I just did a google group search and found the old post I put up in 2004 on oil boiler servicing. Here it is cut and pasted.
There are a number of variants with minor variations but assuming you are asking about a reasonably new boiler with a pressure jet burner try the following.
Have available a vacuum cleaner with hose attachments, A long stiff bristle d flue brush, a soft straight brush such as a clean 1" paint brush, Screwdrivers, spanners, allen keys, scraper, replacement nozzle, replacemen t filter element and joint, every three/four years a new flexible oil hose, combustion analyser kit preferably Briggon or Fyrite chemical type as oil fumes tend to poison oxygen cells in electronic analysers.
Switch off and allow to cool unless you like working with burnt fingers.
Ensure isolation of the boiler from the power supply. time clocks and thermostats can and do switch on while you are working
Shut the oil service valve which should be local to the boiler.
Put down a good sizeable dust sheet
Remove the casing door and if a top entry flueway type the lid also, thus revealing the boiler shell and burner.
Remove the flueway access door to reveal the flueways and removable baffles (retarders)
Judge the amount of soot/dust within and use vacuum cleaner as required, removing the retarders in turn and remembering the position and orientation of them for ultimate replacement. Once all retarders are out brush or scrap e the interior of the heat exchanger clean. Loose dust or soot can slow the rate of transfer of heat from the flue gases into the waterways and reduce the efficiency significantly, costing you money and passing your hard earne d heat out into the open air.
When you are satisfied the retarders and the chamber interior is clean locate the securing nut(s) or clamping screws which hold the burner in plac e and withdraw it from the boiler. There are a number of basic types of pressure jet burner and bear in mind that yours may be different in some respects from what I describe here. If I knew what you actually had it woul d be easier but I describe here the procedure for a Riello burner which has a sequence control/ignition (grey) box mounted on top of the burner unit. As viewed from the rear (non firing end), on the left hand side is the oil pum p with one or occasionally two oil hoses (suction and excess return pipes). You will see a dark coloured protruding screw with a slotted end. DO NOT ALTER THIS SCREW it is the oil pressure setting screw and you will have to set up the whole burner from scratch if you do. Below the setting screw is a hexagonal headed plug which is a pressure test point. Checking of the oil pressure on a satisfactorily running boiler is not normally neccessary unless you are commissioning the unit or fitting a replacement pump in which case it should be used to set the pressure to manufacturers specification. On the right hand side you will see the fan casing and on some vari ants a hydraulic ram operating a flap which closes off the air intake when the burner is not running. Early (long ram) models used a screw and locknut on the ram to set the open position as an air inlet adjustment, later models used a shorter ram with fixed travel and a rotating mask to adjust the air. Both of these types of adjuster should not be moved unless you have reason to do so. Once set they should remain constant. Remove the fan casing, being careful not to damage the oil line to the ram if one is present and expose the fan. Use a brush and possibly a small scraper such as a screwdriver (carefully) blade to clean off the fan blades . A significant amount of fluff and dust can often be found here. Brush clean the fan casing and inlet airway then refit the casing to protect the fan. Turn to the front (flame end) of the burner and locate the screws w hich hold the blast tube in place. Undo these and draw the blast tube off the front of the burner to reveal the nozzle, electrodes and mount. The elctrod e position with relation to the front of the nozzle should be carefully noted for accurate replacement. Locate the electrode securing screw and loosen it to withdraw the electrode mounting (porcelain) block. Clean the elctrodes asembly (it should look like new when you have finished) check its gap (about three to four mm) and put safe to one side. Clean away any dust, soo t or other junk from within the space but do not damage the face of the photocell which is at the rear of the chamber With two spanners undo the nozzle and withdraw it. Stamped on the f lats are details of the size (0.50 USGPH or similar info), spray angle (60 or 80 degrees usually) and spray pattern code (S, H, W etc) Replace with new nozzle of same spec. Reassemble taking care to ensure the electrode clearance(s) are as you found them, refit the blast tube and turn to the grey box. On the left hand side is a clamping screw which should be loosened and the box withdrawn (unplugged) from its seat. The photocell is mounted (plugged in) to the front of this box and it should be cleaned with a soft brush. Check for loose wires in the fixed base of the grey unit and replace it. Replace the burner into the boiler and refit the mounting screw/nut . Turn on the oil service velve and check very carefully for leaks in the oil hoses. These are rubber under the braid and they become brittle. The movement associated with servicing is often enough to crack the rubber and start a leak which is why they should be replaced regularly. Go out to the oil tank and locate the oil filter. Turn off the tank valve (and sight gauge tube if fitted) and remove the filter. Run a little oil through into a clear jar and inspect for water/dirt in the tank Clean i f of the strainer type or replace if a paper element. Refit and turn oil back on. Vent or purge the air from the filter bowl. If there is a drain valve a t the back of the tank run a little into the jar and check for water. Decant any water present off. Inspect the tank for corrosion Go back inside replace/restore all inner parts and casing doors and power up the unit. Run on test and when warmed up draw from the sampling point a smoke sample (should be 0 or 1 on Baccarach scale). Draw a sample o f flue gases from the sample point into the analyser and check CO2 levels (depending on boiler but expect between 9 and 12 %) If all OK put temperature probe into sample hole and take flue gas temperature having allowed to stabilise. New boilers with high eficiency will show around 200 degrees C, older ones could be anywhere up to 450 which gives an idea of ho w much heat they wasted! If readings are not satisfactory you may need to tweak the air sett ing slightly but do not make any big adjustments and mark where you started from. When satisfied record figures and comments preferably on a history card you keep with the boiler Refit sample plug and outer casing, wash hands and put kettle on.
HTH
John