Recirculating Return Line Fuel?

[Big Bart]

I have seen a trick. Drill the hole, use a long piece of stiff tie wire. Put it in the hole you drilled and up through the fill tube/hole. Put your nut on the wire, then a rubber washer, and a bolt or stick to make it so the nut and washer can’t come off. Slide the hose adapter on the opposite side outside the tank. Pull the wire from the outside where you drilled the hole. So the nut pulls inside and up to the hole. Then slide the adapter into the hole and pull the wire. Turn the hose adapter till it threads. The only challenge is you cannot do much about the nut twisting. However many times as you know if you pull out the bolt and turn the nut will grab the other side and you can tighten it. I said add a rubber washer so the nut catches and drags and thus is more likely to tighten. You may want a rubber washer outside to seal.

If not, you can tig weld a female pipe fitting over the hole and go buy a fitting that is male pipe to male hose at Home Depot or Ace. Then screw it in to the pipe you welded on with diesel rated pipe dope or teflon tape.

 

[NeverHave-I-Ether]

I have seen a trick. Drill the hole, use a long piece of stiff tie wire. Put it in the hole you drilled and up through the fill tube/hole. Put your nut on the wire, then a rubber washer, and a bolt or stick to make it so the nut and washer can’t come off. Slide the hose adapter on the opposite side outside the tank. Pull the wire from the outside where you drilled the hole. So the nut pulls inside and up to the hole. Then slide the adapter into the hole and pull the wire. Turn the hose adapter till it threads. The only challenge is you cannot do much about the nut twisting. However many times as you know if you pull out the bolt and turn the nut will grab the other side and you can tighten it. I said add a rubber washer so the nut catches and drags and thus is more likely to tighten. You may want a rubber washer outside to seal.

If not, you can tig weld a female pipe fitting over the hole and go buy a fitting that is male pipe to male hose at Home Depot or Ace. Then screw it in to the pipe you welded on with diesel rated pipe dope or teflon tape.

Good idea, I'll see if I can make this work. I have two metal washers that came with the bard valve. The nut is super thin, about 1/8-3/16, not super impressed with it. A rubber valve may grip it more eh?

 

[The_Josh_Bear]

Wouldn't the obvious placement be right next to the fill hole so your fingers can hold the nut on and all this is easy?

 

[NeverHave-I-Ether]

Wouldn't the obvious placement be right next to the fill hole so your fingers can hold the nut on and all this is easy?

I thought about it, but I don't want fuel line running all the way up and over on the top of the aux tank. Just vulnerable for something getting thrown on it up top.

 

[NeverHave-I-Ether]

Alright installing it today or tomorrow with the trick @Big Bart mentioned. Thanks for the advice btw. I guess I'll install a check valve in this return line, thinking about how the OEM return line has a duckbill and I can't fit one on there so going with a check valve to hopefully mitigate fuel backflowing towards the IP from the auxiliary tank.

 

[NeverHave-I-Ether]

Got the valve on. Took about an hour, used a metal coat hanger I bent and slid everything down it. Used a rubber gasket on the inside and a metal and rubber gasket on the outside. Worst case, I can weld the washer and valve on when the rubber rots away. Win win situation. Used a gasket sealer to glue it all up in case it doesn't seal all the way. Don't look pretty, but who cares? It's not visible.

 

[Big Bart]

Glad the trick worked. Great brain tease, ask folks how you did it? I think you are good to go!

 

[NeverHave-I-Ether]

System is running and works well, one concern I have is the return line on the fuel tank. I'm worried the weight of the diesel would backflow the return line. With the truck idling it's just a dribble coming from the return line, is it possible to put a check valve on it?

Thanks,
Never-Have-I-Ether

 

[IDIBRONCO]

You could put a check valve on it, but you want to be careful. There's very little pressure in the return system. If you have too much pressure, it will cause the injector pump to stop working for reasons that I can't begin to explain. A check valve may give you too much pressure. I don't know for sure, but I did want you to be aware of the possibility.

 

[Jesus Freak]

Maybe a 90° drill? I'm digging this thread, I do the WMO thing too. I have a parts bronco that I robbed the tank from and use it as my wmo tank and I keep diesel in the front tank but if you switch tanks a couple of times your "clean" diesel is pretty dirty.

 

[Jesus Freak]

Need to return the fuel to the tank. Even if the system is "completely sealed", air will still find a way in eventually, and a circulation system like you have will never remove the air from the system. Plus, with your design, I feel filter changes would be a real biotch.

Something that you've overlooked, is that the bypassed fuel is also a cooling feature for the injection pump. With it constantly circulating like that, it would heat up a lot more then it would in a normal return style system, which would be detrimental to pump life.

So on the cooling aspect of the fuel to the IP, how big of a concern is that? Would it have to be an extreme "worse case scenario" to have a problem? Or would it just be a problem?

 

[IDIBRONCO]

I think that it would be a problem most of the time. If you only ran the engine for a short time, I don't think that the IP would heat up very much. The longer/harder you used the engine, the hotter the IP would get. A fairly new IP may be able to handle the heat better, but one with some wear in it would probably suffer. The hot start issue would be magnified. I don't claim to know what happens within an IP, but I'll bet that you could even get it hot enough to cause serious damage. Maybe even ruin it.

 

[NeverHave-I-Ether]

The amount of fuel though from the return line isn't much though in comparison to the amount getting pulled from the tank. I would think it would dissipate the heat by time it gets back to the IP.....

Never-Have-I-Ether

 

[Jesus Freak]

I really appreciate both replies, but you two are all over the map, both ends of the spectrum even! So I tell you what I'm going to do; I'm going to "t" it in and see what happens. I'm about to lay up my CC '86 for some much needed "ministry", not the least of which is an IP rebuild/replacement, and start driving my tow truck as my driver. So I can risk killing it in the interim, to have something to start a new discussion with. And then we'll know.....and knowing is half the battle.

 

[Booyah45828]

So on the cooling aspect of the fuel to the IP, how big of a concern is that? Would it have to be an extreme "worse case scenario" to have a problem? Or would it just be a problem?

Not huge. But the pump will suffer longevity issues over time. Cold fuel is a better lubricant then hot fuel, and the fuel temp will increase with time.

The bigger issue with this is not purging the air from the system. I screwed up my check valve placement on the bus(long story) and basically deadheaded the return system. Made the thing super hard to start, and a poor runner when it was running. The only reason it did run was thanks to the factory air bleed, as it allowed the return fuel to flow back into the supply, which then had the return and supply system both at 5 psi. It still ran, just not well, even with the timing corrected/adjusted several times (5-7-9-12°). Another thing I noticed is it would noticeably run worse the longer(1-3 hours) I ran it, which leads me to believe the injection pump was heat soaking because of the lack of fuel return.

FWIW, when I was troubleshooting the system, I capped the air bleed off and installed a pressure gauge on the return hose to see what return system pressure was. When I did that, the pressure shot up quickly until the engine shut off(I don't remember the exact psi). I then used a tee in that return/air bleed line and discovered my system was at 5 psi, and would go up higher based off of engine rpm, simply because it was flowing return fuel back through the air bleed.

After some more investigating, I realized my check valves were on the return line, not the pressure like I wanted, and because of their orientation, they basically deadheaded the return system. Put them where they were supposed to be, readjusted the timing back to 6.5, and it was a completely different engine.