False start on 200tdi in series 2a 109

There is more for the saga thanks to a drama that played out on the side of the M3 on the way to an event.
First fuel cuts out while driving, drop a gear and pump the throttle and recover.
Fuel cuts out again and all lights go out.
Pull over onto hard shoulder suspecting the fuel cut off solenoid again.
Wobble cable to solenoid and try starter on ignition, absolutely nothing, no starter, no ignition lights.
Out comes multi meter
Power on permanent feed side of fuse box (bottom fuse)
No power on ignition side of fuse box (top fuse)
Pull out dash check ignition switch, no power feed to ignition switch.
Locate wires from ignition switch to a flasher relay that appears to be in use as an ignition feed to fuse box with trigger from ignition switch (why?)
Rig wire from permanent feed to 'ignition relay' to bypass ignition switch, still no power on ignition side.
Rig power feed to ignition switch and bypass ignition relay, power on ignition side of fuse box and ignition lights come to life.
Turn over starter motor and engine starts but quickly dies.
Check cable to fuel cut off solenoid again no click of solenoid, trace wire which is connected to the suspect 'ignition relay'with second wire connected to ignition side of fuse box, neither have power.
Rig permanent power feed to fuel cut off solenoid from permanent power side of fuse box (bottom fuse) nice click from solenoid.
Try starter and engine runs, drive to event.
Stop at event, jump out and disconnect fuel solenoid bypass to stop engine.
At event, wire in a switch to the power bypass for the fuel cut off solenoid so i can stop car from in cab.
Drive home ok, it rains, use lights, heater and windscreen wipers, all working ok.
Get home turn off power supply to fuel cut off solenoid but engine remains running until i switch of ignition.
Switch on fuel cut off switch i rigged on dash and notice ignition lights come on (as if i just turned the ignition switch)
Turn off my rigged switch for fuel cut off solenoid and switch on ignition to see what is working, starter turns but no fuel as solenoid is still off, indicators work with ignition on only as do side lights. Main lights switch on, ignition goes off, both fuses blow.
Refuse and try again with ignition and fuel cut off switched on, all working except when headlights turned to full beam (floor switch) fuse blows unless engine is running.
My best guess is that my bypass from permanent power side of fuse box to the fuel cut off solenoid is feeding power to the ignition circuit through the wire still connected to the ignition circuit but overloads when there is too much power on the ignition when the ignition circuit is on with the headlights.
When running the alternator supplies enough power to overcome this.
I am thinking the solution is to remove the wire from fuel cut off solenoid to the ignition circuit and rely on the feed i have rigged to a seperate switch on the dash.
What does anyone think?

Nothing wrong with your logic, and you're getting good at this - so how about stepping back and planning a proper rewire of the ignition switch connections? I'm talking as someone who was quite happy to drive an S3 with a rat's nest of extra wiring for a while, but did eventually get fed up with things disconnecting, invariably in the dark or the MOT bay.

boguing said:

Nothing wrong with your logic, and you're getting good at this - so how about stepping back and planning a proper rewire of the ignition switch connections? I'm talking as someone who was quite happy to drive an S3 with a rat's nest of extra wiring for a while, but did eventually get fed up with things disconnecting, invariably in the dark or the MOT bay.

Click to expand...

Thanks, new custom loom on its way for when i install leisure battery. I just need to put together something that will get me to my next event as i have been awaiting my new loom for a while now.

More problems while awaiting my new loom, which i hope will fix.
Went to start up today, nothing from any circuit, test battery while connected no volts, yes that's right, none. Disconnected battery leads 11 volts.
Imediate thought, open circuit and attached my jump starter (which has a open circuit alarm) to leads and sure enough open circuit.
Reconnect battery, hear multiple clicks from the infamous unknown relay attached to my bulkhead that has been added to my starter circuit and i bypassed on the m3 to get my fuel cut off solenoid working.
Now charging battery back up after open circuit now appears closed.
What i suspect is happening:
- Mystery small black relay might be connected to the starter solenoid which was installed by my predecessor for reasons unknown, (although i noticed that the ignition circuit has a small current that goes to this relay all the time (even when ignition off) but relay doesn't trigger)
-Starter solenoid appears to occassionally be stuck open causing current draw from battery, either by mystery relay triggering it (note starter motor not turning when this happens).
- possibly an eath out in the wire to the solenoid, draining the battery and causing the occassional fault on the starting
-possibly this mystery relay (looks like a 4 pin flasher relay) is connected to the starter circuit, is faulty and is earthing out.
-possibly starter motor solenoid is faulty and 'half triggering' and causing its own drain
-possibly faulty earth on starter motor.
My question is which as while most earthing, occassional voltage drops and cross connections will be sorted with the new loom?
i don't understand what the mystery relay is doing as it appears to be connected to the trigger wire for the starter solenoid, is this normal or necessary?
If the relay was installed to solve an issue with the starter solenoid, why not just replace the solenoid.?
The starter solenoid is a bugger to get to (under the exhaust manifold) but i am thinking i should replace it anyway but do i need this mystery relay?

Ok,
Here are a few photos of the mystery relay, the yellow wire disapears into the engine loom, the black wire goes to the dash loom, the white wire goesto the bolt holding the relay to the bulkhead as an earth.
The blue wire below used to connect to the 4th pin and run to the fuel cut of relay which had a second wire back to the ignition switch, this has now been bypassed so the blue wire connects directly between the fuel cut off solenoid and a pull switch on the dash with a permanent power supply (the m3 fix)
I can jump the starter motor if i connect a live supply to the 4th pin, otherwise the starter runs from the ignition key in the dash.
This secon photo shows my bypass for the fuel cut off, follow the blue wire.
I am assuming the yellow wire from the mystery relay is the trigger wire for the starter solenoid.

Looks like a glow plug timer to me...dont need one really...just wire to 12v ...never really need em anyway on a 200.

Are you sure your batt is not dead?

Nick.

Holds charge ok when not connected and gives a lovely 12.3 volts disconnected and 14.4 volts when attached and alternator running, will take a charge when i don't have an open circuit, so i think battery is fine.

The correct glowplug relay is much bigger.