Timing chain went out through the cover... could have the engine survived?

[RLWP]

Those pulleys seem to be hard to find, don't wreck it

 

Richard

[bizzard]

There will be a little end float on the crank shaft, how much depends on the wear on the engine crank thrusts, might only be a few thou, could be 3 or 4mm or more .

If you pull the crank shaft forward and tap some little wedges behind the pulley as close to the centre of it as possible, then find a round of hard wood or brass and keep tapping the crank shaft centre, it might shift it, bit by bit by keep altering the wedges. Once on the move it might come easily with a bit of gentle equal levering and squirts of penetrating oil, keep levers clear of the outer periphery of the pulley at all costs or you could bust or bend the belt V part of it

 

Ps If it is an ex vehicle engine and not been reconned since there could be considerable crank shaft end float, 1/4'' even due to the push on it from the clutch release bearing pushing on the pressure plate which tries to push the shaft forward every time a foot pressed the clutch pedal.

Edited December 15, 2014 by bizzard

[Bod]

Well, I think it was a Christmas miracle

 

I took the head off, and all the valves seem to be pretty good, at least nothing noticeable by the naked eye. In petrol engines you check the valves by putting the head upside down and filling the chambers with petrol, if after a few minutes the petrol goes through the valves are leaky. Does it work with diesel engines as well? I just poured diesel over the valves, not much of a combustion chamber there, but they still hold as bit of diesel. Now diesel is way thicker than petrol, maybe I should get some petrol to check the valves?

 

Any other idea to check them?

 

Also, could it be that the engine stopped exactly at the point when at least one valve is open in each cylinder? It was freewheeling after all, but with the rockers removed there is some compression.

 

So I am almost there, if only I could get that pulley off, I am tempted to drill and tap two holes to pull it out and then get a new pulley!

 

Whilst you have the head off. Grind the valves in, gives the chance to inspect, springs, valve stem seals, and the valves themselves.

 

Bod

[Dutchie]

I just poured diesel over the valves, not much of a combustion chamber there, but they still hold as bit of diesel. Now diesel is way thicker than petrol, maybe I should get some petrol to check the valves?

 

Any other idea to check them?

 

 

 

I did this job of checking the valves with unleaded fuel , and found 7 leak valves . this point give me the reason to bring the head to a local engine revise workshop

i know that i can made this job by myself too use grinding pasta , but i take the safe way, its a lot off work too do this job rebuilding etc.it must be good for years after ! , see this topic http://www.canalworld.net/forums/index.php?showtopic=72338

[Alf Roberts]

Well, I think it was a Christmas miracle

 

I took the head off, and all the valves seem to be pretty good, at least nothing noticeable by the naked eye. In petrol engines you check the valves by putting the head upside down and filling the chambers with petrol, if after a few minutes the petrol goes through the valves are leaky. Does it work with diesel engines as well? I just poured diesel over the valves, not much of a combustion chamber there, but they still hold as bit of diesel. Now diesel is way thicker than petrol, maybe I should get some petrol to check the valves?

 

Any other idea to check them?

 

Also, could it be that the engine stopped exactly at the point when at least one valve is open in each cylinder? It was freewheeling after all, but with the rockers removed there is some compression.

 

So I am almost there, if only I could get that pulley off, I am tempted to drill and tap two holes to pull it out and then get a new pulley!

 

As you have it to this stage it would be very shortsighted not to take the head and get it skimmed and the valves can be checked and/relapped at the same time.

And Bizzard's plan for removing the pulley - wedges - they'll shift anything if you get them in the right place.

[Nestor Espinoza]

Hello again,

 

Well, the engine is almost complete, all the important bits are back in and I thought I'd crank her up before installing the pulleys, but I may have made a mistake somewhere, it just didn't start.

 

So, timing chain and gears went in as per the diagram in the manual, with the dots and shaft centres in line. I put the rockers in and adjusted the clearances, a couple of them were way off. The engine can be cranked by hand, all the valves go up and down, there is compression.

 

I didn't mess with the injection pump at all, so the timing should still be right, or wherever it was before when the engine was running. I primed the system, there is diesel everywhere, and all four injectors get diesel, they squirt a bit when I loosen the nuts and crank the engine.

 

The glow plugs are connected, they draw some 30A, like before.

 

Easy Start didn't help, just got maybe a couple of explosions.

 

The strange thing is that if I crank the engine at full throttle for about 15 seconds the engine starts and runs for maybe 3 seconds, then dies.

