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Post by dooroy on Oct 14, 2022 18:27:22 GMT 1
My bro-in-law has a 2007 Mondeo 1.8 TDCi and the cam sensor has let him down a number of times and car won't start. Fit a new sensor and off it goes for a weeks or maybe a few months. He has used mostly sensors from motor factors and one from Ford. Car is at present a non runner - Ford tell him it could take weeks to get a new sensor. I have read up a lot of forums - the sensor has 3 wires ; looking from the front the left wire gets 5.03V , the centre wire is earth so the other one must be the signal wire ?? All the posts I have read about checking the sensor with a multimeter (which is all I have) say refer to manufacturers data which I don't have (and can't find anywhere). With ignition on and engine turning the signal wire reading fluctuates from 3 to 9 approx - but maybe a multimeter is not suitable for carrying out this test  ? I was also trying to find out which pins on the ECU are used by the sensor so I could check continuity of wires and quality of connections. I am strictly DIY so any advice /suggestions greatly appreciated. |
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Post by remmington on Oct 14, 2022 19:09:53 GMT 1
My bro-in-law has a 2007 Mondeo 1.8 TDCi and the cam sensor has let him down a number of times and car won't start. Fit a new sensor and off it goes for a weeks or maybe a few months. He has used mostly sensors from motor factors and one from Ford. Car is at present a non runner - Ford tell him it could take weeks to get a new sensor. I have read up a lot of forums - the sensor has 3 wires ; looking from the front the left wire gets 5.03V , the centre wire is earth so the other one must be the signal wire ?? All the posts I have read about checking the sensor with a multimeter (which is all I have) say refer to manufacturers data which I don't have (and can't find anywhere). With ignition on and engine turning the signal wire reading fluctuates from 3 to 9 approx - but maybe a multimeter is not suitable for carrying out this test ? I was also trying to find out which pins on the ECU are used by the sensor so I could check continuity of wires and quality of connections. I am strictly DIY so any advice /suggestions greatly appreciated. Send me a PM with the reg number - I will see if I have any wiring diagrams for it (I know I will) |
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Post by chippie on Oct 14, 2022 19:13:14 GMT 1
Can’t help with ecu input pins…( maybe Google mondo wiring diagram?)
But to check the sensors output, ideally needs a scope to check for the waveform…and when it’s connected to the ecu…
It is possible that the ecu input circuitry could be at fault, causing the sensors output to be not what it should be…,that is, the sensors output could be a sine wave or square wave…but if the ecu is damaged it could alter the waveform, which in turn could upset the ecu…
If you understand what I mean?
I’m sure some of the other ‘better equipped’ members will be along to offer something more credible…
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Post by remmington on Oct 14, 2022 19:31:44 GMT 1
Can’t help with ecu input pins…( maybe Google mondo wiring diagram?) But to check the sensors output, ideally needs a scope to check for the waveform…and when it’s connected to the ecu… It is possible that the ecu input circuitry could be at fault, causing the sensors output to be not what it should be…,that is, the sensors output could be a sine wave or square wave…but if the ecu is damaged it could alter the waveform, which in turn could upset the ecu… If you understand what I mean? I’m sure some of the other ‘better equipped’ members will be along to offer something more credible… I got the pin outs - just need an email address to send the pdf wiring diagram to... |
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Post by chippie on Oct 14, 2022 19:52:17 GMT 1
I see 🤣 .you posted while I was creating ‘war n peace’
Helpful as ever…👍
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Post by remmington on Oct 14, 2022 19:56:20 GMT 1
I see 🤣 .you posted while I was creating ‘war n peace’ Helpful as ever…👍 "war and peace" that made me smile (made an old man smile).  |
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Post by dooroy on Oct 14, 2022 20:57:48 GMT 1
Thanks for replies - from what I have read over the years I did consider that maybe the multimeter was not suitable for checking the signal wire output ; and the fact that it was 'all over the place' I thought that maybe the problem is with the ECU.
I have read a lot but couldn't find the pinouts for the Mk 4 - plenty for Mk3 etc but wasn't using them.
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Post by chippie on Oct 14, 2022 21:49:08 GMT 1
My suspicion of the ecu is based on the cam sensor being an active device, I.e it is supplied with 5v and has 3 wires, one of which is the ‘signal’ wire…if something is wrong with the ecu it could be causing the cam sensor to fail, but what could be is a good question…
Unless there is something external to both? Maybe a good check on the wiring loom for loss of insulation or whatever..
