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Discussion Starter · #41 · (Edited)
Still pondering the in tank fuel pump build. Just because it is fun to fabricate things. I have been thinking about how to baffle the fuel tank to prevent starvation with EFI and “Spirited Driving”. So, I am building a 4”x 7” well for the fuel pump to sit in along with a wet sock, instead of cutting open the tank and adding baffles.

Of course I will design a leaky bottom in my box for fuel to enter in and exit slowly. My logic on the size is make it more on the scale of a super large carburetor bowl than the scale of a gas tank.

Today I picked up a 2” x 36” stick of 1/8 aluminum from Home Depot, cut it to roughly 4” x 7” pieces, squared them up with an end mill, deburred and cleaned then up with acetone to get ready for some TIG welding fun.
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the volume will be 4” x 7” x 4” deep = 112 cubic inches = 1.8 liters. That is just shy of a half a gallon. So, even if a lot sloshes out, that will still give me close to a liter which I hope will be more than enough for the fuel pump to catch up. And certainly better than no baffling at all.

Below you can see the size of the layout. It is design to go down inside the hole cut for the in tank fuel pump. Now that I am thinking by about it, I may need to trim down the width a bit to do that it fits through the hole I will drill in the top of the gas tank with my 4” holes saw.
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Usually I would just get the proper width aluminum to match the depth of the fuel pump well. But the metal store is far away, I am busy, and gas is expensive. So, in this case I am just going to make several courses and use it for TIG welding practice.

After welding on old intake manifolds, it is going to be a delight to weld some nice clean metal.
 

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Discussion Starter · #42 · (Edited)
I now see the error of my ways and realize that my design would not fit through the opening I am trying to cut. So, I built a Prototype with cardboard before I start TIG welding aluminum.
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the picture above is a box that fits through the opening. It is 3”wide x 2.5” tall and can be 7” or even longer. That is about 52 cubic inches or 0.85l. That is headed back in the design direction of the tanks inc in tank fuel pump module.

I could make the volume larger by making longer.

The other option would be to make a taller chamber that is either round (a pipe) or perhaps octangular. A tube of 3.5 inch diameter 8 inches (Opel gas tank is roughly 10” tall) would be roughly 77 cubic inches which is over 1.2 liters.

I’ll sleep on it and hopefully have a clear direction when I wake, so I can weld on the cool part of the morning.

Let me know if I am over thinking it, or if I really do need some sort of mechanism to combat fuel pump starvation.
 

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Discussion Starter · #43 · (Edited)
So, the pump tray is complete. Except for drilling some fuel entry holes and attaching it to the riser angle aluminum that will attach it to the tank lid.

importantly, it fits through the mounting ring that will go inside the tank to receive the mounting bolts.
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there were moments that the welding went so well and so fun. Definitely some of my best welds ever and quite a rewarding new hobby / developing skill.
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Discussion Starter · #44 · (Edited)
Does anyone know how big the holes should be in the fuel tray? I am thinking maybe a 1/2” hole x 2 (1 on each side).

I am thinking it would be better to put them in the center of the narrow sides. To slow down the emptying when Cornering.

I may start smaller and test how long it takes to drain when filled with water. I believe gasoline is less viscous than water so it will drain even faster.

….

On second thought, after gathering a bit of data, I don’t think I am going to drill any holes. I have a seam in the middle of the bottom that I did not weld. When filled with water, it took about 7 seconds to drain. I don’t think I want any more flow than that and like the entrance / exit being on the bottom plate.
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As long as fuel can get between the bottom of the tank and plate, I should be fine. When placed flat on the bottom of my stainless steel sink, the reservoir filled to the top with water takes about 30 seconds to drain.

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When I welded the vertical bracket to the fuel tray, I ended up with some melted points on the bottom of the tray. I sanded those down and left a little bit as a small spacer. Now the tray drains in about 15 seconds. That seems about right to me. If All works as planned, Hopefully I never experience fuel starvation issues.
 

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Discussion Starter · #45 · (Edited)
In terms of wires passing through the aluminum lid, I was thinking about using a terminal screw. I am trying to get rid of all of the wire nuts and mid wire connectors in my car. I figured this would be a nice clean look. After some front porch time today, I figured out how to make the metal screw electrically insulated from the lid with gasoline resistant seals.

The plan is to seal the screw head and interfaces with nitrile o-Ring’s plus maybdpermatex orange fuel resistant sealer.

In the picture below, you can see the stack. There is a number 10 screw head, then an o-ring under the head, then a 3D printed sleeve, then another o-ring, then aluminum. The stack would then repeat itself on the other side. And of course there would be a nut on the end of the bolt.
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I printed the prototype sleeve with ABS (not gasoline and alcohol resistant). But have a rollo of Nylon filament coming they I will use to print these Components. The nylon filament is supposed to be chemical (gasoline and alcohol) resistant.

I guess another way to so it would be to have just 1 o-ring per side or 1 o-ring total. To do that my plastic inner sleeve would have to get rid of I’m the collars and let the o-ring play the role of sealing and electrical insulation.
 

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In terms of wires passing through the aluminum lid, I was thinking about using a terminal screw.
I’ve built a few fuel pass-thru’s with wires and I’ve had pretty good luck just drilling a hole the same size as the wire being used. Slight countersink on both sides of the metal. Feed the wire thru, then use gasoline-resistant epoxy on both sides, filling the countersunk areas. No leaks.
 
