[TravisT]

FordNut74 and everybody else,

I'm taking out everything in my 1997 except the fuel tanks. I'm going to put in an electric diesel system and stand alone electric veggie system. I now have a greasel kit so there are some parts that I will be reusing such as the diverter.

I was looking at a diagram of the FN74 settup and I will have something in common with that system. That is a looped return and VERY short fuel lines to the heads. What happens when air gets into the line? I would imagine that you wouldn't know it until the injectors starve quickly and completely.

How do you deal with this on your system?

I was wondering if there could be a ball valve that is normally open until it senses back pressure (pump on with looped return). Once an air pocket reaches the ball valve there MAY be a drop in pressure, opening the ball valve to the normally opened possition and diverting the bubble into a return line back to the tank. Honestly I think the air pocket would contain the same pressure as the fuel determined by teh regulator.

But, am I on to something here or do you have another idea?

Any suggestions would be greatly appreciated.

 

[frashdog]

[ QUOTE ]
That is a looped return and VERY short fuel lines to the heads. What happens when air gets into the line? I would imagine that you wouldn't know it until the injectors starve quickly and completely.

[/ QUOTE ] simply set up your purge solenoid to the vo tank.

Besides purging the vo when switching over to diesel, you can purge your rails of air. The solenoid basically bypasses the regulator and returns to the tank. If you're sending the regulated return infront of the pump like some do then you should send a seperate line back to the tank for the purge solenoid.

Steve

 

[TravisT]

Where can I find one of these solenoids? Sorry for the long post but I have to get this right.

Looking at my diagram I think I would be in trouble if air ever got into the return loop. There is such a short line between the regulator and the heads that if air were to pass, the engine would have no fuel so quickly that there would be no way to detect it before half the motor was not firing, and then even if a purge solenoid were used, the line and heads would be full of air and there would be no way to get rid of it.

My idea was to use a Pollak diverter that has two imputs and one output for supply and return lines. This would be placed imediately after the regulators on top of the valley. When set on either mode the fuel would pass through the diverter and straight into the heads. Diesel and WVO will have their own pumps and the pump would be turned off on the system that is not being used.

Bottom line is, I think my system will load the heads with air and it looks like the FN74 one will not do that because of the dual system pumps running at the same time. When air gets in the veggie line, the diesel will have more psi and the ball valve will send diesel without a hitch to the heads. Seems that way anyway.

Does this make any sense to anybody. Do you think I can still use the diverter idea rather than ball valves and be safe?

 

[frashdog]

No problem, pm me if you want. Even though there is little discussion going on here, there are always people getting their questions answered by reading others.

I first bought the pollack valves but decided against them due to their ratings for temps (180?)and pressure (65psi) being close if not just over my needs. YES, some people are getting away with using them ,but I wouldn't. The temp would be your concern and being that the solenoids at the hottest location I would not risk it. Here is where I got mine.

[ QUOTE ]
Looking at my diagram I think I would be in trouble if air ever got into the return loop.

[/ QUOTE ] Where do you think you'd get air? Besides initial setup, or changing a filter if you had one after the pump I do not see where you'd get air. To get air out/ prime system after setup/filter change just start turn the pump on with the purge open. A well designed system would have a gravity fed pump.

Steve

 

[TravisT]

Thanks Frashdog.

I looked closer at the FN74 and it trumps my design in all area that I though I would have trouble. I scrapped the drawing and I'm not going to use the pollak. I'm using it now with the greasel setup with no problems though. But I am using it at a cool point in the lines.

Air? With my current stock 1997 lift pump being right at the heads, the whole system is under a vaccum. All lines and fittings see as much as -30psi (according to my vaccum guage). I use the guage to measure resistance on the main filter to determine clogs. At that amount of vaccum I am sucking in air from somewhere and it gets trapped in the return loop. I just switch to diesel and it blows it out, but that will all be ripped out and replaced with this new system.

I have about 70,000 miles on the modified greasel system and it's relatively worry free, but with the FN74 I can use veggie more frequently with quicker purges and I'm puting elecrtic heaters on so that I can use veggie almost imediately after start up.

 

[frashdog]

[ QUOTE ]
All lines and fittings see as much as -30psi (according to my vaccum guage).

[/ QUOTE ] wow. not sure what the pump you're using is rated for, but for my aeromotive, too much vacume will be the death of it. The aeromotive can push like 90psi, vacume can cause cavitation.

[ QUOTE ]
I'm puting elecrtic heaters on so that I can use veggie almost imediately after start up.

[/ QUOTE ] like these ones? I might use one of those later. If I wanted a bit more heat for my set up I also would use one of these of course they are a bit cheaper if you buy them being sold for the original purpose they were designed for.