BMW Bavaria + Carter 4070 Fuel Pump

When I was unable to successfully rebuild the OE Zenith carburetors on our BMW Bavaria (no patience), I bought a pair of used Weber 32/36 DGAV carburetors (with the linkage and a manifold) on eBay for $99. I bought rebuild kits and some new jets from Pierce Manifolds (because they’re sort of close to me).

Carter 4070 Fuel Pump Mounted on Firewall
Carter 4070 Fuel Pump Mounted on Firewall

For some reason, I also decided to replace the mechanical push rod driven fuel pump with an electric rotary vane pump.

I found that Top End Performance had a discourse on the Carter 4070 fuel pump saying it was a good pump for Weber carbs. I first mounted the fuel pump on the firewall, near the overflow tank.

On the highway, I noticed that the car would occasionally stutter and I realized that the engine was becoming fuel starved because the pump was designed to be more of a pusher, closer to the gas tank.

I moved the fuel pump to underneath the car, just forward of the fuel tank. I used a Napa 1814U “Quiet Pack” that mounts the pump on rubber bushings to isolate it from the car’s frame and ran the 12v+ for the pump from the fuse box.

Carter 4070 Fuel Pump
Carter 4070 Fuel Pump (Note: wiring polarity is incorrect in this photo – it is reversed)

I also bought this Holley shut off switch that works off of engine oil pressure. Joe Weir, on the Senior Six Registry mailing list sent me a diagram that uses a relay (12 63 1 276 165) from a 320i for fuel shutoff.

The only problem I’ve had is with the electrical connections to the pump falling off – they’re held on by friction. To resolve this, I put a dollop of JB Weld on each terminal, then stuck the connectors on.

Carter fuel pump installation notes, pages 3-6 (PDF)