Injector return pipe

[cold comfort farm]

My Lister CS 3hp has what looks like a return pipe from the injector blocked off. Is this a usual mod?  I would have thought it would put the injector under a little strain.

Thoughts anyone!!

Stephen

[ronmar]

I would agree, there should probably be a return line to bleed off the leakage fuel from the injector back to the fuel supply.

Ron

[M61hops]

My 6/1 listeroid has a return line from the injector back to the fuel filter.  It is a clear plastic tube and I can see that it has almost no flow, just a few drops an hour if that.  Can someone educate me as to why that is needed and under what conditions fuel would flow through this line?  I notice that most but not all diesels have such lines and I have tried to find out how they work to no avail.  Anybody know what purpose these lines serve and/or where I can find a detailed explanation of their operation?        Thanks!!!                         Leland

[Geno]

It looks like some fuel leaks past the valve. Lubrication?

Thanks, Geno

[cold comfort farm]

on most diesel engines the pump delivers far more derv than is needed by the injectors so there is always fuel there for acceleration i  suppose.  On slow speed engines it looks like whats needed is whats used.  It is worth having the injector calibrated every year or so.  I had mine done for £15 it made starting very easy.

Thanks for the diagram

[oliver90owner]

Nothing to do with how much the engine needs.  It is simply that the components' fit is only tight/close enough to prevent nearly all the fuel leaking past.  That which is the 'leak back' is required as lubrication.  It should return at low pressure to the fuel supply system.

Regards, RAB

[cold comfort farm]

Thanks Oliver

[Tom]

Some of the older Listers just had a small can to catch the return fuel. I guess it could provide some interesting info such as if the can starts filling faster there is a problem with the injector.

[M61hops]

Great drawing, thanks Geno!!   Is this a drawing of a Lister and Listeroid injector?  (never had mine apart yet)  Has anybody found a filter in the inlet connection of their Listeroid?  For myself this is a perfect example of a picture being worth a thousand words!  I would guess that it is important to have the weep line unristricted to keep the injector sqirting at a constant set point!  If the return line is sealed shut and pressure built up above the spindle it looks like it would take more pressure to crack the injector open and retard the timing of the spray.   This drawing combined with the observation of how little fuel gets returned through my return line gives me some idea of how tight the tolerances are of the injection system and how a little grit would be a lot of bad!  Thanks guys!               Leland

[lowspeedlife]

Air cooled engines will often leak large amounts of fuel from the weep line if loose or damaged, as they use the fuel to cool the injector as well as lubricate it.
                 scott r.

[blacksea7]

Hi all,

As a former HSDE Brat, factory trained... then engineer, I'll  give you what you need to know. The fuel return pipe is a necessity as it handles all fuel bypassing the needle within the nozzle. It is best to run the pipe back to the fuel tank... dont' try to connect it to the fuel supply line. If your engine has a self venting system watch the soldered joints as they've a habit of failing... more engines had the self venting systems discarded as they proved to be less reiiable than the conventional pipe exiting the head, under the rocker cover. Air cooled engines DO NOT bypass more fuel than liiquid engines... this is folklore.. if you're bypassing a substantial amount of fuel, your injectors need to be reworked or replaced. All SR-ST engines use the same fuel return line...

Bill