Wiring

[Ianth]

Hoping someone more technical than myself can shed some light on a problem I have.i am a mechanic but never got into electrics,anyhow here goes....

I purchased a z4 2.0 2017 (must be one of the last registered),it was a cat s salvage but damage was to bonnet,bumper,airbags,certainly not major damage,all bolt on stuff and no way a cat s unless they regard a bonnet as structural.

I have done all the bits,airbags,tensioners,bonnet hinges and locks,all new stuff.
I was waiting of the battery lead which arrived today and I assumed would fix the none start issue I have,but it hasn’t so I am asking for the help now!

There isn’t a ignition feed to the starter,won’t crank.if I remove the ignition wire off the starter and test it there’s no voltage.if I push the key in and press the start button nothing happens,if I at that stage flash a feed to the terminal it starts and runs fine.

I wouldn’t expect the ignition feed to be fused so I haven’t checked any,I was realy hoping the positive blow off cable was the culprit. Carly just says a starter vault

 

[Stuartt]

Starter relay would be the next place I’d be looking, check the feeds to it and bridge to the output from it to confirm it starts from there.

Stuart

 

[Ianth]

Thanks Stuart,dumb question but where is the relay?
There is a white box in the corner under the bonnet and the top unscrews,there is a relay in there,grey I think it is,it was warm when I touched it.
Any idea which points I bridge

 

[Stuartt]

Not sure on exact location of starter relay I’ll have to check.

Standard terminal layout would be
Terminals
85 & 86 are energising coil
30 & 87 main battery input and output to starter.

Grey relay if it’s warm is more than likely the ign relay if warm.

Stuart

 

[Ianth]

I will take the lid off it later and check it.much appreciated.
At least now I have some idea.

 

[Ianth]

Just took lid off and the relay is black not grey.it has a part number 61366901469/01 and the 4 terminals are numbered 1.2.3. And 5.
A quick google just says it’s a multi purpose relay.
Couple of quite heavy duty red wires going into it and a couple of very thin wires.

 

[Smartbear]

Just thought it’s worth asking if you’re depressing the clutch while attempting to start, the ignition is locked out if the clutch isn’t operated :?
Rob

 

[Ianth]

It’s a auto so pressing the brake.
Don’t need to press the brake when I hot wire a feed though,just ignition on.

 

[Ianth]

Still not sorted.
Removed glovebox and checked all fuses (who the hell designed that fuse box accessibility ).none blown.
In the fuse box there is another relay exactly the same as the one under the bonnet so I exchanged them,no luck.

Followed the +ve ignition feed back from the starter,it’s white at the starter to a junction block under the bonnet where it changes to black,but then it runs into the main loom and disappears into the car.
I can run a +ve to that junction block and it starts ok,just won’t without any help when I press the start button.

Anyone got any suggestions.
On a side note I noticed the high level brake light wasn’t working,took the boot cover off and it wasn’t plugged in,bare in mind it’s a 2017 car and looking at the clips the cover had never been off! Looks like the factory forgot to plug it in -

 

[Ianth]

Just a update.
Took it to a specialist diagnostic place and spent £100 for him to tell me the ecu is knackered.
If anything I was expecting the cas to be faulty so it threw me a bit.
When I got home I decided to get to the bottom of it and started going through all the wiring,did not I’ve a pair of wires on the inner sill that looked out of place as they weren’t routed inside the main loom trunking,so followed them up and they was spliced into junction 22 of the cas unit which is the starter output,cut and bridged the wires and starts like a good in now.
Traced and removed all other wiring associated with this pair and uncovered a tracker,with a built in relay to immobilise the car.
With buying it as salvage and a none runner it’s difficult to get info nowadays about the history,even the v5 no longer has previous keepers details.
Anyhow I am guessing that the tracking company whoever it is immobilised the vehicle and left it that way.
Relieved it’s not the ecu or the cas but well p****d off at wasting 100 at a so called specialist.

 

[djstan]

That's a good result! Shame about the £100 but it could have been worse...