Confused, no compression

Scott560 · Post by **Scott560** » Wed Apr 24, 2024 10:27 am

Valves can get sticky/stuck in the guides, especially if there is a history of carbon build up from the leaking seals.

You can try to break the stickiness of the valves by tapping them with a hammer and drift.

NOT bearing on the retainer, but bearing on the valve stem itself with a drift, give them all a decent few taps. This will shock them not only down, but will allow them to slam closed. This might help break any friction that is preventing them from closing fully. Like you say, carbon build up on the stem either preventing the valve closing , or disturbed carbon now stuck on the valve seat affecting the sealing.

The Haynes manual (for other cars) always states to give the valves a whack after disturbing them, I always assumed it was to check the collets are properly locked into place.

If the sound of compression is coming back - then perhaps it is just a bit stuck and it will soon free up when the engine heats up.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Apr 24, 2024 12:27 pm

stinkypaul wrote: ↑
Wed Apr 24, 2024 10:11 am
I took the cams out and raised the rocker arms before doing the job so all the valves were fully up.

Oh that's fine then - no issues there, obviously

stinkypaul · Post by **stinkypaul** » Thu May 02, 2024 1:04 am

So, good news and bad news. I set the valve clearance to the maximum and ran the engine on the starter a few times, and also squirted plenty of carb cleaner in the intake. Let it sit overnight and ran it again. There's now excellent, equal pressure across all cylinders.
Problem now is oil is getting into the cylinders. I'm damn sure the new oil seals went on properly so I'm now wondering if the rotated valves also have guide issues not just the carbon issues.

Scott560 · Post by **Scott560** » Thu May 02, 2024 8:35 am

Are you sure its oil? If you sprayed a lot of carb cleaner into the intake, the dislodged carbon/cleaner mix would look like oil.

The valve guides don't really control the oil, the tops of the valves stems are only lubricated by the odd splash of oil (which sort of sits in the top of the seal).

It's unlikely oil would get in from above, the valve seals can't really be fitted wrong (assuming there were pushed down all the way on top of the guides you normally need a deep socket to push/tap them on, and the little spring around the seal top didn't fall off on fitting (hopefully you lubed them?)). Even if the seals were buggered, you wouldn't end up with more oil in the cylinders than before.

Does it start and run now? It might take a while to blast out all the crap (a good 15 minute drive would clear it).

stinkypaul · Post by **stinkypaul** » Fri May 03, 2024 10:10 am

It's very smoky, and the plugs coke up quite quickly leading to very rough running and it trying to stall whenever I lift off. I'm always up for an Italian tune up though, so I'll give it a go.

stinkypaul · Post by **stinkypaul** » Fri May 03, 2024 4:42 pm

Thinking about the plugs, I wonder if it's excess fuel and not oil. I'll try to find out, but I'm not sure why there would be so much fuel getting dumped in there.

stinkypaul · Post by **stinkypaul** » Mon Jul 22, 2024 1:08 am

So, it took a while, but I eventually found out what was wrong, and thankfully it was excess fuel and not oil in the cylinders. the MAP sensor had gone, and the car was dumping fuel into the cylinders. I put an old one on that I had lying around and now it runs great again.

Post by **Drax** » Mon Jul 22, 2024 9:08 am

stinkypaul wrote: ↑
Fri May 03, 2024 10:10 am
very rough running

have you checked if the belt is on correctly, the cams, camshaft etc line up at TDC? defo worth checking by the sounds of it.

Post by **Vtecmec** » Mon Jul 22, 2024 10:20 am

Drax, he's fixed it.

Post by **Drax** » Tue Jul 23, 2024 8:57 am

Vtecmec wrote: ↑
Mon Jul 22, 2024 10:20 am
Drax, he's fixed it.

"note to self; read the last post"