Oil & Fuel Fuel Pump Timing Help??

[YanmarFever]

Bruce thats good advice and very true, I had an engine do that once also.

Mark the pump offer is still open to you if you decide to go that route, (better than a tear down)
Ernie

 

[gatractorman]

Hello Mark, I've been watching the progress on the engine for a while now but have not posted since I'm not a Yanmar expert as these other fine folks are, however I have been a mechanic for quite a few years.
I'd like to offer my suggestion if you would have it, its going to make a mess but take the RETURN fuel line off the injection pump start the tractor and see how it runs also ensure you have return fuel coming out of the pump. I've seen equipment act this way when the return fuel line is somehow stopped up it creates head pressure in the inj. pump and some machines wont run that way, dont know if Yanmar is one of them but it may be worth a try before you tear it down.
I cant see an internal engine problem and it run ok part of the time.

 

[mark777]

Thanks, good suggestion.

On the Yanmar's the fuel feed is near the bottom of the fuel injection pump, then fed through the top (3) injector lines - direct injection to each injector. The excess fuel from each injector is piped through the top and into the thermalstart bottle (on many) and the overflow directly back to the tank. I have pulled the tank cap and screen and watched the return fuel drip quickly into the tank during all RPM ranges....

I pulled the head (minutes ago) and checked the piston deck height and they are flush. I've rocked each piston to check for end play (slap) and they are snug with minimal movement. #2 cylinder has a beige flashing along with #2 exhaust valve, so valve face and seat are suspect. I will fluid test the valves tomorrow and tear down the head. I hope I have found the problem.

Mark

 

[greatrandini]

I hope u got her wipped now!

 

[mark777]

Purdy sure I do!

It is #2 intake valve face and seat...seat has an area where the valve is obviously not mating perfectly. I did a fluid test this morning and it seeps from 30-45 seconds. I never would have guessed that such a slight problem could create such drastically poor performance.

I have done hundreds of cylinder heads in a machine shop(part time while going to school) and thought I knew most everything about valve problem diagnosing....feeling a little dumb right now.

Mark

 

[LMTC]

</font><font color="blue" class="small">( feeling a little dumb right now.)</font> On the contrary, Mark. You are now at least ONE learning situation SMARTER than you were yesterday. /forums/images/graemlins/grin.gif

 

[kenmac]

Did the hyd. pump seal blowing cause this problem ? /forums/images/graemlins/confused.gif

 

[mark777]

Thanks Wayne.

kenmac, At this point I have to assume it was coincidence. There just is no other explanation I can think of.

The problem with the power just happened immediately after the hydraulic pump repair, and that was why I believed them to be related. I think I would have started weeks ago just pulling the head had it not been a question of two problems happening about the same time.

Mark

 

[greatrandini]

let's hope that was the cause! You found the problem fast in my opinion!

 

[mark777]

Well after valve stem seals, valve and seat grind, head gasket etc. It did nothing to change the running of my tractor. I have the injection pump removed and found a badly broken and distorted timing shim. I mean it is so bad that it measure .014 on one end and .020. on the other. I have made two .011 aluminum shims and installed and reassembled the engine....runs poorly. Removed one of the .011 shims and it runs better...but not good.

It's my understanding, and from what I've read that the shims advance and ****** the crankshaft timing. And this model, 3T75U engine fires correctly around 21° BTDC. So it's become a process of adding or removing shims to attain the best engine performance....or, a real guessing game without the bench equipment.

Anyone ever go this far into injector pump timing??

Thanks,

Mark