Cold start problem - sorted

[RichN]

Morning guys,

Mk3 Cupra which normally runs like a dream won't start today. Car ran fine yesterday, no issues at all, regular temperature etc. Had a freezing night last night (often do, may not be related) and this morning it won't start.

Turns over fine, sounds like battery is healthy at least.
No errors in VAG-COM,
Petrol shows 30 miles range, and just under 1/4 tank.

On first crank, splutterrs for a very brief millisecond and then returns to just turning over with no 'catch'

At one point, possibly 5th attempt, oil light beeped 3 times but has since gone out. This didn't cause any errors to be logged in VAG-COM.

Cheers in advance for any useful thoughts.. I'm away from the car now, had to get train, but will need to take a look tonight.

 

[ian_cupra]

try sticking a bit of fuel in it, you never know, sensor could be faulty in tank, other than that not sure mate

 

[Ibiza125]

Try pumping the accelerator a few times while trying to start it. Do this a couple of times and if it doesn't work then I'm not sure.

My old Ibiza did this randomly one morning and it worked for me... Got me a but confused though!

 

[Atlantia]

Can you smell petrol after you've been turning it over for a while?
Sounds like a fuel pump problem.
Check you're getting a spark first.
I don't know how the fuel pump is set up on these, but if its directly plugged into the tank, and you are getting a spark but no strong smell of fuel when you take a plug out then bang the fuel pump (on the outside being careful not to hit any connections) with rubber mallet (carefully) and see if the car starts straight after. My old Nissan has a similar sounding problem and that got me home, then to the garage the next day. Its not a fix though.

 

[RichN]

Ibiza125 - tried that trust me, but cheers ;-)

Atlantia - thanks I'll have to look in depth this evening - no smell of fuel at all, I'm guessing it's either a fuel pump issue or fuel level sensor issue.

I guess if the pump's working I'll hear it if i lift the seats in the rear - I think that's where it's located..

 

[Riko]

Yeah fuel pump could be the prob. When i start from cold in the mornings (in current freezing weather conditions) my petrol gauge reads lower petrol readings, so after its warmed up I get higher petrol readings!

 

[RichN]

Anybody ever changed fuel pump? Easy? Is it located in the rear bench?

Could be fuel pump relay I guess...

 

[Atlantia]

Anybody ever changed fuel pump? Easy? Is it located in the rear bench?

Could be fuel pump relay I guess...

If its under the back seat then great, I assume it primes when you turn the key to the start position? Make sure you've got the seats up and see if you can hear it.
If not then you need to see if you can find a way to make sure there is power getting to it (carefully), or try the easiest 'bang it' test to see if its jammed and that makes a difference, but remember jammed is probobly fecked so if it starts it'll probobly cut out again after a few miles.
I'd still pull a spark plug, and look for a spark and see if its damp, should be plenty of fuel in the bore if you've been trying to start it. Dunno about the relay. I'm not sure of the specifics of the set up on these so I'm going on what I did with my Nissan.

 

[RichN]

Cheers - Small update..

Now i'm home, if i leave it, then turn it over it will start, and run for about 3 seconds.
It runs for even less if i touch the throttle, or start it with part throttle.

To me this does still sound like fuel pump, perhaps. I can't hear it prime when i switch to "accessory". In my other car (rover based) it's very obvious - in this one it's either very quiet or not working at all.

 

[Myki da Pyki]

Sounds like immobiliser to me mate

 

[RichN]

Why? Barely manages to limp into life, applying throttle kills it in 1 second, no vag-com complaints about immobiliser - surely there would be?

 

[Atlantia]

mate I don't know jack about the immobiliser or how to diagnose it.
Would it stop the pump from priming? Or allow it to prime then cut the engine?
Any ideas how to daignose it Myki? Wouldn't the vag-com pick it up?

 

[RichN]

Ok today's update:

It finally does start if I crank it for about 20 - 25 seconds, it runs rough for about 1 minute, then all seems fine. Leave it 12 hours and try again, same issue.

So it's a cold start problem.

Temperature sensors? I did replace the Coolant Temp' sensor a while ago so it's green top, still nothing logged in vag-com.

 

[daz_cymru]

i have the same problem i think mate....if it happens again try taking the fuel pump fuse out.....turn it over (obviously wont start)....then put the fuse back in and start it up

 

[RichN]

Probably not too keen to do that every time it's cold - not least as the car's been a beauty for 4 years.. I think i'll change the CTS again.

 

[RichN]

Simplest solution sorted it - Coolant Temperature Sensor.

Seems that even the new green top ones don't last that long. £20 from GSF a couple of weeks ago and it starts like it ought to now.