Hot Start Problems

[RJMcLean]

Hi all,

 

I have seen this come up many times on here, but will explain below

 

Octavia Pre-FL 1.9pd dsg elegance

05 plate

108000 miles

Last service 105,535

 

Had issues last month starting the car when warm/hot. First port of call was to change the battery (Bosch S3 096)

 

However, I have the same problem as before with the old battery and no change, so I can now rule that one out.

 

Any idea's, someone mentioned something about the regulator needing replacing?

 

Help would be appreciated

[Anddenton]

Generally speaking if the battery isn't responsible then the starter monitor is pointed to as the culprit, however it could also be something like the cam sensor.

[BlueVRSTom]

I've always been told that if it's hard to start when warm/hot then it's the cars temperature sensor.

Fairly cheap sensor and normally about a 10min job to replace.

This is the temperature sensor and NOT the thermostat so we're clear lol

[RJMcLean]

I've always been told that if it's hard to start when warm/hot then it's the cars temperature sensor.

Fairly cheap sensor and normally about a 10min job to replace.

This is the temperature sensor and NOT the thermostat so we're clear lol

Many thanks will look it up

[RJMcLean]

Just so I buy the right sensor would this be the fuel temperature sensor?

[toe]

Coolant temp sensor

[mannyo]

Could also be the Camshaft position sensor, another common problem. Symptoms of it failing are long cranks needed to start the car when its warm, but its fine when cold.

It takes a long time to crank when warm because the cam sensor is sending the wrong readings to the ECU, so after a short while it fails over to the crankshaft sensor instead of using both.

 

If you have VCDS you can use the measuring blocks to check the coolant sensor, and the readings it is sending to the ECU.

 

Neither sensor will always log a fault to the ECU, it was not until the cam sensor finally stopped working all together did my Superb MK2 diesel log a fault. Once the sensor was changed my months of poor warm starting went away as soon as the sensor was changed.

[RJMcLean]

Narrowed down to three things. Coolant temp sensor, cam sensor or worst case the starter motor. Will start with the cheaper options before getting to the starter motor. Also noticed mpg is down a bit from normal so points towards temp sensor

[mk2cliffy]

If it was the temperature sensor would there not be problems with the temperature gauge not working properly as well?

[RJMcLean]

If it was the temperature sensor would there not be problems with the temperature gauge not working properly as well?

That would be the thermostat

[RJMcLean]

Update

 

Had the car in at my local and trusted independant, but the car was behaving itself. It seems to be intermittent. As standard from them, no fault found = no charge

 

Next step is the local diagnostics place. If still no fault found (when there is) then it will be off to the stealers. 

[Magician100]

Not sure if this is related but i have been having problems with starting for a while when the engine is left cooling for a few hours. The car is a skoda 1.6tdi DSG 2011 and will start fine when hot and when cold, but when left for a few hours from hot, can turn over for a few seconds before starting and will sound like it is not going to start. It can also happen when i drive the car a short journey from cold or leave the car running for a few minutes in the mroning and then stop it. It looks like the smallest amount of heat in the engine appears to cause the issue. I have had it in the dealers a few times, but no faults showing. have replaced both coolant sensors and battery, but no change. Car shows no faults and is fine otherwise. Recently the dealer replaced the injectors as a trial, but no change either. if anyone has any ideas or similar experience, let me know.

[RJMcLean]

Well mine is off to the Stealers on the 30th (Pay Day). Hopefully they can fix the problem

[cmcm789]

Well mine is off to the Stealers on the 30th (Pay Day). Hopefully they can fix the problem

Did you have any luck with the dealers?

[RJMcLean]

Did you have any luck with the dealers?

 

They knew there was a problem, but failed to find the fault. Took it to Grey Gables (Curbridge, Witney).

 

I have bigger problems to worry about now (new shocks, top mounts & bearings, wheel bearing). 

