Technical Ducato starting problem - not the usual

[Blueywr1]

I have some free time in the morning, so I had planned to see if I could trace the red/black from the starter motor, but perhaps firstly from the ignition switch, as I would be in agreement with you that if there is a splice in it to feed the Sigma immobiliser at all, it would likely be below the steering wheel, as it would be easy to get it to the Sigma unit under the dash (nearside).

I fear that:
1) I will require longer test leads
2) I will need the apprentice / or crocodile clips, as with it being an "A-class", there is quite a distance between where this wire starts and finishes

Note: apprentice unavailable in the week - she's got a real job!

 

[Blueywr1]

I know I'm not "fixed" yet, but we feel much happier this evening after today's test, so can I just shout out to the other members of the community who also suggested a similar / same test as @Communicator and to those that have contributed thus far.

 

[Anthony489]

Hi

I don't know which model of Sigma immobiliser you have, but I've been looking at the instructions/data for a range of their products.

This suggests that yes, one of the immobilisation circuits is intended for use in series with the feed to the starter solenoid. It recommends that the relevant wire behind the ignition key switch is cut, and the Sigma connected to the two ends. It also mentions a maximum current rating of 18 Amps.

I am pretty certain that the Sigma will incorporate a relay for this function. It could well be that the contacts of this (fairly small) relay have suffered gradual deterioration due to being overloaded, and are now adding an unacceptably high resistance into the circuit

I think it might be time to restore the original wiring to the starter solenoid.

See attached instructions and extract.

 

[Blueywr1]

Hi @Anthony489

Thank you for the info. Great find!

I don't have the instruction booklet at home - it is in the vehicle, but we are pretty sure it is a Sigma S30, so that would be relevant.
The vehicle only has one door, so no central locking, and I actually don't see a siren in the engine bay. My thoughts are that it is just being used as an immobiliser.
I don't see a relay in the restricted area where the Sigma unit is: Is it likely to be under the steering wheel, close to the ignition switch?

 

[Anthony489]

I can't claim to have digested all 89 pages of the manual, but I am pretty certain that the immobiliser main box will contain printed circuit board mounted relays, i.e. there are no external relay(s) to see. These relays are limited in physical size, this and the need for PCB tracks and connections via fairly small pins on a multi-way connector are what limits the current carrying capability to 18 Amps. In a nutshell, I don't think it's man enough for the job.

 

[Communicator]

The information researched and linked to by @Anthony489 may suggest a simple alternative test. The instructions state that pins 13 & 14 are connected in parallel with pins 1 & 2 respectively, to increase the 18A current carrying capacity on the Sigma unit multiplug, Current sharing does not always balance out equally betwween pins, and the contact resistance can increase overtime.

I am thinking that pulling the fuse for the Sigma unit, and the removing and replacing the Sigma unit multiway connector mentioned, may reduce the contact reistance sufficiently to enable the starter solenoid to operate. Worth a try, as successful result would prove the case. However this may not work if it is only the relay contacts at fault.
It may work until next time it decides to fail, so only a temporary fix.

@Anthony489 , do you have any comments?

For what I think may be examples of poor current sharing, search internet for Sargent EM40 failures.

 

[Blueywr1]

I can't claim to have digested all 89 pages of the manual, but I am pretty certain that the immobiliser main box will contain printed circuit board mounted relays, i.e. there are no external relay(s) to see. These relays are limited in physical size, this and the need for PCB tracks and connections via fairly small pins on a multi-way connector are what limits the current carrying capability to 18 Amps. In a nutshell, I don't think it's man enough for the job.

Suggesting the unit needs removing, because the amps going to the solenoid is greater than this?

Looking at page 12 of the Sigma instructions, bottom right corner shows, "Immobilisation Connections" and refers to both starter circuit and fuel circuit. This would explain why I hear the fuel pump after entering the correct code in to the keypad.

Perhaps I will try to disconnect the pin/wire for starter circuit at the Sigma unit. *

It looks as though when I have previously "disconnected it", I have only taken out the keypad. Not sure about this though.

* or would I best trying to trace the red/black thin wire and test continuity through it? i.e. focusing one one task (especially with it being electrical)?

 

[Communicator]

@Blueywr1 , I was about to enquire, but you have stated that vehicle is an A class. Be warned that on at least some A class models the front u,pper screw securing the lower dash panel can be difficult to reach. It is too close to the sidewall.

 

[Blueywr1]

@Blueywr1 , I was about to enquire, but you have stated that vehicle is an A class. Be warned that on at least some A class models access to the front upper screw securing the lower dash panel can be difficult to reach. It is too close to the sidewall.

Will it not be the same panel I removed to replace the ignition switch?

I'm always fighting with something to get to where I need to be in it! I feel for the workshop where I will take it to replace the CPS.

 

[Anthony489]

To answer Communicator first, looking at Page 36 of the manual there is the statement "Maximum immobilisation current 18 Amps". This suggests to me that even with the use of multiple connector pins the recommended current is less than the Ducato's solenoid requires.

