high fuel pump pressure

[Hilltopper]

My 720d is giving me a fit blowing fuel past the seals.It had run o.k. for 10 years. I checked the pressure and it pegged a 50# guage. I installed a new pressure spring part r227r from Deere and it is now down to 36# with no shims. This is far above the 16# to 26# listed in the manual.
I let it set over night and found fuel on the floor that had run out the drain hole. What could cause all this pressure?

 

[DONMYEIL]

If the new high pressure system installed the pressure is 65psi at wot. Sounds like the pumps need sent to a diesel shop that works with them. The injectors should always go along and be matched to the pumps as different crack pressure can change fuel delievery . Check parts book for late 730 D parts.

 

[F-I-T]

There is an article in Field Service Bulletin #269 that talks about using the correct relief valve washers/shims in the different pumps, and that if you use the incorrect ones, it can in effect "over" shim the spring. Maybe that's what is going on?

Another FSB (# 305) tells that the R227R spring was used in the lower pressure pumps (increased in FSB 269 to 18-26 psi), while the R21723R spring is used in the 62 psi pumps. Says the 62 psi target was only when the improved auto bleed system was installed, up around the 730 S/N 7328622 and up.

That said, the outer seal must be failing, allowing fuel past the seal, across the shaft, to dribble out the pee hole. Good thing that hole is clear. At least it's not getting into the crankcase oil. Probably time for new seals, and figure out if the relief spring is seated properly, and not jacked up too tight by poorly fitting shims.

Those are my guesses.

 

[Hilltopper]

FIT
I did not use any shims under the new spring and it still got 38# pressure at high idle. This is the pump that uses the cupped shims.
I repulled the pump and through trial and error ended up cutting 5/16 off the spring this put the spring resistence pressure in the correct range of 5.5 to 7.5 oz when the bypass piston clears the relief hole. I reinstalled the pump and now the pressure is within specs at 19#. I will need to replace the newer seals as they must have been damaged by the high pressure.
This thing has been rough on 79 year old man, but keeps my mind working. thanks