Function of banjo bolt on top of 1984 300d fuel filter?
 

Can you tell me if the IP and injector return lines that meet at the banjo bolt on top of the fuel filter of a 1984 300d mix fuel with the supply side in the filter?

Thanks, Chuck

Anyone?

ak300dt,

In the top of the fuel filter, under the banjo bolt, there is a small hole to purge any air in the filter, and that is why you don't to have to leave the bolt loose to purge air from the filter. The overflow fuel is not mixed with fuel in the filter because the pressure inside the filter is higher than the pressure in the return fuel lines which have virtually no pressure. So even though the return lines are connected to the filter thru the air purge hole, no fuel will flow into the filter because of the pressure differential and any fuel or air in the return lines flows only back to the fuel tank.

In other words, the banjo bolt is a collection point that allows any air in the filter along with the overflow fuel from the IP and the injectors, to be returned only to the fuel tank.

P E H

Try advanced search, specify diesel discussion forum and keywords: banjo loop

Check the faq over at the SVO forum

Thanks PEH.

I'm installing a two tank wvo system with seperate supply and return lines and filters for diesel and wvo. I want to be sure there is no mixing of veggie with diesel since even a little veggie going to the diesel tank might result in a gelled diesel filter. I'm installing two 3 port valves to allow a few minute diesel purge of the IP and injectors that flushes back to the wvo tank.

With the filter side of the assembly under pressure and the return side not under pressure, I would assume the bleed hole always leaks some fuel into the return lines. That would be an avenue for wvo to make it into the diesel circuit. Make sense?

I was hoping to plumb the return fuel line from downstream of the banjo bolt to the 3 port valve, but it seems like I'll have to connect the IP and injector return together, run them through the valve then back to either the banjo bolt or to the wvo return side depending on whether the valve is energised or not.

Thanks for the advice! Chuck

ak300dt,

Yesit makes sense that some fuel is always going thru the bleed hole and back to the tank and that is what actually happens.

But I don't believe a small amount of WVO getting into the Diesel fuel will hurt anything. Any gelling in the fuel filter will melt when the underhood temperature exceeds 50*F and pass thru into the IP and engine and be burned.

P E H

Yes, don't worry about small amounts of VO getting into the main fuel system. It is much better to have a functioning air bleed - it's such a PITA to get air into the system. Ask me how I know.

Don't forget that the AK in ak300td stands for Alaska. He is in the realm of extreme veg oil conversions. I suspect he is lucky on some mornings to start with diesel. It's probably not as bad as all that.

An involved approach would be to use a separate filter for diesel and veg.

Thanks Twitchy!

As long as I remember to plug in for a couple of hours (and the power doesn't go out) I can get the old Benz to fire without much difficulty. Around here everyone plugs in and outlets are placed convienient to where cars park. Even though I'm becoming a diesel convert, I'll probably always keep a gasser around since even without any plug in time, you can force a gasser to turn over at -30*F. Good insurance...

I will be running totally seperate wvo and diesel fuel supply lines and return lines along with seperate filters controlled by two 3 port valves so after switching back to diesel I can flush the wvo from the IP and injectors back to the wvo tank with a little diesel fuel.

What do you all think of this diagram of my fuel return setup?

Any problem "Teeing" the IP and injector return together?

Any problem plugging the injector return port on the banjo bolt?

Thanks!

That looks like a good idea for separating the returns. Teeing the two returns (injectors/pump) is already done at the banjo connector, so doing it early upstream shouldn't be a problem. Keep in mind you may not be able to bleed the air out running on veggie by bypassing the three-way banjo. That's why I put a 3-way solenoid that switches between a looped return and returning to tank, so I can periodically bleed the air out. Yes, I can get VO in my main tank. I also feel looping the return is important in running SVO in colder climates, as tons of heat is lost running returned fuel back to a colder part of the fuel system.

Thanks for the review Old300D

I'm going to run insulated HIH for supply AND return to an insulated wvo tank. Even the wvo rubber lines between the filter and the IP will be insulated. It is a little over the top, but I want the system to work at any temperature (and besides I tend to do everything a little over the top :D ).

My wvo filter is the high point in the wvo supply and return line system, and it has a bleeder screw and primer pump. I hope to be able to purge air bubbles there if necessary...

Other thoughts?

Chuck

ak,
Have you seem my reply on the infopp forum?
How are you planning on heating your WVO filter?

You will find that WVO in the main tank (especially high melting point WVO) will cause poor starting, which will worsen at higher concentrations of WVO.
Delay the return line solenoid switch back to main tank by the length of time it takes to properly purge the IP.