Idle too high and shuts down when lowered, problems running

[Romario]

I have z750 kubota based engine (it's a marine type AKA Universal 5416 or M20). It's the engine Kubota uses on kubota L185 tractor.

It was recently rebuilt (the head replaced, it had bad compression so extensive work was done to get it up - new piston rings, etc.), injector pump was changed as well.

After rebuilding I installed it and I think it has issues:
1. To start it I need to put throttle pretty high and after it starts the engine runs at high RPM (I don't have a Tachometer but remember it wasn't running as high at idle). If I try to lower the RPM it shuts down.
2. It makes metallic clanking sound when running which I don't think was there before.
3. When I put it in gear it loses a lot of RPM and can shut down if it's not at higher RPM.
4. I think it has less power when running than it had before rebuild.

What could be the problem? I have my suspicions but want to hear your opinion first.

 

[bill in in]

Have you checked the timing?

 

[North Idaho Wolfman]

Valve lash set to tight will cause issues.
Timing gears not set right, or shims not set right for injection pump.
Bad injectors or injection pump can cause issues.

FYI: The Z750 was used in the L175's and the Z751 was used in the L185's .

 

[Romario]

Have you checked the timing?

No, didn't check anything. How do I check timing? I am suspecting the injector pump might be the issue since it was replaced before re-manufacturing the engine and since engine never run after that the guy who replaced it never had a chance to do anything with timing.

 

[Romario]

Valve lash set to tight will cause issues.
Timing gears not set right, or shims not set right for injection pump.
Bad injectors or injection pump can cause issues.

FYI: The Z750 was used in the L175's and the Z751 was used in the L185's .

Injectors and injector pump were replaced, so I don't think they are bad. The timing of injector pump might be though.

So, how do I check the shims for the pump? And how do I check timing gears?

 

[North Idaho Wolfman]

You need the WSM (Work shop Manual) for the engine, or a L175.
I'll send you a link to download the L185 (Z751) manual, I think timing and pump setup are the exact same.

 

[tinkerwitheverything]

First thing I'd do is pull the valve cover off and check to make sure that one valve isn't maybe stuck open or held open. Could be where the metalic noise is coming from. check each rocker arm to make sure it's not loose and like stated check valve adjustment/lash. If a valve is stuck open it's going to run like cr#p.

 

[Romario]

You need the WSM (Work shop Manual) for the engine, or a L175.
I'll send you a link to download the L185 (Z751) manual, I think timing and pump setup are the exact same.

Thanks for the manual! I looked at it, and it says I would need to put shims under the pump to adjust timing. I looked at the parts list from Kubota and I don't see shims that I need, they are not in their illustrated manual.

Can someone point me to the part number I need?

 

[Romario]

Some update on the progress - the hole I need to open to look at the timing mark is in inconvenient place, covered by engine mounts in the boat. I might need to unscrew the mount to get access, didn't have tools to do that.

I can only go there on the weekends, so will update next week.

 

[Romario]

So, I tried to look at the pump over the weekend, here is what I got.

As per manual

To check timing, disconnect fuel pressure line from injection pump front delivery valve holder.
Place throttle control in maximum fuel position and pull decompressor knob out.
Turn crankshaft slowly until wetness appears at discharge fitting of injection pump.
At this point(beginning of injection), "FI" mark on fiywheel should be aligned with timing check window.

After un-screwing the lines on top of injection pump the fuel always comes out, no matter the position of crankshaft, it changes the amount but it always pours, it's nor just wetness. This happens with one injection line, but not with the other.

Does it mean I have problems with the pump?

 

[Daren Todd]

Yes there's an issue with the injection pump. Follow that line back to the injection pump. Directly under that line (what looks like another nut below line) is a port. Loosen that injection line from injection pump. Use a back up wrench right below the injection line.

Where the back up wrench is, check to see if that port is loose. There is a spring and detent ball, or spring loaded direction valve in that port to meter the flow of fuel. Fuel has to reach a certain pressure before it spurts.

If that port is loose, it backs off the spring tension and will cause fuel to free flow.

If it's tight. And still free flowing, then it's time to send it in for a rebuild

 

[Romario]

Yes there's an issue with the injection pump. Follow that line back to the injection pump. Directly under that line (what looks like another nut below line) is a port. Loosen that injection line from injection pump. Use a back up wrench right below the injection line.

Where the back up wrench is, check to see if that port is loose. There is a spring and detent ball, or spring loaded direction valve in that port to meter the flow of fuel. Fuel has to reach a certain pressure before it spurts.

If that port is loose, it backs off the spring tension and will cause fuel to free flow.

If it's tight. And still free flowing, then it's time to send it in for a rebuild

It was never used after the rebuild, so I hope it's just lose. How do I make it not leak? Here is a picture for reference

 

[Daren Todd]

Check number 1 to see if it's tight. I'm not sure if number 4 is reversible or if it only goes in one direction.

I've only taken them apart on a deutz. But are pretty similar in design. I had a tater head reverse the delivery valve on three out of the 4 ports. They were installed upside down and wouldn't seal off.


Sent from my iPhone using Tapatalk

 

[Romario]

Ok, the update is that I fixed it and it was actually the loose #1! Thanks so much Daren Todd with the help, I am a happy camper now, even though the summer is over but the boat runs and that makes me really happy.