I strongly recommend that at least for the time being the OP removes the Sigma wiring from the solenoid circuit, and reliably re-joins the cut ends of the factory wiring. The redundant Sigma wires may be insulated and taped out of the way. The immobiliser will still function but only on its other circuit.

Although in principle the engine may now be cranked by "hot wiring", it is not possible to start it without the Sigma code being entered.

 

[Communicator]

Will it not be the same panel I removed to replace the ignition switch?

I'm always fighting with something to get to where I need to be in it! I feel for the workshop where I will take it to replace the CPS.

I think that you will only have removed the lower steering column shroud to change ignition switch. The part that I am referring to is the one infront of your knees. It has bonnet release, and column adjustment levers passing through it.

To answer Communicator first, looking at Page 36 of the manual there is the statement "Maximum immobilisation current 18 Amps". This suggests to me that even with the use of multiple connector pins the recommended current is less than the Ducato's solenoid requires.

I strongly recommend that at least for the time being the OP removes the Sigma wiring from the solenoid circuit, and reliably re-joins the cut ends of the factory wiring. The redundant Sigma wires may be insulated and taped out of the way. The immobiliser will still function but only on its other circuit.

Although in principle the engine may now be cranked by "hot wiring", it is not possible to start it without the Sigma code being entered.

I agree with the reasoning. I was thinking more of a further test which may be easy to perform if correct connector can be identified.

 

[Blueywr1]

I think that you will only have removed the lower steering column shroud to change ignition switch. The part that I am referring to is the one infront of your knees. It has bonnet release, and column adjustment levers passing through it.

Ah yes, this is correct. I have not had the need to remove the lower panel.

If I have understood the advice this evening, I must identify where the thin red/black wire from ignition switch to solenoid has been cut to incorporate the Sigma system. There a few options for this:
1) Inspect wire from ignition switch to Sigma unit
2) Work upwards (in engine bay) from the solenoid to fuse box
3) Trace wire from Sigma to fuse box

Looking again at page 12 of the instructions, I expect to see continuity when the key is turned to crank, and not before?

 

[Communicator]

Ah yes, this is correct. I have not had the need to remove the lower panel.

If I have understood the advice this evening, I must identify where the thin red/black wire from ignition switch to solenoid has been cut to incorporate the Sigma system. There a few options for this:
1) Inspect wire from ignition switch to Sigma unit
2) Work upwards (in engine bay) from the solenoid to fuse box
3) Trace wire from Sigma to fuse box

Looking again at page 12 of the instructions, I expect to see continuity when the key is turned to crank, and not before?

I would go with alternative 1, as Sigma instructions suggest cut is made behind dash.

I have not studied page 12 of the instructions, but I would not expect the Sigma unit to use the start from the ignition as an input command. What extra security would be gained from this.

 

[Mike1alike]

I feel for the workshop where I will take it to replace the CPS.

You don't need to replace the CPS. When CPS goes bad, the engine cranks but doesn't start, so it's not the case.
You found what's wrong and causing your problem and you're on the way to fix it. Good luck!
PS: I'm happy for you, too.

 

[Blueywr1]

You don't need to replace the CPS. When CPS goes bad, the engine cranks but doesn't start, so it's not the case.
You found what's wrong and causing your problem and you're on the way to fix it. Good luck!
PS: I'm happy for you, too.

Another problem - see post #55

 

[Mike1alike]

Right. I forgot about that.

 

[Blueywr1]

Hi.
Long story shortened.
Dash panels removed, I found the cut in the red/black solenoid wire, actually behind a fuse box - there are several on this vehicle!
I found the relevant wires that were connected to the sigma unit.
I cut those wires and taped them up and reconnected the solenoid wire.
Vehicle now turns over every turn of the key, but.... and I'm happy with this.....
Entering the correct code in to the sigma keypad, the vehicle starts immediately, however, if you don't enter the code, it'll crank, but won't fire up, as the fuel pump is immobilised.

More use will hopefully prove that this is now resolved, but it's looking likely.

Your support and advice has been excellent and we are greatly appreciative.

 

[Communicator]

Hi.
Long story shortened.
Dash panels removed, I found the cut in the red/black solenoid wire, actually behind a fuse box - there are several on this vehicle!
I found the relevant wires that were connected to the sigma unit.
I cut those wires and taped them up and reconnected the solenoid wire.
Vehicle now turns over every turn of the key, but.... and I'm happy with this.....
Entering the correct code in to the sigma keypad, the vehicle starts immediately, however, if you don't enter the code, it'll crank, but won't fire up, as the fuel pump is immobilised.

More use will hopefully prove that this is now resolved, but it's looking likely.

Your support and advice has been excellent and we are greatly appreciative.

Now I will have to check my own 2.8jtd for a similar contact, in the solenoid circuit.