|These are GENERIC procedures that I developed for my class: |
Generic Spill Timing Procedures
Spill timing is a method whereby air or fuel at low pressure is introduced into the pump gallery to surround the barrels. When the plunger being checked is at BDC, the air or fuel will enter the inlet port into the area above the plunger and flow out the top when the delivery valve is removed. Further rotation of the engine will cause the plunger to rise and eventually block the inlet port in the barrel. This is called port closure, or beginning of injection. This point is also where the pumps are static or spill timed at. What follows is a step-by-step procedure for doing this.
1) Determine the timing spec for the engine you’re working on. On most direct injected diesel engines, this will usually be in the neighborhood of 10-30 degrees BTDC. This may be higher for IDI engines, or may even be expressed in inches of piston travel rather than degrees of crankshaft rotation.
2) Locate the timing marks on the flywheel or crankshaft pulley. Also make sure that the stationary pointer for these marks is in good condition and is not bent. If there is any doubt as to the accuracy of this stationary pointer, you will need to verify true TDC. This is commonly done by removing a valve spring from one of the #1 cylinder valves and dropping the valve on top of the piston. At this time, the top of the valve stem can be gauged with a dial indicator to observe piston movement. Be sure to perform this test accurately. You need to be within +/- one degree to be accurate enough for pump timing.
3) Clean and dry the area around the #1 delivery valve thoroughly! Absolutely no dirt, water, paint chips, etc. can be allowed to enter into the pump chamber! Remove the delivery valve holder, delivery valve spring, as well as the valve itself. DO NOT remove the delivery valve seat. You are merely trying to create an open passageway from the top of the plunger to the outlet of the holder.
4) Reinstall the delivery valve holder only (without spring and valve) and snug in place. Install a fabricated spill pipe onto the outlet end of the holder, preferably with a hose attached to it that is long enough to catch the fuel or air into a jar.
5) Rotate the engine IN THE NORMAL DIRECTION OF ROTATION until it is within about 20 degrees or so BEFORE the actual injection timing spec (e.g. timing spec = 20 degrees BTDC, set engine to approx 40 degrees BTDC). This will place the plunger in the pump at BDC. Be sure that you are on the compression stroke of the cylinder being checked, which is almost always #1. Verify this by watching the valves for the companion cylinder and seeing that they are approaching overlap (i.e. the exhaust valve is just about to close).
6) Introduce low-pressure air into the pump inlet gallery; 5 PSI should be plenty. Alternatively, use the transfer or supply pump to pressurize the system with fuel. (Hint: air is easier and far less messy). Fill your glass jar with water, and insert the hose from the spill pipe into it. At this time, bubbles should be observed coming out of the line.
7) SLOWLY turn the engine over in the direction of normal rotation. The engine needs to turn slowly without catching. This can be tricky to do on some engines. Sometimes a socket and ratchet on the end of the crank will “jump” and not allow the engine to be turned smoothly. If this is the case, sometimes removing the starter and using a screwdriver to pry (did I say screwdriver?) on the ring gear teeth can get you the finest measure of control in turning the engine.
8) As you approach port closure (the spill cutoff point), the bubbles will appear to slow down. Keep turning the engine over until the bubbles just stop, or only appear maybe once every five seconds or so. It is at this point that you have achieved spill cutoff. Read the marks on your timing degree wheel. It should coincide with the factory specs for timing within plus or minus one degree. If not, adjust the pump timing as necessary to achieve this.
9) NOTE: If you “overshoot” the point at which the bubbles stop, or you are unsure of the precise point, you do not need to rotate the crank a full two revolutions to redo your test. Simply rotate the engine backwards several degrees, and then sneak back up on it IN THE NORMAL DIRECTION OF ROTATION. This is done to compensate for gear backlash. NEVER check or adjust pump timing by turning the engine backwards!
10) NOTE: If the spill timing does not coincide with the existing marks or pin location on the pump, internal wear in the pump is indicated. If it is much more than a degree or so off, a trip to the pump shop may well be warranted.