Non starting problem, ARC

[937carrera]

I am trying to bring back to life another GTi.

Story is that the car ran out of petrol (fuel gauge not working), someone brought diesel which was poured into the tank and and the car was attempted to be started. Diesel was drained off, petrol put into the tank but the car has not started again. A new starter motor and plugs have been fitted without success, the battery has been flattened, probbaly more than once. I bought the car knowing this was the problem.

First thing I did was to run a scan and got lots of codes. Cleared them and rescanned - this time there were a number of immobilisor codes, but before diving into that area I decided to do some basic checks.

• Removed a single spark plug and checked for spark - very bright and strong
  Removed the fuel rail and watched for fuel from each injector - one looked weak so I removed and cleaned with carb cleaner / compressed air, now better

So I seem to have both fuel and a spark, but not yet known if they are the correct time.

Having worked through the Immo codes I have checked that the ECU resistance between pins 20 and 21 is correct and reset to default the ECU to re-read the key. I now no longer have any Immo error codes.

The car does not attempt to fire, my recollection is that if there is an immo problem the car will fire and start but will cut out after a couple of seconds (is it spark or fuel that is cut ?)

I am now thinking it may be something more basic, some potential ideas

• Check plug leads are correctly connected to the coil pack so that the spark is at the right cylinder
  make sure all 4 plugs are firing in sequence
  Use timing light to make sure No. 1 is firing around TDC (as check for crank position sensor)

Any other suggestions ?

[alexperkins]

Yes that's right it'll start then stop. It's controlled by the Spark from what I recall

I think you are on the right track - have you changed the fuel filter also?

[937carrera]

Thanks Alex, I have a new fuel filter, it came with the car but is not fitted, I may just have to throw that on.

[alexperkins]

Wouldn't be surprised if the old filter is saturated with diesel!!

[937carrera]

You were right, the inlet was clear petrol, the outlet thicker darker horrible nasty stuff.

I checked for spark from all 4 plugs having swapped the coilpack just because I had one and it was easy, plus I couldn't check the ignition timing with no-one to operate the starter.

I had an idea that perhaps though there was fuel, there was insufficient, caused maybe a weak pump, my suspicions being exaggerated when discovered that the fuel pump is in tank and integral with the fuel gauge sender which is giving vagcom errors and a distinct lack of fuel leakage when I removed the lines to the fuel rail.

I decided to remove the pump assembly, followed by the filter on the basis that spillage would be minimal. Isn't it funny how difficult quick release fixings are The ones to the pump were quite easy, but the connections to the fuel filter must have taken me nearly an hour to free off.

I checked the operation of the sender unit on the bench and the resistances checked out throughout the range so that seems OK. I also rigged a battery up to check the pump operation which gave a re-asssuring whirr. So far so good. I checked the electrical connections next; the pump showed an initial 3.7v, followed by 9.5v when cranking and 12.2v when cranking stopped before dropping to 3.7v again. I haven't found any test values, but with the exception of the 3.7v which I don't understand yet, they seem sensible.

That's all for now, tomorrow I hope to extract the old filter from the (broken) plastic clamp, fit the new one reassemble and check fuel delivery before trying to start the car again

[937carrera]

Tonights, little update - and I have found the problem

I fitted the new fuel filter, refitted the pump/sender unit and carried out a delivery test using a separate battery to eliminate everything else on the car. 200cc in 10 seconds is bang on spec so I was now certain that fuel was not the problem.

With fuel and spark eliminated I then decided to carry out a leak test so I removed the plugs and used a long thin screwdriver down the bore to ascertain TDC for number 1. As I was jacking the car up to use a roadwheel to rotate the engine it seemed like it might be an idea taking the timing belt cover off to check the valve timing at the same time.

That was when I spotted the problem......... as soon as the roadwheel was rotated the crank and inlet cam rotated, with the exhaust cam remaining stationary with no drive from the rear belt. I suspect the teeth are stripped from the belt at the rear exhaust pulley

So I guess a new cambelt / water pump is required. The question is, do I do that and then do a leak test, or do I just rip the head off to see what damage there is to the intake valves.

The engine seems to spin over fine, is it possible that the belt could failed without valves meeting piston ?

[alexperkins]

That's interesting. I've never seen th teeth come off the belt like that

I wouldn't risk trying to start that engine until you've taken the head off to check everything looks right and there's noting bent or damaged as the valves could've clashed

[937carrera]

I won't know exactly what the problem is until I have dismantled it a bit further.

Bear in mind I have been merrily cranking the engine over without concern or unusual noise for 3 evenings now - and who knows how long the previous owner did the same. I wasn't intending to start the engine until I done the cambelt and done a static leak test.

I think what you are saying is that it's pretty certain that there is valve train damage and I may as well just get on with the bigger job.

Interesting that you say you have never seen the teeth strip off the small belt. What normally happens, and how else can the exhaust camshaft rotate without resistance, but the small belt not move ?

[937carrera]

Just a little update.

I managed to get an hour to look at the car again today, have almost got the cambelts off, just struggling to get the crankshaft pulley bolt undone.

It's definitely stripped the rear belt as I have now found one of the teeth

[alexperkins]

That bolt can be a bit of a bugger to undo. A breaker bar is normally sufficient

Interesting. Sounds like the exhaust cam mustve locked at some point.

[937carrera]

I got another pair of hands last night and got it undone (having snapped two 3/8" small extension bars

This timing belt is what you might call unserviceable, shorter words also convey the description


The good news is the exhaust camshaft is not siezed and I have been able to rotate it back into the correct position relative to the inlet cam so the locking tool can be inserted.

I have to say that the main belt did not seem sufficiently tight and the indicator for the small belt tensioner was well out of where I expected it to be.

This picture shows the inlet cam was about 90 degrees out of phase (exhaust and crank at TDC)



I'm going to do a trial fit with the new belts and perform a leak test. If that doesn't give good values it's off with her head

[937carrera]

I refitted cambelts and tensioned them, following which I turned the engine over by hand on the crankshaft pulley, plugs out.

There didn't seem to be any issues so I carried out a leak test, results as follows - I wouldn't pay too much attention to the absolute values as I am not convinced the tester is correctly calibrated any longer

Cylinder 1.............2..............3..............4

Leakage 42%.........35%...........48%...........52%

Having increased the test pressure to find out where the leakage was occurring (past the piston rings into the block) I was starting to think that all may be well, but then decided to do a compression test

Cylinder 1.............2..............3..............4

Bar .....10.0.........11.5...........12.0..........0.0

Having rechecked the result there seems to be a fairly significant problem with number 4. Initially it didn't seem to make sense against the leak test but I am thinking that perhaps the intake valve on number 4 must be jammed shut

[alexperkins]

I would tend to agree. I think it's gonna be a head off job sadly

[937carrera]

Well, the results are in, off with her head and two bent exhaust valves stuck open

At first it looked as though they just kissed the piston, but upon removal of the valves (my valve spring compressor is 25 years old, 25 years since I last used it, and clearly designed for bigger/ meatier valves) it was a bit more than a kiss I suppose it could have been worse

Anything else to think about doing while the head is off ?

[937carrera]

Another update:

I fitted the new valves, reassembled the head and cam cover onto the block, new timing belt kit and she started on the first turn of the key.

I have also discovered that the fuel pump wiring is connected to the drivers door. Don't ask how I know , but it's handy to know as it's an easy way to check fuel pump operation