Steve Smith wrote:
Hello and thank you for the posts, images and waveform as I know they take valuable time to complete.
I am intrigued by the event taking place in the cylinder and have some questions (sorry) if you have time to respond?
I'm intrigued also, I will make time as developing skills and knowledge is always good.
Often when we find anomalies it is worth qualifying our measurement.
I have lost count of the times I think I have found something when in fact it was my measurement or technique responsible for the error.
Yep, been there too many times.
Would it be possible to measure all cylinders in the same fashion?
I would like to know if all cylinders replicate this "Blip"
Can we confirm there is no leak on the measurement equipment. (This is not always audible)
Prior to the engine non start were there any customer complaints of excessive noise or exhaust smoke?
Regarding the measurement hose and dummy injector used, are they clear with no unique integrated valve?
OK, I can try and measure all cylinders. I'm a little concerned as the injector was pretty tight in this cylinder. As things stand at the moment I'm leaning towards a cam timing issue (keyway issue??) so in the normal course of diagnostics I wouldn't need to remove injectors. Obviously as they are tight I'm a bit nervous about causing issues removing an injector that I cant justify was necessary for the diagnostic procedure. However, I really would like some more idea what is going on, so If I can get them out to try other cylinders, I will.
I'm 95% sure there is no leak.
No issues with smoke, it doesn't sound great, but I wouldn't say there was excessive noise last time I was in the car. It doesn't use oil.
I've taken the valve out of the dummy injector, the only possible restriction would be the quick coupling on the WPS and a similar style coupling on the sykes compression test adaptor.
Could we try Pico Diagnostics for an Absolute compression test?
Here we can compensate for the volume of your pressure transducer, hose and dummy injector for a true peak pressure value. Please see topic14971-10.html
we can, working out an accurate volume may be tricky. May have to find a syringe or something to work that out.
As mentioned above, could we add other waveforms into the mix?
I would like to see if this blip is visible in the cranking current peaks (or battery volt drop ((troughs)) during cranking)
Yep, will do.
Using the reference waveform feature and a trigger from a fixed input, adding Intake Exhaust and Crankcase presures as mentioned above would be ideal
Yep, I assume you mean use the "in cylinder waveform" as a reference then overlay the other pressure waveforms. May be difficult to keep cranking speed constant enough.
Would it be possible to remeasure via a dummy glow plug? (If applicable and I guess accessible)
Nope, I tried that first, The fuel rail is in the way so I'm pretty sure the connector wont go on, I gave it a try anyway, but didn't like the feel of the glow plugs.
The expansion pocket is large for a diesel engine (As deep and low as a petrol engines intake pocket) at -646 mbar
That's beyond my knowledge at the moment, I have a lot to learn on this subject
This may or may not be relevant and we should not pursue this without comparing to other cylinders and querying the measurement hose/technique
This leads me onto the exhaust value timing based on the position of the expansion pocket. I have attached an image that should help as I fear the exhaust valve opening event is advanced.
Ah haaaa.......now this is where I'm unsure. Using what I would say are the standard timing checks which are widely documented, this does look advanced for Exhaust opening and exhaust closing/inlet opening (when I restricted intake). However, I've spent quite a lot of time looking fault free cars and none of them look correct using these checks, despite cam timing being OK. I have come to the conclusion there are too many variable to check timing using a standard set of values. The only way to be sure is to use a known good waveform from the exact same variant of engine. I've spoken with other people who have come to the same conclusion. However, I now contradict myself by saying, I do feel the the issue with this car is cam timing, I just don't trust the "in cylinder" test without a known good.
Remember, the valve timing can be correct at the timing gears but incorrect on individual cylinders
Yep, which is what I think the issue could be. I just need to get back to it. I do now have a Vivaro van here with an F9Q engine, so if I get chance, I may grab an in cylinder capture from that!
I hope this helps and I am so sorry for all the questions
Thanks for the input, much appreciated.