Using Valve Lifter To Help Starter...?

[charliehows]

yanmar 2qm20 - on the first and frequently 2nd turns of the key the starter doesnt turn the engine past compression, on the 3rd it runs off and starts easily - but i really dont like subjecting the starter motor to those first couple of jams. There doesnt seem to be any prob with the batts or loose connections, i think its just the whacking great fat cold compression stroke. I'm wondering if opening the valve lifter on the first keyturn would help - or if its likely to do some damage - i had an old AJS 500 with a valve lifter many years ago and thats how the valve lifter was designed to be used on them.

[roverhi]

The compression release shouldn't be needed to turn the engine over with the starter. Question whether the starter is getting full voltage and amperage from the battery. Using the compression releases to start the engine can also be harmful to the engine. If there has been a back syphoning into a cylinder, you can do major damage to the engine. Water doesn't compress all that well. BTDT, shortened a con. rod.

[delmarrey]

Another possibility might be a loose or dirty starter cable. It maybe arcing enough to get a contact on the other try's.

But what Roverhi said would be my first suspisson. It could be water or fuel. Does it smoke when you first start it? And what color is it if so?

[RaymondR]

You might need a new set of brushes in the starter motor?

[charliehows]

wouldnt ya know it - back onboard for a couple of days - the bloody motor has been sitting for over a month - thought i'd try something new, turn key to on position and wait a minute - started first bang, no hesitation. Been doing that for the last couple of days, works every time. This seems to work in cars too - but i figure in a car it gives the electronics a chance to wake up and maybe there are a few condensers somewhere that need a little time to amp up - but on a very simple diesel engine? I dont get it but if it works...However - thanks for reminding me - must pull the starter and check the brushes - its probably 30 years old, might be in need of a set...

[RaymondR]

They are pretty reliable, I only had to change mine in my old Yanmar 3GM30 once in 25 years. Brushes are fresh in my mind because I have just had a problem with my anchor winch which had the same symptoms as you describe and it turned out to be the brushes jamming in the brush holders.

[charliehows]

hmmm...heres the latest discovery - the valve lifter lever locks on when the eng. is off - when i then hit the starter it flicks off but its on for long enough to give the starter a chance to kick past the first compression stroke and get up speed - i wonder if it was designed to do this? Apart from this the only use for it is for bleeding the fuel system - it doesnt work for hand cranking because as soon as the lifter drops off the eng. just stops dead on the next comp. stroke.

[Cheechako]

Not sure , but I think I was told to not use the lever on my yanmar... as damage could result. Is that true? hard to figure why you have a lever if it's not to be used...

[SV Dawn]

Charliehows,
I have a 2QM20 (31 yrs. new) and I routinely pull and hold the compression release when starting.It eases the load on the starter, pre-lubricates for a few rpm and if there happens to be any water in the cylinders will tend to prevent hydraulic locks. Energy is stored in the flywheel so when the compression cable is released it starts immediately. If you pull and release the cable before starting it will latch until the first revolution of the cam activates the valves. I'm not sure of the purpose of this feature but it might be to ease start load as you have experienced. None of this is covered in the manuals so take it with a grain of salt but after 31 yrs. service I feel confident.
Andy

[roverhi]

Be very careful doing that. Once got my Volvo MD2b engine started by lifting the compression releases. Cost me an engine rebuild. The cylinders weren't fully evacuated of the water. When the engine started, it compressed the rods instead of the water in the cylinders. Lowered the compression so much on one cylinder the engine would barely run. Luckily Volvo bottom end was super strong so it only required new rods and and rings for the pistons. With the modular construction of the Volvo, didn't have to pull the engine to do the rebuild.

[SV Dawn]

Roverhi,
Yes I suppose that could happen if the decompression rigging was off allowing the engine to start. On this engine the decompression lever opens the intake valves so I don't think it would start. Also years ago before I started this procedure I had water in the cylinders and I heard the deadly "thunk" and stopped the start. How did I remove the water? With the decompression lever. Luckily no damage. Obviously none of this is foolproof and not all engines have compression relief so the first indication you have of water in the combustion chamber is "thunk". So,I guess I shouldn't recommend this to anyone else it just works for me.
Andy

[gjordan]

Andy, I am not 100% sure on this, but I think you will find that the decompression lever opens the exhaust valve, not the intake. With the 2 cylinder Volvo, the theory is to decompress, and crank like hell for a couple of turns, and then whack the nearest lever over to get that cylinder running and then push the other lever over. If it was the intake valve open, you would be pumping air back into the intake which is just the opposite of the direction air is supposed to flow. I cant see any chance of damage to the engine by starting it using the compression release, since the replacement for the MD2 series was the MD11 which had the decompression releases, but didnt have the hand crank feature. If you had a weak battery or starter, you decompress and get it turning. The Yanmar may be different, but I doubt it. There was another brand of diesel (dont remember the name) that you lifted a lever up onto a worm gear to decompress and after 2 or 3 cranks the lever ran off of the end of the gear giving the engine compression, and hopefully starting. This sounds somewhat similar to your Yanmar. Decompression levers are a good thing to have. ____Just my opinion._____Grant.

[SV Dawn]

gjordan,
I think you are right. It is the exhaust valves which are held open. I was working on memory of water coming out of the intake when I had the hydro lock and the decompression lever was held open and assumed it was the intakes. My bad!

[charliehows]

thanks for that gents, I particularly appreciate your feedback Andy, as you have a long experience with the same engine, but i also appreciate the warnings - s^*t does, inevitably, happen...

[bailsout]

Love this thread. I have a Yanmar 2QM15 and it is hard to start after 24hrs. I bled the fuel system following the manual procedures and it finally started. The next day same problem. Bled the system again and it started. Next day-sick of the procedure- I worked the starter a lot with the decompression lever engaged and trying different throttle positions. The engine would try to start but as soon as I released the starter button it would limp a couple of revolutions and die as if starved of fuel or flooded. It finally started when I held the starter button through its limpings and it finally took off. I feel like I just haven't found the right combination. I want to try my hair dryer on the injectors. Once the engine runs it runs beautifully. No smoke and raw water cooled and never runs hotter than 95F. Rebuilt 4 yrs ago, but less than 30 hrs on it. I like using the decompression lever to help lubricate and move the fuel into the injectors. Any other tips? I'll keep experimenting with combinations. I might even try the whisper of ether. Previous owner said it was always hard to start.