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Post by dooroy on Oct 15, 2022 0:18:33 GMT 1
Every time I checked the sensor was getting 5.03 V with ignition on , this never changed. However the voltage on the signal wire was very erratic when checked using the multimeter - but as you explained the multimeter would not be very suitable for this check. And the question I have been asking myself is "What is causing the sensors to fail?" I came across a post on some forum that said that Ford had provided a 'modified' wiring harness for the cam sensor that would supply it with 12V instead of 5V - as it was felt that the 5V was insufficient at times for the sensor to provide a signal. However I couldn't find mention of this anywhere else. Using the wiring diagran kindly supplied by remmington I will do some more 'investigation'. If I could get it started I would bring it to my place and put it on the ramp - I am at the stage where crouching down beside a car (ECU in front wheel arch) is too painful an experience  Thanks for replies ,will update later - hopefully to report success. |
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Post by Joepublic on Oct 15, 2022 10:19:02 GMT 1
To have so many failures I'd be checking the main engine earth for cleanliness and security, a broken earth strap will mean heavy cranking current will try and find an earth path via throttle / clutch cables, wiring to ecu via sensors etc
It could be the cam sensor is the weakest link in the chain?
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Post by chippie on Oct 15, 2022 10:30:18 GMT 1
To have so many failures I'd be checking the main engine earth for cleanliness and security, a broken earth strap will mean heavy cranking current will try and find an earth path via throttle / clutch cables, wiring to ecu via sensors etc It could be the cam sensor is the weakest link in the chain? Great idea...sometimes easier to check the basics... |
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Post by dooroy on Oct 15, 2022 10:50:05 GMT 1
Posted by Joepublic22 minutes ago
To have so many failures I'd be checking the main engine earth for cleanliness and security, a broken earth strap will mean heavy cranking current will try and find an earth path via throttle / clutch cables, wiring to ecu via sensors etc
It could be the cam sensor is the weakest link in the chain?
Thanks, will do that - I remember in older cars when choke cables etc used to burn up due to earth problems.
When the problem first occurred it was a scan that showed it to be a cam sensor - and when he bought one at a motor factors they told him there was a big demand for sensors for the Mondeo ('flying out the door' was their description).
Following 2 failures he then fitted a genuine Ford sensor (over twice the price) which lasted a few months longer but also failed.
The last one only worked for 3 wks.
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Post by OldGit on Oct 15, 2022 21:27:59 GMT 1
The camshaft sensor is a hall-effect sensor, therefore the output will be an asymmetric square wave. the supply voltage should be 5VDC +/-0.25VDC max. you should get approximately 5VDC on the signal wire with the sensor unplugged, an erratic voltage to me suggests bad pin grip at one end or the other, it won't be a poor earth causing the sensor to fail as the sensor body is electrically isolated from the 0V connection. Possibly it's contact fretting brought on by the vibration of the engine wearing away the contact area on the sensor, which is why a replacement seems to 'cure' it for some time. It's possible that the initial poking & prodding after the first sensor failed has made things worse in terms of pin grip. You could try making a small loop in the wiring where it exits the connector and using a cable tie to secure it to the connector, this will reduce contact stress and isolate any harmonic vibration, we tend to use Nyogel 760G to fill the connector housing which is intended for just such circumstances - of course, you'd really need to look at the pins for signs of fretting and check the receptacles for any sign of 'baggyness', if that's all OK then the output signal needs checking for 'cleanliness' and check for volt drop on the signal wire to the ECM.
One thing is for sure, given the number of replacements, it's very unlikely to be the sensor at fault on every occasion.
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Post by dooroy on Oct 15, 2022 23:58:47 GMT 1
Thanks for that explanation - will check out the points you mention once I get the car inside on the ramp as the weather here at the moment is atrocious.
The sensors, as you say, couldn't be all bad so it could be that the problem is caused by poor connections.
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Post by dooroy on Nov 15, 2022 0:41:58 GMT 1
Mondeo still not right. Bro-in-law and his wife got Covid car got a break.
Checked cam sensor wiring to ECU and all was OK there.
Have the loan of a scanner (from another DIYer) and would appreciate the significance of the following under the heading cylinder contribution /balance :
Cyl 1 : 1.17
Cyl 2 : 0.74
Cyl 3 : 1.38
Cyl 4 : 0.61.
When engine is idling - could this point to a problem with the injectors?
Fuel rail pressure when at rest is 430kPa - immediately goes to 30K or so when cranked.
There is a noticeable miss at around 1500 rpm.
Any advice/opinions appreciated - even if it's to forget about it.
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