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Discussion Starter #1 (Edited)
I’m in the middle of converting my old gas 5.7 fuel system for my 6BT swap and had a few questions. Filler neck, hoses, cap, etc. are all original gas components. The tank is super clean inside and I’ve replaced the in-tank pump with a length of submersible fuel hose. Original supply and return lines on the chassis have been cleaned and adapted to 6BT lift pump and return hard line.
  • What to do with the evap/vent outlet on the tank? Just cap it off?
  • What to do with the two in-tank wires for the deleted pump?
  • My 6BT has a fresh lift pump, IP, and injectors and I’m wanting some reassurance that a 1998 gmt400 gas tank won’t create any problems when used for diesel. Internal coatings or anything like that?
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I used a GMT400 tank without problems until I knocked a hole in it then I bought a new GMT400 tank. I believe they use the same tank for both diesel and gasoline but do your own research. Make sure the hose you put inside the tank is the proper type. Using the wrong type will cause you grief. I think I found it on amazon here Amazon.com: Gates 27097 Submersible Fuel Line Hose: Automotive . I had a 1999 GMT400 2500. I removed the inline fuel filter on the frame rail, removed the pump then added the proper inlet hose described above. I can't recall everything I capped off, but I made videos of my build so you should be able to find one that I talked about it.
 
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You can leave all the EVAP hooked up at the tank. As for the wires just make sure the power wire is disconnected outside the tank and you can just cut the wires short inside the tank removing the FP connector. don't cut the sending unit wire or the ground wire as you need those for your fuel gauge. As for the filler neck you will want to drill out the hole so that it fits the larger Diesel fill spouts or buy a filler neck from a diesel model rig. Don't forget to get a Green or Yellow Diesel Fuel cap.
 

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Discussion Starter #4
You can leave all the EVAP hooked up at the tank. As for the wires just make sure the power wire is disconnected outside the tank and you can just cut the wires short inside the tank removing the FP connector. don't cut the sending unit wire or the ground wire as you need those for your fuel gauge. As for the filler neck you will want to drill out the hole so that it fits the larger Diesel fill spouts or buy a filler neck from a diesel model rig. Don't forget to get a Green or Yellow Diesel Fuel cap.
In an effort to tidy up the chassis and engine bay I removed all the EVAP components from the truck (line from fuel tank to engine bay, charcoal canister, related engine bay wiring). I didn't think the EVAP system was needed for the diesels. There was a single wire and sensor/plug on the outside of the charcoal canister that has been completely removed from the engine bay harness though. I that going to be a problem? Everything else I can reinstall if really necessary.
 

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The EVAP system is not needed on the diesel you just need to make sure that the fuel tank has some form of vent with a rollover valve which is usually in the evap system/canisters. If you have removed that all you need to do is verify that the tank has a vent so it won't build pressure an make sure the other extra evap lines are plugged.
 

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Discussion Starter #6
The EVAP system is not needed on the diesel you just need to make sure that the fuel tank has some form of vent with a rollover valve which is usually in the evap system/canisters. If you have removed that all you need to do is verify that the tank has a vent so it won't build pressure an make sure the other extra evap lines are plugged.
In the picture above, the black/brown contraption on the inside of the tank's EVAP outlet appears to be a valve of some sort? Though I suppose I could run a breather hose up into the bedside with rollover valve on it?

The harness leading to the fuel tank has the following wires: black, grey, purple, and black w/ white stripe. Do you happen to know which can be disconnected to cut power to the pump?
 

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You would want to verify with a wiring diagram but the I believe the Grey wire is the fuel pump power. Purple will be the sending unit and the other two black wires will be grounds. The valve in the top of the sending unit will release fuel vapor when pressure builds in the tank it is not a roll over valve.
 

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Run the vent hose up as high as you can get it, then turn it pointed down and put a plastic bodied, old school fuel filter in the end of the hose.

Search roll-over valve as there is one that has been used in a bunch of various conversions, but I'm blanking on the application.
 

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Discussion Starter #9
Run the vent hose up as high as you can get it, then turn it pointed down and put a plastic bodied, old school fuel filter in the end of the hose.

Search roll-over valve as there is one that has been used in a bunch of various conversions, but I'm blanking on the application.
I ended up buying this vent : Tanks Inc. Remote Rollover Vent Valves VVR

I ran the hose up alongside the fill tube and piggy backed a hose strap onto the backside of one of the filler neck mounting bolts. The vent sits a few inches higher than the gas cap inside the bedside.
 
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