, within it is 2 multiplugs, these have 2 sprung loaded tabs under neath,

Press the srpings in then slide the connectors/multi plug out, simples. ;)

[mike 850]

got it all out earlier and spliced a wire to the cam sensor and coil signal wire so i can check what they are doing tomorrow.

[nobananas]

got it all out earlier and spliced a wire to the cam sensor and coil signal wire so i can check what they are doing tomorrow.
This probably won't be of any use to you mike but I noticed when mine died on me on holiday (no spark, no cam signal, was rotten wiring to relay under slam panel) that an 850 won't start with the cam sensor unplugged but if you unplug the cam sensor with the engine running it won't cut out (just runs as normal, but I assume the injectors resort to batch firing rather then sequential)

[mike 850]

thanks mate, i've got a bit more info now just not sure on the solution yet, basically I measured the trigger wire voltage to the coil and i increases to about 0.2-0.3 volts when cranking, occasionally this will spike to 0.4 -0.5 volts and this is when she will start, so the issue i have is the signal is not strong enough, once its started it measures .5v constant, from tests ive read it should be .7v so im wondering if i could use something to step up the voltage a bit? or if anyone has any ideas??? i tested the cam sensor and that works perfectly and I think i can assume the other sensors do to otherwise i wouldn't get a signal at all?
thanks

[mike 850]

also turns out the injectors have power but no pulse while cranking then it kicks in and works and starts pulsing??

[Jamest5r]

Crank sensor playing up?

[mike 850]

not sure, the resistance on the crank sensor is just under 300 so bang in the middle of the recommended 200-400 range,any ideas what kind of voltage or signal the crank sensor should give? just so i can make sure its picking up ok, although there are no fault codes

[nobananas]

I usually check hall type sensors with a multimeter set as low as it will go on voltage then take the sensor out, hook it up to the meter and wave something metal in front of the sensor and you should get a spike on the meter. The injectors are earth switched through the ECU so the ECU doesn't sound like it's receiving a signal from either cam or crank. Sure you have but have you checked the wiring and operation of the relay under the slam panel, your symptoms sound the same as when I found the rotten wiring on mine.

[mike 850]

I have ordered new bullet connectors to re-wire the relay, but it looks like its working ok, i will have a look at the crank sensor, tomorrow

Cheers

[merc85]

I usually check hall type sensors with a multimeter set as low as it will go on voltage then take the sensor out, hook it up to the meter and wave something metal in front of the sensor and you should get a spike on the meter. The injectors are earth switched through the ECU so the ECU doesn't sound like it's receiving a signal from either cam or crank. Sure you have but have you checked the wiring and operation of the relay under the slam panel, your symptoms sound the same as when I found the rotten wiring on mine.

If it was the injector driver rely playing up, He wouldnt have any fuel going into the cylinders, he has fuel, just a intermittent spark.

[mike 850]

i thought i was getting fuel as it stinks of petrol after cranking but when I measured the injector 1 for pulsing it didn't pulse until it fired up so im really not sure although I thought the injector relay is for the power to the injectors not the pulse? as the power is there also the idle control valve works which I thought was driven by this relay too? any ideas what sort of voltage the crank sensor should return or the best way of testing it?

[nobananas]

i thought i was getting fuel as it stinks of petrol after cranking but when I measured the injector 1 for pulsing it didn't pulse until it fired up so im really not sure although I thought the injector relay is for the power to the injectors not the pulse? as the power is there also the idle control valve works which I thought was driven by this relay too? any ideas what sort of voltage the crank sensor should return or the best way of testing it?

Yeah, looking on auto data that relay gives a 12 v feed to the injectors, maf, IAC, evap and the bcs.

[merc85]

When my loom went faulty i had wet spark plugs after cranking, so if yours are dry perhaps it i the relay

[mike 850]

well i think i can rule that relay out then because I am getting power to the idle valve etc, the only thing im finding difficult is testing the signal from the crank sensor as I think this must be the key, I have spliced a external wire from the blue and red/black wires from the crank sensor but not sure how it works? would I measure the voltage across both wires or earth the voltmeter and check 1 wire? hopefully you might know? the resistance of the sensor is fine but that still doesn't mean its picking up a signal and sending it to the ecu.

