VP MD202B - No compression

[Jokani]

In the process of curing an oil leak I completed the following work:

1. Removed timing gear cover
2. Removed intermediate gear - when replaced ensured timing markings were correct, and to be 100% sure I removed the timing gear casing again and had another someone else verify they were correct
3. Injection pump removed and replaced

Since putting it back together it will not fire.

I have checked:

1. Clean fuel with no air at the injectors
2. Glow plugs working correctly & 12v+ at power bar
3. Stop control is working correctly and in the correct position

I have tried cranking with easy start and it still will not fire.

The problem seems to be a lack of compression, I can turn the engine fairly easily just with 2 hands on the crankshaft pulley.

Clearly I have re-assembled something incorrectly - I would suspect the timing, but I am 100% sure that the timing gear markings are correct.

Any ideas of how I could have reassembled incorrectly to cause the low compression, and/or the next steps I should take?

Thanks in advance, Gary.

 

[lw395]

Valves not closing?
If you have the cam timing figures e.g. inlet opens 'n' degrees BTDC closes 'm' degrees ATDC, measure where the tappet/rocker gap actually goes to zero as best you can.

 

[earlybird]

Did you turn the crankshaft while the intermediate gear was removed. If so, you might have reassembled with the camshaft 180 deg. out of position wrt the crankshaft. Not sure that would give low compression , but it's maybe worth checking.

 

[Jokani]

Valves not closing?
If you have the cam timing figures e.g. inlet opens 'n' degrees BTDC closes 'm' degrees ATDC, measure where the tappet/rocker gap actually goes to zero as best you can.

These are the degrees:

But I am not sure how I measure this, I can't find anything in the workshop manual.

 

[Jokani]

Did you turn the crankshaft while the intermediate gear was removed. If so, you might have reassembled with the camshaft 180 deg. out of position wrt the crankshaft. Not sure that would give low compression , but it's maybe worth checking.

I do not think so, I had read in the manual not to turn, and I do not believe I did, but then something is clearly wrong. Not sure I could get it 108 deg out, there is only one dot so to get them to still align/match up, I would need to have turned it 360 deg?

 

[RichardS]

Assuming that the flywheel/crankshaft pulley has not been moved and has a TDC mark for cylinder 1 on it, all I can suggest is to remove the rocker cover and turn the engine to TDC and watch the valves on No 1 to check that they are both fully closed as the piston approaches TDC. You may need to spin it 360 degrees and check again to make sure that no. 1 is on the ccompression stroke.

If you have a decompressor it could be sticking or not adjusted correctly.

Richard

 

[philwebb]

Hi I did something like this when I changed the cam belt on a VW Passat. I was very careful to line up the marks but somehow still got it wrong. I think I was only one tooth out on the belt but it did make a lot of difference. You have to dismantle and try again, it has to be the timing being out. On some engines damage can be done as the piston can bend the valve. The inlet valve is open at 13 deg before TDC, that's not a lot, could be one tooth on a cog. To find TDC you could take out one injector and put a steel rod down to touch the top of the piston. How you measure the 13 degrees I'm not sure. It would be easy if there was a flywheel. I have a 2010 and I seem to remember some graduation marks somewhere on the front of the engine, they must be next to the bottom pulley. Having found TDC you could scratch a mark down there. In the absence of any marks you could try butchering a big plastic protractor and blutaking it behind the pulley, a wire pointer fixed to the pulley would then enable you to estimate the 13degrees. Compare this to the cam opening the inlet valve and you should see how far out the valve timing is. Good luck Phil

PS as previously mentioned you will kick yourself if the decompression lever is stuck in the open position.

 

[earlybird]

I do not think so, I had read in the manual not to turn, and I do not believe I did, but then something is clearly wrong. Not sure I could get it 108 deg out, there is only one dot so to get them to still align/match up, I would need to have turned it 360 deg?

The point of my earlier post was that it is possible to have the crankshaft one rev. out of synch. with the camshaft, (or the camshaft a 1/2 rev. out) with the timing marks in alignment.
As I said, I don't think this would lead to the lack of compression, which you think has occurred, but it would put the injection timing completely out, assuming the pump is driven from the camshaft drive, and definitely stop the engine firing.
Having said that, the de-compressor must be a prime suspect, as suggested by others.

 

[Heckler]

Assuming that the flywheel/crankshaft pulley has not been moved and has a TDC mark for cylinder 1 on it, all I can suggest is to remove the rocker cover and turn the engine to TDC and watch the valves on No 1 to check that they are both fully closed as the piston approaches TDC. You may need to spin it 360 degrees and check again to make sure that no. 1 is on the ccompression stroke.

If you have a decompressor it could be sticking or not adjusted correctly.

Richard

No decompressor on these donks, trying to get my head around it, if he has the timing out 180 deg then closed valves on BDC and open when the piston goes up? Nah, that wont work, piston hits open valves, bent valves. However if timing is a bit out and piston has hit valves? Did he take the head iff?
S

 

[Jokani]

Thanks everyone for your help so far.

Having said that, the de-compressor must be a prime suspect, as suggested by others.

As far as I am aware there is not a de-compressor on the MD20x0 series.

The point of my earlier post was that it is possible to have the crankshaft one rev. out of synch. with the camshaft, (or the camshaft a 1/2 rev. out) with the timing marks in alignment.

Although I do not see how, I could have got them out of synch, at the moment this does seem seem the most likely cause as to why it will not fire

Assuming that the flywheel/crankshaft pulley has not been moved and has a TDC mark for cylinder 1 on it, all I can suggest is to remove the rocker cover and turn the engine to TDC and watch the valves on No 1 to check that they are both fully closed as the piston approaches TDC. You may need to spin it 360 degrees and check again to make sure that no. 1 is on the ccompression stroke.

