slow cranking

A

audinut

Member
hi all,
been a while since i've been on as daughter has taken over the running of the car. she now tells me that the engine turns over slowly but always fires. it has had a new battery at the end of last year and a reconditioned starter as the bendix was weak, but it is still turning over quite slowly. it will fire on the third turn but it sounds as though the battery is low and struggling to turn it over. have put battery on charge overnight and it's still sluggish.
all ideas welcome

simon
 
About three winters ago mine (2002 TDI) started to crank slowly when it got cold - but always did and still does catch on the first turn - i.e. under a second. I was convinced that I'd need to replace the (original) battery but it's still going strong.

Petrol or diesel? If the latter, is she waiting for the glow plug light to go out?
 
It sounds very much like the engine earth connection is corroded. It runs from the bottom starter motor bolt to a fixing under the nearside headlight. It's usually the headlight end that has the problem and if you have the right tools the bolt can be removed and the connection cleaned up and re-fitted in around 30 minutes. You can check by measuring the voltage between the engine and a good earth when cranking, anything more than about 0.2V and the earth is definitely suspect.

Steve
 
After 10 years of faithful service our A2 developed a fault, it would refuse to fire first time, and now it always took 2 goes to turn over slowly. Even tough the battery is quite old I didn't think it seemed dodgy.

A friend code read and it came back as either camshaft/crank sensor, sorry I can't remember exactly which, but it's the sensor that's just below the cambelt [my guess is camshaft sensor!] The replacement part is around £85. Any how when the cambelt cover was removed, there was a fair bit of dust in there. The original sensor was cleaned, and refitted; since then we've not had a peep out of it now, and saved £85!

Might be worth a look?

Good luck, hope you get it sorted.

bba
 
The camshaft sensor tells the ECU which cylinder is on compression and ready to fire. If there are problems with this sensor the ECU relies on a signal from the crankshaft speed sensor. Problem is the engine requires a few revolutions to work out the firing order so starting is delayed.

Starter, battery or earthing problems normally show different symptoms - slow cranking speed, dash lights dimming while cranking etc


Cheers Spike
 
hi all and thanks for the replies,
have always started a car with the clutch depressed and taught daughters to do the same. i'll check the earth lead and sensor at the weekend (hopefully!)
much appreciate the pics spike.

cheers
 
just a quick update, earth strap fine and there seems to be no problem with cam sensor. put the car into the garage and they diagnosed a 'heavy' starter. it had been replaced with a reconditioned one. for those with warning lights coming on in the cold, daughters did as well and garage said it was due to the high current being used and consequently low power in battery as nothing showed up in diagnostics, possibly just the cold weather.

simon
 
Old thread but a subject that seems to affect many on our forum.

My A2 (1.4TDI 75) acquired in Jan this year has always been very slow to crank but has always fired first or second time, so not been a big issue other than leaving that nagging feeling that it might fail next time!

It was particularly bad in cold weather but has persisted into summer.

Consequently I have read all of the associated threads on the forum looking for the most likely cause on an A2:

1) battery/battery connections
2) earthing points
3) starter motor
4) alternator
5) Crank position sensor
6) Temp sensor

Checking battery and terminal connections all were OK. A visual inspection of body earthing points also seemed OK so I was beginning to think of the more costly possibilities. I swapped over the battery but behaviour was the same. It had the original 10 year old battery still installed but it checked out OK as having over 75% of original capacity which is quite remarkable and says a lot about the battery management on the car.

Although the visual on the earthing points seemed OK I decided to investigate the primary earth connection from the starter motor to the chassis as this seemed to be implicated in several of the threads I have read. Access as we know is helped by removing the nearside headlight assembly. On undoing the bolt the faces of the strap seemed lightly oxidised but not heavily, however the facing surfaces of the bolt and washer were a different matter being heavily eroded, as in spark arcing.

Corroded Engine earth bolt.JPG

Cleaned the chassis bolting surface, the earth strap faces and replaced the bolt. This has had a marked improvement, the engine now turns over rapidly and fires first turn.

The lesson hear I think is that the only way to check the earthing points is to disconnect and inspect the actual faces and do not rely on an external visual check. I really did not suspect what I found. I am glad I did as it is the lowest cost outcome one could wish for:)

Geoff
 
Useful thread - mine's a bit slow in winter albeit has never let me down in 8+ years yet. Original 12 YO battery still fitted!

A quick numpty question.....do I need to take any particular precautions when undoing the primary earth e.g. not touching the body work at the same time? (Stop sniggering at the back - I've somehow NEVER needed to replace a battery in 30 years of car ownership!)
 
Gonzo

It is always good practice to disconnect the battery when working on any electrics. (see other threads on the best way to disconnect as it is advisable to have the lights on when you do to avoid surges that could upset either the CCU or the airbags)

However I believe that working on the engine earth strap does not require disconnecting the battery (anyone else please comment as I could be mistaken) as long as you do not try the starter motor whist disconnected. It could possibly try to draw current via a lesser earth point.

Geoff
 
Hi all, new member and A2 1.4se owner here. We've only had the car for a month (a bit of a rushed spontaneous buy with no research at all) and its slow cranking and bad starting (with no fault codes) had then left us on the verge of trading it in for a newer car, then it broke down in the local high street... final straw! Service history showed that it had a new alternator, starter motor and battery in the last few months during the previous owners short ownership so they'd obviously been having problems with it.

After looking through the online forums I had a hunch it could be earthing/connections so took it to a local auto electrician we've known for about 20 years. £58 later he'd renewed the engine earth, checked all the other earthing and fixed a corroded part on the main connection from battery.

It now fires up immediately with no hesitation at all, drives like a car that's 10 years newer, and has put a smile back on the wife's face just before Christmas!

Just the Open Roof replacement to save up for now (and a trip to Milton Keynes in the new year to get it locked down for now).

Kev
 
Hi Kev, welcome to the A2oc.

Glad to hear there still some good AE guys around who can do 'common sense' trouble shooting without just throwing new parts at the job in the hope they will fix it.

Cheers Spike
 
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