Add fuel gauge to GM 4108

[chessie4905]

Ok, I went down and looked. Above the fuel filler is a plate of plywood and linoleum with phillips screws in it. I had to remove couch away from cover and pull back carpet when I changed tanks. From that access, you can see if there is a blank plate with 5 holes, 2 3/4 in diameter. If you have this, you just need to purchase the sending unit and can most likely insert it down into tank. If you dont have it, you would need to pull tank and have a blank mounting plate soldered, not brazed or welded, to tank. Everything can be disconnected from top of tank through this holeAn older radiator shop should easily accomplish this.The sending mounting plate is just to rear of rectangular fuel filler unit, and centered on top of tank front to back. I have the short tank from this coach and one in the parts coach and neither has a block off plate, so likely, yours is the same.
The tanks are 32 inches tall. The sending unit is stamped on resistor hsg 90 ohms. The round top with 5 off center spacing holes is 2 3/4" diameter. The rigid stem that sticks down into tank is 16" . The float arm is 19" pivot point at resistor to tip of float. Max down 31" , max up 1/2" below underside of float mount. Single threaded post on top.

[chessie4905]

I found this so you could mount to top of tank without soldering. Because the sending unit holes are offset, make sure to index correctly when installing ring. I recall that the baffles in tank are slotted for swing of float.

https://www.amazon.com/Auto-Meter-3263-Level-Adapter/dp/B006VNGWI4/ref=pd_sim_263_4?_encoding=UTF8&pd_rd_i=B006VNGWI4&pd_rd_r=28cce7d6-d574-11e8-b4fc-6babf8f7cd8b&pd_rd_w=kt9Rr&pd_rd_wg=qpJ8S&pf_rd_i=desktop-dp-sims&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=18bb0b78-4200-49b9-ac91-f141d61a1780&pf_rd_r=NYCHTDNK1KWB0Y1G941B&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=NYCHTDNK1KWB0Y1G941B

[richard5933]

I don't think I've got the plate on top of the tank. I do have a piece that I can't identify on to of the tank. It's circled in red.

The extra fuel lines on the side of the tank are for the generator.

[chessie4905]

That is the tank vent. The fuel sending unit plate would be just to back side of fuel filler mount.

[richard5933]

In that case, sounds like a hole will need to be drilled to mount the sending unit. Since the pivot type sending units must line up perfectly with the slots in the baffles, I'm not sure how to know where to drill.

Then there is this type of sending unit: http://www.rochestergauges.com/products/9800Marine.html

Looks like they can be had in 4" to 42" lengths, so size should be no problem for the depth of the tank. The hole is a standard 5-hole mount, so I could probably mount it to the tank without soldering by using one of these: https://vwparts.aircooled.net/VDO-Fuel-Tank-Sending-Unit-Mount-Kit-Bolt-In-p/v226451.htm

If I can gain access to the hatch over the tank by going through the base of the couch above it, it looks like the whole thing can be done without pulling the tank. Looks like the only thing would be making sure I avoid drilling over a baffle.

How do I know where the baffles are? Will there be a visible marker on the outside of the tank? Or are they all a uniform distance from the passenger side end of the tank? Or is it only by putting a scope in there will I know?

[chessie4905]

No problem on the baffles. They are placed in the tank where the straps go around the tank, obviously to keep from collapsing tank when straps are tightened.
I prefer the mount I referenced as it is mounted to tank separate from sending unit screws , but do it your way. You can cut a hole with a hole saw to the idor slightly larger of mounting ring. If you load it with grease, it should catch the chips. If you need, I can give you the dimensions where my factory sender is located.
If I was doing it, I would remove the fuel filler neck. That way you can see what you have on the inside of tank when placing sender. You could put a strong magnet inside top of tank to catch any loose chips.

[richard5933]

...If you need, I can give you the dimensions where my factory sender is located....

That would be really helpful when you have a minute to check. Thanks.

[chessie4905]

Threaded electrical stud ( 1) ,11 1/8" in from passenger end of tank. Looking through fuel door stud is approx 5/8" to the right of plate fuel filler neck is connected to. The mounting flange for fuel sender just clears plate and round plate that fuel pickup is connected to. ( it looks like the fuel sender mounting plate, but all bolt holes for it are evenly spaced, and on both my tanks, the plate and screws are soldered to tank.