Posted by Andrew West on February 13, 2009, 10:30 pm
Year of Manufacture *: 2002 Engine Code or Type *: RLZ ( Optional ) ECU Type: siemens sirius 81 ( Optional ) Scanner used: Multiscan & Autodiagnos
This question is mainly directed at Dave Hill, but I'm sure that others will be able to help.
I have the above vehicle in at the moment, which is sometimes cutting out when accelerated. Originally the only fault logged(using eobd) was for P1113 (IAT sensor fault, according to several sources). After clearing the fault the vehicle would start & run ok until it cut out again, sometimes not for several stop starts.When it cut out the only fault logged again was P1113, but after updating my multiscan, now that the new host & operating software is available on thier site, the faults have changed.I am now gettting fuel pressure faults, which make more sense. Any way the question is , should I see a frequency change at the fuel actuator? the live data shows a varying dwell time(%), but on the scope the frequency doesn't seem to change.When the engine cuts, usually on over-run, the fuel pressure drops off just after the actuator frequency seems to increase, but then the amplitude of the actuator deminishes.I haven't yet caught the image(i thought that i had), but i have saved images of when the pressure is high & low, showing the actuator duty staying the same. If the actuator duty remains the same, even though the live data shows a change, could the actuator be faulty? I would have expected to see the frequency vary with the pressure & if the actuator was faulty that the pressure would remain more constant & the actuator duty obviously varying. I hope to be able to get further with it tomorrow , now that I have data that seems to more accurate.
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Just noticed, the scope details are missing. The blue trace is the injector, red fuel pressure, green fuel pressure control actuator, yellow TPS. my gut feeling is that it is a faulty high pressure pump. Sorry for the long post, regards, Andrew
I missed your post or I would have responded sooner. Although I am flattered that you asked me directly for help, I can’t help think that your faith is misguided!
What I would say is, that from your comments about "expecting the frequency to change" in the same sentence that you mention duty cycle, I think you are mixing the two control methods up.
Without trying to teach you or anyone to suck eggs, when looking at a Duty Cycle controlled actuator, the frequency is set & does not alter. In both of your examples there are 8 ON / OFF events on screen in the same time frame. The top image is presumably at idle & the lower image is at high revs & with a lot more going on, the number of ON / OFF cycles is exactly the same. This is known as PWM (Pulse Width Modulation). Modulation meaning "controlled" & the "pulse width" meaning "the width of the pulse" or "ON TIME"
There is another method of actuator control that is easily confused with PWM & that is FM or Frequency Modulation. If your captures where displaying a frequency modulated (controlled) actuator, then you would see the number of events on the screen increase, as the ECU commands a greater effort from the actuator (in your case the fuel pressure regulator). As I said before, yours displays the same amount of events in a 10 millisecond capture at both extremes of fuel pressure control.
Looking at your two captures it is clear that there is a definite difference in the duty cycle. Although it is quite hard to determine by looking at the images alone. Pico does have the facility to display duty cycle as a numeric figure & this helps to see the subtle shifts that can be hard to judge by looking at the waveform alone.
It should also be remembered that there is another factor that effects fuel pressure & that is pump speed. It seems obvious, but I remember looking at a scope trace & wondering why I didn’t see a bigger response in the duty cycle waveform, as I applied the throttle. I had given little thought to the fact that the high pressure pump is turning considerably faster as the RPM increases.
Another method of scoping these pressure actuators is with the low amps clamp. Credit to Frank Massey for this, as it was from him that I learned this method that allows observation of the pressure regulator control effort at much longer time bases. By that I mean, can you imagine trying to observe duty cycle or frequency, on a capture that has 10 or 20 seconds on screen. The amps clamp method allows you to study pressure control in a more useful way.
I am not familiar with the vehicle that you are working on, but the principles are similar across the makes. Is your “Pre supply” pressure confirmed?
HTH
Dave Hill
PS. A cautionary note. As always, my comments are just my own understandings & thoughts. I am no James Dillon & am fairly new to all this myself. Any corrections welcomed.
Hello Dave, Thanks for your reply, it's a great help. I shall test again using the amps clamp. I had the vehicle running saturday morning for quite some time & after cutting out once & giving me a "testing failed" message , then an unknown fault code using the multiscan, I couldn't get it to cut out again. I am hopefully going to get some more time on it today. Thanks again, hopefully post a fix soon, regards,Andrew
I forgot to mention on the previous posts that the engine sounded more like a diesel than a petrol when it came in & at one point when I was accelerating the engine, I heard a thud on the bulkhead. After stopping the engine to check & looking underneath, I found a bit of plastic, which had come from the timing cover where the centre of the balancer sprocket on the rear camshaft had come through. I spoke to the customer and he agreed to carry out the camshaft repair first & then carry on testing for the fault as I didn't think that the camshaft fault was the cause of the intermittent cutting out. After driving the vehicle for about half an hour, I couldn't get it to cut out, so rang the customer, so that he could collect the car. After it had been stopped for a while & just before the customer turned up, I tried it again & sods law , it cut out, but I couldn't get it to do it again & when trying to check the faults, I got the error message again & an unknown code. The customer took the car with the understanding that the fault would probably re-occur, even though the camshaft repairs had been done & it now sounded like a petrol instead of a diesel. So far I haven't yet heard from him, but perhaps he has now decided to take it somewhere else. I will post again, if I get to see it again & sort it. I am suspecting an ecu supply/ ground fault now , due to the fact that it is unable to display the fault correctly, but it's only a guess as I have yet to catch it faultering. Kind regards,Andrew
Hello all, The fault has now developed into something more regular, with the ESP/ABS system now loging faults, one for P0562 system voltage low, one for C1390 Engine torque regulation/torque reduction error and U1208 No communication with ecu/engine control unit information coherence. I am now thinking that the ABS/ESP system could be causing the engine fault. I have checked the ABS CAN signal & found what i beleive to be a fault on the CAN signal coming from the ABS module. WIth the ABS connector disconnected, the signal appears even, with it connected the signal is as follows. I am still having difficulties with extracting reliable fault codes from the engine ecu with the multicscan or autodiagnos. The CAN circuits measured approx 60 ohms with both ecu's connected & 120 ohms with one connected. [img][/img]
I finally decided that the actuator was faulty, which I have now replaced & it now seems to be ok. I am still not entirely convinced though, because of the strange happenings with the scan tool information. Regards,Andrew
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on February 15, 2009, 2:01 pm, in reply to "
