VP MD202B - No compression

[RichardS]

I did get quite excited about this, and took this morning off work, to travel to the boat and check that there was sufficient oil in the engine. It was slightly down, consistent with the earlier oil leak. Topped of, cranked lot's of times, compression issues are still there. Damn!



The rocker cover has been removed, timing on all cylinders appears to be correct. The Yard Manager although not an engineer, has far more knowlege and experience than me, thinks every is working as it should, and tappets having the correct clearance. Itw as by watching the valves opening and closing that we established that cyliner 2 had at least some compression.

Although I have not 100% confidentlyidentified TDC for cyl1, by watching the valve timings, and with a thumb over the injection hole feeling for compression, the valve and fuel injection timing appear to be correct, for that cyl at least seems to be correct.

Ont thing that I observed that may not be correct, both the oil dipstick and the air intake, appear to have some gas/smoke coming out of them when the engine is cranked over.

Looks like I am back a square one :-(

The yard are now going to engage a local diesel engineering company to take a look, which hopefully will initially take place on the boat.

I will update the post as soon as I have some news.

The engineer will be very quickly able to run a compression check on each cylinder which will identify where/if there is a compression problem.

The only experience I have with smoke coming out of the air intake is with older petrol engines if I'm setting the ignition timing by ear. If the ignition is advanced too far detonation takes place before the intake valve is fully closed and there is some firing through the intake. I'm not an expert on diesel engines but the equivalent would presumably be the intake valve timing being incorrect, the intake valve being bent/jammed or the intake valve clearance being much too tight.

As you've ruled out the first and the last, we would be stuck with the middle reason .... which is not good news so I'll shut up.

Richard

 

[VicS]

The rocker cover has been removed, timing on all cylinders appears to be correct. The Yard Manager although not an engineer, has far more knowlege and experience than me, thinks every is working as it should, and tappets having the correct clearance. Itw as by watching the valves opening and closing that we established that cyliner 2 had at least some compression.

Although I have not 100% confidentlyidentified TDC for cyl1, by watching the valve timings, and with a thumb over the injection hole feeling for compression, the valve and fuel injection timing appear to be correct, for that cyl at least seems to be correct.

Ont thing that I observed that may not be correct, both the oil dipstick and the air intake, appear to have some gas/smoke coming out of them when the engine is cranked over.

That eliminates the possibility of bent valves sticking , esp if the clearances are correct.

A bit of air puffing out of the dipstick hole while cranking I would dismiss as normal. I don't know how the crankcase is ventilated except that there some internal arrangement. I guess it must vent to the inlet manifold therefore a bit of air puffing out of the air intake is probably normal too.

 

[Heckler]

That eliminates the possibility of bent valves sticking , esp if the clearances are correct.

A bit of air puffing out of the dipstick hole while cranking I would dismiss as normal. I don't know how the crankcase is ventilated except that there some internal arrangement. I guess it must vent to the inlet manifold therefore a bit of air puffing out of the air intake is probably normal too.

Interesting that I believe he said he had tried a bit of easy start and that it didnt do anything. We all know that the most knackered of engines will usually go with that stuff. His words to me were that he could smell exhaust in the cabin after trying various things. I am leaning more and more to slightly bent valves, no compression so even easy start wont start it but partly combusted fuel being forced out of the "closed" inlet valves in to the interior of the engine/cabin space through the inlet manifold.
Stu
PS to Vic, they only have to be distorted a bit to stop them seating properly, they dont necessarily have to be sticking open.
PPS the rocker box and inlet are weird on this engine, the inlet ports go through the rocker box! They are only separated from the rocker box space by the gasket

 

[VicS]

Interesting that I believe he said he had tried a bit of easy start and that it didnt do anything. We all know that the most knackered of engines will usually go with that stuff. His words to me were that he could smell exhaust in the cabin after trying various things. I am leaning more and more to slightly bent valves, no compression so even easy start wont start it but partly combusted fuel being forced out of the "closed" inlet valves in to the interior of the engine/cabin space through the inlet manifold.
Stu
PS to Vic, they only have to be distorted a bit to stop them seating properly, they dont necessarily have to be sticking open.
PPS the rocker box and inlet are weird on this engine, the inlet ports go through the rocker box! They are only separated from the rocker box space by the gasket

I'll go with that.

A compression test worth doing? Yes if you have the tester I suppose.

 

[olam]

These buckets dont have this sort of system with oil in them. The idea of hydraulic lifters (buckets) is that you dont have to keep adjusting tappets. These engines have adjustable tappets.
Stu

Sorry,thought it was a MD22 engine,should have read more carefully.

 

[mjf107]

Quote "One thing that I observed that may not be correct, both the oil dipstick and the air intake, appear to have some gas/smoke coming out of them when the engine is cranked over."

