Morning all,

 

I have a 2006 Skoda Fabia 1.4 TDi Ambiente (mileage around 114,000). Earlier last year whilst visiting my family in Nottingham (around August) it began intermittently struggling to start a little and producing a lot of smoke, which was easily resolved after a few seconds and pushing the accelerator to push up the revs on idle. I needed an interim service and my exhaust done so I got a mechanic to check it out and also had the following work done:

 

• 3 x glow plugs changed (1 was completely faulty, 1 partially and I thought I might as well get the other swapped whilst I was there)
• Injector seals replaced with Elring ones. This is because the mechanic s said the oil seemed smoky and the smoke was blue colured from the exhaust

 

The same day the work was completed I drove back down to Brighton and there was no problem. However the intermittent fault has continued. In the last couple of weeks, when I turn the engine upon first start, it starts but then immediately (within a couple of seconds) stops again. Then I crank it again and have to keep the key turned and the engoine slowly turns faster and faster before it kicks in. Once started, it runs absolutely fine. There's no engine management light and I don't have a fault code reader/cable. I tested the battery and it's fine and also did a bit of research and thought the cam position sensor might be at fault. I found this video from HatBoyHarvey and followed it. The voltage reading I got with the sensor disconnected were as follows:

 

1 + earth approx: 12.33v (the video description suggest that this should be around 5v on a 1.4 model)
2 + earth approx: 4.98v
3 + battery pos. term: 12.33v

 

I'd already bought the new (aftermarket Valeo) cam position sensor so went ahead and fitted it. Unfortunately the cranking problem is even worse now and I could barely get the car started after a few attempts. However, when I disconnected the cam position sensor and left it disconnected, I was able to get the car started. I'm thinking of putting the old sensor back in temporarily so I can at least get the car started whilst I figure this out!

 

Does anyone have anyone have ideas about what's going on please?

 

Thanks for your time!

 

 

Sorry, just to make this more clear, when I tested the voltage it was done with the ignition in the on the position but without starting the car and I tested it as follows:

 

Pin 1 to Batt negative: 12.33v (the video description suggest that this should be around 5v on a 1.4 model)
Pin 2 to Batt negative:  4.98v
Pin 3 to Batt negative: 12.33v

 

Sorry again (can't edit the post), the last one should read:

Pin 3 to Batt positive: 12.33v

You can edit your post an hour afterwards if you have made about 10 forum posts.  Alternatively you can pay to upgrade your membership.

 

Meanwhile, welcome to the forum 🤝

I was confused when I first read your post, glad you clarified it.

 

Most sensors take in +12v and then drop it down to whatever is needed 1v/5v etc and then this is your signal fed back to whatever is needing it, most likely your engine ECU.

 

 

Might be good idea to post up your engine code as written on your V5 so that wiring diagrams can be found if needed.

Thank you. The engine number on my V5 is: AMF 910059. If that's not what is needed then here's a pic from the V5 (turns out it's 2005):

 

I don't think the cam sensor itself is likely to be the root cause of your problems. You should check the condition of the cam and followers for wear since one bad oil change on a PD engine will wreck the top end.

I am sure some experts will be along to advise you hopefully, best to not replace parts without some proper diagnostic session (live data etc)

Best of luck.

4 hours ago, varooom said:

I am sure some experts will be along to advise you hopefully, best to not replace parts without some proper diagnostic session (live data etc)

Best of luck.

 

Thank you for your response. I have played around with diagnostics before and managed to sort a steering lock fault on my brother's BMW 520 with a cable and some software that I bought from eBay. I am thinking of buying this cable to see if if I can get some more information. I've also checked the VCDS owners map and @paulski I was wondering if I could trouble you to get a fault code reading for some beer money please?

When its struggling to start, does the rev counter register the cranking speed? The crank sensor on its way out can cause a no start/very hard start.

2 hours ago, SuperbTWM said:

When its struggling to start, does the rev counter register the cranking speed? The crank sensor on its way out can cause a no start/very hard start.

Hi @SuperbTWM, yes it does. I've swapped the sensor back to the original so at least it now starts after much cranking. After the initial crank-heavy start, if I turn the engine off and start it again, it starts immediately, without the excessive cranking.

How does it behave if you start it with the sensor completely unplugged?

7 hours ago, sepulchrave said:

I don't think the cam sensor itself is likely to be the root cause of your problems. You should check the condition of the cam and followers for wear since one bad oil change on a PD engine will wreck the top end.

@sepulchrave, I did get the mechanic to visually check the condition and tension of the cam belt last year because the car had incomplete service history when I bought it and he said it was in good nick. I've taken a couple of photos with the cover removed but i'm guessing they're not of much use without seeing it in person?

 

I'm not worried about the belt, I'm worried about what's inside the cam cover!

Hi @Circuital, I can certainly do some fault code reading, drop me a private message, i can do evenings only this week. 

