Fitment of late fuel tank in early model

[rcfanatic]

I've read a bunch of threads on this and the information is a little conflicting about whether the late model tank will bolt in place on an early car. From what I have gathered, it may or not bolt in. I may have to cut a hole under the back seat to access the second level sender, and the fuel return must be re-routed to the side of the tank.

Can someone please verify this? Is there anything else that I need to prepare for and modify? I already have a late model cluster installed and I am deleting the external pump.


Thanks!

[roguetoaster]

It will bolt in, but if you don't have the drivers side cut out you might want to make one. Read this http://www.r3vlimited.com/board/showthread.php?t=278695

[rcfanatic]

Thanks that's very helpful!

I think for now I'm going to stick with a stock, single pump setup. In that case, how do the two level senders connect in series? Will I have to splice the left side into my current right side one? Is there a connector that joins the two? What is the OEM setup?

[roguetoaster]

I would guess in series, but I cannot say for sure as all I have ever owned and wrenched on are M42s. But I should also say one pump ought to be enough unless you are racing, and IIRC there is some sort of anti surge device for the twin pump cars that you probably don't have.

[jlevie]

Thanks that's very helpful!

I think for now I'm going to stick with a stock, single pump setup. In that case, how do the two level senders connect in series? Will I have to splice the left side into my current right side one? Is there a connector that joins the two? What is the OEM setup?

You will have to splice in the second connector. The OE configuration has that splice in the harness.

[StereoInstaller1]

That pump under the tank is the main pump. Transfer pump is in the tank on your early car

[rcfanatic]

You will have to splice in the second connector. The OE configuration has that splice in the harness.

Does the OE (late model) harness have a connector that goes into the left side level sender? In other words, must I source this part of the harness so I can have the terminated end to plug into the left side sender? Or is there wiring on the left side sender that I can just splice into?

[rcfanatic]

That pump under the tank is the main pump. Transfer pump is in the tank on your early car

Yeah I noticed that after I had already hit submit. Thanks, it's corrected now.

[TobyB]

Yes, you'll have to splice in the extra wiring for the second sender.
AND you'll need a late fuel gauge, as the late gauge expects twice the resistance
of the early gauge.
(and you don't have to cut a hole for the second sender, but if it fails, you'd have to
drop the tank to fix it)
Or you could just use the sender in the right side of the tank, ignore the left side, and learn
to live with the odd gauge response, as the late tank tends to pump fuel into the right side
after you get below about 2/5 of a tank.

t

[Bimmerwolf]

Yes, you'll have to splice in the extra wiring for the second sender.
AND you'll need a late fuel gauge, as the late gauge expects twice the resistance
of the early gauge.
(and you don't have to cut a hole for the second sender, but if it fails, you'd have to
drop the tank to fix it)
Or you could just use the sender in the right side of the tank, ignore the left side, and learn
to live with the odd gauge response, as the late tank tends to pump fuel into the right side
after you get below about 2/5 of a tank.

t

sorry to bring this up 10 years later lol but you mean splice from the passenger side (fuel pump level sensor) over to the driver side (single level sensor) ? From the reading the wiring diagrams it’s the brown/green. I did 2 wires from that brn/gr on the passenger side to the driver side sensor . It’s reading full when full but at half a tank light will come on for refuel and it’s technically correct cause when I fill up it’s 14-15 gallons . . Just want it to read correctly . Thanks for any help