>On Wed, Nov 24, 1999 at 08:35:25PM -0500, MVTrucker@aol.com wrote:
>> List,
>> Quite a while back I posted a problem concerning a multifuel engine
>> "making oil". That is, after a drive the engine oil would be over full.
>
>i've seen this problem on detroits. however, i'm not familiar
>enough w/ the multifuels to have seen that problem.
>
Its a necessary commonplace arrangement to have a LP "spill" line connecting the
injectors to carry away fuel leaking past injector seals, at injection pressures
of tens of thousands of psi this is expected. The spill line is normally
pressurised by the feed pump and via a small restriction returns to the tank,
fuel circulates continually and the contents of the tank is surprisingly quickly
scrubbed in the process of being circulated through the fuel filters.
Detroits are unusual in that the injectors are also combined, individual pumps
rocker arm operated and live under the rocker cover (with the exhaust valve
system to add to the confusion about a two-cycle engine with unexpected poppet
valves) so any spill line leak directly lets fuel into the oil-pan (sump).
Conventional diesels can suffer the split lift pump diaphragm, like a gas
(petrol) engine or leaking shaft seal in the centralised injection pump, both
admitting fuel to the lube system.
Any diesel can suffer a failed injector, if the fuel isn't sprayed correctly,
and we're talking here of the very finest atomisation like instant fog, then it
won't burn completely or at all and will steadily find its way past the piston
rings into the oil-pan.
Joe didn't have the benefit of hearing this engine run and its likely one
cylinder would be obviously weak, missing or making regular puffs of black
smoke. With centralised injection it is possible to just crack off each
injector pipe union in turn with it running and by the change in engine note, or
not as the case might be, find the bad cylinder, bit like shorting spark plugs
in turn to do the same with a gas engine.
Although long-lived, the injectors don't last for ever, the nozzle end lives in
a very hostile environment and is usually replaceable, although there's the
hassle of bleeding the injector lines its worth removing the injectors
infrequently and having a specialised diesel injection shop test, calibrate and
replace parts as needed, sometimes you get exchange factory refurbished items
for a nominal charge.
It is totally inadvisable and pointless to attempt to disassemble an injector
yourself, take it to the shop.
Richard
(Southampton UK)
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