 

I remember a petrol engine I overhauled some time ago with an odd system to install the timing chain and it was possible to have the camshaft 180 degrees off, I had to check that the right valves were opening at #1 TDC. Could that happen with this engine? I don't see how, but that is the only thing I can think off now.

 

 

Other ideas?

 

Thanks a lot!

 

Nes

[Nestor Espinoza]

I just found this while looking for a bolt in the bilge, any idea what could it be? It looks precisely machined.

 

http://bmcwoes.blogspot.com/2014/12/the-mystery-part.html

[bizzard]

I just found this while looking for a bolt in the bilge, any idea what could it be? It looks precisely machined.

 

http://bmcwoes.blogspot.com/2014/12/the-mystery-part.html

I reckon its a Reynolds timing chain tensioner piston. The spiral is to actuate it after fitting. usually with an Allan key.

[Tony Brooks]

But it may have fallen out of the timing cover when you took it off. As the chain went through the cover I expect the tensioner was completely mangled so the whole thing may well have fallen apart. If you fitted a new tensioner then hopefully it will not be a problem but if you put an new rubber slipper into the old housing you had better take it all off again and also find the spring that goes with it.

 

The fact that you do not know what it is suggests that you may not have released the tensioner when you fitted the new one an if so it may need doing if oil pressure has not done it already. If it has not released the timing will be all over the place and the chain may well be gnawing at the cover again.

[bizzard]

There's a light spring inside them too, that and oil pressure would probably have popped the piston out of its holder unit when the chain broke.

[Nestor Espinoza]

I haven't replaced the cover, so it is all still visible. The tensioner was almost completely out when I uncovered the mess, I removed it and took the long spring out as well. Something may have fallen later, maybe the piston stayed inside and slowly came out when I was doing something else. The tensioner is doing its job now though, I checked and it moves freely, pressing against the chain.

[Alan Saunders]

On gap - I don't have a dwell meter

 

Manuals, well it's surprising what you can find on the internet these days: http://www.thestraycat.net/files/Volvo%20Penta%20Owners%20Manual.pdf

 

That pair of V6 engines is a hoot. Blipping the speed control makes the boat move because of the torque reaction

 

Richard

The often recomended here Uni-T clamp ammeter, as well a being a competent DVM, also has a Hz/duty% (dwell) range. It may be the only DVM you ever need except that it does not have an Amp range using the leads (for when you cannot isolate an individual wire) and there is no 'pulse-stretcher' on the audible continuity beeper (only found on expensive Fluke meters in my experience).

 

I agree that many manuals are available online but often not from the original manufacturer and it can take some patience and alternative search terms to find the one that you need.

 

For the OP, ask yourself, why would a timing chain break? Either the chain or a related component was faulty or another fault (seizure?) caused it to fail. With data from a decent manual you could check the original chain for 'stretch' (wear, allowing it to jump a cog or two) or look elswhere for the cause.

 

Alan

[RLWP]

To be honest, this is the first time I have had to adjust a set of points in around ten years! My MG has a Lumenition optical set

 

Richard

[bizzard]

To be honest, we only used a dwell meter if a distributor was worn, with side play or worn cams on the centre spindle to get a general average contact gap. If the distributor was in good nick, then just set the gap as per the manual usually 12 to 16 thou for most Lucas distributors or 25 thou for Autolite and AC distributors.And then do either a timing light or static ignition timing adjustment.

[Tony Brooks]

I haven't replaced the cover, so it is all still visible. The tensioner was almost completely out when I uncovered the mess, I removed it and took the long spring out as well. Something may have fallen later, maybe the piston stayed inside and slowly came out when I was doing something else. The tensioner is doing its job now though, I checked and it moves freely, pressing against the chain.

 

It should not move freely once it has been released. The only play you should get on it is the gap between one of those little indents in the slot of the thing you pulled out of the drip tray and the next indent. I am now all but sure it is not tensioned correctly and s not working.

 

Please take the tensioner off again and take the rubber slipper assembly out of the metal block you bolt onto the engine.

 

Memory is a bit hazy here but either down inside the block or inside the "tube" on the back of the slipper you should see a little peg sticking out. The slot in that retrieved thing sits over that peg so you can put an allan key into the end of the thing and twist it in and out.

 

I think the spring (Help BIzzrad/Richard) between the slipper and that retrieved thing and the whole lot is compressed by hand while you turn the allan key to allow the slipper to go as far into the block a sit can. When it is fully in the larger indent in that thing at the end of the slot should engage andnhold the assembly in the compressed position.

