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Hi,

I'm hoping someone may be able to offer some suggestions as to what might have happened to my son's Polo (1.2 Petrol 6R)

Two days ago, the engine was running fine, although my son tells me that over the past couple of weeks he had some (seemingly unrelated?) cautions. Firstly, he had a power steering yellow light sometimes for a few minutes after the car started, with associated lack of PAS. This would always clear and go back to normal after a short while. Then on the last day that the car was driving 'normally' he had the yellow traction control light on. He used the car throughout the day for work with no noticeable engine problems.

The following day, yesterday, the car wouldn't start. I tried too, and the battery seemed a little weak, and coupled with the two caution lights above, I though, well maybe its the battery. I fitted a new battery and tried to start. After several long cranks the engine started, although it was noticeably rough and there was an engine management light. I disconnected each coil pack in turn, and each time the engine became more rough, so no indication of a single coil pack failure. I checked the plugs and they were a bit sooty so replaced all 3. I then tried to start again. It would crank but not start. Spark plugs removed to turn engine over again and I could smell fuel, so I'm guessing fuel was reaching the cylinders.

So, end of yesterday, car had a new battery and new plugs - turned over but wouldn't start. Son called the RAC and they came out this morning. I'd told my son to ask the RAC to do a compression check and the result was no compression in any of the 3 cylinders. RAC say probably timing fault or possible head gasket.

Timing chain, cogs and tensioner were replaced 3 years ago (Oct 19) and 30,000 miles ago.

I'd be surprised if a blown head gasket would result in all 3 cylinders having no compression.

Its probably not worth getting a professional rebuild of the engine so the car may well be off to the scrappies. Before I do that, has anyone got any other thoughts? I'm aware the above mentioned PAS and Traction lights may be red herrings, but mention them in case there could be a bizarre connection that leads someone to diagnose something other than the RAC man.

Thoughts gratefully received.

Paul

Pretty much impossible to say without having a proper diagnosis. It can be anything from a very blown head gasket, timing chain/belt, cam shaft, you name it...

Another thing this engine suffers from is burnt valves or damaged valve seats leading to a lack of compression.
As said without removing the head at least who can tell, if you have access to a borescope camera this may give you an answer

Did RAC man scan for fault/error codes?

Thanks for answers. No unfortunately the RAC guy didn’t scan for codes, which is frustrating. He was certain the engine needed stripping down regardless (from what my son tells me)

I’ve taken the little cam covers off the end of the shafts and the notches appear to be aligned with one another.

So the relationship of the inlet to outlet cams is looking okay, but was that with the crankshaft at the correct position - just in case the belt has jumped a tooth or more on the crankshaft sprocket.

True - could be the chain on the crankshaft has skipped. I'm presuming I can only tell that by opening up the timing chain cover, or can you manually tun engine to No1 Top Dead Centre and check?

Sorry, I forgot it was a chain, my lack of knowledge on that 3 cylinder petrol engine, I'm not sure if there are any easy to view external markings to let you turn it to a position near or at TDC, but if you can't find - scrub that as it seems that the official way to check timing is to, as you have done, turned the engine until the the grooves on both camshafts are horizontal, then having also removed the crankshaft position/speed sensor, there should be a hole/slot to fit a locking key into. So, maybe with all 3 spark plugs removed, insert something long down into cylinder 1, then starting from the camshafts still being lined up, back the crankshaft off maybe 30 degs and watch that thing that you have inserted into cylinder 1, as you then rotate the crankshaft back towards where it started with, you should be able to spot the point where the piston in cylinder 1 reaches its highest position, stop there and recheck the camshafts alignment - maybe 30 degs will not be enough, but you can start with that.

RUM4MO wrote: Sat Aug 20, 2022 5:16 pm So the relationship of the inlet to outlet cams is looking okay, but was that with the crankshaft at the correct position - just in case the belt has jumped a tooth or more on the crankshaft sprocket.

Well, you appear to be correct RUM4MO. I’ve been away from the car for a week or so, but have now tried to fit the timing tools. Although the camshafts are matched to each other, they are both about 20 deg off correct position when the crankshaft timing bolt is in place.

Not sure which, if any, timing tools I need to keep in place now when removing timing cover

maybe if you re-time it, and give the valves a visual check maybe ur lucky and it works.