1.6 tdi cylinder 1 injector

[J04n88]

So a week or so ago I had to pull up on the hard shoulder of the m6 due to the car going into limp mode. I was recovered home and subsequently had the car plugged into my obd11

The code that came up was the p0201 code which after a bit of research I found could mean any of the following, faulty cylinder 1 injector, harness that has an open or short, poor electrical connection in the harness or connector or ECM that is failing or has failed.

I then unplugged the injector and tested across the pins with a multimeter and resistance across it was a lot lower than the resistance shown across the other 3 injectors so i then assumed this would be the culprit and ordered a working 2nd hand injector. After fitting the "new" injector and coding it the car will now not run with injector 1 plugged in. it will start and run on 3 cylinders with the injector unplugged but if its plugged in either whilst running or before cranking the engine will not start. Before installing the new injector the car would run on 3 cylinders with injector one plugged in.

would anyone have any ideas on to what I could try next?? Anything I can do to trouble shoot or give a reason to why the car will no longer run with the new injector plugged in?

My next plan was to buy a brand new injector and then there would be no questions over the injector but as I'm sure you're all aware they aren't cheap!

thanks for reading and any help is gratefully received , Cheers John

 

[andylong]

I think there's an error in coding. Have you tested the new injector for resistance?
Even without coding the injector should at least start.

 

[J04n88]

On obd11 I had to add a zero to the end of the code found on the injector as it wasn't long enough. I did check the other injectors and they were the same, with the zero added. Would you recommend I clear the coding and try it again? I haven't actually checked the resistance of the new Injector, it may still be faulty to be fair. But the fact the car won't start with it plugged in, when the old one ran with the suspected knackered injector connected just seems strange. Thank you for your reply, any other insights would be greatly appreciated. Cheers

 

[andylong]

Hmm what did you code it with?
When you say won't start, does it turn over with it plugged in and stop if you plug it in with it running on 3 cyls.

 

[andylong]

Ah obd11.
Sounds like the ECU is killing the engine for some reason.
What if you plug in the old injector, just the loom, does it still stop?
If it does not there's an issue with the new injector.

 

[J04n88]

It will turn over infinitely but won't start with the injector plugged in. And will start with it unplugged but if I plug it in whilst it's running it just dies, whether that's some kind of protocol on the ecm or not I'm not sure? I was thinking remove injector 2 as 1 and 2 are both easy enough to remove as they've just been out. Put injector 2 into injector ones slot, code it and then leave injector 2 (which is now the new to me injector) unplugged and see if it starts. Then I'd know it was the injector and not the wiring to it? Does that make sense?! Thanks again for your help

 

[andylong]

Unplug 1 and 2 and measure resistance to ground of the connections. There's only 2 pins to measure as you know.
Read the fault codes when no1 is plugged in ignition on.
The coding tells the ECU how much fuel the injector can flow so it knows how long to activate it.
I do not see why the car won't start just because you have a faulty injector.
It feels like software somehow.

 

[J04n88]

Do you mean measure the resistance on the harness to ground on the car, so I would be checking the plugs that connect to the injector rather than the injector itself? I'll do that first thin in the morning after I've put the battery back on. I flattened it whilst cranking it although it had been sat for a couple of weeks as well.

Thanks again for your help, John

 

[J04n88]

If I were to put the car back to how it was originally and leave injector one out, could I then start it and use a test light to see if the harness connector was getting a voltage/turning on and off? Would this be possible with a multimeter?

 

[andylong]

Not easily, you could tell if there was a voltage but not what it was.
It's 100 to 200v pulses on those injectors of varying lengths.
These pulses come from the ECU and are not grounded.
If you measure between the 2 plug terminals on 1 2 etc you should be able to see if the circuit at the end is the same for each one. If 1 is different it's cabling or ECU.
The new injector should be similar to the other 3, in resistance,this will tell you the state of the piezo stacks which actuate the injector.
If the injector is ok, measuring the plug terminals will tell you about the continuity.
However, your engine stops if you connect to the injector which indicates an ECU issue if that no1 injector is ok.
Plugging a good injector into the harness won't create a short so it must be the ECU end.
I don't know what would stop the engine unless the timing is out somehow

 

[J04n88]

I've not had time to check yet, I got up to do it this morning but by the time I'd reconnected the battery the heavens had opened! I'll try again tomorrow morning and hopefully get back to you with something. Your help is greatly appreciated. Cheers, John