That would suggest to me that the swept volume is only being compressed slightly then escaping past the rings into the crankcase ie not enough compression for ignition

 

[drydog]

If the engine was running prior to your intervention, then it most probably will be that something is not reassembled correctly.
In my experience when doing anything with timing be it chains/belts/rods and valves, the engine must not be started until it has been rotated in the right direction a few times through TDC with no locking or tightness.
I'd hazard a guess that the timing is out, a valve has been bent on the first start attempt and now will not start as a result of no compression.
Hopefully thats all there is to correct.
What is troubling is if you now have that much crankcase pressure when cranking the starter then your piston may be holed too.

 

[RichardS]

In my experience when doing anything with timing be it chains/belts/rods and valves, the engine must not be started until it has been rotated in the right direction a few times through TDC with no locking or tightness.

That's very good advice ..... and certainly advice which I've always followed with petrol engines 'cos you just leave the spark plugs out until you're sure that everything turns over smoothly by hand. However, in diesel engines without decompressors, which seems to be most of them these days, it must be very tempting to give the engine a blip with the starter motor as turning it over by hand is such a struggle unless you are prepared to remove injectors or glowplugs.

Welcome to the Forum by the way.

Richard

 

[Heckler]

If the engine was running prior to your intervention, then it most probably will be that something is not reassembled correctly.
In my experience when doing anything with timing be it chains/belts/rods and valves, the engine must not be started until it has been rotated in the right direction a few times through TDC with no locking or tightness.
I'd hazard a guess that the timing is out, a valve has been bent on the first start attempt and now will not start as a result of no compression.
Hopefully thats all there is to correct.
What is troubling is if you now have that much crankcase pressure when cranking the starter then your piston may be holed too.

The OP hasnt mentioned crankcase compression. By the way, if the piston hits the valve with enough force to hole it, then it is pretty catastrophic. Only happens when an engine is going at a good lick. I have had a cam belt let go on swmbo car at 30 mph, bent valves so that they have jammed and broke the valve guide, the pistons were fine. Look at the facts, he is cranking, there is smoke coming out of the inlet, only one place for that to come from, past the valves.
Stu

 

[RichardS]

The OP hasnt mentioned crankcase compression. By the way, if the piston hits the valve with enough force to hole it, then it is pretty catastrophic. Only happens when an engine is going at a good lick. I have had a cam belt let go on swmbo car at 30 mph, bent valves so that they have jammed and broke the valve guide, the pistons were fine. Look at the facts, he is cranking, there is smoke coming out of the inlet, only one place for that to come from, past the valves.
Stu

Errrr ..... surely smoke coming out of dipstick hole = possible crankcase compression.

Richard

 

[drydog]

The OP hasnt mentioned crankcase compression. By the way, if the piston hits the valve with enough force to hole it, then it is pretty catastrophic. Only happens when an engine is going at a good lick. I have had a cam belt let go on swmbo car at 30 mph, bent valves so that they have jammed and broke the valve guide, the pistons were fine. Look at the facts, he is cranking, there is smoke coming out of the inlet, only one place for that to come from, past the valves.
Stu

Agreed, bent valve/s, worn rings/head gasket or worst case scenario would be a holed piston. They all cause crankcase pressure.
What should be discussed is what caused the oil leak in the first place? was that rectified (unless I've missed that post)

 

[VicS]

Agreed, bent valve/s, worn rings/head gasket or worst case scenario would be a holed piston. They all cause crankcase pressure.
What should be discussed is what caused the oil leak in the first place? was that rectified (unless I've missed that post)

It was from somewhere behind the raw water pump

see:

http://www.ybw.com/forums/showthread.php?461986-MD2020B-overheating

http://www.ybw.com/forums/showthread.php?462707-MD2020B-Timing-Gear-Housing-Gasket-will-not-seal

http://www.ybw.com/forums/showthread.php?463112-MD2020-Crankshaft-Pully-Removal

http://www.ybw.com/forums/showthrea...itting-injection-pump-and-timing-gear-housing

read, digest and discuss your conclusions.

 

[drydog]

Bloody hell.
Thats a long list of things to go wrong and not confirmed as 'now ok'.
My gut feeling is, if it's not firing using quickstart then the timings out and or there is probably no compression on cyl 1 & 2 because of bent valves.
Plus there is no confirmed delivery of fuel at the injectors. (may be something as easy as a non energised stop solonoid)
The engine may have overheated so head gasket too may be suspect.

(unknown) No compression test? - which is the holy grail in assessing an engines condition / capability to start.

At this stage THATS where I'd start, everything else is just throwing money away.

 

[mjf107]

Originally Posted by drydog
image: http://www.ybw.com/forums/images/ybw/buttons/viewpost-right.png
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Agreed, bent valve/s, worn rings/head gasket or worst case scenario would be a holed piston. They all cause crankcase pressure.

