Oil & Fuel Fuel Pump Timing Help??

Mickey_Fx · Apr 21, 2006

Gotta give you credit for the effort you're going to Mark. This is out of my area of knowledge but I have a hard time beliving the small changes you've made to shim thickness has such a big impact on running characteristics.

If I understand where the shims are located, I suspect there is a helical gear set at the pump input and the shims are used to fine tune the built-in timing advance due to part/part tolerances. With helical gearset moving in/out will change the timing. I suspect you are correct that if you replace the pump, the shims/timing will have to be fine tuned to ths specific setup.

I suspect there is more to the problem than the shims and every time you remove the pump to change the shim, something else is affected.

Keep us informed and hope it doesn't take too mch more effort to find the cause of the problem.

mark777 · Apr 21, 2006

</font><font color="blue" class="small">( I suspect there is more to the problem than the shims and every time you remove the pump to change the shim, something else is affected.)</font>

Mickey, I suspect you're right. In a few short weeks I've repaired the hydraulic pump which DID have a problem....and repaired everything else that probably didn't, including a valve job.

I do have to make it run right, or well enough to find any other problems. I will include pictures of the pump rollers, pump and timing cover machined platform. And if you can make it out the cam lobes that the pump rollers contact.

The shims radically change the timing and I am surprised by how much. Just like static timing and old style distributor by advancing or retarding the complete unit.

mark777 · Apr 21, 2006

...and one of the pump and shims.

FL_Jerry · Apr 21, 2006

Man, I hope my pump never goes out.............Well if it does, I know who to take it to..lol

Jerry

Mickey_Fx · Apr 22, 2006

As I said before this is out of my area and from your pics, the shim is in a totally different area than I was thinking. Correct me if I'm wrong but looks like the shim is controlling the distance of the pumps to the cam.

Seeing where the shims are located, they do more than fine tune the timing, they affect the duration of the injection cycle.

Is there any way to change the timing without affecting the duration of the injection cycle? Without out going back and reading all your posts, I'm sure you've checked to insure the cam gear is indexed and meshing with the drive gear correctly.

Is there any centrifical advance on this pump or is it just static timing. If ther is an advance mechanism I'd take a close look at that for possible problems.

Hope some of the suggestions and your effort is helping with making progress.

mark777 · Apr 22, 2006

Mickey...yes the shims control the distance, contact pressure and cracking pressure timing between the pump rollers and cam lobes.

There are two distinct timing marks, one on the crankshaft gear and one on the cam gear...although the crank gear and cam gear drive the oil pump and hydraulic pump there are no marks or critical timing for the oil and hydraulic pumps.

No mechanical or centrifugal advance...the hand throttle is converted internally at the pump, to meter fuel volume using a rack and helical gears. The injection pump, when installed, appears to be working normally. The fuel delivery is free flowing and even at all the injectors. IMO as everything seems to be working mechanically, it is a question of the fuel entering the combustion chamber either too early or too late.

Just so you and everyone who has offered advice knows...I appreciate all the input. The tractor is just sitting in the middle of the shop and I walk up to it several times a day....and stare at it for long periods of time, and then walk away. I am grateful that it's my rig and not a customers.

mark777 · Apr 22, 2006

Jerry,

I think you can rest easy as I have heard repeatedly that Yanmar injection pumps just don't suddenly fail. They do however, wear out from fuel contaminents that create wear and sloppy tolerances on the plungers internally.

And WHEN I find out what I did...or what is wrong, I will shout it from the roof tops /forums/images/graemlins/grin.gif

Mark

Jagmandave · Apr 23, 2006

Man that must be frustrating, to work on one thing then have something seemingly totally unrelated act up!

I hope you find it, and I think it will ultimately go one of two ways. You'll either find it was something you did, or forgot to do associated with the hyd pump repair. Or it will be some complete fluke of a thing that just happened.
Here's the good news, you now know that your head, valves and injectors are in perfect shape!

normde2001 · Apr 24, 2006

I'm having a hard time believing this is a pump timing problem. How did it get off in the first place? Someone mentioned that a .004 shim = 1 degree of timing, as I recall you wouldn't even notice a couple of degrees advance or ****** in an old distributor/point ignition setup. I believe I would put the original shim(s) back in and look elsewhere, maybe get one of those $30 Harbor Freight compression testers and see if 1 of the adapters works, or rig something with an injector, and check the compression.

mark777 · Apr 24, 2006

Norm,

1) Hydraulic pump seal leaked, slightly diluting the crankcase oil and creating white smoke and excessive un-burnt fuel.
2) Hydraulic pump seal ruptured enough to dump excessive UTF into crankcase....1 1/2" above the dip stick level mark. Remove, replace seal and reinstall pump.
3) Change all fluids, filters and fuel, start and operate tractor. Severe loss of power, erratic RPM including engine stall. NO blow-by. Removed timing cover and inspect crank to cam timing marks at TDC...OK. Verified hydraulic pump gear has no relation to cam, crankshaft or hydraulic pump timing.
4) Remove, inspect and reset governor at 240° from point of contact (book specifications), reassemble and start engine. NO change in performance.
5) Remove, fuel, fuel valve assembly, clean and inspect fuel tank, flush with denatured alcohol, fuel pipes cleaned and blown out with compressed air, fuel valve assembly disassembled and replaced "0" ring, bleed screws, fuel filter and ALL urethane fuel lines. Pull and inspect all 3 injectors, replace, add fresh fuel, bleed fuel system and restart tractor...NO change in performance. Changed all 3 injectors from another (good running) 3T75U engine, removed exhaust pipe and muffler. NO change in performance.
6) Remove, inspect and fluid test cylinder head. Leaking intake and exhaust valves on #2 cylinder. Lite valve and seat grind and final hand lap. Valve guide bore is tight and within tolerances. Valve stem seals replaced, head reassembled and fluid tested with zero leaks on all valves. Pistons checked for radial play (slop), cylinder walls inspected for scratches, scarring and gap clearance (.002" feeler gauge will not fit in gap). Reassemble with new head gasket, valves adjusted and tractor started and NO change in performance.

At this point in time, and having done everything I could think of at least twice, I had to consider the injection pump timing. Originally (like you and many) I can not see how one problem is relevant to the other, and not a big believer in coincidence, but an approach of process of elimination. So... I removed the injector pump and discovered a mangled, distorted and broken shim that varied in thickness from .014" to .020" from side to side. Obviously (to me) someone has removed the pump before.

Certainly not an expert on these engines and fuel systems, but I have been inside many and even if there were a connection to low compression without blow-by...well that scenario seems highly unlikely. I just put this post up there so that you, or anyone else may see any flaw in my approach to diagnosing and fixing the problem...because if the shim kit does not fix the problem, then I am stumped.

Thanks, Mark