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Can anyone explain how this happened?

Notes:
  • My car is a 2003 BMW 325CI M56 with E46 M3 fuel tank conversion.
  • The fuel pump is AEM 50-1200 E85 installed less than 6 months ago.
  • The fuel pump has no relay but instead uses an EKPS.
  • The most recent work was a water pump replacement about 3 days before this happened.
  • There were no cracks or broken insulation on the wires when it was installed.
The car has been running great since I did the swap 6 months ago. The car failed to start after being parked overnight.

Could excessive current draw from the EKPS to the fuel pump cause this to happen? What other possibilities could have caused this to happen? I hope to replace the wires without this happening again, so I really need to find the root cause. Thanks in advance.
 

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RayMondo
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Can anyone explain how this happened?

Notes:
  • My car is a 2003 BMW 325CI M56 with E46 M3 fuel tank conversion.
  • The fuel pump is AEM 50-1200 E85 installed less than 6 months ago.
  • The fuel pump has no relay but instead uses an EKPS.
  • The most recent work was a water pump replacement about 3 days before this happened.
  • There were no cracks or broken insulation on the wires when it was installed.
The car has been running great since I did the swap 6 months ago. The car failed to start after being parked overnight.

Could excessive current draw from the EKPS to the fuel pump cause this to happen? What other possibilities could have caused this to happen? I hope to replace the wires without this happening again, so I really need to find the root cause. Thanks in advance.
More info needed.
The last time you started it was it just for a short time like on and off to move it a few feet of was it a decent run getting the engine up to normal temperature?
Is the car starter cranking?
What makes you think there's a fuel pump short?
Water pump work doesn't go anywhere near fuel system.
 

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What I see as the biggest issue, is the butt splice wire connectors. Too much current/resistance, producing heat. I would make sure you have the correct wire, solder properly, and cover it with heat shrink tubing.
 

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What I see as the biggest issue, is the butt splice wire connectors. Too much current/resistance, producing heat. I would make sure you have the correct wire, solder properly, and cover it with heat shrink tubing.
This. Spade connectors should be avoided whenever possible and certainly have no business anywhere near the fuel system.

Apart from overcurrent, another possible cause of the failure might be vibration leading to abrasion of the connectors' insulation boots over the six months since installation. Then the two conductors touch, and, zap.

Did the fuse rating on that circuit need to change with the conversion? If it didn't pop, that's concerning.

I hope to replace the wires without this happening again, so I really need to find the root cause.
In that case, in addition to solving the overcurrent problem: Invest in the tools to rebuild that plug correctly. You'll need a tool to unlock the terminals from the housing (a small jeweler's screwdriver can stand in for that) and a crimp tool to install new terminals. Male/female terminal pins and connector housings (if you damage it on disassembly) can be acquired from BMW, or other sources if you're determined (identifying the correct generic parts is challenging).

Do not make any kind of wire splice, soldered or otherwise, inside your fuel tank. Cut the harness well outside the tank, and add enough wire (with the joint soldered & wrapped in heat-shrink as suggested) to make an unbroken run all the way to the connector.
 
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Additionally, bench (or tank) test the fuel pump. My higher-mileage fuel pump recently failed; in the process of failing, it pulled excessive current, which burned the insulation off the tank-side power wire. I replaced the pump and wiring harness.

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RayMondo
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Additionally, bench (or tank) test the fuel pump. My higher-mileage fuel pump recently failed; in the process of failing, it pulled excessive current, which burned the insulation off the tank-side power wire. I replaced the pump and wiring harness.
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