cold start, no decompression yanmar1500

[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..?