Hi all,
My build is progressing well and I am now ready to testrun the engine and powertrain. Why do the injectors need a bleed back to the tank and can I run it back to the low pressure side of the lift pump or must it go to the top of the fuel tank? I also managed to disturb the injection timing which is adjustable by slotted boltholes on the pump, can I reasonably guess this by moving it while the engine is running as you can a petrol distributor to obtain smooth running?
Any advice appreciated John.
Diahatsu Dnepr
Moderators: Dan J, Diesel Dave, Crazymanneil, Stuart
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johnfireball
- I luv the smell of Diesel...
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Hi John
The fuel return should go straight into the top of the tank to allow a free flow with little or no 'back pressure'. The reason for this is to return uninjected fuel back to the tank in a 'loop'. I think the uninjected fuel is sometimes called 'spill' and if it dosent have a free path back to the tank you can get fueling problems. I don't know about injection timing adjustment though
Cheers
Alex
The fuel return should go straight into the top of the tank to allow a free flow with little or no 'back pressure'. The reason for this is to return uninjected fuel back to the tank in a 'loop'. I think the uninjected fuel is sometimes called 'spill' and if it dosent have a free path back to the tank you can get fueling problems. I don't know about injection timing adjustment though
Cheers
Alex
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Diesel Dave
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Return lines and Timing
I have always advocated putting return lines into the tank, usually by welding.brazing/soldering a steel pipe into the base with the top of the pipe near the top of the tank.
Now in theory there is no difference to the back pressure between this type of installation and plumbing into the bottom of the tank as both have the same header of fuel.
I have seem many builds with the spill returned to the feed line and owners report no issues. Whilst this may be true with a relatively new motor, once the injectors start bleeding a little into the spring chambers there will be a lot of returned fuel (as there will be in a used engine), there may be an issue.
Don't spoil the ship for a 'hapeth' of tar, if you get issues with running your always going to suspect this maybe a cause - best eliminate the possibility.
As regards timing, I have never attempted timing a diesel whilst running as there's a lot of force being transmitted to drive the pump. In order to check whilst running you will need a timing gun with an diesel line transducer trigger - usually very expensive.
Most are done by turning over the motor slowly by hand and watching an open injector pipe.
Cheers
Dave
Now in theory there is no difference to the back pressure between this type of installation and plumbing into the bottom of the tank as both have the same header of fuel.
I have seem many builds with the spill returned to the feed line and owners report no issues. Whilst this may be true with a relatively new motor, once the injectors start bleeding a little into the spring chambers there will be a lot of returned fuel (as there will be in a used engine), there may be an issue.
Don't spoil the ship for a 'hapeth' of tar, if you get issues with running your always going to suspect this maybe a cause - best eliminate the possibility.
As regards timing, I have never attempted timing a diesel whilst running as there's a lot of force being transmitted to drive the pump. In order to check whilst running you will need a timing gun with an diesel line transducer trigger - usually very expensive.
Most are done by turning over the motor slowly by hand and watching an open injector pipe.
Cheers
Dave
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andrewaust
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Hi John
Jump on the net and look up "Spill Timing", that is the best way of setting up the timing of a diesel if you cannot get hold of expensive timing devices. Moving the pump whilst the engine is running is not a good idea, it will also give you false results as timing is not like a petrol engine in the sense you won't get the running characteristics like a petrol engine.
Cheers
Andrew
Jump on the net and look up "Spill Timing", that is the best way of setting up the timing of a diesel if you cannot get hold of expensive timing devices. Moving the pump whilst the engine is running is not a good idea, it will also give you false results as timing is not like a petrol engine in the sense you won't get the running characteristics like a petrol engine.
Cheers
Andrew
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johnfireball
- I luv the smell of Diesel...
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- Joined: Tue Feb 12, 2008 10:43 pm