Starting issues. Coolant Temp Sensor unplugged = starts fine

[unitzero]

I've been having issues with starting the engine (BRD 170 TDI) over the last few months, I had thought it was the battery at 1st and swapped that and all was well for a few weeks but the problem returned.
Sometimes it takes about 3 - 6 attempts to turn over after turning the key, Other times it will crank once then pause for a few seconds as if its died... then springs to life.

I was then thinking that the glow plugs may be bad but in the cold frosty morning we had a few days ago the engine started great !

After some misinformation I recently changed my Fuel Temp sensor which made no difference, but after a little research I found the plug for the Coolant Temp Sensor (PITA to get to) I tried starting with this unplugged and the engine fires lovely !

Is this a sign that the CTS is duff and my problems will be cured by replacing this ? or do you think there is an underlying problem ?

also, is it OK to run with the CTS disconnected until a replacement arrives or will that be bad for the engine ? (although, it already has the now infamous rough idle when warming up/idleing along with white smoke)

thanks for any help

 

[joncro]

My previous A4 2.5 tdi had very similar starting problems, i changed the CTS and it did solve the starting issues so fingers crossed mate, it will solve yours. With regard to running the car without the CTS, no idea im afraid.
Jon

 

[SDHA4SLine]

I've got a brand new cts never fitted to my brd £10 if you're interested? Genuine vw part not cheap Chinese rubbish about.

 

[SDHA4SLine]

Sugar hope I haven't broken any rules!

 

[unitzero]

Thanks guys,

SDHA4SLine I'll shoot you a PM

 

[SDHA4SLine]

I see your in Nuneaton, I live in rugby so not far

 

[unitzero]

I see your in Nuneaton, I live in rugby so not far

 

[unitzero]

Huge thanks to Steve (SDHA4SLine) for dropping off the CTS to me this evening. top bloke !

After getting dropped off at home I went about getting the battery on charge as the no.1 priority

(If i'd known the car would die I would have parked nose in on my drive but alas the extra long extension lead needed to come out !)



Then, armed with a camping lamp, a screwdriver, and a torch between my teeth I decided to attack this pesky sensor.
All went quite smoothly and even the small locking clip that could only be located by touch didn't put up too much of a fight. I thought i was being clever by putting a peg on the downpipe from the coolant header bottle but plenty of coolant p!ssed out anyway once the sensor was eased off. I quickly rammed the new one in along with a fresh o-ring and locking clip (this was easier said than done) and then I spent at least 25 minutes trying to re-attach the two pin wiring connector, goodness knows why Audi made the length of wire so ****** short !!

anyway, here is the old manky looking sensor covered in brown gunk :

The battery is still charging so I don't have any idea what the outcome will be but fingers are crossed !!

 

[unitzero]

So... That didn't work.

Have been finding it hard to start most mornings and this morning
It just cranked and cranked - the ESP light decided to flash at me whilst it wasnt starting too. :s unsure if that's significant - I suppose it is.

Had it scanned with my mates Snap-on Solus and it it came up with a G28 Engine Speed Sensor fault. Now the thing is, I need to find out where that sucker is and how to change it!

 

[ajax1976]

Think I'd be looking at the glow plugs and associated wiring, checking voltage and the individual plugs resistance. I'm not sure about the 2.0tdis but the 1.9s were bad for wiring harness faults. I would guess the ESP light could just be a voltage dip when you've been trying to start it and the battery working hard.

Possibly worth a read,

http://forums.tdiclub.com/showthread.php?t=396554

 

[unitzero]

Think I'd be looking at the glow plugs and associated wiring, checking voltage and the individual plugs resistance. I'm not sure about the 2.0tdis but the 1.9s were bad for wiring harness faults. I would guess the ESP light could just be a voltage dip when you've been trying to start it and the battery working hard.

Possibly worth a read,

http://forums.tdiclub.com/showthread.php?t=396554

Thanks, I actually read that this morning whilst searching for some answers ! that guy got charged a hefty sum !

I remember having the injector wiring loom play up on my old 1.9 TDI Bora causing a misfire which was a PITA to change.

I just jump started it so easily with hardly any revving of the other vehicle before hand (albeit with the fuel temp sender unplugged) and it fired up straight away. Wouldn't glow plug issues cause it to still struggle under these circumstances ?

 

[ajax1976]

Thanks, I actually read that this morning whilst searching for some answers ! that guy got charged a hefty sum !

I remember having the injector wiring loom play up on my old 1.9 TDI Bora causing a misfire which was a PITA to change.

I just jump started it so easily with hardly any revving of the other vehicle before hand (albeit with the fuel temp sender unplugged) and it fired up straight away. Wouldn't glow plug issues cause it to still struggle under these circumstances ?

Not really sure tbh but if it was cold enough to require glow plugs today but not when you jump started it then possibly I suppose.

 

[unitzero]

it was 0.5 degrees this morning and around 2 this evening. not sure when the glow plugs decide to kick in tbh

 

[ajax1976]

I think they "glow" for every start and it's purely down to the temps if the engine actually requires them to start it and what extent they are required, could be wrong tho.

