Looping the return?

[gwalker Senior Member Find all posts View Profile Close gwalker]

Why is the excess fuel returned to the tank and not just looped back and 'teed' into the IP supply line, before or after the filter. Are there advocates of doing this?

It seems to me that doing this would help get the fuel quickly up to operating temperature. What am I missing?
George

[Qwarla Senior Member Find all posts View Profile Close Qwarla]

Re: Looping the return?

Why is the excess fuel returned to the tank and not just looped back and 'teed' into the IP supply line, before or after the filter. Are there advocates of doing this?

It seems to me that doing this would help get the fuel quickly up to operating temperature. What am I missing?
George

Air bubble and more air bubbles. That's why.

Diesel systems of old were always an airtight system. Now with the return going back to the tank any small air leaks into the fuel pickup side are not a problem as the system continuly self bleeds.
Just recently I replaced my fuel lines and filters. Without bleeding the fuel system I started the engine to see how long it would run on just the fuel in the IP. It ran and ran as I watched the filter fill with fuel.
The other reason for the return going back to the tank is to provide cooling to the IP. After a long drive grab hold of the return line and see how hot it is.

[bruceT Senior Member Find all posts View Profile Close bruceT]

Re: Looping the return?

Looping the return is not really suited to high flow pumps. Some pumps are designed to supply MUCH more fuel than the injectors need, so the excess flow is returned to the tanks and continually circulated.

The benefits of returning to the tanks are:

*self priming
*warms the entire fuel system and tank
*helps prevent water accumulation in tank if water separating filters are employed
*helps keep "diesel bug" in check
*helps keep fuel cleaner (fuel continually passes through filters)
*air more easily purged

Looped returns are most common in low-flow pump systems.
It is popular with SVO systems for several reasons:
*simpler
*cheaper
*heat conservation at the "business end"
*helps prevent oxidation/polymerisation of tank veg oil (not an issue with dino)

Downside of looped returns:
*difficult to prime
*air can't easily bleed out
*no warming of tank from returned fuel
*water in tank not continously purged
*oil in tank doesn't receive "īn car" filtration

Some of the other guys can probably provide other + and - of each.

[gwalker Senior Member Find all posts View Profile Close gwalker]

Re: Looping the return?

Qwala and Bruce,
You have convinced me.
George

[Qwarla Senior Member Find all posts View Profile Close Qwarla]

Re: Looping the return?

Qwala and Bruce,
You have convinced me.
George

So now can I have a green square under my post count, please?

[Guest Close David]

Re: Looping the return?

There ya go, there's 3!
Thanks for all the good info you have posted.

The way the reputation system seems to work though, it will be about 5 years before I can give any to you again because it locks you out for god knows how long once you have given any to a person.

[bruceT Senior Member Find all posts View Profile Close bruceT]

Re: Looping the return?

Qwala and Bruce,
You have convinced me.
George

Oh, and don't forget to match your fuel filter to your pump (IP). What I mean is, if you have a high flow pump, you need a high flow filter and vice versa. If you install a low flow filter to a system with a high flow pump, you'll have fuel starvation issues.

Like oils, filters aint filters