Richard

I do not believe that there are any TDC marks.

If I follow philwebbs's method and remove an injector to find TDC, then both valves should be closed. If not closed (this i why there is little/no compression) I can presume that I have the camshaft out by 1 revolution, so I would need to remove the intermediate gear spin the camshaft by one revolution, then refit the intermediate gear etc.

 

[Jokani]

Unsure if this helps, I have been looking through photos of the parts in question, on the timing gear casing, there is this 'TOP' mark, but I can't see that this mark aligns with a mark on the crankshaft pulley, but it must server a purpose?

 

[nemodreams]

Dis-connect the pipes from the top of the injector pump - ie the pipes from the pump to the injectors. Turn the fuel on as normal - spin the engine by hand and see when the injector is spilling fuel. With the rocker off you can check the injection point against valve position - and get an idea if anthing is radically amiss

How do you adjust timing ? On the Yanmars the inection pump sits on shims - which one alters to advance or retard injection timing. Have you disturbed or discarded any shims on the pump?

Is the fuel rail on the pump correctly connected to the governor/throttle set up ?

 

[Jokani]

However if timing is a bit out and piston has hit valves? Did he take the head iff?
S

Hi Stu, no the head has not been removed.

When I was talking about the problem in the yard, the timing being a bit out was the main suspect, timing gear casing was removed, and timing marks verified as correct. So I think it will either be spot on or 180 deg out

 

[Heckler]

Hi Stu, no the head has not been removed.

When I was talking about the problem in the yard, the timing being a bit out was the main suspect, timing gear casing was removed, and timing marks verified as correct. So I think it will either be spot on or 180 deg out

Go back to basics then as Rich says. No1 inj out, rocker box off, screwy down the inj hole, turn engine by hand clockwise looking at the front, until you get TDC, rock it a bit to check it is there, keep an eye on the valves on No1 they should be both shut and No3 should be "rocking" one opening and the other shutting., Ill check that in a min and get back by the way. If they arent, turn it another revolution and check it. If not, timing is out. You can time it with this method by the way without marks, although I woukd be surprised if there werent any.
Stu
PS disregard the three cyl rock bit, the spare parts seems to show that that 1 and 3 arent diam opposite, rather the firing is 360 divided by 3 but the getting No1 on TDC and both valves closed still stands.

 

[RichardS]

Unsure if this helps, I have been looking through photos of the parts in question, on the timing gear casing, there is this 'TOP' mark, but I can't see that this mark aligns with a mark on the crankshaft pulley, but it must server a purpose?

Sometimes the mark on the pulley is a tiny little nick. If you weren't looking for it you'd think it was just a bit of corrosion. I usually pick it out with a touch of Tippex when I spot it.

If you can find it I would use that as it's simple, rather than removing an injector and using a stick although that will work.

Richard

 

[Heckler]

Sometimes the mark on the pulley is a tiny little nick. If you weren't looking for it you'd think it was just a bit of corrosion. I usually pick it out with a touch of Tippex when I spot it.

If you can find it I would use that as it's simple, rather than removing an injector and using a stick although that will work.

Richard

Richard
The guy has said he used the marks, he is still not sure if it is right, my way is the definitive way, no possibility off it being wrong. Like you, many years of experience, I took his remarks in to account when giving my suggestion!
Stu
PS Why mention decompressors when everyone knows that the md20X0 series doesn't have them!

 

[Jcorstorphine]

Go back to basics then as Rich says. No1 inj out, rocker box off, screwy down the inj hole, turn engine by hand clockwise looking at the front, until you get TDC, rock it a bit to check it is there, keep an eye on the valves on No1 they should be both shut and No3 should be "rocking" one opening and the other shutting., Ill check that in a min and get back by the way. If they arent, turn it another revolution and check it. If not, timing is out. You can time it with this method by the way without marks, although I woukd be surprised if there werent any.
Stu
PS disregard the three cyl rock bit, the spare parts seems to show that that 1 and 3 arent diam opposite, rather the firing is 360 divided by 3 but the getting No1 on TDC and both valves closed still stands.

Question 1. Can you get a screwdriver or probe down through the injector port as the route does not seem to give a line of sight on the drawing of the head I have from the Perkins manual. Perkins 100 / Perama / VP2020

Question 2. I hope I am wrong but if the OP has got the valve timing wrong, is there a chance that valves / pistons are damaged.

 

[philwebb]

Richard
Stu
PS Why mention decompressors when everyone knows that the md20X0 series doesn't have them!

Hi Stu, I bow to your superior knowledge, but how does the stop cable work on this engine?

 

[Heckler]

Hi Stu, I bow to your superior knowledge, but how does the stop cable work on this engine?

Had to look it up! Its 9 years since I sold mine, http://www.marinepartseurope.com/en/volvo-penta-explodedview-7746800-27-230.aspx cable and lever on pump. He does say that there doesnt seem to be much compression on the engine

 

[Heckler]

Question 1. Can you get a screwdriver or probe down through the injector port as the route does not seem to give a line of sight on the drawing of the head I have from the Perkins manual. Perkins 100 / Perama / VP2020

Question 2. I hope I am wrong but if the OP has got the valve timing wrong, is there a chance that valves / pistons are damaged.

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7746800-21-136.aspx I cant see any mention of pre combustion chambers on here so confident that a wire or similar and wiggling through the inj hole will be able to feel the piston.
Stu