S6 engine not firing after long layup
Discussion
Hi. This question is a bit involved but i'm hoping i've missed something stupid.
So, I'm breathing life into my Tuscan after a couple of years laid up sadly.
Looks like there has been a water leak into the drivers footwell, causing a fair bit of electrical fun. The fuse box had been liberally soaked, so being of an electronics mind i stripped, cleaned and refurbished the entire thing (yes including stripping out the internal copper runs). Suddenly the electric behaviour made a lot more sense.
The engine refused to fire, so having bypassed the immobiliser as the remote wasn't working, fuel pump ran, it cranked, gained oil pressure but wouldn't fire.
Diagnostics show crank speed so sensor appears fine, but removed it and cleaned off some metal shards attached to it.
Still not starting.
Spent time with the fuel injectors, they have +12v, an oscilloscope shows pulsing and they are putting fuel into the cylinders.
Did the same with the coil pack, it had +12v but weird 3-4v signals on oscilloscope for the coil drives. Directly connected a spark plug to the coil pack and earthed it, but no spark.
Traced wires back and found damp in the ECU connector for the coil drives, cleaned it out, boroscope inspection of inside of ECU showed no damp ingress.
Now i have +12v to the coil pack, and each coil drive shows +12v with a nice train of intermittent -ve pulses to 0v during cranking, but still no spark.
Coil drive cables to ECU pcb bus out fine, +12v appears fine.
I've replaced the coil pack with a new item and still no spark.
ECU has power, +5v rail present on pcb, injectors pulse, diagnostics report crank speed, and other info fine, coil drive has pulse trains to it....yet if i put connect a spark plug to the coil pack, nothing during cranking.
Current thoughts:
Drive circuitry for the coils damaged in the ecu but the output looks reasonable on a scope. I've also tried my spare ecu and get the same result.
Cabling from ecu to coils suspect, but seems ok. I'm going to try some direct cables and see what happens.
Dodgy coil packs (including new one ???), but the primaries show a reasonable low resistance and secondaries are reasonable as well for both old and new packs.
+12v supply to coil pack, going to try another direct fused cable and see what happens.
What else am i missing ?
So, I'm breathing life into my Tuscan after a couple of years laid up sadly.
Looks like there has been a water leak into the drivers footwell, causing a fair bit of electrical fun. The fuse box had been liberally soaked, so being of an electronics mind i stripped, cleaned and refurbished the entire thing (yes including stripping out the internal copper runs). Suddenly the electric behaviour made a lot more sense.
The engine refused to fire, so having bypassed the immobiliser as the remote wasn't working, fuel pump ran, it cranked, gained oil pressure but wouldn't fire.
Diagnostics show crank speed so sensor appears fine, but removed it and cleaned off some metal shards attached to it.
Still not starting.
Spent time with the fuel injectors, they have +12v, an oscilloscope shows pulsing and they are putting fuel into the cylinders.
Did the same with the coil pack, it had +12v but weird 3-4v signals on oscilloscope for the coil drives. Directly connected a spark plug to the coil pack and earthed it, but no spark.
Traced wires back and found damp in the ECU connector for the coil drives, cleaned it out, boroscope inspection of inside of ECU showed no damp ingress.
Now i have +12v to the coil pack, and each coil drive shows +12v with a nice train of intermittent -ve pulses to 0v during cranking, but still no spark.
Coil drive cables to ECU pcb bus out fine, +12v appears fine.
I've replaced the coil pack with a new item and still no spark.
ECU has power, +5v rail present on pcb, injectors pulse, diagnostics report crank speed, and other info fine, coil drive has pulse trains to it....yet if i put connect a spark plug to the coil pack, nothing during cranking.
Current thoughts:
Drive circuitry for the coils damaged in the ecu but the output looks reasonable on a scope. I've also tried my spare ecu and get the same result.
Cabling from ecu to coils suspect, but seems ok. I'm going to try some direct cables and see what happens.
Dodgy coil packs (including new one ???), but the primaries show a reasonable low resistance and secondaries are reasonable as well for both old and new packs.
+12v supply to coil pack, going to try another direct fused cable and see what happens.
What else am i missing ?
I'm sure you know but the coils are driven using low side MOSFETs...so ecu pulls them down, current builds up in primary coil...quickly let them go open by turning off mosfet and you get a flyback voltage at the secondary. If you can see the low going drives on the primary but no spark suggests the current build up isn't happening. Suppose the 12v feed to the coil was high resistance...I think this would do what you are seeing. Something to check.
Thanks for your reply.
Turned out to be corrosion inside the plug that goes into the fusebox on the +12v supply to the ignition coils.
Removing fuse 17, then hard wiring from battery to a fuse to coil, cranked it and engine burst into life.
Worked backwards and found the cruddy connection.
For the life of me though i can't see where water is getting into the drivers footwell, i've checked the usual suspects. A garage would be very good idea.
Turned out to be corrosion inside the plug that goes into the fusebox on the +12v supply to the ignition coils.
Removing fuse 17, then hard wiring from battery to a fuse to coil, cranked it and engine burst into life.
Worked backwards and found the cruddy connection.
For the life of me though i can't see where water is getting into the drivers footwell, i've checked the usual suspects. A garage would be very good idea.
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