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DieselAutoPower.com
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Discussion Starter #1
I'm having a problem with my fuel system. After I shut down the truck from using my secondary fuel system. I believe the tank located up in the toolbox is draining into my main tank via the return line. I verified it's draining by removing the prefilter before the pump on my secondary fuel system. I was able to watch the fuel level drain down in the clear filter. So much so, that fuel leaks out of the main tank because of overflow. It's also being a pain to crank at times on either fuel system. Sounds to me like the overflow valve is shot. Anyone have any suggestions?
 

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I would start with the Overflow valve and then go from there. good luck
 

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Fuel 101:
Overflow valve - A banjo bolt fitting on VP44 for controlling fuel return.
Rollover valve - A valve in top of fuel tank designed to keep fuel in tank after rollover. Does not necessarily block air/fuel when upright. Very possible leak at fuel module.
Poor engineering to have siphon feed from aux tank to main tank. Need vavle to control at least. Recomend dual valve for feed and return control. Guess you are running some exoctic fuel in aux tank and may be causing starting issues. JMHO
 

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DieselAutoPower.com
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Discussion Starter #4
Worked fine for months with two tank setup. Now it started doing this. I'm going to replace the overflow valve first and see what happens. It's set to hold fuel in up until 14psi from the VP44. Rollover valve doesn't even come into play in all of this.
 

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DieselAutoPower.com
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Discussion Starter #5
I believe the valve is the problem. I pulled it today and sat it upright on the battery. Poured a little ATF into the inlet of the bolt, sure enough it leaked down. ATF is thicker than #2 or JetA so that's likely how things keep on running past the main tank. I need to find a new one of those valves.

I'm also replacing my splitter valve on the return, it's also leaking as well. I've got a nice billet valve to put in place now. Also have some spring loaded check valves for the fuel intake side to the pump.
 

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Did you notice the small orfice in the side of overflow valve??
 

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IF the Fuel cap is faulty it will allow the tool box fuel tank to overfill the main tank IF its gravity fed, I had a silimar set up in my chev,
 

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DieselAutoPower.com
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Discussion Starter #8
Did you notice the small orfice in the side of overflow valve??
I recalled a small hole on the side. But didn't realize it went all the way through. I was reading up, and the relief is set to unload over 10psi?
 

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Mopar1973Man.Com
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