I'd be tempted to spend an hour or two with a multimeter to confirm battery volts, volts at glow plugs and if all checks out pull the plugs and do resistance tests on them. Could be as simple as a duff battery etc so you really need to establish the conditions of everything first and go from there, I wouldn't be rushing out to buy other sensors until you've ruled out the easy things.

 

[unitzero]

That is a good idea. I did some investigating today at work (the car actually started this morning after a motorway blast and leaving it on charge all night)

Before digging too deep and testing glow plug voltage/ resistance I decided to look at the battery first - it's only 6 months old so if it's a dud then maybe I can get a replacement under warranty.

After sitting for 7hrs at work we read the voltage on the battery and it was sat at 12.8v. Tried to crank and it dropped to 9v but wouldn't start until I had another go, this time I got in and pressed the clutch and gave it some gas as I usually have to do. Still dropped to 9v whilst cranking and sat at around 14v whilst idling. We then used the meters negative probe on the engine block and noticed about half a volt drop, My work colleague thinks that this may point to a bad ground problem. Sounds a little strange but we have made a short "jump" cable to go from the negative terminal of the battery directly to the metal of the engine which I'm going to try in the morning after it's been sat all night and see if it's any easier to start and hopefully give me more insight.

 

[ajax1976]

Sounds promising but when your jump starting do you connect the neg lead to the battery neg or to the engine etc on your car? Only asking as I would think if you're connecting it to the battery neg that would rule out an issue with the block/chassis earth.
Cranking will pull the volts down but 9v sounds a bit too low but thats just my gut instinct, not actually sure what a normal cranking voltage would be. Your charging voltage is ok, 7hrs isn't really that long tho so I think I'd be testing it once parked up at night then again in the morning to see if battery is holding charge over night or if there's a draw on it that's draining it over a period. I have read of an issue/fault with RNSEs that can drain the battery fairly quickly.
Do you access to a tong multimeter? It makes testing any draws on the battery when the cars switched off dead easy. If not you can still do it with a normal multimeter, just means you'll have to disconnect one of the battery cables and connect the multimeter in series.

 

[unitzero]

As you say, 7 hrs isn't a very long period. I will stick a meter on before starting *touch wood* in the morning and see what it's reading after a cold damp night.

When jumping I did have the neg. on the battery but also had my fuel temp sender unplugged which I'm led to believe would cause the car to go into cold start mode and fire up nicely like it did.


By Tong Multimeter do you mean a current clamp / clamp meter that clips around a cable ? If so then yes, we have those at work ( we service electric fault equipment so we have all kinds of stuff, which is useful )

RNSE fault sounds like it's worth looking into

 

[ajax1976]

Yup that's the fellow, will save you a lot of hassle.

 

[Jimbo.King]

Cranking voltage ideally wants to be no less than 9.6v, on my 3.0tdi engine I had 2 glow plugs that were faulty, when I did an engine scan the computer told me which cylinders had the faulty plugs, does the 2.0tdi engine do the same by letting you know which cylinder has faulty glow plugs ?
The G28 sensor fault is the crankshaft sensor by the flywheel, if this is faulty it would definitely cause you starting problems, has it cut out on you at all while driving ?

 

[unitzero]

Unfortunately I don't have VCDS and the local VCDS map on here doesn't really help as I've just been ignored by people I've PM'd about it.

Never cut out on me whilst driving thank god. Was one of my many concerns when buying a 2.0TDI but as the injectors were changed at recall I was hoping that wouldn't happen any time soon !

I have come to the conclusion that my short commute (3 miles) and the air ride compressor kicking in every trip isn't doing my battery any favours as the drain probably outweighs the charging.

 

[unitzero]

Had the battery charging all day yesterday and it still struggled to start when it was time to go home.

This morning it was struggling so I unplugged the temp sensor and used my makeshift jump cable to get it to fire before killing the battery again.

I'm thinking it may be a fuelling issue ? It keeps cranking but if the fuel isn't there to fire then it won't turn over ? God knows.

 

[unitzero]

OK, so now it has the hesitation almost every time.
(Although it actually started today at 0 degrees)
Turn the key and then it pauses for a second then cranks a few times and then starts. It does the same with the fuel temp sensor unplugged too. My mechanic says it sounds like the starter motor playing up so I'm planing on getting that replaced this week - fingers
Crossed.

 

[unitzero]

The plot thickens... After booking in for starter and G28 sensor replacement. I thought I would just try and start again with the CTS unplugged and it fires great.

Ive bought a sensor from VW today to rule out a duff one.

 

[SDHA4SLine]

did you fit the new cts yet? did it cure the problems?

 

[unitzero]

did you fit the new cts yet? did it cure the problems?

I did fit it and it fired up ...but slowly.
We did a little bench test on the one that you gave me and it seems to work perfectly so the CTS was definately ruled out.

I bit the bullet (and borrowed the Mrs' credit card) had a new starter fitted and *touch wood* it's fired up straight away every time. I must have been used to the slow cranking thinking it was normal, but hearing it now it cranks quick and starts so well.

 

[SDHA4SLine]

phew its good to know I didn't sell you a duff one

Maybe you could sell the spare on to the guy on other thread you've commented on?