Fuel Pump Re-wire Necessary? Testing Video Inside
 

Before I install the walbro fuel pump I wanted to test how much voltage drops to the stock fuel pump and if a re-wire was necessary. So, I made a little video of how I did it and wanted to share the results with you all.

In short, there was about a 0.5 V drop across the harness. This was at a light electrical load with no lights on, no radio, no ac/heater/fan, etc. I may do another test later to see how much voltage drops with all these systems on.

I mean... I'd rewire it... It's ancient wiring. Wouldn't you prefer the peace of mind that you've got healthy power and ground being supplied? Considering if it takes a turn for the worst when you're having fun with the car, it'll go kaboom and ruin your day.

That's my point exactly. With a light electrical load on the car, I already saw a drop of roughly 0.5 Volts in the old wiring harness from what it should have been. I just wanted to show some actual numbers because a lot of people say you should re-wire the fuel pump, but don't provide any numbers as to why. This voltage drop is the reason why.

Id say its fine. Half volt is ok.

I ran a new + wire to the fuel pump, just in case, didnt really measure the voltage before or after, but while working with all the wiring in the car, basically all my body wires are quite bad, not enough current to properly move windows/sunroof and so on. Corroded inside.

Yeah, it's nearly impossible not to encounter corrosion on these old systems that wear the component. I think what I'll do next is record the voltage changes along with the fuel pressure changes that occur. 0.5V does not seem like a lot but how does that affect fuel pressure and alternatively, the AFR ratios? I need the proper gauges to record all this data though. So, once I finish my turbo swap I'm going to revisit this with some more data to back it up. However, having a solid 12V with extra fuel pressure during light loads may be better than vice versa.