 

After it ha seen fitted the allan key is used through a hole in the end of the "block" (maybe a hexagon set screw in it to block it ) to release the slipper so it tensions the chain. As the slipper wears oil pressure keeps pushing the slipper against the chain while the helical slot with the indents in prevents whip in the chain pushing the tensioner back in.

 

The manual I have access to for the 1.5 is not much help and has no pictures.

 

Do not fit the cover until you have checked the tensioner is correctly assembled, with all its parts, and the chain tension is correct.

[Albion]

To be honest, we only used a dwell meter if a distributor was worn, with side play or worn cams on the centre spindle to get a general average contact gap. If the distributor was in good nick, then just set the gap as per the manual usually 12 to 16 thou for most Lucas distributors or 25 thou for Autolite and AC distributors.And then do either a timing light or static ignition timing adjustment.

Our specialism was in engine tuning and, equipped firstly with dwell meter, timing light etc and then later with Crypton tuner and then Bosch tuner/s we always used dwell as every degree of dwell is a degree of ignition timing. What you do is fine for a new set of points but if they had the slightest pip and depression on the mating surfaces you can't use a feeler gauge accurately. You could often have a situation where that applied but the points were still within acceptable tolerance for wear, and electrical condition on the tuner. Difficult to use a tuner in a boat I grant you.

Roger (ex Bosch Systems Technician)

Edited December 21, 2014 by Albion

[RLWP]

 

It should not move freely once it has been released. The only play you should get on it is the gap between one of those little indents in the slot of the thing you pulled out of the drip tray and the next indent. I am now all but sure it is not tensioned correctly and s not working.

 

Please take the tensioner off again and take the rubber slipper assembly out of the metal block you bolt onto the engine.

 

Memory is a bit hazy here but either down inside the block or inside the "tube" on the back of the slipper you should see a little peg sticking out. The slot in that retrieved thing sits over that peg so you can put an allan key into the end of the thing and twist it in and out.

 

I think the spring (Help BIzzrad/Richard) between the slipper and that retrieved thing and the whole lot is compressed by hand while you turn the allan key to allow the slipper to go as far into the block a sit can. When it is fully in the larger indent in that thing at the end of the slot should engage andnhold the assembly in the compressed position.

 

After it ha seen fitted the allan key is used through a hole in the end of the "block" (maybe a hexagon set screw in it to block it ) to release the slipper so it tensions the chain. As the slipper wears oil pressure keeps pushing the slipper against the chain while the helical slot with the indents in prevents whip in the chain pushing the tensioner back in.

 

The manual I have access to for the 1.5 is not much help and has no pictures.

 

Do not fit the cover until you have checked the tensioner is correctly assembled, with all its parts, and the chain tension is correct.

 

Tony, I'm sitting back on this one. There are too many mysteries in this already. How can you break a timing chain and not have the valves hit the pistons? How can you turn the engine over with a broken chain? Why are some of the tappet clearances too big - and how much is too big? And - how on earth do you break a timing chain

 

I'm out of my depth on this one - either the story doesn't add up because the OP has missed something, or I don't understand BMC engines enough to advise

 

Richard

[Tony Brooks]

Yes, I have been wondering if for some reason the camshaft or injector pump seized and snapped the chain, but then again the OP says he spun the engine over afterwards and that should have bent or dented something. I am sure the piston bump clearance is only a few thou so there is no way I can see the piston not hitting valves if things happened as described.

 

I really wanted someone to confirm where the spring went in that tensioner - I am sure the OP has not assembled it correctly and does not know it should all but lock in the tensioned position.

[Nestor Espinoza]

Yep, the mystery little piston is part of the tensioner. I first put it together with just the spring and thought that it was the spring that pushed it against the chain. The little piston compresses the spring and you can use an allen key to adjust it and select a notch. There is no hole on the block, you can't do anything after the tensioner goes into it, so I reckon the piston is to adjust the force the slipper exerts against the chain by adjusting the oil flow. With the slotted piston all the way in the oil will push the tensioner against the chain with maximum force, with the slipper all the way out the oil would easily flow throw it and then through the hole in the rubber. Pretty clever device, higher rpm, higher force against the chain. I left it in the almost closed position for maximum force, given that the parts are old and clearances are surely larger than they should.

