730D Fuel in base

[ET]

I'm working on a friends 730 that is getting fuel in the crankcase. The leak is easy to locate but hard to fix. The fuel return check valve that goes through the fuel pump cover and screws into the casting that the fuel pumps are bolted leaks where it screws in to the casting. It is a taperd pipe thread that has been over tightened to many times. It screws so far in through the top cover that you can't catch a wrench on the top of the valve. Lots of teflon tape only works for a short while on the streched hole. I'm thinking of drilling and retapping for a pipe bushing but that might be to tall and there is the metal fileing issue to deal with. JB weld might work but where else will it get and what about later dissasembly. I do need to look real close and make sure there is no hairline crack in the casting. I'm wide open for ideas here. As a last resort ,and maybe the only real fix, we can get a new casting but we will get into the expense of redoing the pumps and switching them over.

 

[Mike M]

As long as the casting isn't cracked ? you might get some hardening permetex I think it is #1 ? and use it on the threads or if that don't do it go ahead with that JB Weld because it may not bond that well that you won't be able to crack it loose later as it is kinda brittle.

 

[Bob]

They make "thread repair inserts" for pipe thread, as well as for standard bolt thread.

Obviously, you need to keep things "clean" while making that repair!

 

[hunting4junk]

along with the standard style of thread repair you might look into what is called a tyme-sert. it installed like a heli-coil but is actually a bushing. these work very well as do the helicoil type repairs if done properly. There is some stuff on the market now that works similar to JB weld but you can actually remove the bolt when you finish and it will remain leaving threads for you to screw the bolt back into.

 

[gpuller]

The only real fix is to replace the broken bridge. Remove the lines from the pumps, the 4 bolts that hold the bridge/pumps to the block. The pumps can be transferred to the new bridge, make sure the pumps stay with the same cylinder. The gaskets for the pumps, and bridge to block are still available from Deere. Also remember to change the o-rings on the oil feed to the pumps. Recheck the injection timing and your good to go.

 

[msb]

If you replace the maifold then the pumps need to be recalibrated on a test stand, so they will be in balance with each other,especially if you are a perfectionist. Even when only replacing the pump gaskets will throw off the balance.No way, short of a miracle, to place the pumps exactly on the manifold as before. White Teflon tape will not hold diesel fuel for very long.Use the pink stuff.

 

[ET]

Back in my days at the JD dealer we never removed the pumps from the mounting manifold. That was all done at the pump shop.

 

[ET]

Thanks for all the input. When the owner and I decide what we are going to do I'll let you know. I personally think a good used part is the best way to go in the long run.