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P1166 fuel deviation is this a rare EMI case? PLEASE HELP
Re: P1166 fuel deviation is this a rare EMI case? PLEASE HEL
Hi Rym and thanks for sorting things out!
That is a nice setup that hopefully lead to success! If the fault occur you will probably have all evidence needed, at least what the regulator circuit concerns. Yupp! I noticed that it starts a bit earlier and gets worse with a peak voltage drop to approx. 7 volts every 15-40 ms, depending on where in the trace you look, until the pressure reaches the roof and the injectors shut off.
Please have a look at where the voltage drop still exist and the pressure fluctuation disappears, IE when the pressure is flat-topping (reaching the roof). I do not know, but I guess that it passed the most upper limit for the pressure sensor so the fluctuation cannot be seen. Am I right?
Well then, no uncertainties whatsoever that this voltage drop really coincide with a firing injector. I would also say that it lean to a faulty ECU, but since you got a new one with same symptom I would rather keep my mind open for a more deep going thinking with lots of fantasy.
Of course it has to be on the ground side to make this happen. The theory about some sort of modulated DC on the supply side - which could actually happen, see attached schematic with example wave forms that may sheed some light on what I meant - was more like a long throw before I studied the PWM B-trace thoroughly. So, with other words; there is no evidence in the PWM´s duty cycle that show such an activity, IE the duty cycle would have, I think, increased in this case because of current loss through the inductor / regulator. Furthermore, I cannot see anything that could create a precise repeated voltage drop like that between the regulator and the ECU, unless there is a short to ground causing a repetitive voltage drop, which is more or less impossible, but on the other hand, end up with same symptom because the regulator actually gets grounded in that way. However, interferences picked up by the regulator wiring going into the ECU could be possible, but I do not think so.
Well, that is all I have for now, but promise to have another round with this and along with a couple of beers.
Regards
Bjorn
That is a nice setup that hopefully lead to success! If the fault occur you will probably have all evidence needed, at least what the regulator circuit concerns. Yupp! I noticed that it starts a bit earlier and gets worse with a peak voltage drop to approx. 7 volts every 15-40 ms, depending on where in the trace you look, until the pressure reaches the roof and the injectors shut off.
Please have a look at where the voltage drop still exist and the pressure fluctuation disappears, IE when the pressure is flat-topping (reaching the roof). I do not know, but I guess that it passed the most upper limit for the pressure sensor so the fluctuation cannot be seen. Am I right?
Well then, no uncertainties whatsoever that this voltage drop really coincide with a firing injector. I would also say that it lean to a faulty ECU, but since you got a new one with same symptom I would rather keep my mind open for a more deep going thinking with lots of fantasy.
Of course it has to be on the ground side to make this happen. The theory about some sort of modulated DC on the supply side - which could actually happen, see attached schematic with example wave forms that may sheed some light on what I meant - was more like a long throw before I studied the PWM B-trace thoroughly. So, with other words; there is no evidence in the PWM´s duty cycle that show such an activity, IE the duty cycle would have, I think, increased in this case because of current loss through the inductor / regulator. Furthermore, I cannot see anything that could create a precise repeated voltage drop like that between the regulator and the ECU, unless there is a short to ground causing a repetitive voltage drop, which is more or less impossible, but on the other hand, end up with same symptom because the regulator actually gets grounded in that way. However, interferences picked up by the regulator wiring going into the ECU could be possible, but I do not think so.
Well, that is all I have for now, but promise to have another round with this and along with a couple of beers.
Regards
Bjorn
- Attachments
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Re: P1166 fuel deviation is this a rare EMI case? PLEASE HEL
Sorry, it should be 3,5 amps peak current, used 12 volts as B+ in my formula... 
Re: P1166 fuel deviation is this a rare EMI case? PLEASE HEL
After hours of heart ache and a very patient and understanding customer and a lucky fault code appearance I have nailed it 
. For the first time since I have seen this vehicle an EGR fault code got logged. So I checked it, and the wiring to it with no fault found. Now just due to the shear randomness of the fault I unplugged it. As expected the the engine management light came on. So I explained all of this to the customer and gave the vehicle back to her. She has currently had it back and has driven it daily since my last post, It has not cut out ONCE. so all of the scope captures and fuel pressure regulator fault codes were just symptoms and not causes. HOW an EGR can cause a fuel pressure reg to short out internally inside the ECU I cannot answer! I hope some one on here can? When it comes in for the EGR replacement I will certainly scope it and post the waveform.
. For the first time since I have seen this vehicle an EGR fault code got logged. So I checked it, and the wiring to it with no fault found. Now just due to the shear randomness of the fault I unplugged it. As expected the the engine management light came on. So I explained all of this to the customer and gave the vehicle back to her. She has currently had it back and has driven it daily since my last post, It has not cut out ONCE. so all of the scope captures and fuel pressure regulator fault codes were just symptoms and not causes. HOW an EGR can cause a fuel pressure reg to short out internally inside the ECU I cannot answer! I hope some one on here can? When it comes in for the EGR replacement I will certainly scope it and post the waveform.-
Dcunning35
- TwoWaves
- Posts: 239
- Joined: Thu Jan 28, 2016 12:33 pm
Re: P1166 fuel deviation is this a rare EMI case? PLEASE HEL
The egr is quite common to short the reference voltage in these engines in fords , it usually spikes the frp giving a code respectively for the fuel pressure deviation and bloody never gives an egr code or ref voltage code in my opinion poor calibration of the dtcs .
But well done for your persistence.
Danny
But well done for your persistence.
Danny
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ben.martins
- Pico Staff Member
- Posts: 543
- Joined: Tue May 16, 2017 1:02 pm
Re: P1166 fuel deviation is this a rare EMI case? PLEASE HEL
Hello RYM6746,
Good to hear you got to the bottom of it great work sticking with it. I'd not thought of the EGR valve and the one time when I've seen this fault occur, the vehicle wouldn't start at all. It was only when disconnecting the EGR did the engine come to life, but this was going back a few years now before I got into scope diagnostics! As Dcunning mentioned, it never flagged an EGR fault code which is ridiculous.
Again great work and most importantly tremendous patience!
Kind regards
Ben
Good to hear you got to the bottom of it great work sticking with it. I'd not thought of the EGR valve and the one time when I've seen this fault occur, the vehicle wouldn't start at all. It was only when disconnecting the EGR did the engine come to life, but this was going back a few years now before I got into scope diagnostics! As Dcunning mentioned, it never flagged an EGR fault code which is ridiculous.
Again great work and most importantly tremendous patience!
Kind regards
Ben