Why bother with a return valve? What do you think?

[BobTheRussian]

I have an issue with my return valve.

But why do we bother having them anyway? Whats wrong with constant purging?

Why not just have a constantly looping system going back in to the T and towards the IP?

I never turn it off so the return fuel goes back to the diesel tank anyway...

I was thinking of just skipping it and plugging the line that returns to the diesel tank...

Could this cause any issues?

Maybe pressure issues in the diesel tank?

What do you think??? Am I missing something here?

Cheers

[BobTheRussian]

Well I guess I'll just do it. If anything goes dramatically wrong I'll let all you grease monkeys know!

Happy ho ho! Tis the season to drift ones Delica! :)

[Mr. Flibble]

I am not totally sure the context her, but you have a return to return extra fuel to the tank. This also helps warm the fuel in the tank, helpful on cold days.

The other reason for the return is that the pump pulls up more than the engine needs, this way you don't get starved for fuel when you put your foot down. The bonus is that the extra goes back with some heat.

I don't know your setup, but I think stopping the return would cause a buildup of pressure, probably a leak, or over fueling and possibly run on.

[BobTheRussian]

i have a two tank setup, two valves - supply and return

return positive = veg/diesel goes from the return to a 'T' connection that goes back to the injection pump.

return negative = veg (hopefully not)/diesel goes through the valve and back to the diesel tank...

I can draw it out for you but I think a lot of people have this kind of setup.

The return valve positive is for purging veg out of the system when shutting the engine down and when your running veg so it doesnt contaminate the diesel tank... but I really dont think it is necessary at all unless for some reason you had to send fuel back to your diesel tank. Comprende? It would just be like having the valve on + all the time...

Thanks for the reply!

[kayacraig]

heat in the loop generated from high injection pressures might be a problem for DSL lubricity. also apparently bubbles get out of the loop when opening the loop for DSL return. my sailboats volvo has a stock looped return. if you are always on veg for long trips, no worries... except for trapped mystery bubbles....

shred some pow for me out there.
craig

[kayacraig]

I assume you know the benefits of V/O RTN looping . all that heat needs to stay in the 'critical' injection loop, less v/o refiltering (pump strain), etc. comox ben spoke about injection pressure bypassing the injectors and power loss in a looped setup??????? I couldn't comprehend that theory. what is this "run on" mentioned earlier. not a run away engine, hopefully.

[kayacraig]

experimental DATA;
left the rig idling on veg with the 32amp mega vegtherm and injection line heaters on. return fuelling immersed temp probe read 110F. usually reads 100F on highway speed fuel flow. the turkey probe read temps of 280F(yikes?) inside of my insulated megatherm placed before IP. so seems like a lot of heat is lost on the way back.

QUESTION:
do the experts think I need that vegsensor to turn my therm off and on due to overheating. the therm is supposed to be self limiting? but is that just the current draw , not necessarily correlating to fuel temperature?.

Another pondering:
is the nichrome wire injector line heaters output equal alone its length? the test light brightness varies along its length, dimming towards ground point.

250 hours sailing the grease sea, so far so good.

[delicat]

Hello

To the OP, you have a two tank system right? From what you're saying you'd eliminate all and any returns to either tanks and simply loop the return back into the fuel path prior to the IP?

I see at least one big problem...

Any trapped air won't have a chance to escape and soon enough your engine will stall. The reason for the 2 valves is so your diesel can be returned into the diesel tank along with any air bubbles. Your tank is vented so air escape through the tank.

I'm sure there are other issues but that's the main one I can think of. You probably think then why isn't it an issue on veggie with its looped return? Not sure, might have something with the switching between veggie and diesel or the diesel itself. On my truck if I forget it on purge (diesel supply, looped return) my truck will die after a while.

As for the following topic with heat and idling, keep it simple and don't idle on veggie. Bad idea! Try it and you'll notice your van will start to smoke at the exhaust and stink. You can install a veg sensor on your injector line to control your Vegtherm or have it on a on/off switch. I don't use mine much in the summer and in the winter mostly for the first 5km or so simply cause my alternator can't keep up and by then my oil is hot enough without it...

Cheers
Mr. D