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'75 FI fuel sender and pickup

The 71-74 tank has the sender on the passenger side, and has a smaller outlet for the fuel. The 75 tank has the sender on the driver's side, and the fuel outlet is much larger to handle the volume of the EFI hi-pressure pump
. . . to elaborate a bit more, the '75 sender/fuel pickup has a long tube with a cylindrical mesh filter on the end and extends to about the center of the tank to fit inside a baffle welded to the bottom of the tank. This baffle keeps the fuel from sloshing away from the pickup during cornering when fuel level is low.
 

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Is there a difference in the fuel level sending units?

I put a '75 tank in my '72 wagon and used the '72 sending unit. The gauge never reads "Full". I always thought it was due to a bad sending unit.
Is there a difference in the fuel level sending units?

According to Gene evidently there is a difference.

The 71-74 tank has the sender on the passenger side, and has a smaller outlet for the fuel. The 75 tank has the sender on the driver's side.

Harold
 

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Is there a difference in the fuel level sending units?

I put a '75 tank in my '72 wagon and used the '72 sending unit. The gauge never reads "Full". I always thought it was due to a bad sending unit.
Gary;
When you installed the 72 sender, did you install it on the driver's side of the tank? Also, all the Mantas/Asconas I have ever driven have never had the gauge read "full", even when you just pumped it full. My current Wagon does this too, as well as my Wife's Wagon.
 

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Gary;
When you installed the 72 sender, did you install it on the driver's side of the tank? Also, all the Mantas/Asconas I have ever driven have never had the gauge read "full", even when you just pumped it full. My current Wagon does this too, as well as my Wife's Wagon.
This is typically due to fuel saturation of the cork float. My solution has always been to take an already dried float (takes a few days to dry out), then coat it in a good marine-grade epoxy. This will seal the float, but in itself will add a bit of extra mass to the float.

So, I will then make a jumper wire from the sender connection to the sender (as a well as a ground), and with the key in the 'on' position but with the sender in my hand, I will procede to cycle it through the range of 'empty' to 'full', and observe the gauge readings.

To compensate for the heavy float, the steel float arm needs to be bent slightly, so that it reads correctly. It tends to sit lower in the fuel than usual thanks to the extra weight of the cork, you simply need to bend the arm slightly downwards at the float end to fool it.

Bob
 

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When I dropped off my tanks to be modified, I requested that my early manta tank be modified to be functionally identical to the 75 tank. The tank will be split apart, baffles welded in, and the sender area will be made identical as well (i.e moved). With the tank apart, I can have any fittings (i.e. like NPT fittings) welded in as needed. At this point, I'm wondering if I could just have them weld in the baffles like the 75 and add a fuel pickup line (inside the baffled area)? I would then leave the sender in its normal location and use the fuel line in the sender as a fuel return line.
Any reason why this wouldn't work? It would likely be cheaper since the sender location wouldn't have to change. Any comments or recommendations?

Todd K.
 

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Sending Unit Blooper

It's also a good idea to ensure the little red straw is firmly stuck on the nozzle of the card cleaner. As I found out the hard way, when the straw is stuck into the hole in the bottom of unit, the pressure blew the straw right up into the unit necessitating removing the tiny screw on the bottom and opening the unit up to retrieve it. At least I got it cleaned real good inside!

Oh well, just one more valuable learning experience as a direct result of not thinking about the obvious ....

Rick


BTW... if you stick the tube from the can of carb cleaner into the sending unit.... its best to it while the entire unit is covered with a clean lint free towel .AND USE SAFETY GOGGLES!!!! Unless.... you enjoy the taste of that stuff. LOL
I'm sure you know this, but I've seen and had a few bloopers in my day!!:ugh:
HTH
Joe
 

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I picked up my manta fuel tanks this evening. They both have 1/2" fuel pickup tubes going to internal spiral baffles adjacent to the sender mounts. So, with the new setup I can use any manta sender on either tank and just block off the fuel line in the sender. What's the "safe" way to block off this line? Just crimp off the sender section inside the tank?

If anyone is interested, I can highly recommend Moyers if you need a fuel tank refurbished. The tanks are coated inside and out with some kind of baked-on pvc/rubber-like coating that is warranted for life.

Todd K.
 

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Todd, rather than destroy the pick-up tube by crimping, how about a short piece of fuel hose with a shanked bolt in one end and a couple of hose clamps to tighten everything up.
 

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Good recommendation Ron...thanks!
Todd K.
 

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As with OPELMN70, with a full tank on my GT and the key turned on, the fuel gauge reads empty. When I disconnect the fuel sending unit wire at the tank, the gauge still reads empty and when I ground that wire in metal the needle jumps to full.

I don't remember that people responded to this but this is the opposite from the GM sending unit wiring example in the attached link (from near the beginning of this thread) and is opposite from what was said earlier about Opel fuel gauge wiring....that empty was at 0 Ohms and full was at 90 Ohms.

Does this reading mean that the wires are switched at the fuel gauge?
 

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When I disconnect the fuel sending unit wire at the tank, the gauge still reads empty and when I ground that wire in metal the needle jumps to full.
Seems the gauge and wiring are working then. Problem appears to be in the sending unit.

Float stuck
Wire broken or covered in crud (inside sending unit)

Harold
 

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Does this reading mean that the wires are switched at the fuel gauge?

No, what it means is that you lost the ground circuit in the fuel gauge sensor.

To verify this you would have to measure the resistance of the sensor's signal terminal and the case ground. It should be around 80 to zero ohms depending on where the float is. If you get an OPEN reading then you lost your ground connection or the slide wire is broke. I got pictures in my album on what I did to get the ground connection back.

pictures
 

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Bdd, When I put my car back together I had the same problem. The wires to the sender were fine and the tank was grounded fine also. The problem was the grounding inside the sender. If you take the sender out You will see a brass tube that encloses the float and reostat that makes the sender function. I removed the brass tube and exposed the sender and float. The end of the reostat wasn't grounding to the aluminum housing that bolts to the gas tank I assume because the soldered connection corroded. I went out to the parts car I was using at the time and tested that one, same problem - so I don't think it is an isolated condition. I just used a small metal screw and screwed it through the grounding connection to make a new connection. I'm not saying this is your problem or that this is the best way to fix it but it worked.
After I posted I looked at sawdusts pictures, Looks like we did the same thing.
Good luck, Tom
 

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This thread also has info on fixing your sender.
 
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