350c running rough at lower rpm

[Mechanickyle]

Hi
New to the group. Just purchased a 1985 350c and it runs rough between idle and about 2000 rpm at 2200 smooths out and runs great with plenty of power. No white smoke
Installed new injectors fuel filter and no help
Checked the check valve at the stanadyne pump and the ball and spring are missing.
Any thoughts or has anyone else experienced this problem?
Thanks Kyle

[Jim B]

Welcome to the board.

The ball and spring missing from the check valve is often a sign the pellethane ring inside the injection pump is breaking up, repair means a pump overhaul. When the ring breaks up it shows up as small bits, often referred to as mouse turds. They plug the check valve preventing excess fuel from returning to the fuel tank. Without free return, pressure builds in the pump and leads to stalling. Some people remove the ball and spring to gain run time, rather than have the pump repaired. Another place to check for mouse turds is the behind timing window cover plate on the side of the injection pump. Put a clean rag under the plate and carefully remove the two small screws. See what you find behind the plate. It is also possible the injection pump was repaired but a new check valve was not installed. It is also possible someone did a home overhaul of the pump and it isn't set up right. Pump overhauls should be done by a qualified pump shop that has the equipment to properly set them up and test them, in my opinion.
Jim

[Mechanickyle]

Jim
Thanks Good advice

[Mechanickyle]

Update
Talked with a pump shop guy and he recommended removing te timing cover on the pump and carefully separating the weight cage to see if I could tell if the flex plate was intact
I couldn't see the flex plate but was able to turn the weight cage about a 1/4 turn so I told him what I found and he recommended pulling the pump and bring it to the shop
So I did
Patiently waiting Will update layer

[Mechanickyle]

Update
Pulled the injector pump and took it to a diesel shop in Birmingham to have it rebuilt 3 days later they called me and had it ready They told me that the weight cage was loose on the shaft and that the flex ring had failed
Installed the pump and it runs better than ever
Now that all the mechanical issues are resolved I will begin to prep it for painting

[Mechanickyle]

Ok
So as I mentioned I had the injector pump rebuilt
And runs great. I noticed oil level going up so I changed the fuel pump and oil ran for a couple hours and oil level coming up again so I pulled the injector pump and found the umbrella seal towards the pump had been rolled over I assume while installing injector pump so I installed new umbrella seals used the sleeve tool and the seal compression tool and very carefully installed the pump making sure the seal went into the pump bore correctly
Ran for a couple hrs and the oil level is back up 2 inches above full mark
I've ordered another set of seals
What am I doing wrong
Thanks for any input Kyle

[Jim B]

The transfer pump can dump fuel into the oil as well, a common failure. I would advise changing the transfer pump, given the issues you have had, the new style, not rebuildable, without the sediment bowl made on it is not that expensive. Check the inside of the bushing in the injection pump the umbrella seas run against. Grooves worn in those can cause the seals to flip or not seal well. I expect it is ok or the shop would have changed it but take a look if you pull the injection pump again.

[Mechanickyle]

Jim
Thanks for the reply As I mentioned I did replace the fuel pump first I will inspect the bushing when I pull the injector pump off
Thanks again Kyle

[Jim B]

Sorry, I apparently missed where you had already replaced the transfer pump. I suppose it is possible it is defective. That or the umbrella seals are the only things I can see to put that much fuel in the engine, that quick.

And I'll ask this just as a double check, not doubting you have it right. The lips of the installed umbrella seals are pointing away from each other, right. I have seen them installed facing each other.
Jim

[Mechanickyle]

Jim
Yes facing away from each other