Starting issues when hot?

leej666

Active Member
Jan 7, 2016
7
0
Ireland
Hi, just wondering has anyone else had this issue or can shed some light on it...
Car is Leon MK2 1.9tdi 2005
When the engine is cold or warming up it starts every time perfect.

However once the car is fully hot I.E. 90'c, when the engine is turned off and back on within a reasonably short period of time (before it cools much) it struggles to fire first time and takes a few seconds of cranking to start.

It starts a bit rough but only briefly. I was told it's something to do with priming the injectors and could be a case of too much/too little fuel once the car is at full temperature. Once it starts it runs perfect but it's shaking the engine quite a bit each time.

Only way to describe it would be similar to taking off with too little throttle and the engine shudders until revs increase...

Could it be a Crank position sensor or similar?

Thanks
 
Last edited:

mty12345

Active Member
Jun 17, 2011
3,727
450
bristol
Thats usually the coolant temp sensor that has failed. The car thinks it's cold all the time so it adds too much fuel when trying to start the hot engine. If you have vagcom/vcds then look at the coolant temp on that for confirmation.
 
Last edited:

leej666

Active Member
Jan 7, 2016
7
0
Ireland
Great thanks for the info. Would the coolant temp sensor not affect the dash gauge? This reads perfect. 90'c exactly?

Cheers
 

leej666

Active Member
Jan 7, 2016
7
0
Ireland
None of that makes pretty reading...seems like a nightmare. I'll try the temp sensor first. Prob cheapest d.I.y.option..

Thanks for all the suggestions
 

stu 157-330

Active Member
Aug 6, 2009
80
0
West lothian
Hi, I've got A 2l tdi.. But the car had a similar issue late in 2014 which turned out to be the cam sensor was getting warm and sending a distorted signal to the ecu

A new cam sensor fixed it, a pig of a job to fix without the cam belt coming off☹️
 

leej666

Active Member
Jan 7, 2016
7
0
Ireland
That sounds like what I originally suspected in my first post. I have a saab 9-5 2.0t petrol as well and it would sometimes not start when hot for up to 15 minutes. Most notably when driving for a while and the engine was at full temp. Refused to start until it cooled down a bit. Turned out to be the Crank position sensor. Cheap sensor and was easy to replace on the saab.

I'll swap this on the Leon before the water temp sensor and post the results...
 
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