Trying to fix Volvo Penta 2001 that refuses to start

[nick.theboatman]

Thanks for these..

Originally Posted by Hesti

The piston does go right up to the top of the cylinder, doesn't it? I've had that ages ago on a small motorbike, that at some time, they had changed connecting rod length and also the position of the eye in the piston in the design. A short rod with a piston that had its eye nearer to the top didn't give enough compression.

He hasn't changed the con rod (so its the same one that was running before) Piston rises to about 2mm short of the top.

Originally Posted by Hesti

The valve timing thing sounds like it is worth investigating further. If the intake valve does not open at all, you would also see not enough pressure when spinning the engine with the starter motor.

Intake valve opens ok. Question is: does it also close ?!! lol

Originally Posted by Hesti

The "some oil into the cylinder" (something like a teaspoon full) is always worth trying.

Yup we tried that but it didnt really make a difference and there was so much other diagnostic noise at the time we moved on.
This stuff might be good - just expensive.
https://www.amazon.co.uk/Piston-Seal.../dp/B072XF7GLH
Anyone used this stuff?

Originally Posted by Hesti

Some engines have decrompession levers on the head to support hand starting. That might also be something to check on your engine.

Yup that one is "in our faces" and as he is doing the tests with the rocker cover off we can check in real time that we are not getting deco because of the lever...

[nick.theboatman]

Originally Posted by Lou-In-NJ

Yes, with the operating rpm of a diesel, there is little "volumetric efficiency" to be gained by allowing the intake valve to be open after BDC, I'd say double check your timing marks, and don't rule out the idea that you may be looking at an erroneously marked gear. Search online for a picture of that part and see if the keyway and timing mark match what you see on your engine. If you do the trigonometry, you might find that if the intake valve closes 23 degrees late, that only gets you about 10:1 compression, and that might be the entire issue.

So we did a bit of maths and have 1.17 mm per degree. Good starting point.
We then identified the "crossover" between the exhaust valve shutting and the inlet opening (TDC #1) and found that the crank was originally retarded by at least 20 deg (the crossover was happening 20 deg after TDC #1). When we opened the crank case up we found that the registers on the teeth were off by 2 crank teeth (18 deg). When we fixed this we then found that we were still behind by 5 deg. So moving forwards by 1 tooth ahead of correct registration gave us the crossover 4 deg BTDC #1. The manual for my BMC (not the VP 2001) shows inlet valve opening 5 deg BTDC. Close, maybe

We then spotted that when set to the 5 deg after TDC #1, the inlet valve closed at approx 30 deg ABDC#1. So to make the inlet valve shut by BDC#1 we will have to advance the crank by 2-3 teeth from "true". Remember that before we opened the thing up first of all it appeared to be retarded by approx 25 deg and we found that it was in fact retarded by 2 teeth (plus that the crank has been made so that TDC is 5/9 of a tooth retarded anyway).
Was retarded "advanced" and have we been chasing ghosts? I dont think so becuase we did verify that the error was a retard and not an advance.

So if the thing was originally retarded by 25 deg AND the inlet valve closes at approx 30 deg ABDC#1... how on earth was it working at all?

[CORALSEA TRAMP]

Errors i have witnessed with GOOD mechs (not me- i am only 94) trying to start lh motor with rh settings-lh starter on rh motor- diesel inject timing dead right but 360 out-(Lots white smoke!!)--hydraulic cyls installed with bleed at the bottom---Look for something silly-inlet/exh confused. Age is correct and time to witness many odd things

[nick.theboatman]

Originally Posted by CORALSEA TRAMP

Errors i have witnessed with GOOD mechs (not me- i am only 94) trying to start lh motor with rh settings-lh starter on rh motor- diesel inject timing dead right but 360 out-(Lots white smoke!!)--hydraulic cyls installed with bleed at the bottom---Look for something silly-inlet/exh confused. Age is correct and time to witness many odd things

Lol yes was alerted to that sort of thing... like the fuel hose hanging out of the container and the calendar saying "August"

[nick.theboatman]

So I bring news.

Following the advice of @Hesti we tried the "oil in the pot" approach. Not so much a tablespoon as 1/4L. We didn't like that before we put the compression tester in (taking advantage of the opportunity to mop up all the oil that came flooding out of the exhaust when we turned her over) we got a faceful of oil as it went shooting over the workshop floor 2m away (note to self: don't get in the way you muppet).

The oil worked. Compression went from 140psi to 375psi. We liked that.

However it needed some more (this time 30ml from a syringe down the injector port) 2 hours later after it had stood for a bit and we fixed a few other things like a badly bent rack support pin (the rack now runs really well) and measuring the 2mm of shims necessary because he'd advanced the timing by 18 degrees ...

Anyway she fired up pretty much on the button - with the hot air gun treatment - and then she ran like she had a supercharger on her. You know: ear defenders and 6" of flame shooting out of the exhaust...

Still a bit rough but what do you expect when there is no water in the cooling jacket, no back pressure on the exhaust and not much oil in the sump?

Analysis:

the new valves were ok; the old valves were almost certainly knackered and after grinding a bit were pretty useless;
the catalogue of things that were damaged or not working or not set properly didn't help;
the main thing appears to be the new rings in the old bore - which must be off-round - an that was enough to wreck the compression. The rings will probably need a few hour of bedding in and then she should run good, seeing as she has basically been rebuilt.

