handcranking and decompression levers

[FairweatherDave]

I have an elderly Volvo Penta MD11C engine on my Westerly Centaur. I also have the workshop manual and the instruction book. Both the boat and inboards are new to me. I had the engine running today in the yard for the first time after the winter and realised the ability to handcrank would be very useful. I tried to do this but realised I did not know what I was doing with the decompression levers. I can hand turn the engine easily with the levers up vertical but the turning stops once the levers are down. Is the engine supposed to start and then you push the levers down? And what happens if you start the engine using the battery with the decompression levers up? My manual and book don't answer this. Thanks for any replies.

 

[Salty John]

The engine won't start without compression. The idea is that with the decompression levers up you can get the engine spinning and then you drop the levers and she fires up.

 

[mick]

The engine won't start without compression. The idea is that with the decompression levers up you can get the engine spinning and then you drop the levers and she fires up.

I would only add - don't expect it to be easy.

 

[ghostlymoron]

I've never tried handcranking a boat engine as mine doesn't have the facility. It would be a useful thing to do if your battery failed but, in the confines of a boat, it's difficult to see how you could position yourself to get a good swing and, at the same time drop the decompressors. If you have a multi-cylinder, it is alleged that you can start it on one cylinder first (by dropping one de-compressor) and the drop the other(s).
If you battery is weak but not flat, you can decompress to get the engine spinning, and then drop the decompressor to start. You don't need a starting handle to do that.

 

[FairweatherDave]

Thanks both. A bit more truth...
I failed to hand start but one reason was that a battery isolation switch was turned the wrong way . (Its a whole new world to me!). So from your suggestion really you need a second person to be flicking the levers down to try and get the compression while you spin the engine. (And then still some luck). That is what I am expecting.
Also I managed to start the engine with the battery with the decompression levers up (following some futile handcranking). I think a lot of oil blew out the exhaust, but that may have been the throttle set too high. I know you need compression for ignition so I'm not sure I have the whole picture (understatement). More comments welcome....

PS Thanks too Ghostlymoron. Your comments are making sense. I have two cylinders.

 

[FairweatherDave]

Thanks Sailorman. I think I would still need someone else in charge of the levers, but one at a time makes sense. And positioning the second person will be a bit tricky but there is a fair bit of room.
PS Sailorman, your post has disappeared...

 

[prv]

Thanks both. A bit more truth...
I failed to hand start but one reason was that a battery isolation switch was turned the wrong way

If you're hand-starting you don't need power, so the position of the battery switch is irrelevant. (Though they say you might fry your alternator if you do manage to start it.)

So from your suggestion really you need a second person to be flicking the levers down to try and get the compression while you spin the engine.

Yep - although if on my own I would try with a string led to where I could step on it to flick the levers over.

Also I managed to start the engine with the battery with the decompression levers up

Seems unlikely. If the valves are open there is no pressure, and if there is no pressure then the diesel will not ignite. You have something mixed up.

Pete

 

[VicS]

Thanks both. A bit more truth...
I failed to hand start but one reason was that a battery isolation switch was turned the wrong way . (Its a whole new world to me!). So from your suggestion really you need a second person to be flicking the levers down to try and get the compression while you spin the engine. (And then still some luck). That is what I am expecting.
Also I managed to start the engine with the battery with the decompression levers up (following some futile handcranking). I think a lot of oil blew out the exhaust, but that may have been the throttle set too high. I know you need compression for ignition so I'm not sure I have the whole picture (understatement). More comments welcome....

PS Thanks too Ghostlymoron. Your comments are making sense. I have two cylinders.

