JD 644 A Starts runs for a few seconds and shuts down

This is a 1972 JD 644 A with the Stanadyne pump. Ronnie told me it is the same engine as the 4320 JD. After much reading I think it may be the PELLETHANE RING...
What cover do I remove to look for these---mouse droppings----There isn't a window to look thru, but there is a rectangular cover that I can see.

Thanks for any help---len clare michigan

Disconnect the fuel return line from the IP, then remove the fitting/housing pressure regulating valve that the return line connects to from the "top" cover of the IP (for reference about what area we are talking about, that cover is retained to the IP by 3 screws).

Look inside the pump side of the fitting for "coffee grounds" that indicate the originally CLEAR "governor damper ring" has blackened from fuel, heat, and age and broken up.

If you feel you can do it safely, and deal with the trickle of fuel that will come out of the IP, start then engine and see if it continues to run now.

If it does, either the regulating valve/fitting is plugged with damper ring debris or the return line is plugged or crushed somewhere between the IP and the tank.

If there's debris in the valve/fitting the IP will need to be torn down and repaired.

Some guys condone breaking the glass checkball out of the valve so it will pass debris easier and continuing to run the engine 'til a "better time" for repairs.

I don't believe in that because the valve is there to maintain a fixed housing pressure for proper operation of the pump, and continuing to run it risks the governor parts going "metal to metal" after all the plastic is gone, wearing off the pins, then the engine will overspeed.

(BTW, "PELLETHANE RING" refers to the type of plastic that one poster here believes the ring is made out of, NOT sure if that's correct or not, but I'm gonna GUESS you'll get a pretty blank stare at most IP shops if you tell them your "PELLETHANE RING" is bad.

Bob Thanks for the good info. My injector pump is a JD8635JT2488 and the model number is 102908BRST.
MY return line to the IP goes into a housing that attaches with --4-- screws and they are on the side of the housing. Take those 4 screws out and pull away from the IP and look for coffee grounds. Is that correct??
AGAIN THANKS ND fellas are great..............

You do not have to take the cover off the pump. Your pump is mounted vertically. This cover would be more commonly called the top when it is mounted in the horizontal position. Just remove the line and then the fitting. If the dampening ring has started to come apart you will find small pieces of it in the fitting the return line hooks to.

To remove the entire pump take the small cover that is held on with two screws on the side of the pump. Slowly turn the motor over until the two lines line up. Then remove the lines and pull the pump up and off.

Len, I was thinking about the email you sent me, the fitting you pulled is the fuel inlet, on the transfer pump if it had a screen. The transfer pump is made into the rear of the pump and has 4 screws that hold it together. JD is right, the return fitting/line would screw into the big rectangular cover that is held on with 3 screws, if yours is so equipped.

IMHO removing timing window outlined in red is a lot easier than removing fitting(key 25) to check for coffee grinds in IP. Engine should run fine with window off IP if mouse droppings(coffee grinds) is blocking check valve in fitting(key 25)