Thanks

[Jamest5r]

Try testing the actual plastic bit that the crank sensor join's the loom, yeah its a long shot but your in that area now lol, few years back i had a problem and no matter how many crank sensor's i changed was always the same, it was the plastic bit on the loom side at fault snipped one from a breakers twisted 2 wires together about 5 mins works to solve a problem id had for months lol.

[mike 850]

tried swapping both cam and crank sensors also bypassed the connectors and still no enough signal to the crank, im starting to wonder if its my ecu? i will rewire that main relay next after that im stumped

[Jamest5r]

tried swapping both cam and crank sensors also bypassed the connectors and still no enough signal to the crank, im starting to wonder if its my ecu? i will rewire that main relay next after that im stumped

Time to hard wire the cam and crank to the ecu then.

[mike 850]

I think so too, I'll keep you posted! thanks for the help so far, im sure ill be asking for more....

[merc85]

Time to hard wire the cam and crank to the ecu then.

Da ja vu! it would seem...... doh:bricks:

[mike 850]

well, hard wired the crank sensor and cam sensor, still no different. i did notice with a voltmeter that the power to the cam sensor is about 10v and drops to 8 when cranking so I wonder if its not getting enough power when cranking? anyone any ideas where to go from here?

Cheers

[nobananas]

When mine broke down on holiday the cam sensor had lost it's 12v feed but that was that relay wiring again.

[Jamest5r]

well, hard wired the crank sensor and cam sensor, still no different. i did notice with a voltmeter that the power to the cam sensor is about 10v and drops to 8 when cranking so I wonder if its not getting enough power when cranking? anyone any ideas where to go from here?

Cheers

Merc85 is the one to ask mate he's been a lot further down this route than i have.

[mike 850]

well im stumped now, measured the output from the cam sensor and fluctuates from 0-5v likes it should, resistance on crank sensor is around 280 which is spot on, all this measured by the ecu wires so its getting everything it needs? the main relay is fine, getting 12v to the fuel injectors, fuel pump is priming and there is fuel at the rail, no pulse and no spark, ecu gone maybe???? anyone have an ecu i could try?

[merc85]

Are the injectors opening? if not it may be the injector driver relay. Is the crank sensor sending a (definitive) clear pulse, if its hazy the ecu wont be able to read it properly.

[mike 850]

How do i check if the injectors are opening? i only have a voltmeter. also how would i check for a clear pulse, there is definitely a signal with a voltmeter but not really sure how to read it either, thanks also where is the injector driver relay, i just thought there was a main fuel relay?

[nobananas]

The injectors basically will have a 12 v feed on one wire then the other wire is switched to earth through the ECU (earth switching means that the ECU is only switching a very low current ) so in theory if you disconnect an injector plug then use a test light or multimeter between the connector plug contacts you should see a flash or a pulse on your meter whilst cranking. A test light is always best for this type of testing as it gives an indication of current flow rather then just showing a voltage. Alternatively a very low tech way would be to spray a little brake cleaner or 'start yer' b'stard' spray into the intake. If it fires up then spark is all good but no fuel is getting in.

[mike 850]

just put a voltmeter on results are:
ignition on 11.5v
cranking about 9v fluctuating but no real switching

[merc85]

just put a voltmeter on results are:
ignition on 11.5v
cranking about 9v fluctuating but no real switching

Crank it over a few times, take a plug out and see if its wet, if its wet the driver is working, if there dry the relay isnt switching.

Its the grey relay under the front slam panel, other side to the cooling fan relay. :)

With regards to the signal you need to get what they call scoped., to check the wave pattern. its displayed on the laptop if its distorted that means there is a problem with the cranks sensor/ crank sensor plug or the flywheel.

