high diesel temp at IP concerns... return loop people - PeachParts Mercedes-Benz Forum

Jimmy Joe · #1 05-12-2004, 08:37 PM

Hey veggy minded people,
Have you been following this thread:
http://biodiesel.infopop.cc/eve/ubb.x?q=Y&a=tpc&s=447609751&f=159605551&m=740601947&p=3
Tony has a great idea for looping via swapping banjo bolts, with diagram.
But this would mean the diesel would be looped too, and never returned to the tank for cooling.
Is this dangerous to send hot diesel to the IP?

coachgeo · #2 05-12-2004, 11:13 PM

Now your caught up with me Jimmy. This is one of my concerns too.

Add another 3way valve in the loop from the IP Unused Fuel and where you loop it too. Set the switch to be *unpowered at the diesel setting. On this setting have the hose off of the switch "T" to the return line. You will still have the Injector overflow going into the IP (assuming you use Tony's arrangement) but thats minimal. On the switched side have the oil set for looped return as per Tony's Diagrahm.

*all switches should be set to be unpowered at diesel use incase you have an electrical problem.

Jimmy Joe · #3 05-12-2004, 11:34 PM

Great idea Coach!
It is all coming together

I do wonder how much fuel will be looping through the injector overflow...though clearly from the size of the lines the majority of the problem will be tackled.

Yes! I am soo close!

TonyFromWestOz · #4 05-13-2004, 08:43 AM

If you want a switched loop, here is one thought on that option.

Jimmy Joe · #5 05-13-2004, 01:12 PM

Hey, shouldn't the first solenoid (and the filters) be before the lift pump?

coachgeo · #6 05-13-2004, 01:38 PM

Quote:

Originally posted by Jimmy Joe
Hey, shouldn't the first solenoid (and the filters) be before the lift pump?

sitting here on break from teaching reading this and my memory says that on the diesel side the lift pump (along with hand primer) is low on the block. The fuel line then travels upward to the filter etc. just like Tony's drawing.

You can't put the solinoid before that mechanical lift pump because you dont want this pump under load without any fuel in it. Fuel is probably part of it's lubrication and/or cooling.

Jimmy Joe · #7 05-13-2004, 02:16 PM

coachgeo said :"You can't put the solinoid before that mechanical lift pump because you dont want this pump under load without any fuel in it. Fuel is probably part of it's lubrication and/or cooling."

It seems to me, though, that there must be a switch before, or else you need two pumps. And the switch is either on diesel or veggy, never unlubricated.

coachgeo · #8 05-14-2004, 03:22 AM

Quote:

Originally posted by Jimmy Joe
coachgeo said :"You can't put the solinoid before that mechanical lift pump because you dont want this pump under load without any fuel in it. Fuel is probably part of it's lubrication and/or cooling."

It seems to me, though, that there must be a switch before, or else you need two pumps. And the switch is either on diesel or veggy, never unlubricated.

There is two pumps in this drawing from Tony. one is the OEM and the other is I assume to be a 12v.

Jimmy Joe · #9 05-14-2004, 04:09 AM

Ahhh, two pumps. The plot thickens.

Just when I think I'm getting close, there is more to think about...

TonyFromWestOz · #10 05-14-2004, 07:29 AM

Coachgeo,
Thanks for the comments and explanations of my diagram.
Jimmy Joe,
The diesel lift pump in this case is a mechanical fuel pump. As I have not dismantled one of these, I can only guess that it is a diaphragm pump, like the old gas cars had (before fuel injection). This is self regulating, and has a limit to the pressure it can provide. If I am wrong, someone here will enlighten us all, I am sure.
If I were to replace this lift pump with another electric one, and they both had non-return valves as part of their construction (like the Facit fuel pumps) I could simply switch the power to the lift pumps, to pump the fuel of choiuce to the IP, and Tee the outlet from the two fuel filters together at the IP inlet and avoid the need for the fuel selection solenoid.

I currently have 2 solenoid valves and one electric lift pump, so I will not be going down that path.

coachgeo · #11 05-14-2004, 10:24 AM

Tony,

Thinking of your above comments on having two 12v pumps. If Im right I think the cost of two faucet lift pumps is the same as one switch over valve, (unless its junkyard found) . Least I think I remember reading 60 bucks was the cost of that valve. hmmmm? Just thought I would throw that out to add to the confusion LOL.

oh.. and thanks for the info about the faucet having a non return feature. Good to know stuff.

Jimmy Joe · #12 05-14-2004, 10:05 PM

I hear you all, but I still like the idea of the stock pump for both lines. That way, the stock pump is getting lubed at all times.
And I don't have another switch to throw at veggy time.
Before I proceed, though, I will have to get a definitive reassurance that for sure the stock pump does regulate itself, and won't over pressurize a looped return.

TonyFromWestOz · #13 05-15-2004, 09:40 AM

Quote:

Originally posted by Jimmy Joe
I hear you all, but I still like the idea of the stock pump for both lines. That way, the stock pump is getting lubed at all times.
And I don't have another switch to throw at veggy time.
Before I proceed, though, I will have to get a definitive reassurance that for sure the stock pump does regulate itself, and won't over pressurize a looped return.

Jimmy Joe,
The switch which changes over between the fuel tanks would be used to switch the electric fuel pumps (you can get an electrical changeover switch) and the return line solenoid too.
If you are interested, I can draw a circuit diagram of how to hook it up, and post the diagram here.
BTW, in my diagram, the stock lift pump would be pumping fuel all of the time, with the only flow being what the bleed line from the fuel filter allows thru.
If an electric lift pump were fitted to replace it, the stock pump could be removed and a blanking plate fitted.

Jimmy Joe · #14 05-15-2004, 04:12 PM

Tony, you have been such a big help, I can't thank you enough.
I would like to know how you draw those diagrams so nicely, and I would like to make one with the fuel filters before the lift pump. I am also wondering how to effectively link the IP overflow with the injector overflow in your idea of looped and return.
I still think just the lift pump is what I want...
Maybe I am just stubborn...