Caterpillar D2 3J

Martin, I would start by mounting the injector pointing upwards as shown in the operator's manual and check the spray pattern. Or put it on a test pump. No use disturbing the others if that one isn't spraying. If it sprays normally, then swapping is in order.

Another idea is that the pump plunger on that one might be mis-timed to the rack when it was installed last. Have seen a later model engine with a different pump housing that had the pumps put in without timing them. Lots of black smoke and strange noise.........but it did run.

I think you found your problem. Maybe Eddie B will come along and confirm, but I am betting the cylinder is threaded into the pump body and this is used to adjust the fueling rate. Can you see that there are more threads showing at the top than the other pumps.

I run a small business just for working on Cat pumps and old style injectors. I rebuild injectors and can take the pumps apart and resurface the check valves. I can also recalibrate the pumps to preform near new.
If I can be of help, call 816 891 8654 or E-mail [email protected] Bill Walter 7602 E. Forest Lks. Dr. parkville,Mo. 64152

Marvin, I doubt the plunger can disengage from the rack. Easy to check though.......just take the cover off the side of the housing and check the dots on the plunger quadrant and the rack are aligned. Have heard Eddie B caution against tapping the rack with a stuck plunger because of the possibility of changing the indexing of the plunger gear quadrant to the plunger body.

I'm thinking the problem is related to the lock screw coming loose. Not sure the cylinder is threaded into the pump from the top, but from parts book, it looks like it is. The later U series tractors don't have that design with some sort of hex just under the nipple where the injector line screws onto the pump. I'm thinking it is either threaded in to screw up and down (changes the stroke length) or slides in and is twisted slightly to set the fuel delivery rate because of how it interacts with the helical passage machined into the plunger.

Need an expert to weigh in, I'm out on a limb and sawing for all I'm worth! Not sure which side I'm sawing on either😆

Hi Martyn,
second writing of this, other one lost.
Study of the scan below may assist in following my dialogue.
Bear in mind that these pumps were designed and machined to not need any field adjust to replace an injection pump assembly/unit individually or other. They are ALL matched from the factory.

The screw holds the pump barrel in a factory set position. This being loose may allow barrel to be turned in the main housing if the pump seized and was forced around by pushing on the rack--as said above-- usually it is the pumps quadrant/sector gear that turns on the pump plunger in this scenario.
I suggest remove the screw and check to see if the indexing slot machined into the barrel is aligned or even the tip of the screw sheared off.

From the scan below you may be able to see how the unit is assembled. The locking dowel driven into the top of the housing, at the castellated nut, needs to be removed and the nut unscrewed to relieve the tension on the inner parts to allow the barrel index to be realigned by turning the barrel--maybe another pump would be a safer way to go depending on your ability to reset things.
If the quadrant/sector gear on the plunger has turned it needs a test bench and savvy operator to reset it by comparison of other pump units on your inj. pump.
Hope this helps.
Cheers,
Eddie B.

Seems if the barrel rotated you'd have less fuel, not more...as it would tend to cut off the supply passage.

Thanks guys
Tip of the screw not sheared off, looking at the diagramme,looks like the screw came out enough not to become an effective lock, but the screw has gone in ok and flush like the other three ,I made sure that the barrel slot was in line using a small screwdriver, this pumps segment is delevering lots of fuel to that cylinder hence the black smoke and chuffing,seems that its in max fuel position.I think I will check that the gear and rack marks all line up.
Martyn