 

Now summarising,

 

-timing chain broke at idling speed and went through the cover. The chain did not seem to have any play, the surviving bits could not be flexed sideways and there wasn't noticeable play lengthwise. It cut in two parts.

-After the chain broke the engine cranked and freewheeled, no compression at all, so I expected the worst.

 

Then I took it apart:

 

-the head seemed fine, all the valves were seated perfectly. I filled the ports with water and they held the water for an hour, no leaks whatsoever.

-The pistons went all the way up, flush with the surface of the block, so I guess no bent conrods.

 

Putting it back together:

 

-New chain went in, dots and centres aligned, i don't think you can get it wrong here, even one tooth off and it is clearly misaligned, so I am sure I got that one right.

-Put the rockers back in. Before I removed them I noticed some clearances were way off, so I suspected some valves were bent and stuck open, but nope, they were fine, just the clearances needed adjusting. Most were almost there, two were almost 1mm instead of the 0.38mm. Now there are all at 0.38, all the valves go up and down, and there is compression when turning the engine.

-Fuel system was primed just in case, even though I did not mess with it at all, other than disconnecting the injectors. I cranked the engine and got diesel squirting from all injectors.

 

And I tried to start it, but got nothing, nothing at all. Even with easy start.

 

And I rechecked everything. I watched a youtube video, with engine at 22 degrees btdc I removed the injection pump and the master spline was at 5 o'clock, it all seemed to be as it should.

 

Still no joy, though I got the feeling the engine was closer to firing up, so I turned the pump a bit, as far as the slots allow, and still nothing.

 

I am about to hand it to a professional, but it is very frustrating, it is an old and simple diesel, I should be able to get it running.

[RLWP]

 

 

two were almost 1mm instead of the 0.38mm

 

Those two - have you checked the pushrods? I suspect that they are bent. It's the only way I can see that the pistons can knock back the valves without bending the valves or rods, or breaking the rockers or cam followers

 

 

 

And I rechecked everything. I watched a youtube video, with engine at 22 degrees btdc I removed the injection pump and the master spline was at 5 o'clock, it all seemed to be as it should

 

You aligned the pump with the timing mark?

 

Richard

Edited December 21, 2014 by RLWP

[Albion]

 

Those two - have you checked the pushrods? I suspect that they are bent. It's the only way I can see that the pistons can knock back the valves without bending the valves or rods, or breaking the rockers or cam followers

Richard

Agreed but the original description in the OP's first post says:

 

"At the first crank nothing happened, but at the second attempt it turned freely, so much so that the crankshaft now keeps on turning after stopping the starter." ..................(my underlining)

 

​So how does the engine run on with just the inertia of the flywheel when there should, in theory, be good compression if the valves are OK? There is something most odd about the analysis/reporting of this problem.

Roger

Edited December 21, 2014 by Albion

[RLWP]

Agreed but the original description in the OP's first post says:

 

"At the first crank nothing happened, but at the second attempt it turned freely, so much so that the crankshaft now keeps on turning after stopping the starter." ..................(my underlining)

 

​So how does the engine run on with just the inertia of the flywheel when there should, in theory, be good compression if the valves are OK? There is something most odd about the analysis/reporting of this problem.

Roger

 

Dunno. At that point all the valves should be firmly shut with consequent compression. Even if the head gasket had somehow been disrupted across the whole head I wouldn't expect that there is a big enough gap to allow free running.

 

Something not obvious being missed

 

Richard

[Nestor Espinoza]

I agree, the freewheeling still puzzles me. You know when you crank an engine and it doesn't start, it always goes back a little, because of compression of course. Now when this engine failed I could see that the main pulley kept turning after cranking and then stopped slowly, without reversing at all, which is why I thought the engine had become the new anchor.

 

I agree with the comments/questions, there should always be at least one cylinder with the valves closed, so the freewheeling was most confusing, unless there is a point when at least one valve in each cylinder is open?

 

I checked the pushrods by rolling them on a flat surface, I didn't notice anything wrong.

[Bod]

Can you put the gear box in gear, and turn the crank pulley nut, to check the prop shaft turns?

Make very sure the engine cannot start, first.

This will confirm whether the crank is in one or two piece's.

Other than that, back to basics. No. 1 cylinder on tdc, recheck cam timing. Injector timing...recheck, fuel tap, on.

 

Bod

[RLWP]

Not if its a PRM gearbox it won't

 

But taking the starter motor off and wedging the flywheel would

 

Richard

Edited December 21, 2014 by RLWP