Hi--

The original fuel pump (part number 0 580 464 019) in my '75 914 recently failed, it draws current but won't pump (turn). I'm replacing it with a new Bosch fuel pump (0 580 464 070) which, according to Bosch's conversion table is the correct replacement pump.

Before installing the new pump I compared the resistance of the stock pump and the replacement pump. The stock pump's resistance is 3.7 ohms, the replacement pump's resistance is 1.7 ohms. Doing the math the original pump's current draw is 3.2 amps, the new pump's draw is 7 amps. Does anyone have experience with the new pump? I haven't looked at the wiring diagram in awhile. Is the pump circuit designed to handle 7 amps?

Note: I checked out AWG's current draw chart and found that a 20 gauge wire can handle 11 amps in free air and 1.5 amps for "power transmission". Here's their definition of ampacity.

Ampacity is the current carrying capability of a wire. In other words, how many amps can it transmit? The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility.

Thanks,

Papermaker