Fuel Level Sender / Pickup

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greggers
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Tue Jan 17, 2012 8:35 pm

Just been looking at the fuel level sender we took out at the weekend and it doesn't look to have any kind of in-tank pump, it's also in a pretty grotty condition and the fuel gauge never did work correctly.

We've got an M52 under the bonnet, so we'd be relying on just the external pump to feed it, whilst it seems to run OK, the single pump does whine and the car is yet to be driven in anger.

Does anyone have any thoughts... Upgrade the external pump, convert to an in-tank pump to complement the external pump or leave it as is???

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DanThe
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Tue Jan 17, 2012 10:56 pm

What car? Early 325i at a guess?
Unless the tank has a bowl for the in-tank pump to sit in you will have to either use an external pump or change the tank
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greggers
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Wed Jan 18, 2012 8:52 am

It's an earlyish 320i, mid '87 coupé... Looking in the tank there is something that resembles a bowl. I will try and get a picture of what I have tonight.

The pick-up and return is pretty clagged up with rust and flakey white stuff, but it will probably clean up OK, so may not be worth changing.
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greggers
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Wed Jan 18, 2012 9:50 am

Ah, just had a look on eBay, most tanks on there seem to have two holes on top, I guess one is for the level-sender (left side) and the other is for the pick-up/pump (right-side). Does the return on the two hole tanks go back to the pick-up as well?

Our tank only has a single hole on the right hand side, the pick-up is integrated with the level-sender.

ECP lists the same in-tank pumps/senders regardless of whether you put in a pre-87 or post-87 model, which is complete horse-sh*t.
Grrrmachine
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Wed Jan 18, 2012 10:05 am

You might want to read the Wiki about the differences in tanks, pumps and senders:

http://www.e30zone.net/e30zonewiki/inde ... #Fuel_Tank
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greggers
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Wed Jan 18, 2012 10:47 am

Thanks, that clears up what the extra hole is for, the article doesn't describe the tanks that aren't fitted with an in-tank pump.

If the internals of our tank are no different from the 55l tank that's fitted with a pump and a return on the pump housing then it looks like we can upgrade.
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Brianmoooore
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Wed Jan 18, 2012 12:11 pm

Two hole tanks are 62 litre, single hole tanks are 55 litre. The 55 litre tank uses a simple external pipe at the bottom to equalise the level in each side of the tank, whereas a much more sophisticated internal syphon, primed by the returning excess fuel from the engine, is used in the 62 litre tank.
As long as your tank has a shallow cup welded to the bottom of the tank, directly below the single hole, you can fit it with an internal high pressure fuel pump and combined level sensor. The pump assembly will need to be the version that has two pipe stubs on it - one fuel out, and the other for returning fuel back to the tank.
A 62 litre tank can be physically fitted, but will need changes to the wiring and plumbing, plus a different fuel gauge for the instrument cluster.
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