cold start, no decompression yanmar1500

[ziggywiggy]

What happens if you cold start without using the decompression? I did this accidentally and the motor seemed to start right up and then there was a lot of white smoke from the crank case exhaust. I'm trying to figure out if it was just because I started it wrong or something else is amiss. It also shut off when I moved to the area I was going to cut.

Thank you

 

[ziggywiggy]

As an afterthought, I realized "cold start" might not be the right term, as it's definitely not cold outside, but I've never started the tractor without using the decompressor.

 

[4get gto]

I'm just the opposite. I never use the decompression until colder weather or it seems as though my battery is low. Guess it doesn't matter either way..

 

[winston1]

The compression release does several things. It eases the pain on the starter by and easier and faster spin. It also allows oil pressure to come up without as much pressure on crankshaft journals. The fast spin also helps with the starting.

Having said all that, starting without it should not damage anything. My old 2002D always fired on the first couple of revolutions but I use compression release just to gain oil pressure before bust off.

 

[thepumpguysc]

The faster spinning, heats the cylinders so the atomized diesel fuel will ignite faster.{starting}
I've seen the other end of that spectrum also.. engine would NOT start unless it was spun up w/ the decomp. pulled..
The engine would "lug" under the pressure of the fuel being sprayed into the engine & wouldn't have the rpm's{speed} to start.
I like the idea of getting the lube oil moving before it starts also..

 

[RalphVa]

Never had a diesel engine with decompressor. In my experience, diesels tend to start with about a 1/2 turn of the crankshaft. If they have to "spin", something isn't right.

Almost the same way with fuel injected gasoline engines now.

Ralph

 

[careyo63]

Always use mine every start. 1, easier on the starter which is one of the biggest repair I had to get done since I've owned it. Besides regular maintenance since 2/08. 2, Is let the oil Pressure come up before letting go of the Decompression. This 2000 is Original as far as me or the seller could tell. He's Fredrick supplied so I pretty much knew it just looking at it. Honestly just kicking tires so to speak but I left him a check until I could get back with a trailer in a few days. Not far from putting a thousand Hrs. on it. The Original rear tires started to dry rot and crack at the Lugs. The Lugs are HUGE still to the day. So I opted to reline them which was the only other major repair to keep it functioning. I still chuckle to the day when I asked the seller were the He!! did he get it. He mumbled something besides trade in. He didn't want to disclose it..............LOL.

 

[CoyPatton]

It is my opinion that you are doing a ‘cold’ start anytime the motor is not at operating temps when you start the tractor. Others may not agree but that is my $0.02 worth.
I try to use the decompression feature every time I do a start. Mainly because I like the ideal of lubing the engine and reducing the strain on the starter. I find that by doing so the motor fires with a couple of seconds. In cold weather starts I use the thermo start function in addition to the decompress feature.
Beyond these habits that I do, I doubt you are harming anything more than the strain on the starter.
Hope this helps.

 

[ziggywiggy]

Ok, so it sounds like I didn't mess anything up. I'm going to try and start it properly this afternoon and see if I have the same white smoke/sputtering out issue. If it still happens I'll look for another problem, it's just frustrating because it ran beautifully last week when I replaced the fuel return hoses. No overheating or anything and now this, but I guess that's just how it goes :confused3:

 

[CoyPatton]

White smoke generally means moisture. This could be from lots of sources. Your profile does not mention where you live, so unsure but it could be your moisture issue is from overnight temp drops and then warmer temps during the day. I would not be concerned if the white smoke goes away as the tractor warms up.
Now if it is a gray color, it could be an unburnt fuel issue. If it starts harder than it did before or runs rougher than before, you may have issues of it sucking air through the lines you replaced recently.

 

[California]

Never had a diesel engine with decompressor. In my experience, diesels tend to start with about a 1/2 turn of the crankshaft. If they have to "spin", something isn't right.

These old Yanmars are a little different. In contrast to modern design, a relatively weak starter plus heavy flywheel. I think the engineers had in mind the old 500cc single motorcycles where you had to get the crank to a certain position before leaping down on the kickstarter, if you ignored that step then your kick wouldn't get it through TDC.

His 1500 has only two cylinders so similar reasoning. It is customary with these to use the starter to get the heavy flywheel spinning, then drop the compression and have flywheel inertia to help the starter push past the first TDC. These generally will start on the second TDC (first time fuel injected into a compressed cylinder) but it feels strained to not use the decompression to have that flywheel assist.

All this aside from the benefit of pre-lubing with no compression. He's doing it right, as far as Yanmar intended.

 

[ziggywiggy]

Ok say I started it this morning, and it ran fine until I ran the pto, then it started to stall, I increased the throttle a bit and it hung on for a couple seconds but ended up sputtering out anyway. I restarted it and let it run on idle, and it sputtered out after less than a minute, and bunch of white smoke came out of the crankcase exhaust. I replaced the fuel return lines after they fell apart a couple weeks ago, and it ran for 6 hours of bushogging perfectly. I'm going to go bleed the lines today just in case and maybe check the radiator to see if it bubbles because I read a blown head gasket could cause the white smoke, other than that I'm not sure what else to check.

 

[California]

If you suspect the head gasket, be sure to spin first decompressed, to clear out any water in cylinders. Water cannot be compressed, stuff can break.

 

[CoyPatton]

Ok say I started it this morning, and it ran fine until I ran the pto, then it started to stall, I increased the throttle a bit and it hung on for a couple seconds but ended up sputtering out anyway. I restarted it and let it run on idle, and it sputtered out after less than a minute, and bunch of white smoke came out of the crankcase exhaust. I replaced the fuel return lines after they fell apart a couple weeks ago, and it ran for 6 hours of bushogging perfectly. I'm going to go bleed the lines today just in case and maybe check the radiator to see if it bubbles because I read a blown head gasket could cause the white smoke, other than that I'm not sure what else to check.

You might want to retorque your head bolts just to reduce the potential loss if coolant. I think you will need to replace the head gasket if that is what you confirm is wrong.

 

[careyo63]

I would go by a Auto-parts store and rent a Pressure tester. Esp. before I would torque on the H-bolts. Break a bolt and then you will have Big Problems.. Just sayin.https://www.tooltopia.com/_img/STN/STN12270.jpg

 

[CoyPatton]

Using a antifreeze/coolant tester is not the best way to check a blown head gasket. A diesel compression tester would be better. But best would be a leak down. The issue will be getting the adapters and getting the injectors out.
Also check your oil for the milkiness.

 

[careyo63]

Using a antifreeze/coolant tester is not the best way to check a blown head gasket. :laughing: You need to recheck what you think or how you think it works......

 

[CoyPatton]

Using a antifreeze/coolant tester is not the best way to check a blown head gasket. :laughing: You need to recheck what you think or how you think it works......

To each his own, but I really suggest you do your research! A weak hose and you made a mess and still do not know about the head gasket.
A pressure leak down test, allows me to chase down exactly where that pressure goes!

 

[careyo63]

To each his own, but I really suggest you do your research! A weak hose and you made a mess and still do not know about the head gasket.
A pressure leak down test, allows me to chase down exactly where that pressure goes!

Just how does a pressure leak down show the back pressure in a radiator and It's getting pressured up by a bad head gasket or warped head. How do you test the Anti freeze with it?

 

[4get gto]

Just how does a pressure leak down show the back pressure in a radiator and It's getting pressured up by a bad head gasket or warped head.

I believe either one the two methods you guys mentioned would work. Maybe end up using both to find the problem.

("How do you test the Anti freeze with it?" )
That is used to check pressure in the system. Not the antifreeze. Thinking you knew that..?