 

On 22/01/2023 at 19:14, SuperbTWM said:

How does it behave if you start it with the sensor completely unplugged?

Sorry about the late reply, early starts and late finishes this week!. I unplugged it yesterday morning and it was exactly the same as the video - lots of cranking and took ages to kick in. I then turned off the engine, plugged it back in and started the engine again and it started no problem. I drove to work and then the next time I turned the engine (without any messing about with the sensor) was when I left work 11 hours later and again, it started fine. Then this morning, it needed lots of cranking again and then this evening, lots of cranking again.

My gut says you have a fuel problem, an intermittent lift pump or possibly a loose hose somewhere allowing air to enter the fuel system and air locking the injectors or losing prime, this is causing the seemingly random but mostly when the car has been left a while - hard start issue. 

having a hard start, then shutting the engine off and plugging the cam sensor back in and having a good start proves nothing. You should have really stopped the engine and tried to start it again without touching anything to prove the fault repeats itself before you then change a variable when fault finding. 
 

like I said, it’s a hard diagnosis over the internet but I have a feeling you are barking up the wrong tree. 

 

@SuperbTWM "having a hard start, then shutting the engine off and plugging the cam sensor back in and having a good start proves nothing. You should have really stopped the engine and tried to start it again without touching anything to prove the fault repeats itself before you then change a variable when fault finding."

 

Thanks for your time again. I have done this too and the result is always the same - once the engine has successfully started, turning it off and then on again results in a good start. I'm also thinking the cam position sensor isn't the root cause now. To be honest it was a lazy stab in the dark and I should've got diagnostics done first, which will be my next step. If that doesn't yield anything clear then i'll take it to a mechanic. I guess I was hoping i'd be able to have a go at fixing it myself like in my younger days when i'd do bits and bobs on my old Citroen C15D van - more for the satisfaction than anything else!

When you haven’t got a lot to go on all you can do is go round and check the obvious or get an idea or have a guess and then try and prove it’s not that and move on to the next. 
 

last fuel issue I had on a polo 1.4 PD about 10 years ago took me a while to sort. Most mornings it would start and then die instantly and then take a lot of cranking to get going. 
 

To cut a long and boring story short I faffed around for weeks trying different things with the lift pump, hoses and filters working my way through the fuel system.

 

I then bought a second hand tandem pump and when I came to fit it the suction hose to the pump came off really easy, it never leaked a drop but it must have been loose enough to suck a load of air in on the first start of the day. A 50p hose clip later and it never failed to start again!

 

Nobody ever has the same fault, but it’s worth checking round at all the fuel

hoses, injector connector, sensors, anything you can see just give it a prod or a wiggle, you might just be lucky enough to find something!

 

Good Luck!

Edited 24 January, 20233 yr by SuperbTWM

Just to add to this thread.  The OP popped to see me for a VCDS scan.

 

I noted that there was no sign of an engine management light being on when we had engine running. So it might not have logged any faults anyway. 

 

My fully up to date and licensed VCDS hex V2 could find no modules to communicate with, it just hung and all it could read was a voltage in the scan popup, (there are no issues with my VCDS as I checked it worked absolutely fine on my Octavia straight after this happened in case). 

 

I need to use the VCDS  interface test function when I get the OP back next week as it's bugging me that I couldn't assist them in their quest to fix this car. 

 

Anyone seen a 6Y platform with no Comms in VCDs on here? 

 

Thanks. 

 

 

 

 

Edited 27 January, 20233 yr by paulski

HI all,

 

Just a quick update:

 

-A couple of weeks ago, the hard starts seemed to stop and it now starts up fine each morning

 

-However, until last week it was pumping out horrible white smoke like nobody's business. Again, sometimes it would do this and sometimes not. For the past week, it's been absolutely fine though - no smoke, no hard starts, nothing untoward

 

-I took it to a garage last Saturday and despite using two different Snap-On diagnostic kits, he couldn't communicate with the car, so @paulski, don't worry it's my car being an idiot, rather than your kit

 

The mechanic rang two of his Skoda-specialist mates and since the faults are intermittent, the conclusion is that i've probably got a faulty ecu. I asked whether he could recommend a decent auto-electrician and he basically told me it wouldn't be worth the amount of money it would cost to trace the fault 🤦‍♂️.

 

Thanks for all your help anyway and i'll let you know if I get to the bottom of it. Hopefully it'll continue to magically work fine, as it has been doing for the past week!

Edited 13 March, 20233 yr by Circuital

If it does go south and you fancy trying a different ECU you can pick them up second hand with the immobiliser disabled which means its plug and play

 

They can be picked up for around £100+ on the famous auction site depending on what engine code you have

 

It's far more likely to be an engine loom failure somewhere than the ECU itself, an auto electrician could probably get to the bottom of if, the cost would be for their labour rather than new parts.