Stan944

I've done the engine compression test:
cylinders 2,3,4: 170-175 psi OK,
cylinder 1: either nothing or one spike at about 100 psi. Repeated many times, also after pouring some oil into the cylinder.
So looks like cylinder #1 is not working.

I did a crude test to localize the source of the leak, by pumping air from a mini tire compressor through the spark hole in cylinder #1. I put the other sparks back in; set the engine at the belt alignment marks (i.e. TDC for cyl. 1), plugged the end of the j-boot and the exhaust with latex gloves.

The glove at the j-boot inflated rather quickly, while the exhaust glove remained flat.

My conclusion is that the intake valve on cylinder #1 doesn't close. The exhaust valve is OK, provided I don't have a hole in the exhauset. I hope I didn't miss anything and my results are correct.

At this point I would appreciate comments. Is there a likely culprit, I understand that in addition to broken intake valve, it could be chipped-out camshaft, valve spring, etc. In any case, I believe I can consider everything below the head gasket to be OK.

Is there anything else I should do before opening the engine?
I believe I need to take the valve assembly out. Do I need to remove the actual head too (I think I do)?

I still don't understand why disconnecting the injector on cyl #1 slowed the rpm similarily to cylinder #2, while #3 and #4 showed little change.

P.s. this is the continuation of the topic started in posts:
engine died
Leak down test
when are all valves closed?
Compression test - tutorial needed

Calmchaos

Could it be a broken spring?
Because that would be easy to check. And you could also check the cam at the same time.

Just an idea.

-Brett

Zero10

Something seems fishey. If disconnecting the injectors at #3 and #4 resulted in no change then you must have something else going on.

Stan944

agree. Maybe I have multiple problems (I've had lots of engine problems this summer), e.g. also head gasket is sligtly blown between cylinders #3 and #4 ? although the compression test should have shown it.

I just did my "glove test" on a healthy (I hope) cylinder (#3). The intake glove was clearly inflating on 0 deg cam, and the exhaust glove on 180 deg cam. Both cam angles measured from the belt alignment marks. Also both gloves were flat at 90 deg cam angle, although there was tiny amount of inflation on the intake glove. This is what I expected, except the tiny inflation of the intake glove: maybe there are some soubtle issues in valve operation under static conditions (these are hydraulic valves, I believe).

meewosh

I had 150-160PSI on mine 87 N/A, not using oil, should I be wondering?

tod84944

160psi on a 87 is great. That is what it had when new. The main thing, you want even #'s across all 4 cyl.
Stan, sounds like you need to pull the head. Even it just a broken spring, which I doubt, you say you have a leaky head gasket.
You can the head gasket set from Vertex for around 70.00. It has every gasket that is in the top end, including new valve stem seals. Find a maching shop local, take the head and stem seals and have them fix it up for you.
Todd

Stan944

yeah, I think I'll take the head off. If I really have a bad head gasket, will I be able to confirm it upon taking the head off, or even a good gasket gets damaged upon dissassembly, and it's hard to say if it was good or bad?
How hard is it to do the stem seals myself?

Dennis Wilson

Broken valve spring(s) or bent valves would result in near zero readings. Since the wet test didn't change the pressure your rings and cylinder walls are apparently in good shape. That leaves burnt valves, valve seats, cracked head or head gasket as possibles.

Dennis

Dennis Wilson

Stan,

You should be able to check the head gasket by looking closely at the inner metal rings. A leak would show up as stains/residue from combustion gases in one small area.

Dennis

Stan944

Thanks guys, I'm taking the cylinder head off.

Zero10

This doesn't sound like a head gasket problem.

You are talking about rotating the cam when doing a leakdown test....
What you should do for one is test each cylinder both at TDC and at BDC. TDC on the compression stroke obviously. Make sure that the valves to each cylinder are closed when you do this (done by applying pressure, if you hear it all blow out the intake or exhaust rotate the engine 180* and try again)

By testing both at TDC and at BDC you can also help to indentify cylinder wall problems. You will have to place a large socket and breaker bar on the crankshaft when you test this, as the engine will try to roll from TDC when you apply 100psi of pressure.

Stan944

I took the intake manifold off, and found the (hopefully not 'a') problem. The intake valve on cylinder #1 (the one with zero or 100 psi compression; tried it several times) doesn't close entirely. There is an almost 1mm wide gap. Otherwise, the valve moves properly when I rotate the cam/crank shafts. All other intake valves close nicely. I called it a day, so I don't know what exactly is the problem.
I'm trying to figure out if these are hydraulic or not valves. Anybody?

special tool

The lifters are hydraulic, yes.

You need to remove the cam tower now, because the small gap you see could be caused by the cam lobe still or lifter.
You will know positively if you have valve damage only when you remove the tower.

Stan944

I took the top of the engine apart, and found one valve spring broken, and the hydraulic valve lifter was stuck in the extended position. Probably the latter caused the former. My guess is that the hydraulic lifter seized due to dirt getting inside. After all, I found lots of black or white deposit on the pistons and the valves.
These deposits were probbaly caused by numerous electrical issues with the timing.
In any case, I wonder if an engine in good shape creates this sort of deposits over a longer period of time, e.g over 20 yeaars?

special tool

Interesting.
What chips are in the car?