vr6 non start when hot !!!

[macas32 0]

can anybody give any clues as to why my corrado vr6 wont start when it gets to 80 degrees it just turns over but wont fire unless i let it cool a little, it starts ok on (second) attempt when cold and revs and drives fine until it gets to 80 degrees then drives rough and tries to cutout and if you stop and turn it off it will not start until it cools ??? it has no fault codes being flashed up and is getting on my nerves now .its a coilpack engine obd2

its had new plugs

leads swapped for original ones

coil removed and inspected

crank sensor checked

aftermarket airflow sensor fitted to cure excessive fuel consumtion and very high emmisions (not sure on this aftermarket sensor though)

evap system dissconected

new coolant temp sensor

fuel filter changed

new fuelpump relay

 

 

on one occassion it would not start and spotted fuel leaking from under the car at the drivers door area but has never done that again !! and checked lines for leaks and all seems ok.

 

any clues would be nice !!! :shrug:

[Bruno 4]

can anybody give any clues as to why my corrado vr6 wont start when it gets to 80 degrees it just turns over but wont fire unless i let it cool a little, it starts ok on (second) attempt when cold and revs and drives fine until it gets to 80 degrees then drives rough and tries to cutout and if you stop and turn it off it will not start until it cools ??? it has no fault codes being flashed up and is getting on my nerves now .its a coilpack engine obd2

its had new plugs ...

 

Assuming you have checked really carefully all the vacuum lines - do this carefully - then try this sequence:

1. Unplug the temp sensors altogether. Drive it until it is hot (dont worry, the rad fan will cut in anyway at the right time), turn off, then see if it develops the problem. If it does start then you need to check the wiring to the temp sensors (both of them, starting with the blue one).

 

2. Failing that, do a complete ECU reset when it is piping hot, ie deliberately undo the battery, etc. If the reset clears it, then you are trying to chase down an intermittent sensor. Then you need to watch the message blocks as the engine is running to find out which one it is.

 

3. If it is an intermittent sensor, and you dont have a way of reading those whilst the engine is running (not just the error codes), then unplug the following one by one to see if them being unplugged makes a difference between 71 and 80 degrees, not quite hot:

- cam sensor;

- knock sensors;

- MAF sensor;

- lambda probe.

You may be lucky.... one of these, if it makes no difference to your engine's behaviour when unplugged may be the source of an intermittent signal. Check the wires, the connections, etc.

 

3. If the ECU reset made no difference, then the Fuel Pressure regulator might be a problem. Tap it, sometimes this gets grit into the grommet and locks up at high temps. If that works, take it out, clean it and/or fully replace.

 

4. Go get a new ECU relay (thats if your OBD2 wires through relay 109), and relay 167 or 67 (fuel pump). You'd be amazed at the nonsense these two relays get up to in older cars.

 

5. Failing that, see if you can borrow another owner's ECU.

[volksworld13 0]

the ecu is coded to the immobiliser module and the keys, so if you swap that you will need it to be recoded with either vagcom or the stealers!

[Reggit 0]

the ecu is coded to the immobiliser module and the keys, so if you swap that you will need it to be recoded with either vagcom or the stealers!

 

Only on the later cars. The earlier ones non't have the immobiliser on them. think it was introduced some time in 1994, so if the car is earlier there ain't a factory immobiliser on it.

 

I'm interested in this as mine sometimes exhibits this issue - won't start first time when hot, it needs a 2nd turn of the key then always starts.

Mines had new ECU and fuel pump relays and a new ignition switch. No fault on VAGCOM.

 

I'll watch the thread with interest.

[macas32 0]

will try that today thanks, just noticed on the live data that the coolant temp the code reader is showing does not match the gauge in the car as its saying 105 degees and the gauge is about 65 and i put my finger in the coolant and would have expected it to be very hot and it was more like 65 so gonna change that for a genuine vw one toady as euro seem to be selling crap parts these days and the dealers didnt have one in stock whitch would suggest its vr6 specific and would not be suprised if euro are supplying a generic :cuckoo: one.

[-=Kris=- 0]

i have a very similar issue... it wont start if the engine is hot and then left off for about 10 mins... go back to it and it takes 2 attempts to get it going...

 

car is in the garage ATM and they are looking into it...,

 

I'll keep you posted as to what they find... won't be till sat...

