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Safe wire for fuel tank.

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hello all,

I know it was mentioned but I can’t find where without rewatching all the videos again. What wire is safe to use inside a fuel tank for E-85 and pump gas? I’m running duel Walbro 450’s and want to make sure I do it right the first time. The previous wires were swollen and the shielding was just falling off when I removed the pump. Thanks for any help you can provide.

Michael Scott

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Hello i use 12 awg wire for single pump power and earth wires but i am not a wiring specialist, but i am experienced in building cars that don't have issues

i prefer tefzel my self

check this thread for some further info,

https://www.hpacademy.com/forum/efi-wiring-fundamentals/show/mil-spec-wiring-question-of-wire-size

Thanks for the reply! I should have been a little more clear in my question. What type of wire is safe to be submerged in the fuel. I have 12 gauge mill spec and also 12 gauge TXL. I just wanted to be sure to not have what happened in the photo to happen again. Thank you again. That was entirely on me for now explaining clearly.

Wire coated with PTFE is a safe bet. PTFE is used for the white plastic convoluted hoses in many modern fuel tanks. A lot of M22759/16 wire (aka tefzel) will not break down in fuel. DR25 heatshrink holds up well in fuel if you need heatshrink, and I normally use SCL for any connection points.

If your fuel setup permits having the wire sealed also helps any wicking up the core of the wire.

As Nathan said, PTFE should be an "excellent" choice, as can be seen in this manufacturer's guide - https://www.sycor.com/blog/post/wiring-insulation-types/

As with all electrically powered devices, the pumps output under pressure will vary significantly with the voltage drop across them, as may be illustrated by these 12V to 13.5V charts, with lower voltages faring even worse - https://walbrofuelpumps.com/fuel-pumps-pressure-charts

As such, I'd be looking at running a couple of sizes up from the suggested values, to maximise the drop across the pumps and minimise the drop in the power/earth wiring.

If using a contact type relay, I'd also look at "up-spec'ing" it/them, or at least using premium quality relays, as running close to their rated max' will increase the risk of their failing.

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