Moral:

believe the compression tester and _do everything_.

I don't know if I can work out how to post a video here - we liked the 6" of flame out of the exhaust bit

[Lepke]

Besides timing problems, you need a minimum cylinder pressure of 285psi or more depending on the starting air temperature. The colder the air, the higher the pressure needed to ignite diesel. Most diesels are designed for a cylinder pressure of 350psi or more to avoid cold starting problems.

If you have a compression test of 140psi, the engine will never start because the cylinder air pressure will not increase to above 500°F needed for auto ignition.

[Lou-In-NJ]

30 ml is a lot! I'm surprised you didn't hydro-lock the engine. But unless it now starts reliably, you still have to figure what's going on with your compression.

1. Did you do a leak-down test as that video demonstrated?

2. Maybe you cracked a piston ring during assembly?

3. Having your intake valve close 30 degrees ABDC sounds a little late to me on a diesel, but it looks normal for a gasoline engine, according to what I see online; if the leak-down test doesn't yield any leaks, maybe advance the cam 1 gear tooth and see what happens to the pressure.

[Hesti]

Yes, keep the posts going.

If the problem persists - I do not know the engine, but this "Piston rises to about 2mm short of the top." sounds just a tiny bit strange ... Perhaps someone who knows the engine can comment.

[Sailing_Beard]

Originally Posted by Hesti

Yes, keep the posts going.

If the problem persists - I do not know the engine, but this "Piston rises to about 2mm short of the top." sounds just a tiny bit strange ... Perhaps someone who knows the engine can comment.

How does it sound strange? It is about 2mm clear at TDC, which seems about right for these type of engines.

[MicHughV]

140 psi is on the low end for gas engine....just had my 150 Yahama's checked at 300 hr service..140-160 psi....
diesels use internal cylinder pressure to provide combustion.....no pressure.....no combustion...
it would be a simple matter to do a compression test...
start there...

[MicHughV]

the piston top has a lot to do with compression and combustion...pistons come in many varieties....
I've always known diesel pistons to come all the way to top of the cylinder walls.....ie, the top edge of the piston being level with the top of cylinder, even the cylinder head is shaped to accommodate the piston crown.....a 2mm gap here simply does not sound right to me...
if there is a gap....the cylinder head gasket is where the gap will be.....this thickness can be added to the 2mm....diesel cylinder head gaskets usually have a metal ring around the cylinder...and I would guess that gasket thickness is probably in the 1mm range....so now you have a 3mm gap....doesn't sound like much, but if you are using compression as the combustion agent...it's a lot...enough to prevent combustion....

diesel engines are built to extremely fine tolerance to make this all work.

the piston rings MUST be placed on the piston in a certain way...another area where compression could be lost...doing this wrong could also lead to compression problems..

finally, doing your own valve job is an art....the slightest imperfection will allow combustion pressure to escape at the valve seat.

I've seen cams/valve springs/valve retainer clips being placed back on valves, that were not done correctly....another source of compression leakage...

all these things need to be reviewed and addressed.......a compression test will tell you if you have sufficient compression, but won't tell you where the problem is.

The smaller Volvo engines can be hand cranked....this is done by a lever that changes the cam position to reduce the compression so you can crank it...another possible area of concern, if so equipped.....this is a good example of how even a small difference in cylinder head pressure allows the engine to be hand cranked. It's not possible to hand crank even a small diesel without the de-compression lever...

the injectors and fuel delivery system are precision made, the average home mechanic cannot service these...they must be taken to an appropriate shop for service...

many things......

[vic008]

Copper washer with the injector. Are you sure? Injector goes into a copper sleeve that must be replaced if disturbed.

[Lowesmarine]

I have uploaded a 2000 series workshop manual. This may help in diagnosing the starting issue. Compression should be 290 - 362 Psi, Check the Decompression Lever adjustment, it may be holding the valve open.

[Icarus]

Originally Posted by nick.theboatman

Forgot to add that we did bleed the system (properly) and have been running these tests with the front off the govenor and operating the rack by hand. There is no question that it is trying harder when the rack is at the 1/2 way point than "full" - at full we get lots of puffs of white smoke (and black smoke when we push in the Easy Start and get the hot air gun going) but "pops" when the rack is at 50%. But no starting. And she's also had a new starter motor and we are supplementing the bench battery with a 100A bench PSU
No slouch here...

Timing is out, compression should be 300 to 400 psi for starters.
Hard to say not seeing the engine.
Why only 180 psi compression?

[MicHughV]

I've had two Volvo engines in a previous boat...the MD7B and the 2003..I've had them both apart for various reasons..
the white smoke is typically indicative of incomplete combustion or sometimes steam, I'd have to be there to tell..........opening the rack more will likely just flood the piston.. ...

you've got to step back and go over every little thing one item at a time...for one thing, I'd have the injector(s) checked by a company that is qualified to do so...the spray pattern of an injector is also a leading cause of black and white smoke.....but it takes a diesel specialist to check this. While the injector is out, do a compression test.

If the injector checks out....move on to the next thing....compression...

how about the fuel...the filter....is there water in the line...air ...etc ...??

if all that checks out, you will likely have to open the engine again, to go over the pistons, valves, cams, as previously described.

but at the moment, you are not going anywhere from the sounds of it...trying to do odd things to get it running will just frustrate you more and more....