New guy with JD301A

micallahan · Oct 25, 2014

Hey all, picked up a 301A a few weeks back and am getting all the little details worked out. Biggest issue is rough running. Have been through all the troubleshooting lists in the service manual and also for the injection pump. No fuel restrictions on inlet or return. Starts easily even cold, no smoking or other bad signs, runs great, no lack of power, seems fine other than not running smooth at any speed. Just getting second opinions before replacing the injector pump.

Bob · Oct 26, 2014

NOT sure exactly what you're experiencing, but " Starts easily even cold, no smoking or other bad signs, runs great, no lack of power, seems fine other than not running smooth at any speed" is not the typical behavior of a "bad" IP.

Tx Jim · Oct 26, 2014

I'll suggest to test injectors and check inj pump timing.

micallahan · Oct 26, 2014

Thanks, guys. I did check the timing and it was WAY off. Specifically the advance. Static timing was about 6 degrees retarded, so adjusted for that. Put the window in the pump, started it and throttled to 1300rpm where advance was supposed to be 4 degrees BTDC and the cam mark went out of sight. Got all that adjusted and it doesn't knock like before, but it still runs rough.

I am thinking something is wrong internally in the pump because the glass check ball is not in the return line, so I feel sure the plastic retainer ring has disintegrated decades ago and the ball was removed so the engine would keep running. Once running gain, I suspect they just ran it with the governor cage flailing around. It could be the injectors, but if I go to the trouble of taking them out, I'm going to just replace them, since they are 40 years old.

JDemaris · Oct 26, 2014

The timing would not make it run overall "rough" as you describe. Not unless it was much further out then you described. Bad injectors wouldn't either. Bad injector can make it skip, knock when cold, or have a weak cylinder. Not going to make it run overall "uneven" or "rough" though (by my connotations of the words). A worn injection pump with the plastic dampener long gone, and metal rivets hammering against steel in the governor can do it. Note your timing advance was probably out of wack because the ball in missing from the housing-pressure-regulator-valve at the pump fuel exit. when that ball is in place, it lets the internal housing pressurize to around 6 PSI and that pressure pushes against the charge that powers the fuel timing advance.

micallahan · Oct 27, 2014

jdemaris, now that's the information I have been looking for! I have cracked loose the injector lines one at a time and nothing changes the rough running, just makes it miss on that cylinder, so I pretty well ruled out an injector. Best way to describe it is that it sounds like a small block chevy with a big cam in it at idle, but persists to some degree or another throughout the entire operating range. It's not a single cylinder and it is a totally random pattern, which leads me to believe it's something internal in the injector pump. I have checked every single point in the Stanadyne/Roosa manual troubleshooting guide except valve adjustment and all the internal component failures and misadjustments. Think I ought to adjust valves as a last ditch effort before going for a rebuilt pump?

ronaldj44 · Oct 29, 2014

Hi I am new here. I have a 300B that had the same problem. It was the gov in the injection pump. Stanadyne makes a replacement gov that is all steel no plastic. It is about 50 dollars from usdiesel.com in fort worth tx. My is running great with the new gov and a thirty dollar seal kit.
Ron

micallahan · Oct 30, 2014

Thanks much, Ron!

New guy with JD301A

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