55 -> 63L fuel tank swap - what all is needed?

[roguetoaster]

^ it would likely just churn up the fuel around the second pump's pickup. i'd run both pump outputs to a Y fitting and on to your FPR/fuel rail. do the same for the return... single line to a Y and then back to both pump return fittings.


from this thread it seems it could be achieved using two late model 318i/is pump/sender housings. or some fabbing if you're cheap.

The life of the left side pump may be short. High pressure pumps don't like to run dry which will happen on the left side. Transfer pumps are far less sensitive and don't usually suffer damage from running dry.

Thanks for the input! Looks like we are going with the DS low pressure pump feeding the PS high pressure pump. Very helpful thread thus far.

[roguetoaster]

We finally got around to doing this swap and we found we had to relocate the fuel filter on our M42 car. Mainly because the tabs that hold the bracket in place were in the way of the tank install and were bent out of the way. Not to mention the fuel filter would not fit the area near the tank without one of the lines being dangerously near to kinked. We then relocated the filter to the engine bay right next to the charcoal canister.

[NigelStu]

Pics incoming of the surge / routing - once testing the system is complete.

Setup:

• 88+ tank.
• 2 early low-pressure lifter / supply pumps, feeding 0.5 gallon surge tank via t-fitting (return inputs on LPP capped)
• gravity feed to stock early external high-pressure pump -> fuel rail
• return line to surge tank
• surge tank overflow -> return / siphon input on 88+ tank

Only thing I'm concerned about is the left-side low-pressure feed pump. Since the pump AND whatever the siphon capability is will drain the left side). At this point we have no idea how quickly the left side will empty, I wouldn't think the pump would not like running dry for much time. I highly doubt both sides will empty at the same rate (unless some of the fuel entering the siphon line ends up on the left side?) I'll wire the second level sender into the data acq to monitor it, possibly add in a switch to turn on/off the left side pump.




I also had to remove the pump/filter bracket from the car, but since nature had already done most of the work it was easy (enough rust that it couldn't be reused anyway)

I also had to grind off some of the tank flange - the one I picked up had excess metal outside of the weld/seal.... in one spot, tank was nearly 1/2 wider than than the space available for the tank.

[NigelStu]

The surge setup -