fuel system, no return line

Barry33 · #1 (**permalink**) 10-04-2009

HELP !! I had a new Yanmar 3YM30 installed 3 yrs ago, I just now found that the yard did not install a fuel return line to the tank. The motor has run well for 175 hours, but what have I done to my fuel system?

I will fix this in the spring.

Thanks,
Barry

Waltthesalt · #2 (**permalink**) 10-04-2009

Doesn't compute. The extra fuel has to be going somewhere or it wouldn't run. Perhaps its' teed into the vent line or somewhere that you don't expect. Maybe the yard can tell you.

captbillc · #3 (**permalink**) 10-04-2009

did you ask yanmar if a return line to the tank is needed on that engine?

TQA · #4 (**permalink**) 10-04-2009

The fuel return does not have to go back to the tank, just to the inlet side of the lift pump. Look for something coming from the top of the injector pump.

roline · #5 (**permalink**) 10-04-2009

I've seen several installations where the return line is plumbed back to the filter inlet. That way only the consumed amount is drawn from the tank. On fuel injected gas engines, this is not a good idea if a heat exchanger is not used. The fuel would heat up and require cooling. Don't know if the same issue holds true to diesel applications..

Barry33 · #6 (**permalink**) 10-05-2009

Thanks for the great input...there is really no return line, the outlet is literally plugged.

If I Tee in a return line to the fuel line (between the tank and Racor) do I need to worry about aerating the fuel?

Thanks again,
Barry

tommays · #7 (**permalink**) 10-05-2009

Well

It clearly works NOW and i would do a bunch of asking Before i did any changing

TQA · #8 (**permalink**) 10-05-2009

I agree with tommays on this. Look really hard for an alternative return line. All injector pumps have internal leakage. They are designed that way. This needs to be returned somewhere. Although it is possible to do this internally it is usually on an external line. This is diesel 101 stuff. Your installer should have known what he was doing. Hmmm OK he may not, but as it has run for some time without leaks then it is probably OK.

timebandit · #9 (**permalink**) 10-05-2009

As my old Pappy used to say---------

If it ain't broke, don't fix it!

nuffoftexas · #10 (**permalink**) 10-05-2009

Quote:

Originally Posted by Barry33

If I Tee in a return line to the fuel line (between the tank and Racor) do I need to worry about aerating the fuel?

I would have thought aeration was already going on with cavitation in the pump. Maybe not. You really should get a "release" of some sort on there though. I bet it will run better.