No compression on cylinder 3, help needed

[bobob]

Looking for some help as am drawing a blank here.

Have had a misfire since owning our 83 1.9 DG. Tried plugs, leads, cap, rotor arm etc but didn't solve anything so went to see a chap who I knew had worked on these in the past. Compression test showed there was zero compression on number 3.

So, head off, found I had a bent valve, both surfaces black, tried lapping it in but 'shined' on just one edge, popped the valve in a drill and it wobbled from side to side. Problem found, hoorah! Well, one new valve later and lots of lapping in, put the whole thing back together, fired it up and voila...... oh, no change, great.

So, once again, took the head off, supported it upside down and poured fuel into the valve seat area to see if there were any leaks, left it ten minutes and nope, no leaks so the valves are sitting firm.

Now I'm stuck, why is there zero compression? Rings? What signs should I be looking for if it is? valve guides, there isn't a 'pop' when drawn out with a finger over the end, but checked the other bank which has normal compression and theres isn't a pop there either, apart from the inlet manifold which is fine.

One gasket set later, and about to buy another, I want to make sure the next rebuild is the last!! Help!!!

Any advice greatly appreciated.

[CovKid]

Valve clearances correct?

[ajsimmo]

^^That's where I'd be looking ^^ Did some kind PO stick a solid tappet in there by mistake? Then set them all as hydraulic? Or maybe you have a completely jammed hydro tappet. No compression, bent valve, misfire since owned etc all point that way.

[bobob]

Well that was an area with we were unsure about, how to set up valve clearances and searching didn't really help us.

When running, theres a rhythmic pop pop pop pop, but not back firing, and the chamber is soaking wet with fuel.

[bobob]

There was a bent valve yes, which we thought was the culprit, but after fitting a new valve which is properly seated, the fault still exists.

Stuck hydro tappet, how would one diagnose that?

[Paul Weeding]

Rotate the engine over by hand and check that the valves are opening and closing... Next stage would be to measure the lift on the valves too

[kevtherev]

So are the clearances set for hydraulic or solid?
I'd have the lifters out and check.

[itchyfeet]

Reads to me like the head is still off, if so easy to get to the tappets, hook them out and check they are hydraulic and check pushrod length, from photos we can usually tell you if it's right.

there was a chap on here recently with a valve train so bodged it was unbelieveable, as said above the most likely reason.

[ghost123uk]

Well, one new valve later and lots of lapping in, put the whole thing back together, fired it up and.... no change.

Just for clarity, I take it you did check the compression at this point, before to took the head off again?

And =

there isn't a 'pop' when drawn out with a finger over the end, but checked the other bank which has normal compression and there isn't a pop there either, apart from the inlet manifold which is fine.

Am I understanding that bit ^^^ correctly, I read it as you are checking for compression in the spark plug holes with your finger, yes?

Also, one has to wonder what caused the bent valve in the first place. It's normally because it has hit the piston and that can of course damage the piston as well as the valve. I take it the piston crown was examined?

[bobob]

Thank you for all the advice. Greatly appreciated. Am heading down to the workshop this afternoon so will take some photos of the head, piston heads and everything else!

The 'pop' test was done with finger on valve guide top and whip out the valve. It pops on the inlet, but not on the exhaust, the advice I was given was suggesting compression was whipping up th me valve stem, but I guess that would only happen if the valve wasn't seated correctly, which it is.

I'm not sure how to tell the difference between hydraulic and non hydraulic so will upload some photos later for all to see! Thanks again folks.

[bobob]

Ok, here are some images. The cylinder with no compression is on the left of the photos shown, and the piston that is out, not in.

Compression test was done before and after valve replacement.

We haven't adjusted any clearances, yet, waiting for advice first! Thanks all.

[bobob]

First question is this, is that notch on both piston heads supposed to be there, or is that where maybe in the past the valves have hit?

[itchyfeet]

Looks right to me except the strange centre punching around the valves, looks too uniform to be accidental. Perhaps seats changed badly in the past and one is not square.
need to see the tappets also , at least the one from the bent valve, not shown

you will find them here under push rods/tubes


should look like upper one ( lower one has been taken appart)

[bobob]

I saw those lurking inside, how does one get them out?!

[itchyfeet]

Small electrical flat blade (electrical terminal block style) screwdriver will just get purchase on the circlip inner groove, bend the tip of one at and angle if you have to, then pull it out.
be careful not to score the bores.

Alro remember valves rotate so while it may be fluid tight in one position when rotated it may leak if those valve seats are in wrong.
if it were my engine I'd be changing that head looks very suspect