tdi hard to start, now no start

[rjd1284]

hi everyone,
was just wondering if anyone had any suggestions.
i have read countless forums and threads on the hot start issue but mine is a little different and havent been able to find anything.

the car is a 2001 passat tdi 130 pd (awx engine)

bought the car 7 months ago and it has always had the hot start problem as in cranking for a while when it is at running temp (90 degrees) until it fires.
changed the battery and starter as well as coolant temp sensor. nothing worked so i just lived with it.

but now it wont start at all when it is at full running temp. it cranks well at 5-600rpm but will not fire at all, i am on my 3rd starter motor.
like i said its only when its at 90 degrees.
its starts perfect from cold everytime.
even if i let it cool for 10mins so it drops from 90 it will fire straight away.

any help appreciated as it keeps leaving me stranded, oh and no fault codes are being brought up

[snapdragon]

Have you checked for fault codes?
I would check the coolant temperature signal to the ECU matches the coolant temperature sent to the gauge.
I am wondering if you are getting cold start timing advance when you shouldn't.

[rjd1284]

Its not bringing up any fault codes. The coolant sensor is new. Not sure what temp its reading tho.
All dash lights are normal. It just wont start from running temp. Used to just take a bit of cranking til it fired.
But now wont fire at all at running temp. Oh and it bumps start fine as well

Cheers for reply

[snapdragon]

You mean it bump starts when hot easier than it does with the starter motor?
Is the crank speed low when hot?

[rjd1284]

It is cranking at about 600rpm when hot, so should be injecting fuel from what ive read. It just wont fire like its not getting fuel. When hot it just sits there at 600 rpm and wont do anything. But if i let it cool for 20 mins it fires right up. When it was being towed i bump started it fine. But this could of been because it had cooled a bit.
Ive ruled out most things like
Starter motor
Battery
Immobiliser (as its only wont fire at running temp)
Coolant temp

Im stuck now, was thinking fuel temp sensor but apparently that wouldnt affect starting.

[martin1810]

An engine measuring block read when it is hot may give a clue to what is happening. A fuel temp sensor fault can make starting difficult. It depends what the coolant sensor is reading at the same time.

[rjd1284]

Thanks.
Just a bit of an update as i know a lot of people are having similar trouble. I have cured the problem of it cranking and no start. It was the wire to the fuel temp sensor had snapped.
So anyone having similar trouble. The fuel temp sensor can prevent engine from firing when hot and it will just crank.

Now its back to the hot start issue of it cranking a while before it fires when hot.
Found if i disconnect the coolant sensor it fires right up. But the sensor is new so not sure what is causing that.

Thanks 4 replies

[passat tdi130]

what do you call cranking a while mine turns over about 4 times when hot before it starts and straight away when cold..?

[rjd1284]

mines the same as yours. cranks for about 6 seconds when at full temperature then straight away when not at full temp.

found that disconnecting the coolant sensor cures this and it fires straight away when hot, so obviously temp related. its had a new sensor (green)

but not a permanent fix as ecu thinks its cold all the time and injecting more fuel.
cant think what is causing it now. been same since i bought it 6 months ago.

[denz]

just a quick question have you tried starting the car with the clutch pedal pressed down ? had it a few times when duel mass flywheel has to much play in when hot so crank signal is all over the shop ?? just a thought :D

[rjd1284]

ive not tried that to be honest, but i know the dual mass has had it.
ive got the parts, was going to have it done next week.

ive looked into this hot start problem for months now all over the internet and vw specialists, wonder if the flywheel could be causing it.

the battery is good
coolant sensor is new
starter is good
timing on cambelt is good

if the flywheel solves it ill let everyone know.

[yaman]

have you tried starting the car with the clutch pedal pressed down ?

If this works, it could mean that the fuel cut-off rpm needs remapped, since
clutching at start gives fuel immediately, like an auto-box.

Regards
Jim

[rjd1284]

Unfortunately putting the clutch in didnt make a difference.
Strange thing is it does appear to start then dies after a second or two. Unless this is because of the heat in the engine.