how do you go from carb to injection?

[themills]

My carb engined car obviously has no electric fuel pump or outlet for a return (or a return pipe)

Whats the best option for running an electric pump with a return?

My tank only has one "access hatch" under the rear seat that only houses the sender unit for the fuel level.

Can i "T" into the pipe between the split tank under the rear and just bolt an inline electric pump or do i have to change the whole tank?

Cheers Millsy

[Brianmoooore]

An in tank fuel pump from a later E30 with the smaller 55 litre tank will fit into your tank in place of the sender unit that you already have, BUT apparently earlier carb. fuel tanks do not have the cup inside the tank, spot welded to the bottom of the tank, that the electric pump draws fuel from.
A post facelift 316 (carb. engine) that I scrapped had a tank with the cup, and had the fuel pump supply wire in the main loom as far as the socket on the RH side of the rear seat pan.

[themills]

I have a fuel pump supply under the seat but still need to "T" somewhere for a return. also i took a in tank pump from a late 325 but had the sender seperate to the pump. if i were to swap my sender for the pump then id have noe sender?

Could i T into the pipe that joins the tank halves as a return?

ps, thanks for the reply

[Brianmoooore]

Wrong pump! You have one from a 62 litre tank, which has an internal syphon system to transfer fuel from the LH side to the right, primed by the returning fuel.
The 55 litre tank pump (ex. four pot saloon), has the return pipe as part of the pump assembly. If you look at the top of your 325 pump, you will see the chopped off and sealed return pipe.
Level sender is bolted into the fuel pump frame by four small nuts - one package which has level sender, switch for low fuel light, pump and fuel return pipe.

[themills]

Yes, the one I have does have the 4 small nuts but only has the one outlet.
So looks like ill need another pump then with the twin outlets.
Thanks for that.
Millsy

[Brianmoooore]

I you already have a 325 pump, then all you really need is the pump frame. The actual pump is the same, and easily swapped over, so a duff. two pipe pump assembly could be obtained and used, but check that the correct cup is in the tank first.

[themills]

Just had a brainwave.

Can i scource a twin inlet/outlet sender from a single hole tank and use an external pump, therefore not needing to change the existing tank as it has no welded bit inside (i checked today)

I have another tank available to me from a late 325i touring, if idea above does not work, will the touring tank fit?

Millsy

[Brianmoooore]

Touring tank is the way to go. 7 litres more capacity and much more sophisticated internally, plus your 325 fuel pump will fit.
It will fit in place of the smaller tank OK, but you'll need to wire in the second fuel level sender on the RH side (in series with the one combined with the pump), and you'll need to change the fuel gauge in the cluster for one for use with a 62 litre tank.

[themills]

Ok, but i dont have a second hole under my rear seats in the shell so wont be able to see if its leaking etc on the second sender, its also a pain to get the other tank as its on a car with no wheels and is on the floor (but i will get it if i have to)

Will the other option i said work? external pump and a twin sender unit?

Although i think as i sit here typing it, the touring is the better bet......(i wont have the sender from the clocks though as they are gone. Will that matter too much temporarily?

Millsy

[Brianmoooore]

Very rare to have to remove the LH inspection cover, so I wouldn't worry about the lack of one too much.
Wrong gauge will read full when the tank is full and read empty when the tank is still half full, although the low fuel light will still work as it should.
External pump would be going back to more primitive technology, and you'd have to arrange mountings and wiring for it, so not recommended.

[e30topless]

done this a few times, you will need the return hard line, still available from the dealers for around 20 quid, while your there it's worth replacing both,

use an external fuel pump from a pre-face 320i or 325i the wiring is already in there under the rear seat base (passenger side ) just need to poke it through to the underside, you will also need the correct fuse in the fuse box (can't remember which one ! )

you won't need to swap tanks this way

[themills]

Ive already got the wiring etc poked through for an external fuel pump and ive scourced and fitted a return fuel pipe but i have no outlet for it to connect to.

Millsy