My way of clicking almost everything fuel related with my little diesels is to "simply" disconnect the fuel return line at the tank, or some convenient place, put it into a clear clean glass jar. Start the engine, high RPM in gear if you like. If it runs clear and clean then just about all the common problems are eliminated.
If the flow is low there is a clog. You'll simply need to know what the flow normally looks like. Mine looks like what might come out of a soda straw if you are bored at a bar.
If there a bubbles, even just one, you have an air leak.
If there is water or crud find a new hobby not involving things with moving parts.
If there is no fuel flow....well you either have much more work to do or simply need to buy some fuel.
None of those thing? You can probably move on the non-fuel problems. However with small diesels it is almost always a fuel issue.
If there has ever been water thru the injector pump it is probably ruined. Likewise if there has been water in the engine oil...the mayonnaise problem...the injector pump is ruined as it is by far the most rust sensitive part of a diesel. It is built like a pocket watch inside.
Good post by aloof !!!!!!
A good (and continual) way to do this and without having to 'guess': is to place vacuum gages on 'downstream side' of every damn 'filter' and then monitor them on a routine basis ..... and then when 'crap' happens simply check and compare against your written log of indicated pressures with the current reading.
A drop in vacuum from 'normal' indicates an air leak, or a filter that is 'bypassing', or has a broken 'pleat' in its filter media, empty tank, etc.
An increase in vacuum indicates a filter that is 'plugging' with debris
An increase in vacuum across all filters indicates a plugged dip tube or blocked tank vent; OR, that the 'first' filter downstream from the tank in the series is blocking. etc. etc. etc. etc.
How to set up the parameters to know when
to change filters .....
With 'brand new' filters, run the engine at near wide open throttle and full load .... and very S-L-O-W-L-Y close the tank valve until the engine begins to 'stumble' and lose rpm; then quickly read EACH of the gages for that maximum vacuum value. This will indicate the maximum VACUUM possible in the system before engine 'shut down'.
Take those values and multiply by .9 (or .8) .... that will establish 'new' maximum 'operational
' vacuum gage values for Wide Open Throttle Operation ... the vacuum on any
gage in the fuel system that indicates that one or ALL the filters HAVE to be changed AASAP (as you only have about 10% (or 20%) of filter 'dirt capacity' remaining before complete engine 'shut down').
With gages installed, you don't have to agonize over 'what the hell is going wrong
' and can quickly locate, identify, and then remedy 'the problem'.