MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: George10 on January 11, 2014, 12:28:41 pm

Title: Diesel starting problems when hot
Post by: George10 on January 11, 2014, 12:28:41 pm
Hi,

Does Anyone know why my cars taking ages to fire up when warm ?
Start on one turn when cold so it's not the glow plugs. This is happened to a few people I know so something must need replacing.

Title: Re: Re: Diesel starting problems when hot
Post by: RetroRaz on January 11, 2014, 12:58:26 pm
Really common issue. I had it on my tdi too but just ignored it. I think its something to do with the crank sensor or something like that

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Title: Re: Diesel starting problems when hot
Post by: Matto on January 11, 2014, 01:14:47 pm
I think it can also be related to the thermostat aswell.
Title: Re: Diesel starting problems when hot
Post by: Viking on January 11, 2014, 03:29:16 pm
Most likely the crank sensor as said. Sometimes throws up a fault code and also occasional limp mode as it gets worse (when you're booting it usually).  If the battery is getting old this can also cause hot starting problems, as can the starter motor. These two issues are related to crank speed as there's a minimum rpm for the ecu to enable fuel injection. When hot the starter motor can give slow cranking speeds (as can the battery).

Thermostat wouldn't cause the hot start problem as it's purely mechanical so nothing to report to the ECU, although the temperature sensor possibly sensing incorrectly could be causing problems. However, the temperature is a red herring as it's usually the crank speed which is critical when the coolant temperature is above 70°c.
Title: Re: Diesel starting problems when hot
Post by: Andy on January 11, 2014, 03:35:42 pm
can have issues with starter motor
Title: Re: Diesel starting problems when hot
Post by: Viking on January 11, 2014, 03:39:24 pm
That's what I just said.  :P
Title: Re: Diesel starting problems when hot
Post by: Andy on January 11, 2014, 03:47:04 pm
well that will teach me to read previous posts :signLOL:
Title: Re: Diesel starting problems when hot
Post by: George10 on January 11, 2014, 04:36:01 pm
Thanks for all your comments. Anyone know how much a crank sensor is ?
Title: Re: Diesel starting problems when hot
Post by: Viking on January 11, 2014, 05:26:41 pm
About £80 - £90 or so I reckon.
Title: Re: Diesel starting problems when hot
Post by: martin@gti.co.uk on January 11, 2014, 07:16:14 pm
Check advance timing. Could be water temp sensor. But as mentioned above..probably starter motor spinning bellow 250 rpm.. get a tuned starting map..cheapest solution or resistor on temp sensor..
Title: Re: Diesel starting problems when hot
Post by: JoeDarKa on January 11, 2014, 07:55:05 pm
Mine was the crank shaft position sensor. VW did it for free i think
Title: Re: Diesel starting problems when hot
Post by: xjay1337 on January 11, 2014, 07:57:22 pm
It's nothing to do with any sensors 90% of the time.
It's starter motor not spinning the engine fast enough. After X seconds cranking it just dumps a load of fuel in, you might notice a bit of smoke is puffed out after starting.

It's also fuel/map related so after a remap the problem should be fixed as it just fires in more fuel earlier rather than waiting for the RPM to be reached.
New starter/battery/replacing any worn wiring/earths etc will also help.
Title: Re: Diesel starting problems when hot
Post by: doylebros on January 11, 2014, 10:30:35 pm
Thanks for all your comments. Anyone know how much a crank sensor is ?

Noticed this but the part is chassis number dependant just a guide!

http://www.ebay.co.uk/itm/VW-GOLF-AUDI-A3-OCTAVIA-LEON-1-9TDI-CRANKSHAFT-IMPULSE-SENDER-036-906-433-B-/280903993896

TPS price  for 036 906 433 B - £61.53 full retail inc vat

Also this is worth a read

http://www.rmitechnicalforum.co.uk/topic182-vw-golf--diesel-bkd---non-start-when-hot.aspx

Title: Re: Diesel starting problems when hot
Post by: Viking on January 11, 2014, 11:37:37 pm

Noticed this but the part is chassis number dependant just a guide!

http://www.ebay.co.uk/itm/VW-GOLF-AUDI-A3-OCTAVIA-LEON-1-9TDI-CRANKSHAFT-IMPULSE-SENDER-036-906-433-B-/280903993896

TPS price  for 036 906 433 B - £61.53 full retail inc vat

Also this is worth a read

http://www.rmitechnicalforum.co.uk/topic182-vw-golf--diesel-bkd---non-start-when-hot.aspx


There are two versions of the crank sender as you say. Later ones are different and more expensive.
Title: Re: Diesel starting problems when hot
Post by: G40will on January 12, 2014, 02:09:10 pm
My mk4 golf had hot start issues just before the starter packed up!

Just my 2pence :happy2: