Confused, no compression

[stinkypaul]

I'm pulling my air out with this, so if anyone can help I'd really appreciate it.

Currently I have barely any compression in any cylinder, it's like 20psi across the board.

But I did have 130psi across all 4 cylinders.

Here's the deal: Timing belt snapped. Now it snapped out of vtec, and as people have informed me, out of vtec the engine is non-interference. It would be easy to say that the valves did get bent, but, after putting a new belt on I did a compression test and that's when I saw 130psi.

So, more info. After putting a new timing belt on, and getting everything back together the engine wouldn't start, it just wasn't having it. This is when I compression tested it, while I was trying to diagnose the fault. In the end I concluded that the distributor had gone bad, so I changed it for a new one. After putting the new distributor on the engine fired up, and then died a second later. I tried to start it again a few times but I was just getting a whirring as though there was no compression. I checked and it's about 20psi for all cylinders. After saying several situation appropriate words I called it a day. Fast forward to this weekend, and I'd concluded that the timing belt must have jumped teeth. Today I took everything off to take a look and the timing belt looks fine, everything is spot on at no1 TDC.

So more situation appropriate words, and then I remembered I own a leak-town test kit, but I don't own a compressor, so I improvised:

OK so no1 is at TDC, valves are up, and I can wiggle the cam followers, so the valves should be closed, with the leak down pipe in the spark plug hole I blew down it, and I can hear air escaping. Sounds like the exhaust. So I vaped down the pipe and into the cylinder, and eventually vapour started to come out of no2 cylinder spark plug hole. While no1 is at TDC, no2 cylinder has its exhaust valves slightly open.

So it looks like the exhaust valves are leaking, but I don't get it. The compression was fine until I started it up and now I've practically no compression on any cylinder. Timing belt is fine, hasn't jumped.

If the timing belt snapping bent the valves I shouldn't have got 130 psi when testing it after putting the belt on, so why have I lost compression.

Aaaargh. Head is spinning on this so if anyone can suggest anything I'm all ears. Thanks

[Scott560]

Is there a little history to the car? is this a project you bought with broken belt, or is it your car and you drove it and it all works but just the belt snapped?

Seems odd that the dizzy would die during the work. I cant see how timing could go wrong, the lower sprocket is keyed to the crank with the key (i assume the key is still present?)

If it deffo had compression and now it doesn't, sounds like something is cloggy the valves stopping them from closing? old rag get sucked into the inlet? valves gone rusty if it hasn't been used for several years? valve clearances been set too tight so they are held open?

try a little oil in the bores in case the rings are a bit stuck?

compressions tester could have bit the bullet or the pipe damaged? hard to test unless you have another working car to test it on.

[stinkypaul]

Hi @Scott560 Many thanks.
OK, I've had the car nearly ten years. It did drive great, smooth, with plenty of power. I was driving home a few weeks ago and the engine died without warning. Got it recovered, checked it out and the timing belt had snapped (7 years old, so probably fair enough).

I killed the dizzy :/ I read on a few forums that testing the spark plugs against the block can kill the dizzy, well I'd already done that. Seems odd to me, but a lot of people were saying it. Well, I didn't just do that, I accidentally touched the alternator cable to the dizzy (big spark etc.) Dizzy seemed to work but maybe not quite right, and everything pointed to that. When I put the new dizzy on it fired up which was the first time it had.

So, you've given me some confidence in something you've said about something stopping the valves from closing. I didn't give full disclosure in my original post, I didn't want to muddy things. While the car was off the road and seeing as I was doing some work on the engine anyway I thought I'd tackle a job I'd been meaning to do, and I replaced the valve stem oil seals. I did it with the head on using the magic rope trick. So, one thought I have is that because the valves have rotated they aren't sitting the same now because of carbon build up. I'd considered dry cutting them. kind of wish I had now. If it is that, then if I can get the engine running then I think they'll sort themselves out.

also I've just checked the valve clearances and they were way off, and when I released the tension I could tell that they were sealing better, so I'll set them properly.

I might try buttoning it all back together and see how I get on.

[Scott560]

It'll sound clattery, but just loosen them way off and get it to fire. Once it's ran for a bit and compression is back, you can then let the car cool completely overnight and then do the clearances.

I wrote a long post ages ago about the written service manual method (and how I didn't like it). It always ended up too loose the manual method (and very clattery).

[stinkypaul]

Thanks. Wish me luck. I'll report back

[JEBB4]

You say you did stem seals with head on, I recently did the same, I know how fiddley those collets can be maybe check that one hasn’t become dislodged and fallen out..

[Drax]

if you have a leakdown tester but no compressor to run it, either borrow one or hire one from a shop - will only need it for a day so should be pretty cheap. this way you get an accurate picture of what is going on and where its going wrong.

i had to do the same to my 4G, it showed the air leak past the rings - i took the pistons out and i'd broken all 4x pistons. you wont have done the same as me, but running a proper leakdown test will help point you in the right direction.

[wurlycorner]

If you've filled the cylinders with rope to hold the valves up, it is *possible* that you've bent the valves - if there is too much rope on top of the piston, as you wind the piston up it could contact the valves too soon (before they've fully closed). And that could bend them.

Did you do a compression test and get good results *after* doing the stem seals, or before doing the stem seals?

If not, then yes - as Drax has suggested, do a leak down test properly with an air line.
A bore scope (with side view) down the spark plug holes to look at the valves would be useful, too.

[stinkypaul]

You say you did stem seals with head on, I recently did the same, I know how fiddley those collets can be maybe check that one hasn’t become dislodged and fallen out..

The collets are fiddly little suckers. I ended up making a little plastic funnel to slide them on top of the valve retainers, then used a greasy stick to fit them in place, all the while bricking it, in case I drop them into the engine.
I've checked again and all the collets have stayed in place.

[stinkypaul]

If you've filled the cylinders with rope to hold the valves up, it is *possible* that you've bent the valves - if there is too much rope on top of the piston, as you wind the piston up it could contact the valves too soon (before they've fully closed). And that could bend them.

Did you do a compression test and get good results *after* doing the stem seals, or before doing the stem seals?

If not, then yes - as Drax has suggested, do a leak down test properly with an air line.
A bore scope (with side view) down the spark plug holes to look at the valves would be useful, too.

I took the cams out and raised the rocker arms before doing the job so all the valves were fully up. I did each cylinder in turn and lifted the pistons with the crank pulley until I started feeling pressure from the rope. As soon as I could feel the pressure I stopped turning, so the pressure on the valves was minimal.

While doing the stem seals the valves will have turned a bit, so they won't be sitting in the same position now.

Compression tests were done before and after the stem seal job and they were the same, so this is really weird.

I haven't had much time to work on the car, but I have checked that the valves move up and down, all the way, smoothly, and without sticking.

I've adjusted the rocker arms all the way up and I've turned the engine over a bit on the starter, and I can feel the compression improving, so I'm hoping it's just carbon.
I've got a borescope but it's a bit naff, I'll see if it will let me look at the valves.