warm starting problems

[bo]

hi ihave a sharan 1.9 tdi 130 first thing in the morning it starts no problem but during the day when its warmed up it takes loads of cranking to start but sometimes it will start  right away have changed filter and all pipes are dry  no faults coming up when plugged in it feels like a fuel problem some times when it stsrts its lumpy for a few secs also changed t piece on top of filter also my cooling fan is stuck on i have changed the two coolant sensors   temp guage still reads fine

[bo]

sorry forgot to mention its mk2 2004

[johnnyroper]

Try fitting a clear pipe between tandem pump and engine to see if it gets any air bubbles after being parked up. Could be injector seals leaking slightly losing prime,hotter fuel is thinner than cold fuel.

Also starter motors can go weak over time,a PD engine needs to crank over at 250+ rpm to start.

Cooling fans run all time even with air con off?

[alial]

hi..had the almost same problem ... changed the coolant sensor on the back of the engine block and played with egr to reduce it to minimum performance ... car running great with no issues now..fans will work as far as i know when temp over 90...hope this will help.thnx

[bo]

yes ive already changed both sensors temp gauge has never gone over 90 but fan is stuck on never used to be thanks for your reply

[johnnyroper]

Is fan on while time even after cold start? Have you had vcds connected to see what temp the ecu is seeing? The temp gauge on these will show 90 if at normal running temp it does not mean it is actually 90 through.

When it is running when hot do you get any black smoke from exhaust?
Also how quickly does temp gauge reach 90 after cold start?

[johnnyroper]

Thinking about it the fault could also be faulty air con switch as that controls fan when refrigerant is hot to cool condenser. In terms of checking I would assume pulling air con fuse to kill power to it should stop the fan if this is at fault?

Have you tried unplugging the coolant temp sensors to see if fan stops when they are disconnected?

Did the warm starting problem start at same time as constant fan running?

[insanitybeard]

I've had a similar problem intermittently where the car starts fine from cold but occasionally when it's driven a short distance and part warmed up it can be an absolute pig to restart, also when it restarts when warm it's not such a 'clean' start as it is from cold, it's a little spluttery. We plugged in a fault reader last time it happened and a fault code relating to the cam position sensor came up, so in my case it could either be a sensor fault or my timing is ever so slightly off- I changed the cambelt a while ago and the basic mechanical timing was spot on so it may be that it just needs a slight tweak using VCDS to set the torsion values.

[johnnyroper]

I've had a similar problem intermittently where the car starts fine from cold but occasionally when it's driven a short distance and part warmed up it can be an absolute pig to restart, also when it restarts when warm it's not such a 'clean' start as it is from cold, it's a little spluttery. We plugged in a fault reader last time it happened and a fault code relating to the cam position sensor came up, so in my case it could either be a sensor fault or my timing is ever so slightly off- I changed the cambelt a while ago and the basic mechanical timing was spot on so it may be that it just needs a slight tweak using VCDS to set the torsion values.

I would suspect the sensor at fault because when I was setting my torsion value I could go one end of slot to other and it did not throw a fault code. All it did was go out of range and either not start or would start and run rough depending which end of slot it was. If I remember correctly a reading of 5.5 was the figure ecu reverts to if beyond limits.

[insanitybeard]

Ok, thanks, I'll try substituting the sensor first and hopefully that'll put an end to the issue!

[johnnyroper]

It's not a belt off job to get it out is it?

[insanitybeard]

Nah, pretty sure you only need to unclip the top plastic timing belt cover to access it, the sensor (circled orange) is held on by one bolt and you just pop out a little grommet (arrowed red) to feed the cable and multiplug through. Quite a sensible design! (the picture shows the belt removed for clarity but you can access the bolt, sensor and grommet etc with the belt still installed)

[attachimg=1]

[johnnyroper]

It does look fairly straight forward to do without disturbing much more than the top timing cover.