AH cant get no satisfaction erm compression

[currylager]

I thought my new engine was a bit sluggish for a 1641, turns out no 4 cylinder isnt doing anything, have spark and fuel, but compression is non existent, so i think the cylinder head must be cracked??, the valve gear is seen to be operating fine and have new pistons and barrells so i think i will have to try and remove the head with engine in situ, could be fun but think it might be possible with engine lowered at the rear. Any input or other things i could try before the carnage starts anyone :?:

 

[gninnam]

Could be ill fitting rings :?: if its had new barrels and pistons

 

[currylager]

When i fitted the kit i fitted the pistons and barrels in one lump to each con rod to avoid using a piston ring compressor, so if it was ill fitting rings they have been supplied like that. The compression tester needle hardly moves after 10 seconds of cranking and reads healthy on the other 3 cylinders, so whatever it is it's pretty drastic, if the rings were ill fitting i'd still expect to get some compression surely? :?

 

[gninnam]

OK, lets see what the experts say then

 

[currylager]

I just hope when i have ripped the head off i can find the cause and be confident i have rectified the cause before it all goes back together again, i think i'll use the head off my old engine which was a bit tired but ran ok i believe the twin port heads crack between the inlet/exhaust valves so i'll go there first.

 

[Scampi]

Something I read about dripping a little oil into the cylinders to see if it seals the rings or not!

That should give you an idea if it's rings or the head dude!

 

[lucifar666]

If it is just the heads that are cracked you will still get a compression reading, both mine were cracked and it still registered quite good compression when cold, it was when it warmed up the, cracks opened and it wouldn't tickover. You may need to check for piston damage on No4, Did you check the spacing between the head and the top of the barrel on each barrel when fitting when I did mine I was told to check about 2mm?

 

[slammedkustom]

think you will have to pull the engine, it could be a damaged piston or rings, valve damage, valve seats or a combination.
have you checked the valve settings? it could be that simple
good luck :wink:

 

[Scampi]

Like Slammed Kustom said dude.

I don't think you can do much without pulling the engine!

 

[pete nice]

2 things:

1) you should check/set the valve clearances before you do a compresion test as a tight valve will give you a low reading & make you believe you have bi problems.

2) when you buy new barrels & pistons, the rings a not set in the correct loaction. You may have all the gaps lined up together at the bottom, you will not know. You should always pull the piston free of the barrel & check the ring status.

Try step one before pulling your engine, but you should really do things properley if you want your engine to last...

 

[currylager]

Ripped the head off yesterday and did this with the engine in situ, a bit fiddly but better than ripping bumpers and valances and plugging fuel hoses. lowered the engine at the back which gave me sufficient clearance to remove tinware and slide head off. The head was cracked with cracks spreading from spark plug hole to both valves. Took the head off my old engine this afternoon and 3 hours later took the bus for a spin, i am pleased to say its running much happier now. Thanks for all the interest/ input :wink:.

 

[Scampi]

Glad to here you sorted it dude! :wink:

 

[gninnam]

Well done

 

[currylager]

At least the van is running again!, I am sure i have a lot to learn and and probably do judging by what Pete says but its a start. I am hoping to rebuild the original engine when i have the time and keep it as a spare. Unless i have a go at these things myself i will never really understand the technical aspects of our beloved Vws . Just waiting to see what will go wrong next lol!!!

 

[Justin & Muttley]

...Unless i have a go at these things myself i will never really understand the technical aspects of our beloved Vws...

Well said that man!!!