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Old 09-02-2013, 07:43 PM
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Join Date: Jan 2012
Posts: 22
Old Frybrid kit - need help PLZ!!

Hello -

A friend started the WVO conversion on my 1979 Merc 300td years ago. We were using a Frybrid kit purchased 12 years ago. He decided to stray from the original plans to have a looped return. I'm finally getting back to the project and spent a long time wiring up the microprocessor. I'm now getting into what I thought would be a simple task of rerouting a few hoses but the diagram he drew is illegible and I'm mystified. I was tempted to just go back to the original frybrid plan but have discovered that of course there is only one hose in hose going back to the in tank heat exchanger. The other hose is just running coolant.

I altered and attached the original Frybrid diagram to show what I currently have going on under my hood. I guess I'm committed to the looped return as I am in a very remote location with limited access to additional parts and I really don't want to pull out that coolant hose running back to the VO tank.

Thanks in advance for any advice.


Fuel schematic .pdf

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Old 09-02-2013, 08:53 PM
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Join Date: Jan 2012
Posts: 22
Revised diagram - any thoughts?

I think this looks right but would really like some feedback from smart people. And will this effect the way the microprocessor works?

Attached Files
File Type: pdf Return loop diagram.pdf (272.4 KB, 94 views)
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Old 09-03-2013, 05:09 PM
dieseldan44's Avatar
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Join Date: Nov 2006
Location: Boston
Posts: 2,040
Im pretty sure Frybrid is less than 12 years old :-)

I can help you out here. your setup is similar in plumbing to that of a Greasecar system - Return line is fed back into the feed line. The advantage is that this keeps the WVO hotter, the downside is that purge times are much longer (30-60 seconds instead of 7-14) and some WVO gets into your diesel tank.

At some point the Frybrid system included an option for a third valve (this is what I have). It gives you the best of both worlds.

Can you send a pic of the black box microcontroller that you have?

Also, the Frybrid manuals are here
Frybrid Vegetable Oil Fuel Systems -- Manuals

Hope this helps to start...

'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car
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Old 09-04-2013, 04:27 PM
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Join Date: Sep 2003
Location: Ft Lauderdale FL
Posts: 204
Looped return

You should return to the tank. I am betting that the microprocessor will function better as originally designed. If you have the fuel line for the return just zip tie it to the return coolant line. Unless you are in Alaska it will work fine if you are in Alaska wrap it with insulation. This HOH (Hose On Hose) works perfectly and especially if it is just the return line.

If you really want to loop it. Two valves work fine. I could not see your diagrams. Sorry.
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Old 09-09-2013, 07:56 AM
oldsinner111's Avatar
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Join Date: Nov 2008
Location: bristol,tn
Posts: 5,716
I used a FM100 fuel manager filter I took the cigar hose and mounted a tee in it,I then used a short hose sections and mounted a ball valve to the line to the return .Then mounted the feed line back into the filter to refilter the hot oil.If I needed to purge lines I open the ball valve to the return line I also ran a boost pump to bleed lines in a few seconds.Then when running a loop I closed the ball valve.I bought my ball valve at lowes and reduced to 7/16 hose.
Running in loop I could mantain 225 degrees as I used injection line heaters in addition to my FPHE.Returning fuel to tank can because of heat make more moisture in the oil.I heated the fuel not the tank

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