[mike 850]

I think I may have it, was speaking to my neighbor and he had something similar with another car a few years back and it was an earth problem, try putting a jump lead from the negative terminal on the battery and clamp it to the block. Done this, fired up straight away, the test will be in the morning as it always struggled in the morning and slowly got to not working at all....

[merc85]

I think I may have it, was speaking to my neighbor and he had something similar with another car a few years back and it was an earth problem, try putting a jump lead from the negative terminal on the battery and clamp it to the block. Done this, fired up straight away, the test will be in the morning as it always struggled in the morning and slowly got to not working at all....

Finger's crossed unfortunately it didnt help mine :( keep us informed bud nowt worse than a Volvo not starting

[mike 850]

im much more confident this time as when I had the jump lead attached it starts up, take it off and it sits there cranking again, replaced the jump lead with a nice thick earth strap so hopefully. thanks for all the help though (trying not to get my hopes up too much!)

[Jamest5r]

I think I may have it, was speaking to my neighbor and he had something similar with another car a few years back and it was an earth problem, try putting a jump lead from the negative terminal on the battery and clamp it to the block. Done this, fired up straight away, the test will be in the morning as it always struggled in the morning and slowly got to not working at all....

Result :), will await the morning post :)

[mike 850]

Well, it started, took about 8 cranks but it started, so definitely better. the cranking was really slow but i have ran the battery down with all the messing around, gonna give it a good charge and see how it goes...

[merc85]

Well, it started, took about 8 cranks but it started, so definitely better. the cranking was really slow but i have ran the battery down with all the messing around, gonna give it a good charge and see how it goes...

Sounds like mine did :/

[mike 850]

did it just stay like that or did you solve it?

[V70 Graham]

did it just stay like that or did you solve it?

Afraid he didn't :(

[mike 850]

well, it let me down again this morning, although bumped it and it started first time!!! I think im on to something with the earth though, it would make sense because the coil is getting a signal when cranking, just not strong enough!! anyone know where the ecu earths? think im gonna take the inlet off, swap the starter and clean all the earthing points on the block, im also wondering if the gearbox has anything that needs a good earth?

[merc85]

God this is exactly what mine did, Earthing points two on the back of the engine at the top of the cam cover, Two on the front above the starter motor, And one on the front of the gearbox, think there is one on the front of the subframe to.

The earths are brown wires i believe which connect to the ecu. Be careful some are switchable i think.

This is where i called it a day im afraid as this sort of wiring was way above my station lol

Just one more thing, Have you checked the imoblizer ring around the igntion switch? these can act up. My car was obd1 so didnt have one.

[mike 850]

mine is obd1 too i think, 94 m plate with the a/b sockets in the engine bay? I keep reading stuff about starter motors spiking and blocking the other sensors, just bought a starter and will give everything a clean up, I WILL FIX THIS!!! lol

Cheers

[nobananas]

I did have a problem on a customers car a few years back that was similar to this. The starter motor was pulling so much current that it wasn't leaving enough for the ignition system and management. If you hooked up the coil direct to the battery it was fine but otherwise it wouldn't start. Changed the starter and it cured it. Would explain why your's starts if you bump it.

[mike 850]

yeah, its other than bad earthing its the only logical thing left, gonna clean the earthing points and run fresh wires directly to the battery too, will keep you posted. It starts instantly bumping it! everytime

[merc85]

I swapped a starter motor on it and it started 1st time ONCE! then went back to cranking and cranking, got fed up in the end as it couldnt trust it. Hence she went bye bye

21308

21309

[mike 850]

nnnooooooooo..... i'll give it a go, its got to be something...mines red too!

[merc85]

nnnooooooooo..... i'll give it a go, its got to be something...mines red too!

The trouble is some of the earths are common earths, and they go everywhere. Wiring was beyond me tbh and i had all the spares from two cars to play with, in the end i just ran out of things to try. And believe me i tried

[GreenMachine]

We've just had something like this on my old man's 850, - 95 obd1 - new starter motor fixed it, good luck.............

