97 Sharan VR6 cut out now wont start Help pls !!

[iholly01 0]

Apologies first for this long winded post but wanted to try to give as much info as I could here

We have a 97 Sharan VR6 (AAA) which has recently developed a fault and to be honest have managed to sort most of its strange habits but this one has me stumped.

Recently driving fine, no problems at all, parked and switched ign off. 5 Mins later came back to car started as normal but ran for about 10 seconds then shut down.

No warning lights etc. Cranked perfectly fine, plenty of fuel judging by the smell !! but would not even attempt to start.

Towed it home and left overnight as was getting late. Following morning car started first turn of the key !!! Not wishing to trust it I decided to start checking relays etc as have had the fuel pump relay 167 go intermittent before so decided to swap that out. Switched off swapped relay and hey presto wouldn’t start ! Exactly the same as the evening before cranking fine but no attempt to fire.

And that’s what it is like at the moment, leave it overnight and normally will start sometimes will run for 10 - 15 mins, sometimes just 20 seconds or so but then will suddenly cut out and will not restart then unless left for a good few hours.

I checked when it is cranking and there is no output at all from the coil pack and although this does obviously work when the car is running I have swapped it out with a known good spare I had and the same problem persists.

Relay 167 for fuel pump checked tested and good and even swapped out but the same.

The car does not have the key transponder immobiliser so not the issue with the coil on ignition barrel either.

One thing that is confusing is many people talking about relay 30 or 109 for the ECU supply that can fail. Well there is not one in this car?? Have looked and the position for it in the fuse box is empty so can only assume that it has never had one well certainly not in the last 6 years anyway. Have since been told that not all were fitted with this??

Have gone through all fuse boxes including the engine bay and the one next to the ECU behind the clocks but have identifed all of the relays and their uses with the exception of one or two 53 units with misc functions etc and nothing at all like a 30 or a 109

Connected to VAGCOM and only fault stored is 00533 – relating to the idle speed. When it does run I can clear this etc although it immediately reappears at the next start. Has been like it for a while and am pretty sure there is a small air leak upstream of the MAF and that’s the cause. This has been a problem for a while so i am fairly sure it is unrelated to the starting issue.

Other than that no faults stored in either Immobiliser/ Alarm modules or Engine ECU.

The live data from Vagcom does show that when cranking it is picking up the engine RPM at about 200rpm with starter running so I am assuming from this that the crank sensor is ok as it is picking up a pulse from there.

So now im sitting here scratching my head and starting to look for some straws to grasp at as am running out of ideas and options.

If anyone has got any ideas or hints of where to maybe go next it really would be appreciated .

Cheers to you all

Ian

[iholly01 0]

Ok, Here is todays episode in trying to sort this fault out.

First thing this morning car started fine as it always will do! as soon as temp started to rise engine died as expected. Does not cough splutter etc but is exactly the same as if you turned it off with the key!

Decided to try and see which if any of the various sensors i could test to try to elimante them so the following were tried one by one and then the fault codes read back from the ecu before clearing and moving on to the next

Crank Sensor when disconnected gives Fault Code 00513 3-10 (No Signal) and ok when connected.

Tested resistance between Pins 1+2 and gives 644 Ohms with pins 1+3 and 2+3 open circuit

Cam Sensor gives fault code 00515 30 (Open circuit) when disconnected.

Blue engine coolant temp sensor gives Fault code 00522 29 (short to ground) when disconnected

Disconnecting the Evap Valve connector gives fault code 01247 31

Removal of relay 53 in the engine bay fuse box removes the power to the secondary Air Pump and throws up a 00758 Fault and when running can be heard in any case when engine is started first from cold.

Removing the MAF throws up a 00533 31 Fault and I managed to disconnect this today on one of the occasions I managed to get the car to run and immediatly idle became very lumpy reconnecting cured this so i guess this is doing its

job (well at the moment anyway !)

Checked between pins 1+5 on coil Pack for +12v with Ignition on and during cranking and thats fine, also checked for any resistance between the coil pack ground wire and the engine block and battery -Ve terminal and all fine

Have not yet tested for Signal on Coil Pack pins 2 3 4 and Ground and will do but at the moment I am assuming that signal is not present as no spark from any of the pairs.

So I am tending to believe that all the above are doing exactly as they should be or at least thats what they seem to be telling the ecu.

The only exception I think could be the crank sensor as it appears from others experience that this could still have an intermittent fault that will not cause a fault to be logged in the ecu.

Car got up to around 60c Engine Temp and Air temp of about 54c before it cut out the first time this morning. After letting it cool down to around 25c (both readings) It has once again started and run fine until it got to around 67c according to the dashboad MF display. Vagcom live data actually shows engine temp at 79.5c and air at 30c when it cuts out

Managed to log channels 001 002 and 003 with vagcom this time and have the log file which i can pass on if it may help ?? But looking at it all values seem pretty constant right to the point when it stops logging

Asi write that I need to check next time if vagcom actually stopped logging or lost communication with the ecu?? IS the ecu loosing power for some reason ?????? Mmmmmmmmm

Anyway seems a bit strange that both times it has got to around the same temp give or take a little and then dies completely.

Once it has died there is still power present at the coil pack and checked the resistance at the Crank Sensor pins and is still pretty much the same give or take an ohm or two.

And so the saga continues Will keep updating this till i either find the fault or decide to take to the thing with a disk cutter !!!

This could turn out to be the longest thread here !!! lol

[iholly01 0]

Ok Here we go and finally I think it may be sorted :):) Well I hope so cause after 4 days of it sitting in the garage plugged into the pc and scribbling down diagrams on paper everywhere i think i would have gone nuts if it had gone on any longer!!!

The Crank sensor arrived late yesterday so feeling pretty confident i fitted it started car but again it cut out at the same temp Managed to get the engine cool enough late last night with the air con unit freezing the garage so i could have another attempt.

While things were cooling down I had been checking and re checking everything again for the umpteenth time still getting no where. Finally cooled enough to start but this time it ran up to normal temp and kept going ??? Ok so why? Well I couldnt find any reason at first checked and re checked everything but nothing found. Put old crank sensor in and ran fine. Puzzled? I flipping was !!!! :? :?

So left it at that last night, still none the wiser but happy that it was running.

First thing this morning started fine and ran fine, straight to normal temp and kept going. So i started bolting all the plastics etc back on the engine, refitting all the bits that had been out but when i had finished the damn things refused to start!!!!

Back to square one but what had i done to cause it? took everything back off that i had just refitted but no joy wouldnt start. So once again turn the garage into a freezer and 2 hrs later it started, ran to temp and kept going !!!!

Thats when the penny dropped :) It ran as long as the coil pack was off the engine as soon as it got hot it started to break down !!! Bolted it back to the block and cut out almost immediatly it got warm. swapped it out with a spare and again worked fine till it got hot then failed the same way.

Tested this out on the bench after cooling it down and warming with a hot air gun and it did the same broke down when hot!!

Swapped it out with another new coilpack and all now fine :) Well it is at the moment anyway Taken care for a fairly swift 30 mile run and going very very well indeed so fingers crossed!!

Just goes to prove i guess that although the two original coilpacks both checked out fine they had faults on the amp in the rear of the pack which would fail after it had been tested and passed as good as such.

So fingers crossed this is an end to this saga ! If nothing else i have learned a great deal more about this bl**dy car in the past few days.

Hopefully this is the last post in this thread !!!

Cheers for reading & all the best

Ian

[bungy 2]

Glad you got it sorted. This sort of fault is hard to diagnose by description but your write up will undoubtably help others in the future.