[Toad 0]

Kris. That sounds like leaky injectors. Just need to get them cleaned.

[volksworld13 0]

you need to distinguish weather it if fuel or spark causing non start, check fuel pressure is within spec ,may have blocked fuel filter , and check for a good spark when hot.

[-=Kris=- 0]

Kris. That sounds like leaky injectors. Just need to get them cleaned.

 

Sweet... i'll gat Jason to check that out... cheer matie!

[macas32 0]

Fitted a new coolant temp sensor (genuine vw one) and reset the ecu and seems to be running better than ever it was smooth as silk and telling me i was getting 29.9 mpg witch is better than average and waited for the fan to cut in to make sure it was hot enough and it started perfect, so hopefully it is fixed !!! :salute:

You had your car back from the garage yet with their diagnosis as keen to see what they came up with.2.8l 24v Climatronic system.pdfCIMG1376.JPG[/attachment:2xuc4rum]

[-=Kris=- 0]

Fitted a new coolant temp sensor (genuine vw one) and reset the ecu and seems to be running better than ever it was smooth as silk and telling me i was getting 29.9 mpg witch is better than average and waited for the fan to cut in to make sure it was hot enough and it started perfect, so hopefully it is fixed !!! :salute:

You had your car back from the garage yet with their diagnosis as keen to see what they came up with.2.8l 24v Climatronic system.pdfCIMG1376.JPG[/attachment:19xen8qp]

 

 

yeah i got it back but unfortunately my budget had run out by the time they had finished with the ABS! :(

 

at least i know what it what it could be now tho... i'll let you know what they find when it goes back in...

[poll250 0]

I have this problem sometimes.

 

It mostly happens when I go into a shop quickly/fill up with petrol. When I go back to the car it wont start for a few mins. Turns over fine but won't fire.

 

I've replaced the ignition switch, fuel pump relay, fuel pump itself and sender unit recently and all was well, but then it happened again yesterday, so I guess I haven't fixed it after all :(

 

The problem seems to be that the fuel pump doesnt always prime when I turn the ignition on: sometimes I can turn the ignition on and just wait 30 seconds and then I'll hear the pump prime and it'll fire straight up.

 

It's got me a bit confused as I've replaced nearly all parts I can think of!? I'm not sure what other parts affect the fuel pump priming but I guess maybe the ECU relay is next on the list.

 

One day I'll get to the bottom of this!

 

Andy

[macas32 0]

poll 250 have you checked to see if the pump is getting power to it when you turn the ignition on when its playing up, as if it has got power and earths then its either a bad connection at the pump end or a faulty pump at least yours is giving you an idea what is wrong if the pump isnt priming.

prob hard for you simulate this fault at home if its sporadic but you need to establish wether its not getting power or the pump or wiring is at fault.

[harryc 0]

Sorry to revive this but i ve been getting similar probs from my obd2 vr6. Car starts on the button from cold (despite having an intermitent missfire) but when its hot (having reached operating temps) and then left for 5-10mins it wont start just turn over and over. Turns over really well but just shows no intention of firing up. If i leave it for 5-10 mins it takes some turning over but then starts. Once cool it will start on the button again. It seems the starting problem is proportional to the oil temp, the higher the temp the longer it takes to start.

Im guessing once its up to temp and not starting i;

1.Check for spark by removing plug leads and wathing for an arc against body work.

2. Listen for fuel pump priming and check fuel pressure some how/where?

 

Its starting to get embarassing when you get petrol during rush hour and you end up sitting at the pump for ten minutes waiting for the engine to cool :camp:

[volksworld13 0]

a faulty fuel pressure regulator can cause this concern, maybe worth swaping it for a know good one.

[harryc 0]

Thanks, im trying to narrow down the problem as much as possible. The last week the car hasnt been doing it but the weekend before last when we had the really hot weather the car just wasnt starting when hot. Could external temps in some way be linked to the problem? possibly higher water temps causing the trouble? Oil temps seem about the same this week as they were the other week when the car wouldnt start from hot...very confusing.

I checked relay 62 and it seemed almost brand new gave it a clean, checked the earth and gave that a clean but i couldnt get access to the gearbox connection. Will have to see if i get the problem again when the weather warms up...