diesel return(spill)pipe,petter

[kieronriley]

hi should i change or what.my petter mini twin does not have a return pipe to the tank,it is just fed back into the injector pump and has been for about twelve years,but a diesel enginere in our club tells me that i must take the spill backm to the tank as leaving it the way it is will lead to diesel spilling back through the pump and cause pressure resulting in fuel getting into the sump which may in turn cause allm sorts of problems,i seem to have a memory of reading an article once explaining that the was the way my fuel is piped was the correct way for a petter mini twin,so am i dreaming or should i fit a spill pipe back to the tank,or is there anywhere else like the filter maybee that i can run it to.thanks.Kieron

 

[TopDonkey]

I'd leave it as it currently is

the reason modern diesels, especially common rail ones return to the tank is that pressurising the fuel heats it up a huge amount, and if you returned spilloff to the pump again, it would very soon overheat.

In fact, common rail diesels heat the fuel so much that they actually run it through a fuel cooler before returning it to the main tank !

 

[Appledore]

Hi Kieron,

Not really any idea about your mini twin, but I have had 2 x mini 6's, and the excess fuel was returned from the injector banjo connection direct to the fuel tank.

This return pipe snapped off at the banjo on our way to Guernsey 3 years ago, and we couldn't fix it, and due to the pressurised diesel spraying everywhere, had to do without the engine!

Hopefully someone here will have the definitive answer for you.

 

[grumpygit]

hi should i change or what.my petter mini twin does not have a return pipe to the tank,it is just fed back into the injector pump and has been for about twelve years,but a diesel enginere in our club tells me that i must take the spill backm to the tank as leaving it the way it is will lead to diesel spilling back through the pump and cause pressure resulting in fuel getting into the sump which may in turn cause allm sorts of problems,i seem to have a memory of reading an article once explaining that the was the way my fuel is piped was the correct way for a petter mini twin,so am i dreaming or should i fit a spill pipe back to the tank,or is there anywhere else like the filter maybee that i can run it to.thanks.Kieron

Listers and Petters always had a leak off to the tank, in fact most other diesels do have a leak off also.

 

[doug748]

Well if it has worked for twelve years I would be tempted to keep it as it is. However my Mini Twin did have a return to the tank.
I kept it unchanged when I fitted a modern 20hp engine and I can confirm what TopDonkey has said - it does heat up the tank a great deal. In fact given the feeble nature of my return arrangement I am surprised it has not leaked or split (touch wood).
I must check it out and improve it.

 

[TopDonkey]

Well if it has worked for twelve years I would be tempted to keep it as it is. However my Mini Twin did have a return to the tank.
I kept it unchanged when I fitted a modern 20hp engine and I can confirm what TopDonkey has said - it does heat up the tank a great deal. In fact given the feeble nature of my return arrangement I am surprised it has not leaked or split (touch wood).
I must check it out and improve it.

You can make a mini fuel cooler radiator out of a long length of copper piping, just bend it back and forth with a 1-2" bend radius at each end and about 12" wide and you can build a little radiator that will passively cool the fuel before it goes back to the tank, thats how cars do it, and they mount it under the car in the airflow, but car ones are made of steel, so not best to reuse on a boat because of rust

 

[Quidi Vidi]

My return goes to the tank too

 

[rob2]

I have a Sole Mini-14 (600cc Mitsubishi twin) and the return goes to the line from the lift pump to the final filter - a closed loop. I was surprised at that, as I was expecting a return to the tank, but it seems to work OK. On a previous boat we converted from a petrol installation to a Yanmar 2GM, so the tank didn't have a return pipe fitting. We took the return to the secondary input on the main filter. We never used the motor other than to pick up or leave the moorings, but the new owner has not complained of losing power as it warms up.

Your Petter should be fine as it is. Can't comment on the situation with a more modern common rail engine, though.

Rob.

P.S. I was reminded of injected aero engines which are notoriously difficult to start when warm. The successful technique is to turn them over with the ignition off so that the fuel flows through the supply pipes and cools them before switching on to start.

 

[ianabc]

Diesel return Yanmar

Yanmar 2QM20 have the diesel return direct

to the engine mounted fuel filter.

Some owners may have altered the return to the tank?

 

[kieronriley]

my spill pipe

thank you all again very much for your comments and advice i think i will folow the first bit of advice and what i think seems to be the general feeling and let it be.Kieron