Engine running on 3 - 2.0 Aircooled

[T25rc]

After buying new plugs/leads and distributor cap for the 2.0 a/c in an attempt to make it run better it hasn't. I noticed one of the old plugs was very oily, so pulled the lead off that cylinder while it was idling and it makes no difference to the running at all... revving or just idling.

What is the problem likely to be?

Thanks a lot

[kevtherev]

poor compression

[Red Westie]

What he said lol.
But you need to find out why.....could be your tappet clearances have closed up for some reason.
More seriously it could be a burnt out valve, broken rings or cracked head.
Did you check the spark to that plug?
Martin

[T25rc]

Could the distributor not supply spark to just one lead?

How would i go about fixing it then, would one job ie head replacement with new rings solve all possible causes?

Can the head be replaced in situ, and how difficult/expensive is it usually?

[kevtherev]

Could the distributor not supply spark to just one lead?

"After buying new plugs/leads and distributor cap"

no mate, sorry.

How would i go about fixing it then, would one job ie head replacement with new rings solve all possible causes?

not heads, barrels and rings if the pistons and valve seats are good... you need to do a leak down to check what's up

Can the head be replaced in situ, and how difficult/expensive is it usually?

yep... but it's easier with the engine out and on a bench.
easy and fairly cheap.
cheaper than a recon that's for sure

[Red Westie]

First things first...do a compression check (this will check the mechanical fitness of the engine, all fourcylinders should be within 15% of eachother) clearly one cylinder that is very low compare to the others could have serious mechanical issue ie; burnt valves, broken rings, cracked head etc but do the check first.
Martin

[T25rc]

I think i'll get looking for a 2.0 engine to just replace it with... Its a shame, i thought the problem was electrical until the day it passes its MOT and i want to be using it - i'm not sure it would make the cornish hills though.

What should the compression be?

I'll try and test it in the next couple of days, should i do it wet ad dry? For wet i just drop some oil into it? How do i do a good compression test, i have the tester.

Just the one plug out at a time? Spin it over with the tester attached for how long?

Cheers

[Red Westie]

All four plugs removed, attach tester to Number 1, crank with full throttle until the highest reading is attained 4-5 seconds usually. Carry out the test on each cylinder.
All DRY at first then if you have a low compression 2-3 squirts of oil in the cylinder and carry out the test on that cylinder again.
If there is a significant rise it indicates worn rings, if you only a slight increase from the low reading then you have a burnt valve/cracked head or failed gasket.
Martin

[kevtherev]

perfect.. do it like that^^^^

[T25rc]

I'll hopefully get on that tomorrow then, thank you..

Shameless plug - check my wanted for a 2.0 CU Aircooled engine