674 INTERNATIONAL DIESEL FUEL SUPPLY PUMP ?

Here are things I would check:
1) The proper adjustment of the STOP/START/RUN control rod on the injection pump. As you probably know when the STOP/START/RUN lever on the dash is about 1/4 of the way up to the RUN position that this is the START position and it gives the injectors extra fuel just like a choke on a gas engine and in this position the tractor will smoke really bad. Next when the lever is in the RUN position the control arm on the side of the injection pump should be against the HP adjustment screw. Now check if this adjustment screw still has the wire seal on it. If the seal is gone chances are someone in the past has broken the seal and adjusted the HP adjustment screw out to increase the HP. We would do this on our 684 when we were using it to chop corn because the D239 would produce over 70HP with the screw turned out a couple turns. When the HP is adjusted upward the engine will smoke bad when it is idling. One way to correct this is to push the RUN lever down about 1/2 inch from top and this reduces the amount of fuel going to the engine and less smoke. We would do this when we used the 684 on the wood splitter or using it for light work. 2)Injection pump timing: a quick test of timing is after the engine is up to running temp. shut it off and then start it again if the engine starts right up with less than a rev of the crank then the timing is good, if it requires 3 or more revs then it is probably timed to slow and will smoke and slobber bad. If the engine kicks back on the starter it is timed to fast.
3)I am suspicious of that electric fuel pump putting to much pressure on the injection pump and causing over fueling and hence smoking.
Normally these tractors were gravity fed but they had a habit of getting junk in the fuel tank and restricting the fuel flow to the fuel filters. If you take the fuel line off at the inlet to the first fuel filter the fuel should flow the full of the pipe. If it doesn't there is a problem usually requires taking the outlet fitting out of the fuel tank on both sides. Don't let fuel tank lever get below a 1/4 tank or you could have fuel feed problems going up steep hills.
4)Make sure injector return line to the fuel tank is not clogged.

Another hint, add Diesel fuel conditioner or a tablespoon of engine oil every time you refuel the tractor. This is required to lube the front lip seal on the drive shaft of the injection pump. 40 years ago when the Bosch injection pump was designed Diesel fuel had a higher sulphur content thus providing good lubrication to the injection pump.

Hope this helps
JB2

I have some other ideas will post later tonight.

JB2

Re injectors, according to I&T Shop manual:
Nozzle showing visible wetting on the tip after 10 seconds at 2700 psi is permissible. Maximum leakage through return is 10 drops in one minute at 2700 psi. The manual does describe how to clean the nozzle tip and spray holes. It warns that valve and nozzle tips are mated parts and not to be interchanged.

Did you check the HP adjusting screw on the side of the injection pump for a broken or missing wire seal indicating someone has turned the pump up?

Hope this helps
JB2

Scotty