Hot start smoking - Specific Circumstances

[Laird Scooby]

Originally Posted by StrongSpearWorks

I'll be up early cutting open the cable jacket and splicing in some new wire... FTP - no start?

Edit. Two wires go to a connector, a third black wire goes to a push-plug with a green cable. Is that the 12v supply?

The green wire is the sensor output in a range of 0-1V, if you put 12V on that you'll fry the sensor, the ECU or both!

FTP covers a multitude of sins but in this case would have been no start + blown fuses etc.

[StrongSpearWorks]

Originally Posted by Laird Scooby

The green wire is the sensor output in a range of 0-1V, if you put 12V on that you'll fry the sensor, the ECU or both!

#gulp
Doesn’t sound like something I need today.

[Laird Scooby]

Originally Posted by StrongSpearWorks

#gulp
Doesn’t sound like something I need today.

Definitely not!

New sensors are around the £60 point so if you can recover the wiring, so much the better but be careful with it!

[StrongSpearWorks]

Originally Posted by Laird Scooby

Definitely not!

New sensors are around the £60 point so if you can recover the wiring, so much the better but be careful with it!

It’ll be careful cutting and a steady hand kind of morning...

[StrongSpearWorks]

So the Lambda sensor seems to not be the reason for the light coming on. I read the codes from the box and got 121 mass air flow meter missing or faulty and 224 off the ezk, suggesting the coolant temp sensor missing or faulty.

Could the temp signal being missing lead to an assumed cold-start scenario and he dumping more fuel than needed into a hot engine and causing me all the smoke?

Update: I reseated the MAF connector, pulled fuse 1.
The light is out and code 121 has gone but the coolant temp sender error remains.

[Laird Scooby]

Originally Posted by StrongSpearWorks

So the Lambda sensor seems to not be the reason for the light coming on. I read the codes from the box and got 121 mass air flow meter missing or faulty and 224 off the ezk, suggesting the coolant temp sensor missing or faulty.

Could the temp signal being missing lead to an assumed cold-start scenario and he dumping more fuel than needed into a hot engine and causing me all the smoke?

Update: I reseated the MAF connector, pulled fuse 1.
The light is out and code 121 has gone but the coolant temp sender error remains.

Quite often those two codes come up with a faulty Lambda sensor but no codes for the Lambda.

Have you got and know how to use a multimeter?

Set it on a range that covers up to about 6k Ohm, locate the CTS (Coolant Temperature Sensor) under the inlet manifold about halfway along (roughly under #3 inlet tract) and unplug it.

Connect one probe from your meter to the block and with the other, check both pins on the CTS read ~2500 Ohms when cold.

As a final check, use both probes on the CTS and check for a total resistance of the sum of the readings you got from each pin to earth.

Note that there shouldn't be anything like PTFE tape on the threads of the sensor, misguided people do that to make it seal but it is designed to seal purely on the threads as they also provide the earth point necessary for correct sensor operation.

If you need to replace that sensor, it needs to be genuine Bosch for some unknown reason.

It's worth looking into as a possible cause of the smoking at least.

[StrongSpearWorks]

Hmmm.
My meter does 2k or 20k.
Either way I get no reading at all off of it. Absolutely zip.

In other news, the date stamp on the thermostat was 1992. Probably about time for a change.

[Laird Scooby]

Originally Posted by StrongSpearWorks

Hmmm.
My meter does 2k or 20k.
Either way I get no reading at all off of it. Absolutely zip.

Seriously? Just open circuit from BOTH terminals to the sensor body/earth?

That is really unusual!

Usually if they fail the resistance goes higher than it should be, they are NTC Thermistors (Negative Temperature Coefficient) so as the temperature drops, the resistance goes up, as the temperature goes up, the resistance drops. Normally if they fail, the resistance is about 20% higher than it should be when cold and doesn't drop much when hot. Very unusual for them to both go completely open circuit!

[StrongSpearWorks]

Unless I’m being dumb, that’s correct.

Red to OHMS
Black to COM

Touch ground to either pin, no fluctuation.
Pin to pin, same.

[Laird Scooby]

Originally Posted by StrongSpearWorks

Unless I’m being dumb, that’s correct.

Red to OHMS
Black to COM

Touch ground to either pin, no fluctuation.
Pin to pin, same.

WHat about the range selector switch? Can you post a pic of it?