Posted by Craig Hewison on September 23, 2013, 3:10 pm
Year of Manufacture *: 2004 Engine Size and Code *: 1998 TDCi ( Optional ) Scanner Used: IDS ( Optional) Fault Codes: none
YL04 AYX WF0WXXGBBW4D28523 Ford Mondeo 2l TDCi 115ps
Hi guys,
I have the above vehicle in at the moment which intermittently cuts out, more so when cold, and pumps white smoke out of the exhaust. I took a capture of the camVcrank. see below
I have a known good example from a '06 which shows my timing to be out, however, whilst browsing for something else i stumbled across somebody elses known good from a 06 115ps which show mine to be correct. See below
without questioning the reliability of the captures people have donated, could somebody please provide a known good nexample for this vehicle or confirm if either of these actually is what it says?
I have seen quite a few of these "known good ones" that display a degree of variation & I don't place a great deal of faith in the usefulness of the cam crank waveform on this engine.
The reason I think we see so many different "good" captures is, due to the way that the cam signal is generated. The cam position sensor signal is triggered by cylinder 3 intake cam lobe, which is a far less precise method compared with the usual dedicated machined trigger that most cam sensors collect their signal from.
Of course the cam signal is not required to be "super accurate" as it is only needed for the purpose of cylinder identity, so anywhere "there abouts" is good enough.
It is a while since I looked hard at one of these, so my information may need verification, but I think it is about right.
Thanks for your response Dave, I've never heard that before, why do you deem it less accurate to use a cam lobe, lobe wear? How would you suggest assessing the state of the timing without expensive stripping?
As a Pico fanatic, it might seem strange that I am suggesting that the cam crank relationship waveform is flawed in this case, but I think we have to accept & understand the limits of any test method. For the most part, a cam crank waveform is a great way to expose a problem. But if it doesn't expose a problem, it can be easy to read too much into the result of the waveform & accept that everything is good. But what about the other cam that is not monitored by a cam sensor? this could be two teeth out & no scope in the world will display it (at least not with this approach).
In answer to your question....
>>why do you deem it less accurate to use a cam lobe<<
If you think about how the "average" hall sensor is triggered, i.e. by a precisely engineered "squared off" trigger wheel, passing closely to the tip of the sensor. Compare this to a sensor that is triggered by the approach of an offset ferrous object (the cam lobe).
Okay the cam lobe should share the same profile of each & every other cam shaft, used in the same engine variant, but there are bound to be some manufacturing tolerances that will effect the trigger point. Then you have to consider the same manufacturing tolerances effecting the hall sensor performance & lastly there is the potential for variations in the fitting. If a sensor in this application is "driven home" slightly more than on another car, then this will have an effect on trigger point & this will throw your cam crank capture out.
If you have ever observed a hall sensor response on a scope, as you wave a screw driver across the sensor tip, then my points will become clear.
>>How would you suggest assessing the state of the timing without expensive stripping?<<
Simple answer is.. I wouldn't suggest that there is an easy way. After all the cam crank waveform would at best, only provide a degree of confirmation about the intake cam shaft alignment. The position of the exhaust cam shaft is a complete mystery when using these cam/crank relationship waveforms.
Maybe a pressure transducer waveform would be a more useful test? I don't think it very easy to plumb the tool in though. Perhaps someone who uses one might be able to add to this?
Thankfully it isn't a massive task to pin these up manually & confirm things the old fashioned way.
Thanks for your post Dave, the part about the exhaust cam makes perfect sense of course. I have never waved a screwdriver across a sensor before but I certainly will as I'm intrigued now by the result! I have a wps but as you say connecting to a diesel maybe a little 'awkward'!
I can't be certain but i think Darren Cotton (AVC) who used his WPS with an adaptor he made to fit in a glow plug hole.
Think it was on a Renault but he did mention it got very hot quick. The problem with the Ford diesel is the glow plugs tend to break in the head so that maybe puts paid to that idea.
Wouldn't a relative compression test against ckp vs cmp help determine a timing issue if a known good one was found but then i'm not sure how you'd determine a cylinder without a sync unless you have spare injector to fire off. (is that possible)
A reletive compression test still shows a peak of the compression stroke and i've seen scannerdanner on youtube testing petrol engine timing using
WPS in cylinder or Reletive compression test
all synched from an ignition coil primary signal or ign control module and to me both looked accurate but i'm no expert.
Being diesel i suppose its alot more difficult.
thanks lee
p.s
edit
actually now i've read the post again i think its not a very good suggestion but i'll leave it up so you lot can have a laugh at my expense.
on September 25, 2013, 9:36 pm, in reply to "