QUOTE from VicS "What should be discussed is what caused the oil leak in the first place? was that rectified (unless I've missed that post"

Indeed we should. It will be interesting to see what the professional makes of it as post #60

 

[Heckler]

Errrr ..... surely smoke coming out of dipstick hole = possible crankcase compression.

Richard

I spoke to Gary, he did some motoring after fitting the engine which he had bought second hand, it ran fine, the only change is his dismantling and re assembling. Logic tells me that if it was running fine before hand and his work hasnt impacted on the rings or bores, then that is a red herring.
Stu

 

[Heckler]

Bloody hell.
Thats a long list of things to go wrong and not confirmed as 'now ok'.
My gut feeling is, if it's not firing using quickstart then the timings out and or there is probably no compression on cyl 1 & 2 because of bent valves.
Plus there is no confirmed delivery of fuel at the injectors. (may be something as easy as a non energised stop solonoid)
The engine may have overheated so head gasket too may be suspect.

(unknown) No compression test? - which is the holy grail in assessing an engines condition / capability to start.

At this stage THATS where I'd start, everything else is just throwing money away.

He told me he saw the fuel spraying from one of the injectors when he had it out and connected. The engine was running fine before he made a start on fixing the oil leak.
S

 

[drydog]

He told me he saw the fuel spraying from one of the injectors when he had it out and connected. The engine was running fine before he made a start on fixing the oil leak.
S

So to re-cap, he's fitted the engine, which ran fine but seemed to be overheating. He also found an oil leak during the running period.
Stripped the FIP and timing case components to access/repair the leak.
Then he's re-assembled it, tried starting and found he has no compression.
Stu, you have been in contact with him, has there been any mention of a compression test?
In my view, apart from confirming the engine timing is CORRECT, nothing further should be done to the engine before it's compression tested..
Once compression has been confirmed as within spec, then and only then I'd look at FIP.
Diesel engines - especially this type are really basic and reliable for it...even without fuel if the engine timing & compression was correct, it would still start and run for as long as quickstart was being sprayed into the air intake. (in fact even with low compression on 2 cyliunders the engine will still fire/start with the quickstart spray method)

Thats why I'm fixated on timing STILL being out. Despite potential damage to valves etc.

 

[RichardS]

I spoke to Gary, he did some motoring after fitting the engine which he had bought second hand, it ran fine, the only change is his dismantling and re assembling. Logic tells me that if it was running fine before hand and his work hasnt impacted on the rings or bores, then that is a red herring.
Stu

I'm even more confused now.

Gary told us the smoke was coming out of the dipstick hole, which understandably led to speculation on the thread that perhaps a piston has been damaged by a valve resulting in crankcase compression rather than cylinder compression.

You say that there is no mention of crankcase compression and that the rings and bores are almost certainly in good condition.

This seems like a non-sequiter to me but it's not helping Gary so let's leave it.

Richard

 

[VicS]

So to re-cap, he's fitted the engine, which ran fine but seemed to be overheating. He also found an oil leak during the running period.
Stripped the FIP and timing case components to access/repair the leak.
Then he's re-assembled it, tried starting and found he has no compression.
Stu, you have been in contact with him, has there been any mention of a compression test?
In my view, apart from confirming the engine timing is CORRECT, nothing further should be done to the engine before it's compression tested..
Once compression has been confirmed as within spec, then and only then I'd look at FIP.
Diesel engines - especially this type are really basic and reliable for it...even without fuel if the engine timing & compression was correct, it would still start and run for as long as quickstart was being sprayed into the air intake. (in fact even with low compression on 2 cyliunders the engine will still fire/start with the quickstart spray method)

Thats why I'm fixated on timing STILL being out. Despite potential damage to valves etc.

Gary says he has checked , doubled checked and even asked a third party to verify that the timing marks are correctly aligned. If they are the timing is NOT out.

He also says he is aware of the warning in the manual about turning the camshaft or crankshaft while they are not synchronised with each other and that to the best of his knowledge he did not do that.

I fear he may in fact have tuned either or both of the shafts while the intermediate gear was removed. Perhaps he failed to align the marks before removing the intermediate gear, failing to realise the significance of doing so, and then turned them in order to refit the gear with the marks all correctly aligned.

I cant see the point now of a compression test. I think everyone accepts that there is little or no compression, at least on two cylinders. Next stage I feel must be to take the head off to see just what is wrong in there.

He did not do anything to the injection pump(s) only lifted entire the assembly out of position to disconnect the regulator arm.

 

[RichardS]

Stu, you have been in contact with him, has there been any mention of a compression test?

The engineer has not been to check the engine yet, as per post #61.

Richard