Trying to start by itself!!

[Grimbo]

Where on the vehicle is J17 "junction connector" ....... separating the wire from pin 9 on the engine ECU will further limit where the 9v is coming from .

I'm beginning to wonder if it's not an internal ECU fault .......it seems you need or have 3 separate ECU outputs to the coil side of the start relay .....
What does "NSW" "STAR" and "STA" stand for ?
STAR...... I presume is start.....
Is the symbol on the B-R wire from pin 17 of the engine ECU indicating a diode at whats marked as "12" ?

On many machines I work on they have a 12volt system but then also a 10v and 8v and often a 5v processor supplied voltage used for sensors , switches and potentiometers ......

10V is often a clean stabilised voltage and is pretty close to the 9volts you are seeing .

Pull the engine ECU multiplugs and look for corrosion on the pins that maybe allowing voltage to track from another pin .

Also you can measure 9v but can it do any work ? Maybe try using a 5amp sidelight bulb in a bulb holder with 2 wires and put them in either pin on the coil side of the relay connector ....... with the multimeter also connected in parallel ........you may find that because you are then requiring amps the voltage measured drops away . If the bulb glows then you have a definite short to a 12v supply or poss fault with the engine ECU......

My only reservation with using the bulb to add a load to the 9v is if the engine ECU is supplying this voltage even 5amps maybe too much .....

 

[Jamsy]

The black/white wire on the multi-plug at the bottom of the ignition barrel shows 9v with the ignition on. 0v with it off.
0v at the relay with the multi-plug disconnected as expected.

Is there anyone who could do a quick check at their starter relay to confirm there shouldn't be 9v with the ignition on?

 

[Jamsy]

Where on the vehicle is J17 "junction connector" ....... separating the wire from pin 9 on the engine ECU will further limit where the 9v is coming from .

I'm beginning to wonder if it's not an internal ECU fault .......it seems you need or have 3 separate ECU outputs to the coil side of the start relay .....
What does "NSW" "STAR" and "STA" stand for ?
STAR...... I presume is start.....
Is the symbol on the B-R wire from pin 17 of the engine ECU indicating a diode at whats marked as "12" ?

On many machines I work on they have a 12volt system but then also a 10v and 8v and often a 5v processor supplied voltage used for sensors , switches and potentiometers ......

10V is often a clean stabilised voltage and is pretty close to the 9volts you are seeing .

Pull the engine ECU multiplugs and look for corrosion on the pins that maybe allowing voltage to track from another pin .

Also you can measure 9v but can it do any work ? Maybe try using a 5amp sidelight bulb in a bulb holder with 2 wires and put them in either pin on the coil side of the relay connector ....... with the multimeter also connected in parallel ........you may find that because you are then requiring amps the voltage measured drops away . If the bulb glows then you have a definite short to a 12v supply or poss fault with the engine ECU......

My only reservation with using the bulb to add a load to the 9v is if the engine ECU is supplying this voltage even 5amps maybe too much .....

I think only "STAR" is an output. NSW is Neutral Start Switch which tells the ECU when the gearstick is in P or N.
"STA" is a signal to tell the ECU the engine is being cranked and to send more fuel.

That symbol from ECU pin 17 is just a wiring harness connector.

I think its looking like the ignition barrel. Could be a short further down between the ignition and the ECU but im thinking ignition barrel is more likely.

 

[StarCruiser]

Hi Jamsy,
It’s likely to be a wiring fault with damaged wiring feeding the relay coil for it to start cranking at will and be stopped by pulling the relay. So trace and inspect wiring. Put a multimeter between the contact for the coil + (the one where you were getting 9V) and earth and start wiggling wiring. My first port of call would be the wiring to the gearbox P/N switch. There could be some damage there, cracked insulation, that sort of thing. It’s a shame it’s gone away as while the fault was present was the perfect time to troubleshoot.
Open up some of the looms and check wiring condition. Look for melted insulation in case something has overloaded or shorted in the past.
The clue here is cranking but no fire. This rules out the ignition switch itself as the start contact is beyond the run contact. Wiring could be damaged anywhere though but likely places are anywhere that has had work since new. An aftermarket radio for instance, pushing or pinching wires.
As a trial, if it does it again, try taking it out of Park with your foot on the brake and see if it stops. That will tell you which side of the gearbox switch has the fault. It may be then just a case of replacing that bit of wire but if it were me, I’d rather find the actual fault than bypass it.
Keep at it and watch for it running the starter while the engine is running. Not good for starter internals or ring gear/pinion.
One last thing, did you put studlock on the solenoid screws? If not, do yourself a big favour and pop some low strength Studlock on them.

 

[Grimbo]

I think only "STAR" is an output. NSW is Neutral Start Switch which tells the ECU when the gearstick is in P or N.
"STA" is a signal to tell the ECU the engine is being cranked and to send more fuel.

That symbol from ECU pin 17 is just a wiring harness connector.

I think its looking like the ignition barrel. Could be a short further down between the ignition and the ECU but im thinking ignition barrel is more likely.

If the gear leaver is in D will the engine crank but not start.....?
If so then STA is the output and it then feeds back through the N / P switch to the engine ECU to tell it to then allow the FIP to deliver fuel and the engine run.

Hopefully it's the ignition switch .....9v is just a strange voltage ......

The other bit I'm unsure of is if it's the ECU that gives the crank command or if the crank command so to speak just passes through the ECU .....

On some of the vehicles I work on they are common rail but the start circuit is not via the engine ECU..... so the engine will turn on the starter even with an engine ECU removed.... others the engine ECU initiates the crank command and will keep cranking even with the key released until the engine runs .

 

[Jamsy]

The fault is back again folks.
I have 12v again on 2 pins so the fault is there and will try to start with the ignition off.
Putting the gearbox in 'R' or 'D' didn't stop it. Only when I pulled the Starter Relay.

Its not the Relay or the Starter motor.

 

[Jamsy]

If the gear leaver is in D will the engine crank but not start.....?
If so then STA is the output and it then feeds back through the N / P switch to the engine ECU to tell it to then allow the FIP to deliver fuel and the engine run.

Hopefully it's the ignition switch .....9v is just a strange voltage ......

The other bit I'm unsure of is if it's the ECU that gives the crank command or if the crank command so to speak just passes through the ECU .....

On some of the vehicles I work on they are common rail but the start circuit is not via the engine ECU..... so the engine will turn on the starter even with an engine ECU removed.... others the engine ECU initiates the crank command and will keep cranking even with the key released until the engine runs .

The 9v is now 12v and that's with the ignition off.

When I jumped in and put it in 'D' it didn't stop it trying to start.

I put it back into 'P' and turned the ignition to 'ON' and it started started away but I could hear it was still cranking even once it was running.

 

[Jamsy]

Just removed the glovebox and there's water getting in behind it from somewhere. I removed the ECU for better access, still 12v with the ECU removed.
I suspect it might be water sitting in a wirings harness connector and shorting between two pins.

Makes sense as it has been torrential rain all day and the LC has been parked facing downhill, this is the same as the last time it happened.

 

[Jamsy]

Another update. Removed the plug from the bottom of the ignition barrel - still 12v.
I left it dry out overnight and the 12v is now gone. Think the best plan is to try to stop the water leak.
Anyone any idea where to look? All the bolts for the roofers are in with silicon so don't think its that. Also the passenger sill fills with rainwater.

 

[Grimbo]

Sunroof drains or scuttle under the windscreen.......