Need injection pump timing help with y485 on Jinma 354

[Tim Berframe]

After much procrastination, I finally tackled the repair of the broken timing gear case. Thanks to those who responded with helpful advice. One must tear a lot of things apart to do this repair! I was afraid of getting the timing out of whack so took lots of photos as I tore things apart. I put everything back the way I found it and ( after learning the hard way about air bleeding a new fuel filter install) it runs again. However, after reading some posts here about operating rpm I have serious doubts as to whether the timing is correct.

Some folks say to run this machine above 2000 rpm. The green indicator on the tach is 2200 to 2400. I have never ran it above 1800. Any more and all it seems to do is get louder, vibrate more - no more power or speed. To run at 2300 rpm feels like serious abuse of the engine. This engine is a bear to start in winter even with inline heaters and powerful batteries and fully functional electrical systems. ( I live in Alberta. -20C is a normal winter day where nobody minds working outside. -35C is common and one sometimes must plow snow to get to work at these temps)

Before dismantling things, I pulled the glow plug from #1 cylinder so I could find TDC. I couldn't get it to stop exactly when rotating by hand, it rolls slightly past. The timing marks are not quite fully lined up at TDC but do line up a degree or two after TDC. The photo shows this position.

The manual for the 485 says advance angle of supply fuel/speed(before TDC) is as follows:
10+- 1/3000 with advance device
18 +-1 2800rpm
16 +- 1 2600 rpm
15 +- 1 2400 rpm

The photo shows the engine sitting at about 8 degrees after TDC when the timing marks are aligned. The scale only goes to 10 before TDC.
The three bolts holding the injector pump timing gear were barely more than finger tight. It appears that the slots are chewed up. I think maybe it has slipped and is now incorrectly positioned (but it is possible that it was just roughly machined).

Question: How do I determine the advance angle of supply? The timing marks confuse me because I would assume they would exactly meet when engine #1 is TDC.

How do I determine if my engine has 'advance device' ?

How do I determine the exact moment the injector pump 'fires' #1 ?

Thanks for any help,View attachment timing_before.bmp

Tim

 

[pmsmechanic]

One method for finding TDC that I have succesfully used is to prop open a number one cylinder intake or exhaust valve with a suitable socket, set under the rocker arm. Carefully turn the engine over until the piston touches the valve. Mark that spot on the front pulley or flywheel. Then turn the engine over carefully in the opposite direction until the piston again touches the valve. Again mark that spot on the front pulley or flywheel. Exactly half way between those two marks is TDC.

To figure the mark for the advance you want, take a tape measure and measure around the pulley or flywheel. Divide that measurement by 360 (360 degrees in a circle). Mark TDC between the two marks you made. Multiply the advance you want by the figure you came up with in the first calculation and mark the pulley or flywheel before TDC and that is the mark you set your timing at.

I'll give you an example. Say the measurement around the pulley is 15 inches. 15/360 = .0416666667. So if you want your timing mark to be at 12 degrees than multiply .0416666667 x 12 which gives you a measurement of .5000000004 which is close enough to half an inch. So you make your timing mark half an inch before the previously marked TDC to give you 12 degrees BTDC.

 

[quicksandfarmer]

Other members have successfully used spill timing. I don't have the link offhand but Google "spill timing" for info on it. You need to know the 0 rpm advance.

I have the same tractor and engine. I used to run it at 1800 rpm but I've evolved to running it at 2200. It's louder but definitely more powerful.

I think your timing gear is fine but if you have doubts it's a $65 part.

@pmsmechanic -- a math tip from someone old enough to remember before calculators: if you have to multiply and divide a bunch of numbers you reduce the rounding error if you do all of your multiplication and then the division. So instead of doing 15/360 *12, if you do (15*12)/360 you get (180)/360 or 1/2 and eliminate that pesky four billionths.