[ste1234]

Has anyone actually found the fix for this lol??? this ongoing with me for last 4 wks,have changed fuel pump,coolant temp sensor,crank shaft sensor,starter motor,checked battery,absolute madness! some say cut wires in and put in a bypass relay switch to trick ecu to think cold starts but seriously the problem must be something and solution surely isnt to cut wire looms and install a make shift button???

[pikpilot]

Did you use a genuine VAG coolant temp sensor? It is very fussy.

[ste1234]

12 minutes ago, pikpilot said:

Did you use a genuine VAG coolant temp sensor? It is very fussy.

This the box so not sure how good this brand is, I wouldn't have thought be much difference? Again no fault logged 

[ste1234]

20 minutes ago, pikpilot said:

Did you use a genuine VAG coolant temp sensor? It is very fussy.

 

[pikpilot]

The febi bilstein may be ok as it is the same colour green as the genuine VAG unit. If you can find someone local with VCDS, they could read the temperature indicated to the ecu by the sensor. And while they are doing that, get them to do a full VCDS diagnostic scan.

Look in the VCDS section of Briskoda to find someone local to you who will do the scan a few beers.

[ste1234]

Hi, was colour grey in it since I bought it 2.5 yrs ago so replaced with grey, why do you mention green lol? I have had it in diagnostic machines few times but no faults coming up whatsoever 😞 so puzzling cause problem just came into it overnight, it was starting extremely easy till 3 wks ago and cold starts are as normal, split second and fires 

[PipH]

May be one of these would do the trick for you.

https://www.ebay.co.uk/itm/Hot-Diesel-Start-Starting-Fix-VW-Golf-Passat-Audi-Seat-Skoda-1-9-2-0-2-5-TDI/201911548894?epid=0&hash=item2f02ddbbde:g:Ry0AAOSw0vBUgZKs

[ste1234]

7 hours ago, PipH said:

May be one of these would do the trick for you.

https://www.ebay.co.uk/itm/Hot-Diesel-Start-Starting-Fix-VW-Golf-Passat-Audi-Seat-Skoda-1-9-2-0-2-5-TDI/201911548894?epid=0&hash=item2f02ddbbde:g:Ry0AAOSw0vBUgZKs

 

 

Hi thanks for reply,problem was found today,apparently the timing had went out a bit 😞

[Papfox]

10 hours ago, ste1234 said:

 

 

Hi thanks for reply,problem was found today,apparently the timing had went out a bit 😞

Glad you found it.

 

If the timing was off, do you know when the last time the cam belt/chain/tensioner were changed? My vRS was getting grumpy on starting. My local independent ran the car over with VCDS and the timing angle was 3 point something degrees out. They inform me that something very bad (replacement engine bad) happens at 5 degrees and the speed of the angle increase goes up as the chain gets more worn. The spec of the tensioner I believe was revised on some engines so you may not have the latest part and it is a worthy improvement.

 

I'm not sure which engine you have but the cam belt replacement interval on my old vRS was 3 years so, if you've had the car for 2.5 years then it could well need doing.

[ste1234]

1 hour ago, Papfox said:

Hi pap,

I had the belt done 2 yrs ago around the june month,when miles were 78k and now at 114k miles,i had complete timing kit done then,im surprised timing was out to be honest as apart from the hot starts the car ran perfect,no stalls and very responsive! skoda octavia 1.9 tdi 2009,have asked couple mechanics and they said never heard of adjusting the timing to fix hot start problem but that is what garage that fixed it told me was the problem.interesting

 

 

 

 

 

Glad you found it.

 

If the timing was off, do you know when the last time the cam belt/chain/tensioner were changed? My vRS was getting grumpy on starting. My local independent ran the car over with VCDS and the timing angle was 3 point something degrees out. They inform me that something very bad (replacement engine bad) happens at 5 degrees and the speed of the angle increase goes up as the chain gets more worn. The spec of the tensioner I believe was revised on some engines so you may not have the latest part and it is a worthy improvement.

 

I'm not sure which engine you have but the cam belt replacement interval on my old vRS was 3 years so, if you've had the car for 2.5 years then it could well need doing.