JD 4620 retiming with no TDC mark

jd 4620 retiming with no tdc mark Problems

The one I’m working on has added the starter rubbing (I think) on the flywheel, and the TDC mark is gone. I thought I had found something but the tractor won’t start so I guess I was wrong.

The mark on the injection pump was not very good either.

The 120d mark is still there so I was thinking of using duct tape on the front pulley to find the TDC. So I think with this I will get it. At this point, I’m also going to remove the rocker cover just to make sure I’m not 180d out.

So what if the mark on the governor’s ring is wrong? I have heard of the “dropp method”, used in the CAV pump for example, but have never done it.

Could you just energize the solenoid, full throttle, disengage the 1st injector, increase the pressure with the fuel pump, and watch the “end of the drop”?

Any help getting it right in less than 20 tries will be great!

The pump timing mark is checked on the degree wheel plate while the pump is detached. Does the pump turn when the engine starts? JDC four-roll pumps can have head / rotor seizure and the manifold plate will continue to rotate, unlike JDB two-roll heads, whose driveshaft will break in the shear groove. The best way to see if the four-roller head is spinning is to remove a banjo bolt and accessory, blow out the fuel, and dump the engine. If the rotor is spinning as it should, you will see the rotor port open / close at the screw hole. If you don’t see that happening, the hydraulic head is seized.

The TDC can be found with the valve cover off, look at the rocker arms for cylinder # 6. When the exhaust is almost closed and the intake starts to open during the overlap period, the pump marks should be on the window, and the TDC of the steering wheel also in your window. Was the pump removed during the review? Have the cylinder head valves and seats been ground, setting the valves too deep and causing heat loss from compression? Have you tried heating the block with the heater, if it has one?

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