Monaro not starting ??? Technical

[Loveit]

Hi

As some of you might of recognised i had a problem starting my monaro a few weeks back but i fixed that with a new bcm fuse ( even though the fuse was perfectly fine)

Now i can only start the car by bridging the starter relay pins 87 and 30 the car will start perfectly when i do this

I checked all the wires coming into the start relay and one is suspect which is pin 86 i think this is an ignition source but not sure its a small grey wire .... I dont know where it comes from

A wiring diagram i found says it goes to a fuse .... The fuse box lid confirms this but the fuse is non existant and there was never terminals for a fuse in that location

Does any one have any idea where this wire goes???

Vx monaro

 

[Nut Kracker]

Hi

As some of you might of recognised i had a problem starting my monaro a few weeks back but i fixed that with a new bcm fuse ( even though the fuse was perfectly fine)

Now i can only start the car by bridging the starter relay pins 87 and 30 the car will start perfectly when i do this

I checked all the wires coming into the start relay and one is suspect which is pin 86 i think this is an ignition source but not sure its a small grey wire .... I dont know where it comes from

A wiring diagram i found says it goes to a fuse .... The fuse box lid confirms this but the fuse is non existant and there was never terminals for a fuse in that location

Does any one have any idea where this wire goes???

Vx monaro

I have an idea that grey wire might go to the inhibitor switch. Check to see if that switch is ok.
According to my diagram for the VT, bridging pins 30 and 87 will start the car as you described. Pin 86 (grey or grey/blue) goes to the inhibitor switch. Pin 85 comes from the ignition switch.
It may be the same on your Monaro.....worth a try at least.

 

[aussie4life]

Auto or manual? If auto try going down and back up thru the gears while holding the key to crank. If you hear the starter click or clunk at all, you may just need to re-align the switch

 

[Loveit]

Its a 6speed manual

Nut kracker... I dont think it will have an inhibitor switch yeh all other pins work perfectly like the start 12v supply

So i guess it comes down to where this grey wire goes

Ps the grey wire has 4.7volts when ignition is on

 

[Nut Kracker]

Ok......Looks like the grey wire goes to the PCM for the manual and via the inhibitor switch to the PCM for auto and that looks to me that it's an earth from the PCM that goes to one side of the relay and the other side comes from the ignition switch to fire it.
Tell me if this is right.....pin 86 Grey wire. Pin 30 red wire. pin 87 violet/white, then changes to violet to the starter. Pin 85 violet wire.
Have you checked all the fuses and fusible links????
Is the relay working properly?????

By the way, What year/model is your Monaro???

 

[Nut Kracker]

The ignition relay fuse. Have you checked that???? probably 7.5 amp inside the car.

 

[Loveit]

Hi nut kracker

Yeh those colours are right.... The ignitiom relay fuse inside the car does not exist.... It lists it on the cover but no wiring exists for the fuse

I swapped the relays over and nothing fixes it.... Then i noticed a very weird signal coming from this grey wire .... Seems to give me 4.6 or 4.7 volts with ignition on.... No ground ?

Pin 30 has constant 12v pin 87 is to starter pin 85 has 0v but changes to 12v when key is turned to start

I cant seem to find any fusible links .... Other then this start issue the car works perfectly if i bridge relay she runs great
I thought grey was supposed to be an ignition signal it would be great to see what someone elses read on a multimeter?

2002 monaro v2

 

[Nut Kracker]

Hi nut kracker

Yeh those colours are right.... The ignitiom relay fuse inside the car does not exist.... It lists it on the cover but no wiring exists for the fuse

I swapped the relays over and nothing fixes it.... Then i noticed a very weird signal coming from this grey wire .... Seems to give me 4.6 or 4.7 volts with ignition on.... No ground ?

Pin 30 has constant 12v pin 87 is to starter pin 85 has 0v but changes to 12v when key is turned to start

I cant seem to find any fusible links .... Other then this start issue the car works perfectly if i bridge relay she runs great
I thought grey was supposed to be an ignition signal it would be great to see what someone elses read on a multimeter?

2002 monaro v2

Yep that's right as far as you described the relay. You've got some power to the relay. It's that grey wire that has my head spinning.
That wire comes from the BCM. It sounds like there is a problem there not being able to fire the relay.
I would try and maybe concerntrate on that wire. There could be a short or a fracture in it.

Anyone else have any ideas?????????

 

[Alloytec]

okay ill do my best not to explain this simply, that 5 volt signal is a reference signal the ecu uses to switch components on etc, your sensors also run off a 5 volt reference signal aswell... you ask why ? because 5 volts in a 12volt system is a stable voltage for the computer to run all its sensors at and switch and turn different things on and off where and when needed.. eg injector pulse width, this is so in the event of a low battery situation the ecu can still have full control over everything even with less then optimum battery voltage for the engine to crank...

So all your dash switches etc work with this 5volt reference signal and all accessorys are negatively switched so thats why you see the 5volts at that wire but no ground.. its that earth that will complete the circuit for the trigger wire which will turn your relay on, let the 12v to pass thru and your accessory will get power.

 

[Nut Kracker]

Cool thanks for clarifying that.
It sounds to me that you are getting all the voltages, connections and signals you need at the relay. The car starts when you bridge the relay.
Silly question, but did you change the relay?
Has the relay got any gunk on the terminals?
Are the wire terminals clean.
That Grey wire from the PCM has only 5 volts running through it and any gunk or corosion can easily reduce the voltage trying to get through.