DISMANTLING PUMP AND INJECTOR
A few tips on general removal / dismantling:-
1) NEVER EVER hammer or knock a seized rack, as you will quickly destroy the fragile element inside the pump. Leave it to soak in WD40 and take your time about it.
2) Get a couple of small plastic boxes to hold dismantled parts, and put half an inch of fresh diesel in the bottom to keep the bits from going rusty. Use one for newly dismantled parts and the other for cleaned up parts. DONT use paraffin, which absorbs water and leaves rust everywhere.
3) Clean all or as much as you can of the surface dirt from the pump/injector before dismantling.
To dismantle the standard pump, you only need to undo the top delivery valve housing and remove the lower cam bucket circlip, and everything drops out !
BUT-
The relative position of the governor rack to the pump element will affect the output of fuel relative to the position of the engine governor arm. If you alter this relationship then you may find that your engine is ungovernable !
The pump element is normally marked with a dot on the small rectangular head which contacts the cam bucket, and there is also a mark on the rack or housing to line this up with. If you are not sure, then get something to mark the rack and element with which will enable you to re-assemble the two together in the same relative position. Pattern elements do not always have the mark, and while diesel repair houses can assemble the things with their eyes shut, the likes of us may get it wrong !
Once the bits are out (and you have taken note of how they are assembled haven't you ?) they can be cleaned and inspected. The delivery valve and spring in the top housing are there to act as a non-return valve and to make sure that the supply shuts off with a bang when the pressure falls from the pumping element. If the spring is intact and the valve face is clean and bright without any pitting, then it is OK to re-use.
The element has two pieces, the inner plunger and the outer housing. The diameter of the plunger is reflected in the part number, the most common size is 5mm or 7mm for 3/1 and 5/1 respectively. Thus you will be able to start identifying pumps from their element size.
The fit between the two pieces is the make or break of the whole thing, and as long as the wearing surfaces are bright with no long scratches down the length of either, then they are re-usable (as far as eye inspection can tell)
RE-ASSEMBLY
Re-assembly is the reverse of dismantling, making sure that the cam bucket is free and lubricated, and the element alignment in the main body is correct.
The rack gets a lot of stick from the governor arm, and if the hole at one end is elongated and sloppy, you will not get decent speed control. Better to open the hole up and bush it or use a larger cotter pin. If the rack is sloppy in the pump body, you can get the holes line bored and bushed back to size (11mm) or look for another pump body.
PUMP OPERATION
The operation of the pump element always seems a mystery to 'outsiders', but like most things is very simple:
The element has a spiral groove cut in it's outside diameter, that has a connecting hole through to the inner pumping cylinder. The element is rotated in the pump housing by the rack, and there is a relief port in the body of the pump that will communicate with this spiral groove in certain positions of element height in the body and rotation.
When pumping fuel at full throttle, the element is rotated to the full extent of the rack and each pumping stroke will eject the full volume of the element plunger and cylinder. Allowing for losses, this is pretty repeatable, so the speed / fuel relationship is very tight, subject to load.
If the engine governor decides that it wants to lower the speed, the the rack is pulled back (or forwards, depending on the governor configuration) and the element is rotated in the pump body. This time, the spiral groove will meet the spill port in the pump body and fuel pressure will fall away before the end of the pumping stroke, thus limiting the amount of fuel pumped. Note that the pump stroke is unchanged, just the volume has been reduced.
This constant stroke/variable volume system was the basis for the original successful Bosch pump, and forms the basis for probably 99% of injection systems.
EXCESS FUEL TOGGLE
The excess fuel toggle is fitted to all CS engines, and probably others as well. It allows the pump rack to go further when it is flipped over, thus giving more fuel than normal for cold starts. If the toggle sticks open, not only will your engine start well, it will also get too much fuel at full load, with possible expensive consequences. Make sure that the little weight is free to rotate.
Stripping is done from two ends: the top delivery edge filter and the bottom nozzle.
The delivery edge filter is contained in the tube which the injection pipe connects to. You can blow them out against the direction of fuel flow, but not much else. The Top cap covers the injection pressure adjustment screw, locknut and spring. Once out, the bottom nozzle cover can be removed and the nozzle taken out.
The fit of the nozzle pin in the housing is as critical as the pump element plunger in the housing. Too much clearance will see increased leak-off of fuel back to the tank and loss of power. It is all relative though, and a clean system will deteriorate very slowly over time, especially if the filters are kept clean.
NOZZLE TYPES
There are thousands of injector nozzles in use. There are one or two which will suit your particular engine, and mixing nozzles from different engine types will cause all sorts of problems.
To give an example, the CS Lister engines all used the same nozzle body, but the 3/1,5/1,8/1 all used different nozzles. If you take that series of older injectors, there are about 500 nozzles listed for the range of applications, and unless you have the equivalents and supercession lists, it is a bit of a minefield.