I'd have said it would be the next thing to impossible to hand start an MD11 in a Centaur..... The person I sailed with for many years lost ( or threw away) the starting handle for the MD11c in his Berwick

If the engine starts with the levers up they are incorrectly adjusted. See the workshop manual ( Bluemoment.com/downloads) and adjust them correctly. ( p30)

Be sure you know how the cold start button on the injector pump works. (when they get worn they dont latch properly)

Owners manual available from VP's website http://www.volvopenta.com/volvopent...lication_search/pages/publication_search.aspx

 

[FairweatherDave]

Thanks Pete. I agree! Except I did see the levers up while the engine was running. It is perhaps possible that they were not quite vertical and so the valves were partially (or even fully) closed. There is quite a range of movement yet but perhaps only 10% of the movement is where the valves are actually open (if that makes sense)

 

[FairweatherDave]

Thanks again Vic....
I thought I'd try handcranking while I was in a safe position to experiment (high and dry) (except for my hose pipe into a bucket ). Would be useful if I could.

Re-reading Ghostlymoron's bit about low batteries and decompression levers seems a good tip.

 

[Searush]

There is a cold start button at the back of the engine, set the throttle to fast idle (you will feel the "notch") then push the button down & it will stay down. Lift the decomps & turn the engine over a few times to get fuel thro the system Then really get it turning fast & drop one lever. With luck it will fire on one cylinder, then drop the other & it will run fine. It is almost impossible to do this on your own unless you can arrange a string around the starter handle to wind itself up & operate a decomp lever.

If you fail to start it after 2 goes, give up, you will be utterly knackered. Try again after a cup of tea. I used to start mine when the battery was flat as above, Hand cranking to prime the cylinders, spinning it with the starter & dropping one lever. It puts far less strain on the starter & batteries. & I could reach a lever from the cockpit while turning he key.

I have to say that since replacing the engine I have never felt the slightest need for a hand crank capability! The new engine always starts immediately, it never even seems to turn over at all, it just starts. It was worth the King's Ransom just for that!

 

[drawp]

I regularly hand start my old MD11C engine - batteries are pretty ancient and do not have much capacity anyway. As prv said, it is much easier with two people - one to wind the engine up as fast as possible and the other to throw the levers over. The trick with the string to the levers does work but requires a bit of timing and finesse. Practice after you have warmed the engine up before hand. On a cold day, it can be a real ball-breaker.

Another thing to remember with the engine; set the throttle first and then pull the cold start lever. Have fun!

 

[FairweatherDave]

Thanks Searush and drawp. That's perfect. I'm getting the full picture now.
I am giving myself this season to see how the engine performs before considering a replacement. Fingers crossed its a good un but I'm not deluding myself....

 

[VicS]

Another thing to remember with the engine; set the throttle first and then pull the cold start lever.

Explain please

 

[ghostlymoron]

You can get a spring operated starter which you wind up and then let rip!

 

[Salty John]

I think these discussions on hand-cranking of diesels are most useful because they highlight the use of decompression levers rather than the use of a cranking handle.
I've often started my engine when the batteries have been run so low that they won't turn a compressed engine but they'll get the decompressed engine spinning fast enough to fire up as soon as the decompression lever is dropped.

 

[johnalison]

If you have the facility, it is well worth practicing hand starting in case you need it one day. If you are doing it for the first time I would recommend doing it when the engine is warm, when it should start fairly readily.

How easy it is depends on the engine. I remember being in a group when an old Lister was started. Someone wound it up to speed and then the skipper gave the order to drop the levers, which was done in a leisurely fashion with no more cranking needed. I have never had enough flywheel action to do this and have always needed to go on cranking.

I used to hand-start my Dolphin petrol, but that involved running some cord over the motor and round the clutch plate and was an entirely different cup of tea.

 

[Bobobolinsky]

Now is it easier to start with a handle or 300 pumps of a hydrastart?

 

[sailorman]

Now is it easier to start with a handle or 300 pumps of a hydrastart?

 

[tomdmx]

I've an old lister 18hp (water cooled) with two decomp levers and hand cranking ability...tried a few times but no avail...but its good that the option is there

I always start off the battery with decomp levers raised, running to max speed on the flywheel, then lower one then the other decomp lever and she normally starts second go (even after a week or more break)...no dramas...as someone said I always have my throttle on 3/4 full in neutral and choke out to help it start