Case 730 (731?) diesel no fuel pressure

swanders · Sep 18, 2020

Case 730 SN 8192332 runs good just very low fuel pressure. I changed all three fuel filters..tested gauge..no luck...took it in to a mechanics shop who has
worked on tractors for 40+ years..he replaced the "primary fuel pump" as that what he was told it was from some oldtimers...no luck
Still pressure is low...Any ideas...he and I are both stumped...
need to get this back and ready for winter ....any ideas would be great...had great help from here with setting the brakes and getting the fuel filters primed..

Straw Boss · Sep 18, 2020

I'm no mechanic but I wonder if you have a blockage in your tank before it gets to the filters?
Not sure of your 730 but some Case diesels have a water/sediment trap under the tank itself.
Have you tried draining it, or cleaning it, or checking flow from the tank somehow?

mEl · Sep 18, 2020

w
Would you please post a picture of the rear dual filter body?
Most but not all had a relief valve in them and maybe that could be checked.

Al Baker(pumpman) · Sep 18, 2020

Fuel pressure in a Bosch inline pumps build head pressure by restricting the return fuel flow. I have seen MAY that have come to my shop with nothing wrong with the pump, but something wrong with the return fitting on the pump head. Doesnt the 730/830 return fuel to the secondary filter? I would be checking the return system. Al

mEl · Sep 18, 2020

Yes Al, the first filter is gravity fed and bleeds easily, the other two are force fed by the transfer pump and most but not all have a relief in the filter body that is a 7/8 thin nut that holds a relief valve spring and plunger, in addition to that the return fitting in the pump fuel rail return port has a very small orifice to allow air to escape easily but act to create back pressure to keep the transfer pump pressure up. I have an early 830 which has a actual relief valve screwed into the top of the filter body which was replaced by the internal relief previously mentioned, that internal relief spring can be tweaked by stretching it a little and I do not think the system would over pressure under any circumstance. On stubborn bleeders I have already removed the relief spring and plunger as it is the separation between the gravity and pressure fed side and the system bleeds by gravity much easier.

mEl · Sep 18, 2020

To answer your question which I did not cover, the restrictor fitting outlet goes up to Injector return then to tank. The other flows are primary first stage gravity to the transfer pump - transfer pump output to 2nd stage in the main body and the fuel then goes to the top mounted 3 rd stage then to Injection pump, only the second and third are pressurized by the transfer pump. The second and third stage do not bleed easily as fuel has to flow through the transfer pump valves. removing the relief plunger effectively takes the transfer pump out of the bleed circuit if you can visualize what I am saying, the second bleeds very quickly with the plunger removed and the third also if there is sufficient fuel in the tank so gravity can supply the fuel pressure needed.

swanders · Sep 23, 2020

thanks very much for the help!!!...I will get this information to the repairman..he is sort of pre-internet.
I do not recall any line returning into the tank...just the outlet on the bottom of the tank
Does this return go into a different line coming into one of the filters?
I dont have the tractor at home to look at or get pictures easily.

mEl · Sep 23, 2020

(quoted from post at 16:09:47 09/23/20) thanks very much for the help!!!...I will get this information to the repairman..he is sort of pre-internet.
I do not recall any line returning into the tank...just the outlet on the bottom of the tank
Does this return go into a different line coming into one of the filters?
I dont have the tractor at home to look at or get pictures easily.

On top of the injection pump up front on top opposite end from where the main fuel feed to the pump goes in there should be a fitting with a return pipe that goes up to the injectors so fuel can flow back to tank unless someone has cobbed it up, the fitting on the front toward the radiator is the one that should have a very small orifice to allow air to bleed but supply a restriction to fuel flow back the return so transfer pump pressure can build. if someone replaced that fitting with an open flow fuel pressure can never build, something to check. follow the return line off the rear injector, it probably goes up to a tank return port on the front of the tank.

swanders · Sep 29, 2020

pictures of the rear fuel filters...you can see the return line..and that all the connections have been connected and reconnected a lot lately to determine where
the issue is.
Any further advice is welcome

mEl · Sep 29, 2020

The tee fitting on top of the filter body is the fuel pressure regulator and has a plunger and spring to serve as a relief valve, I would remove the top nut, check the spring and plunger to make sure it is free in the body so fuel pressure can push it up, if it is free the spring may have weakened over the years, you could try shimming it up with a small flat washer or two ,when running the 1st filter is gravity flow and the 2nd and final should be pressurized and you can tell that by removing the second bleed screw, there should be transfer pump pressure, a definite squirt instead of just flow. That is the same system I have on my 61 830, Is your pressure gauge functioning, does it show any pressure or just low?

swanders · Sep 29, 2020

Pressure is low when running. Goes up slightly with more RPMs tested gauge and it works. Will tell the mech about the relief valve
Thanks for all your help. Very frustrating

Joe (Wa) · Sep 30, 2020

mEl is this the correct tractor and fuel system relief valve? If so I can probably come up with other views and p/n's that you may want.

Joe

mEl · Oct 1, 2020

Yes Joe, the fuel pressure regulator is the cross shaped thing above the filter housing, there are two parts shown as internal parts and is the valve clearly shown in the photos.

swanders · Oct 1, 2020

thanks for the drawing...hope that helps us out in identifying where to look next...
you can email any drawings/pdfs such as that to me and then I can print em and get them to him.
Again..thanks everyone for the help!

Joe (Wa) · Oct 1, 2020

Better yet this link has the 730 Case parts catalog. Your sn 8192332 is 1962 model year, keep your sn in mind as you scroll through the parts diagram titles as some diagrams & part nrs have sn break.

Joe
https://avspare.com/catalog/case/57676/

swanders · Oct 30, 2020

Got it back from the mechanic...all the tips listed here he had tried..he pulled off the whole filter body, cleaned it and replaced the gasket on it and we have fuel pressure...must have been something sucking air in that body/gasket...who knows...its working now...runs good...
Thanks SO MUCH to all for your expertise...
Now to find a new loader for it..the DUALL on it is in poor shape and not worth repair...but I hear its hard to find loaders for this tractor? Will be a new post for this
thanks again....

John Deere D · Oct 30, 2020

Quote:
Now to find a new loader for it..the DUALL on it is in poor shape and not worth repair...but I hear its hard to find loaders for this tractor? Will be a new post for this

I recently removed a loader from a John Deere 3010? 3020?

Not without time fitting /fabrication..........however a great final outcome.

Bob..

Case 730 (731?) diesel no fuel pressure

swanders

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Straw Boss

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mEl

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