Deere/Yanmar Injection Pump Static Timing - 5 Qs

[paroxysm3]

This is for a JD 855 w/Yanmar 3TN75. I had the injection pump rebuilt, but in the battle to remove it (I broke one gear puller) I lost the alignment mark I'd painted on the gears. The Component Technical Manual (CTM3-10AUG93) has a procedure for setting the timing, but I have a few questions to understand if I've done this correctly.


Q1. Is the timing set at the beginning of the injection cycle or the end?


First is confusion over whether the timing mark is set by start of the injection or at the end. The CTM calls for a Timing tool "No 1 fuel injection line cut off at first bend." Later the manual asks to observe when the "tip of the timing tool becomes MOIST [sic] with solid fuel."

I'm not cutting off my fuel line, so I've been doing this by observing the smallest change in the number 1 injector. However, I've also read about doing the timing using the "Spill Cut Off Point" method which waits till the pump cycle is finished. Is this the purpose of the Timing Tool? That is, is the fuel line cut off at first bend approximately one "dose" of fuel?



Q2. Are the injector lines labeled correctly?

"The number one injector is toward the flywheel." I had thought the number one injector was closest to the radiator, but the 855 flywheel is at the "back" of the motor. See photo below.



Q3. Turn flywheel counterclockwise from driver/operator seat point of view?

The manual says to "turn flywheel clockwise(as viewed from the flywheel end). I've been turning the fan clockwise. It's the only way the BTDC marks show up before TDc.

The spec for the 855/3TN75 is 16 deg. BTDC. The manual illustrates the timing marks behind a rubber plug in the flywheel housing. My 855 has no such housing. I found TDC by observing the piston rise and fall. At TDC the TDC mark on the flywheel lined up with the cutout shown in the picture below.


Q5. Should I try to get another degree closer?

The photo also shows the timing at what I make to be 17 deg. BTDC. Whithin the 1 deg spec. However, there is no fine adjustment left to advance the timing. When I look for index marks on the drive gear I find a "b" only 4 teeth away from an "a" on the drive gear. The manual doesn't mention these marks,

 

[dfkrug]

I think you are making this harder than it has to be. To get the FI pump
off, you had to remove the front cover. If you look closely, there are
letters stamped into the gears that drive the FI pump. There will be an
'a', a 'b', and a 'c'. You found a couple of them. The letters must be
aligned on each of the gears. There is only one way that all the letters
will be aligned, a-to-a, b-to-b, and c-to-c. The center gear has all
3 letters, and the FI gear has only one (a 'b' if I recall). Cam gear might
be 'c'. Crank the engine around until you get all the letters aligned.
Put the FI gear on the FI pump so that it aligns b-to-b. You will
have to rotate the pump shaft for that to happen. Put everything back
together.

Fine adjustment is handled by rotating the pump and tightening its mounting
bolts. Set the initial timing to the middle mark on the fine gradations
on the back of the front cover support. If the eng does not run well, you
can advance or ****** the timing slightly until it does.

I have the TM1360, but not the CTM3 manual. I used the I&T manual for
my 955 engine rebuilds.

 

[paroxysm3]

Thanks for the reply. I didn't remove the entire front cover, only the FI gear access plate. Thus I can't see if "c" aligns to "c". Why wouldn't they mention this in the manual?

Won't I still need to know the other answers to my Qs to fine tune it?

 

[dfkrug]

I didn't remove the entire front cover, only the FI gear access plate. Thus I can't see if "c" aligns to "c". Why wouldn't they mention this in the manual?

OK, I see what you did. When removing the FI pump access panel, you
marked the 2 gears before removing the pump. Is that correct? I would
have rotated the engine until the two b's lined up, but that does not help
you now.

The relationship between the FI pump gear and the timing of the injectors
should remain the same, even with a rebuilt pump, so using the proper
gear alignment method I described above would still work with no special
fine timing adjustment. Unfortunately, that requires removal of the front
cover if your gear tooth relationship is lost. The timing procedure in the
manual assumes that you can not get the FI gear back exactly as it was
when removed.

Removing the front cover while the engine is installed is doable, but it may
not free up from the oil pan if that is not removed first. My engines were
all out for rebuilding when I did this.

You could try this to avoid removing the front cover: Rotate the engine to
get the 'b' showing on the middle gear. Install the FI gear and pump so the
b's line up. Do a rough check (cam position and injector activation) to see if
that is the right timing. There are several crank/cam positions where the
b's will align, as I recall.

I am surprised that the JD manual does not cover this essential aspect
of engine rebuilding. I guess that the I&T manual on the engine was not
as bad as I thought. At time I bought it, I had not found a good deal on
the JD TM1360, which I now see does not even cover engine rebuilding!
(I eventually found a PDF of the TM1360 for $30 or so on eBay.)

 

[Spudland_Dave]

I am surprised that the JD manual does not cover this essential aspect
of engine rebuilding. I guess that the I&T manual on the engine was not
as bad as I thought. At time I bought it, I had not found a good deal on
the JD TM1360, which I now see does not even cover engine rebuilding!
(I eventually found a PDF of the TM1360 for $30 or so on eBay.)

Looking at my digital version of CTM03, Deere DOES go over the timing marks...and the procedure to install & time it...I guess because i've never had to do this I'm not seeing the problem with the Deere manual...

 

[dfkrug]

Looking at my digital version of CTM03, Deere DOES go over the timing marks...and the procedure to install & time it...I guess because i've never had to do this I'm not seeing the problem with the Deere manual...

Glad to hear it, Dave. The rest of TM1360 looks pretty good....I was
very disappointed to find it did not include the engine info (CTM03). That's
a shock, and this thread is the first I have heard that.

With respect to the FI gear, my 955's engine was easy to preserve the
timing relationship with disassembly/reassembly, if you lined up all the
letters on the gears. With my 4300 engine, the FI gear is mounted with
oblong slots for the bolts, so you could REALLY mess up the timing if
you did not get the bolts on just so. Fortunately, I saw that before
removal and scribed some lines on one of the slots. It makes no sense why
the designer did that....the x55 engine was much easier/safer.

 

[paroxysm3]

I stand corrected. The timing marks are alluded to in a prior section. They are not mentioned at all in the FI removal section. It's odd because they suggest one chalk mark the gears before ren=moval, when one could simply align them to an exiating mark.

I'll try this once the weather warms up above freezing.

I would still like to know if on the static test the state at 16 deg BTDC is fuel injection initiated or complete?

 

[dfkrug]

I would still like to know if on the static test the state at 16 deg BTDC is fuel injection initiated or complete?

I sure don't know. Maybe someone on TBN has actually done the FI timing
adjustment they talk about in the manual. I would like to know, too.

What happened to the pump to cause it to fail and need rebuilding? Where
did you take it for rebuilding? I have never been inside a Diesel FI pump.

 

[paroxysm3]

I'm not sure it's the root cause, but once removed it was found that all its seals had been eaten by biodiesel. I run B-100 most of the time.

I took it to Fisher Implement in Oregon, but they farm it out to another shop. $895 later it's better than new.

 

[dfkrug]

I'm not sure it's the root cause, but once removed it was found that all its seals had been eaten by biodiesel. I run B-100 most of the time.

That's good to know as one of my 955s was being run on new vegetable oil
for a while....I am not sure what mix w/ Diesel. Possible 100% at times.
I imagine B-100 is more caustic. I will tell the owner (again) not to do it.