Fuel Injection Pump Problem

[Tillikum]

First thought that comes to mind is air leaks, as in air getting into the fuel lines or connections: a system is air-tight enough to idle, but the vibration and increased suction of higher RPMs may be enough to start pulling air through the leak point.

I've one or twice resorted to running a "new" hose directly from the tank to as close as possible to the IP inlet pipe as possible in order to diagnose/rule out leaking inlet lines. A piece of clear hose put into the line as close to the IP inlet as possible will show if air bubbles are getting in. Then the fun begins finding out from where!

A clogged or partially clogged intake screen in the tank can sometimes cause odd behaviour, as can a fuel return line outlet too close to the intake pipe.

Dirty tanks and fungal growths would be another possible complication.

[Shaneesprit]

Sounds like you miss diagnosed in the first place - went for the most expensive rather than the basic.
If it starts you have fuel pressure, from the injection pump if it then stops you have no supply gravity feed the fuel pump from a can, ideally with an inline filter.
Yanmar Lift pumps can be an issue - start with the basics

[NNBill]

Don't rule out the possibility of an exhaust system blockage, if you engine has one of the silver 180 degree cast steel mixing elbows they can do all sorts of strange things when they plug up. Also exhaust hose becoming delaminated internally causing blockage also can be a problem.

[aleggert52]

Hello Skipperpete,
Update. injection pump still not working. Filled the crankcase with diesel fuel. Had to drain and put new oil and filter. Ordered a good used injection pump from Hoye Tractor they don't have any new ones in stock. They sell marine engine parts as well good source for parts at reasonable prices. Took me a while to find them. As of now it will take about 5 week or a little longer to receive the injection pump because they do not ship to El Salvador. It will go from Texas to Minnesota where my daughter lives and then she will forward the injection pump to me here in El Salvador. The governor on the 2QM15 is actually pretty simple only one spring in the assembly and it is good. I'll keep you in the loop!

[skipperpete]

Hi aleggert, thanks for keeping us informed on your progress toward a happy little 2QM.

[Compass790]

Hi aleggert,
thanks for update, Interesting that it filled crankcase with diesel.
If I was you I'd strip the lift pump & check the diaphragm as that is, 9 times out of 10, the cause of diesel in the crankcase. Only 4 screws hold it together once you remove it from the block.It tells you in the service manual how to check it.
Basically I hold it up to a light & look for holes if it's not obviously holed/torn.
Hard to believe the diesel techs would send you back the injection pump leaking that badly.
I could have got you a new injection pump out of Japan but a good used one should be fine.
Good luck

[skipperpete]

You’re right about lift pumps and crankcase dilution but maybe the diesel in the lube oil on this occasion has to do with what MBWhite mentioned back in post #20.....plunger head clearance but rather than too much clearance this pump had too little clearance, or no clearance at all resulting in the plunger colliding with the delivery valve holder. If the pump tech set the clearance with his cam on the test machine and the cam lift varied from the Yanmar cam it’s easily possible to inadvertently create a damaging contact, certainly enough to cause a hp fuel leak back into the cambox. No one really at fault, just a difference between cam lobe lift height.... it happens.

[Compass790]

Skipperpete I would have thought if plunger went so high in the barrel that it contacted delivery valve it would lock up the engine???.
But yes I can see if the pump had a lot of timing shims or plunger guide shims installed & they werent replaced the plunger head gap could be affected.
I cant remember but it shows in manual that the delivery valve has a smaller i.d. than the plunger o.d. & the delivery v/v holder holds the delivery valve barrel solid.
Anyway aleggerts could ask them if they changed the plunger guide shims.
Still doesnt get away from aleggerts initial statement saying the the problem occurred suddenly & I cant see how the plunger head gap could change suddenly unless something jammed between cam & roller & I'd imagine that would wreak havoc with the injection pump.
Still struggling with the idea that pump shop could get it wrong 4x but it's possible I suppose.
Many times in this thread checking the lift pump has been mentioned but aleggerts was happy with his fuel flow however if it was me I'd definitely be checking it or bypassing it before I replaced a 1700 hr injection pump that had been checked 4x.
Those Bosch PFR pumps are very reliable if filtered dry fuel is fed to them.
Also I think cam lobe wear is not to be considered as it wouldnt happen suddenly.
Long time to wait for Op's injection pump to arrive & pretty easy to test out lift pump or seperate feed in the meantime.....

[skipperpete]

Compass you’re absolutely right about engine lockup and it’s the reason why an engine with a cassette type injector pump should be rotated by hand for at least 2 full revolutions after reinstalling a newly serviced pump or after removing timing shims to advance injection timing. However , if the interference is only small, the impact on rotation might not be all that easy to feel with the 2:1 cam reduction through an 18” breaker bar but the contact between the plunger and the delivery valve body is still very damaging. It can be as simple as the delivery valve body getting whacked hard enough to loosen it or in the worst instance the plunger head can shatter and the plunger bore gets scored (a lot), in either case fuel will leak from the hp side into the cambox and crankcase.
And yes again, this does not explain the sudden original change in engine behaviour, that’s still a mystery and I sincerely hope the new pump will solve problem.

[Compass790]

The 2QM15 has decompression levers so OP should be able to rotate it & feel any impacts without too much trouble when he is checking the new pump.
I can rotate our ysm8 decompressed by hand from the PTO pulley so if he did that it may not smash anything.
Made me recall the diesel tech that encouraged me to have a go at rebuilding our injection pump told me to do the rotation check as you described.