186d with 3t72ha Runaway

[Jtthebrick]

Hey Guys, Just purchased a 186d with a runaway situation. I was confident that it would have a stuck rack and that would be that. Unfortunately no dice. Linkage is moving and no matter where rack is positioned, I'm getting full throttle. I've rebuilt the pump for the second time (I've been told its been done once already) with no luck. I'm thinking possible stuck injectors or someone replaced the pump elements on the first rebuild with the wrong ones. Any input would be appreciated.

 

[California]

Couldn't be the injectors, rather, they are being over-fueled.

Maybe sent the pump in to ThePumpGuy, a poster here?

 

[Jtthebrick]

Couldn't be the injectors, rather, they are being over-fueled.

Maybe sent the pump in to ThePumpGuy,

Strange, they seem like simple pumps. I cant wrap my head around why it would over fuel.

 

[thepumpguysc]

The engine control rack may have fallen from its perch.??
It happens when the pump is removed and the rack is allowed to “fall”..
Remove the pump and feel the rack back and forth ..
U can pick it back up and feel the stop screws..
Hope that helps..

 

[thepumpguysc]

I say you’ve been into the pump.. if u put the plungers in backwards, it’ll run hi at shut off and low when you want hi..
Is it black smoking A LOT.??
That would be an indication of an open injector..

 

[Jtthebrick]

I say you’ve been into the pump.. if u put the plungers in backwards, it’ll run hi at shut off and low when you want hi..
Is it black smoking A LOT.??
That would be an indication of an open injector..

The plungers could have been swapped. There is a dot on one side which I assumed lined up with the marks on the rack. I may pull it back apart and turn them 180. Yes a bunch of black smoke.

 

[ponytug]

Since the tractor has never worked in your hands, I wouldn't assume that anything is good until proven so.

I recognize that you have been into the fuel pump, and I give you the benefit of the doubt that it is ok, but that is an assumption that I think ought to be questioned at some point.

I would check the injectors; either take them to a diesel shop or build your own tester (there are reasonable instructions out there).

If they pass, I think that you need to check the fuel lines for air leaks as that will definitely cause an overfuel/overspeed situation. These engines seem very sensitive to small air leaks. And I mean tiny air leaks! Look for dirt on threads, a hair on the fuel filter gasket, diesel weeps, cracks on fuel lines and fittings. Use lots of compressed air and brake cleaner, with brushes and rags to get things spotless. Given where things are, I would check for tightness every fitting on the fuel system from the tank onward. If that doesn't fix it, I would disassemble the system, replacing any rubber that doesn't act new, the fuel filter... I would assume that the prior owner left dirt somewhere until proven otherwise.

It may be easier for you to do the fuel system overhaul first, but it is more work.

There are some ideas on this older thread;
Post in thread 'Governor adjustment'
Governor adjustment

All the best,

Peter

 

[Jtthebrick]

Since the tractor has never worked in your hands, I wouldn't assume that anything is good until proven so.

I recognize that you have been into the fuel pump, and I give you the benefit of the doubt that it is ok, but that is an assumption that I think ought to be questioned at some point.

I would check the injectors; either take them to a diesel shop or build your own tester (there are reasonable instructions out there).

If they pass, I think that you need to check the fuel lines for air leaks as that will definitely cause an overfuel/overspeed situation. These engines seem very sensitive to small air leaks. And I mean tiny air leaks! Look for dirt on threads, a hair on the fuel filter gasket, diesel weeps, cracks on fuel lines and fittings. Use lots of compressed air and brake cleaner, with brushes and rags to get things spotless. Given where things are, I would check for tightness every fitting on the fuel system from the tank onward. If that doesn't fix it, I would disassemble the system, replacing any rubber that doesn't act new, the fuel filter... I would assume that the prior owner left dirt somewhere until proven otherwise.

It may be easier for you to do the fuel system overhaul first, but it is more work.

There are some ideas on this older thread;
Post in thread 'Governor adjustment'
Governor adjustment

All the best,

Peter

Thanks for this. There is a link to a portion of the manual which is coming in handy. Any idea on a source for injectors? They seem to be tough to find.

 

[thepumpguysc]

If you’re in the States, I can do them..
Why do u want to get new injectors.?? Is it rolling black smoke.??

 

[Jtthebrick]

It is rolling black smoke however I now see that only cyl 1 and 3 are over fueling. Going to swap plungers between 3 and 2 and see if the over fueling moves. Also looking for a good source for parts in general. I would have thought yanmar parts would be easy to come by.