Porsche Repair: fuel pump power, fuel pump relay, mechanic friend


Question
I bought an 85 911 that was flooded about 10 inches in to the car. Neither fuse box got wet.  A Mechanic friend (and flood car expert) who is just learning about porsche has replaced the starter,DME, fuel pump relay, and both crank sensors on the flywheel housing. We just realized the fuel pump is down low by the gas tank. It spun after he tapped on it and hot wired it to the battery but is not receiving power from the car.  I plan on replacing the pump.  Any leads on how to get power to it?  

Answer
Paul,

Sounds like quite an interesting project.  

I'm sorry, I can't quite understand exactly what you're asking.  You asked how to get power to the fuel pump.  Yet I understand you plan on replacing the pump, meaning you'll be removing the ground AND the power wire that 'isn't' powering the pump now.  So once it's disconnected you'll be checking the connectivity between the fuel pump relay and the end of the offending wire.

If you find there is no connectivity, this wire is toast, and will have to be replaced.  Are you asking how to run a new wire from the relay to the pump?  Are you wondering the best way to route the wire?

If you find there is connectivity, then make sure there is a very high level of connectivity.  If so, then this wire will not have to be replaced.  In this case something is preventing the relay from passing on 12V+ battery power when the relay is energized.  Conceivably, this could be an oil pressure issue.  Unfortunately, my 356 experience doesn't translate over to 911's when it comes to this possibility.  No 356 had any such safety factor.

I'm not sure if 911's had this, but many cars of this era came with wiring that would not allow the fuel pump (or the relay) to operate if the oil pressure was insufficient.  If you don't have a wiring diagram you could determine this by tracing the wires from the relay (or the pump itself) back to an oil sender wire or equivalent.

Anyway, this is a long commentary trying to guess a bit what you're looking for.  Please ask a follow-up question and let me know which area you'd like me to expand on.

Thanks.

Dave