Hey team, I replaced the remaining 3 injectors yesterday. So, all 6 have been replaced at this point. The engine still sounds really good and starts with no issues, but has high fuel pressure that is completely pegged on the gauge even at idle. It also has some white smoke and occasionally makes a popping sound. Any pointers on where I can investigate next? I'm really hoping this is just a fuel issue that can be chased down and not a compression issue with the cylinders.

Is the gauge reliable?
That engine still had the gear type transfer pump. Check and see that the pressure relief valve plunger is not stuck in its bore and the spring is intact.

Old wrote:

Is the gauge reliable?
That engine still had the gear type transfer pump. Check and see that the pressure relief valve plunger is not stuck in its bore and the spring is intact.

Thanks OM, the gauge is new aftermarket so I'm honestly not sure about its reliability. I will swap it out with another one and see if the reading changes. I will also check the pressure relief valve plunger. Do I need to remove and disassemble the transfer pump to do this?

No need to disassemble the pump. The relief valve is accessible behind a plug on the pump body.

If you are going to remove the fuel gauge install a regular 60 PSI gauge and read the actual pressure25 to 32 PSI.
Get a pint of Stanadyne injector cleaner and dump enough fuel out of the filter you can dump the pint of cleaner in the filter .
Run the tractor for an hour or so and maybe the miss will go away.
Bob

Old wrote:

No need to disassemble the pump. The relief valve is accessible behind a plug on the pump body.

Thank you OM, I will check it out asap and report back.

bluox wrote:

If you are going to remove the fuel gauge install a regular 60 PSI gauge and read the actual pressure25 to 32 PSI.
Get a pint of Stanadyne injector cleaner and dump enough fuel out of the filter you can dump the pint of cleaner in the filter .
Run the tractor for an hour or so and maybe the miss will go away.
Bob

I will get a 60 psi gauge and test it. I'll try the injector cleaner as well. I did just replace the injectors and there was no change to the way it runs. Do you think the injector cleaner might free up something downstream from the injectors?

Also, to add a little extra bit of info. I noticed that there is a small gap where one of the turbo inlet tubes makes a connection with the head. I don't think things lined up perfectly with the newer 3306 and the inlet tubes of the old 977H that originally had a D333C. Some air must be getting in here that could possibly affect the turbo operation. The gap is maybe 1/4" at its worst point. Could this be enough to noticeably affect the way the engine runs? I was thinking of just getting some rTV gasket maker or high temp silicone and sealing up the gap.

Fix the leaks, there shouldn't be any, intake air or exhaust.

A picture would sure help as your description needs more information.
If by chance you are looking at the cold end of the turbo those joints are usually sealed with a couple of yellow O-rings that allows for some misalignment.
If you are looking at the hot end those joints are sealed with metal piston type rings.
Bob

Old wrote:

No need to disassemble the pump. The relief valve is accessible behind a plug on the pump body.

 
 

OM, I looked very carefully at my transfer pump today and I don't see a plug for the relief valve. I looked at the manual and I don't think my transfer pump has a relief valve on it. In the manual, I can see where other transfer pumps have it, but mine doesn't look to have it as seen in the diagram below from the manual. With this particular engine arrangement, is there a relief valve somewhere else in the fuel system perhaps? Interestingly, I can see where there is a capped line coming off of the fuel pump assembly near the transfer pump. I am wondering if this could be a return line that went back to the tank? If so, with it capped off, could that explain the high fuel pressure I am seeing?