[mike 850]

yeah fingers crossed! I also have my bike if all else fails! ;)

[mike 850]

Well, new starter motor yesterday, started 1st time. try this morning, crank crank crank!!! I can't help thinking im close as it started immediately with the new starter but something is happening when its being left overnight, I wonder if its getting any interference or I'm sure I read somewhere about rerunning the main power to the starter, any ideas?

[RiPsTa33]

Can you write a short list of what you've done as earlier you just say you've tried everything, have you changed the fuel filter?

[merc85]

Well, new starter motor yesterday, started 1st time. try this morning, crank crank crank!!! I can't help thinking im close as it started immediately with the new starter but something is happening when its being left overnight, I wonder if its getting any interference or I'm sure I read somewhere about rerunning the main power to the starter, any ideas?

Yep as id said before in a previous post, exactly what happend to mine.,

[mike 850]

I have changed:

fuel filter
fuel pump
FPR
crank sensor
cam sensor
coil
battery
Starter Motor

hard wired cam and crank sensor
crank sensor has approx 300 ohm resistance
cam sensor 0-5v
signal to coil is too weak

having taken the inlet off again I have stripped all 3 earth connections on the block and the wire looked bad on the end, fitted them all to a beefy connection to the block and also another thick earth cable directly to the battery, also got the wire brush on the earth connection to the gear box, it looked ok until i cleaned it (its supposed to be brass) its nice and clean, put it all back again an instead of 8 cranks it fired on what felt like half a turn, it must be something to do with the earth.

pretty sure its not a component as you can bump the car and it fires straight away, will see if what I have done today works tomorrow

[merc85]

I have changed:

fuel filter
fuel pump
FPR
crank sensor
cam sensor
coil
battery
Starter Motor

hard wired cam and crank sensor
crank sensor has approx 300 ohm resistance
cam sensor 0-5v
signal to coil is too weak

having taken the inlet off again I have stripped all 3 earth connections on the block and the wire looked bad on the end, fitted them all to a beefy connection to the block and also another thick earth cable directly to the battery, also got the wire brush on the earth connection to the gear box, it looked ok until i cleaned it (its supposed to be brass) its nice and clean, put it all back again an instead of 8 cranks it fired on what felt like half a turn, it must be something to do with the earth.

pretty sure its not a component as you can bump the car and it fires straight away, will see if what I have done today works tomorrow

I Replaced,

ECU
Cam sensor
Crank sensor
Knock sensors
Fuel pump relay
Fuel injector driver
Maf
Leads
Plugs
Cap
Rotor
Plugs
Bypassed imobiliser
Ignition coil
Fuel pump
Charcoal canister vac line
Purge valve
Fan relay
Temp sensor
Starter motor
Cleaned all earths of the block at front
Earth on the back of the cam cover
Hard wired Cam
Hard wired crank
Hard wired Trigger wire to coil
All the fueses in the fuse box
All the relays in the fuse box
Intake manifold
Idle control valve.

Then had enough of the sack of **** and scrapped it DOH!!!!

[merc85]

Oh if it helps, i had my car scoped, And the computer showed that just 100ths of a second before the ecu sent the trigger wire pulse to coil the ecu lost a partial ground?? But changing the ecu didnt make starting any easier.

[mike 850]

UPDATE: for the first time in 6 years, she fired up first time this morning! gonna give it a bit of time before relaxing but I think I have fixed it....

[merc85]

UPDATE: for the first time in 6 years, she fired up first time this morning! gonna give it a bit of time before relaxing but I think I have fixed it....

Fingers corssed Mate ;)

[mike 850]

thanks mate, I also re routed the main power cable to the starter as I read on another forum this can cause interference with the cam/crank senors in the loom when drawing power.

[Jamest5r]

Happy days :) nice work mate

[mike 850]

day 2 just to make sure it wasn't a fluke, car has started on the button today too, looks like its a winner!