Fuel Injection Pump - Mitsubishi 4DQ50 Service Manual

5) To service nozzle tips, wash them well in clean cleansing oil, carefully fit
valves onto their respective seats in oil and after washing them clean once
more, put together in clean gas oil. Never wipe them with waste cloth, etc.
6) Nozzles usually let a little fuel go back. Excessive increase of return fuel is an
evidence that they must to replaced with new ones.
7)
To install nozzles, clean off carbon from nozzle seat packings, but be careful
not to scratch or otherwise damage seats. Any seat notably sunken in the
surface must be replaced, for it will spoil air-tightness of cylinder even if
clamped down tight. To install, screw nozzles by about 5kgm of clamping
torque. To strain them.
4-4 Fuel injection pump
1) For checkup of oil level and change of oil, refer to Sect. 1, "Lubrication".
(Mechanical governor is forced lubrication by engine oil, so it need not check
up of oil level and change of oil)
2) Being precision-machined and adjusted like nozzles, injection pump will not
require any particular adjustment but at the time of over-hauling, it should be
thoroughly adjusted by means of a pump tester. If anything unusual noticed
with it. have it examined and if necessary. serviced by your dealer or at a
service shop. In such a case that. nozzles having nothing wrong at all.
combustion does not go well in any of cylinders. check as follows.
a) With the engine running, loosen either cap nut on one injection pipe after
another. So you will fined the cylinder from which the symptom comes. Such
symptons come from. for example, the following causes.
b) Set screw on pinion is loose. In this case. injection rate is out of perfect
control, that is to say. not varying exactly in conformity to control rack
travel.
c) Plunger spring is broken.
d) Delivery valve spring is broken. To inspect it. loosen delivery valve spring.
Broken spring keeps injection from breaking clean off for poor sucking back
of fuel.
Inspect the contact of delivery valve seat. too. If badly worn or otherwise
defective. pull it out to replace by means of a special tool intended for that. In
putting together again. attach a new gasket to valve so far as possi~le. In these
operations. take every possible measure to keep off dust. Remember that valve
holder must be screwed exactly to 3.5kgm of clamping torque wit~ a torque
wrench ..
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