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Discussion Starter · #48 · (Edited)
Here is the Walbro / TI (made in USA) fuel pump sitting in the fuel reservoir tray. The pump came with several in tank filters and a nice thick insulating sleeve. Hopefully this will help dampen vibration combined with it being submerged. I used a pair of stainless hose clamps to mount attached it to the vertical riser.
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Cost of the project so far is the $80 for the fuel pump kit. And $12 for the 2” x 1/8” aluminum from Home Depot. But the cost of the fittings and submersible fuel line will drive it over $100.

Next I need to get some submersible fuel line for both the pump output supply and return (to drop it low in the tank).
And I need to commit to an approach for sealing the wires as they pass through the cast aluminum upper plate.

and once I get the tank out of the car and cut the mounting hole, I’ll be able to do the final trim on the vertical support member.
 

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Discussion Starter · #49 ·
Tosay I cut a notch out of the in tank fuel pump module inner mounting ring so that I can slip it inside the 4” diameter hole I’ll cut in the Opel GT fuel tank.
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And drilled, tapped and threaded 1/4” NPT to AN-6 fittings into the lid.
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i plan to screw on 1/4” NPT to 5/16” barbed fittings for both the fuel pump supply line and return line from my fuel pressure regulator. I am having trouble finding reasonably priced submersible fuel line.

I found universal Aeromotive fuel pressure regulator that comes with 2 springs (one for EFI and one for Carburetor pressure levels) and a fuel pressure gauge. This is great news, since I will be able to install the in tank pump and run my my car with my Weber carburetor until I am ready for the EFI install.

I am pumped as this will also allow for the removal of the mechanical fuel pump and free up those bolts for the block off plate and enable me to finalize my design of the trigger wheel sensor holder.
 

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To feed wires though your top plate, I would look at something like this...


It's possible that you could use a threaded port on the side and just screw this in to the port.

I looked at Permatex and they do have a fuel resistant sealing material...


I would trust that over a product that doesn't say it can be used to seal against fuel. Nitrile would be the best option, but this will require a bit more work. You can buy a roll of nitrile rubber on Amazon and then cut out a gasket. The tricky part will be to cut it out. You would need to sandwich the nitrile between your cast aluminum pieces and then cut it out. The gasket can't be a perfect circle or it won't fit right, due to the mating surfaces not being flat.
 

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Discussion Starter · #51 ·
Here is the top of the in tank fuel pump assembly.
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i ended up using 1/4 to AN-6 fittings. I drilled and tapped the top plate for 1/4 NPT threads. I did end up using permatex fuel resistant sealing material on threads. Then I screwed on 1/4 NPT stainless steel 5/16 barbed fittings from the bottom. I have some submersible fuel line on the way (pricey stuff!).

I used a nylon wire glands for the wires with a nitrile rubber seal.

The final length of the riser will be cut once I cut the hole in the top of the tank.
 

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Discussion Starter · #52 ·
Pulled out the fuel tank (thanks to the forum, I knew about the nuts in the wheel wells buried in undercoating that secure the back shelf tray). Then took it to bare metal with a wire wheel.
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Then primed it.

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And painted it metallic aluminum.
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I cut the hole for the electric fuel pump module. But hit the baffle in the tank, so had to sort of trim and bend it out of the way the best I could through the 4.125” hole.
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lastly, i removed the bottom fuel outlet fitting. But I could not find an M12 x 1.5 pipe plug that would arrive within the next week. So, I drilled it to 7/16 and tapped it with for 1/4 NPT threads. The 1/4” NPT pipe plug is readily available.
 

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Discussion Starter · #53 ·
I finalized the fuel module assembly today with 5/16” submersible fuel line. I had to heat it up with heat gun to soften it enough to get it over barbed fittings and fuel pump outlet.
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then, I taped the module in place and drilled a mounting hole. Then threaded in an 8mm bolt to maintain alignment. Then repeated the process 8 times.
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i need to figure out a way to keep my threaded cast retainer plate in place while I get the bolts started. I wonder if my permatex fuel resistant seal want would be stronger enough?
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it turns out that the tank baffle holds the inner ring in place just fine. That Just proves the power of prototyping.
 

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Discussion Starter · #54 · (Edited)
Well, back into R&D mode. I could not get the inner threaded ring to stay in place to mount the pump. So, I drilled some shallow 15/64 holes in the aluminum and pressed in some 6 mm diameter rare earth magnets. This would Not be practical for manufacturing on large scale, but free and works for me, since I had the high strength magnets laying around the shop for another project.

magnets below are circled in red.
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Update. Magnets were pulled out of there aluminum sockets, so added a drop of isocyanate adhesive to each.

Finally got it to stay put and started the bolts. It took some grinding on the aluminum ring, a few more magnets, and getting rid of some big metal burrs on the underside lid of the tank that I could not see, but were keeping the ring from sitting flat. Here is the installed cross section view of the fuel tank, gasket, and cast aluminum fuel pump top.
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Discussion Starter · #56 ·
Way to go! Looks like your fuel tank project is close to done. Remember to close the gravity feed if you haven't done that yet.
Thank is for the note. I could not find an M12 pipe plug in stock anywhere. So, I tapped the old gravity feed to 1/4” NPT for a pipe plug. Nice tight seal.

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Discussion Starter · #57 · (Edited)
Just passed the windex leak test at several psi. I definitely don’t want gas smell in the GT after all of this work. It did not pass the first round windex test, so pulled the pump back out. Then epoxied the nut of the nylon wire gland inside, and permatex on wires and on both sides of the gasket plus the fuel pump flange bolts. I had a few small bubbles at one bolt/area, but with maybe 10 or so pounds of torque a little of the sealant squeezed out and no leaks via windex bubble test! Yeah baby!
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