STM Wire Bulkhead Fitting

STM Tuned Inc.



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The STM Wire Bulkhead Fitting is primarily used in fuel tanks to get wires through to your pumps. Requires a 3/4" hole to be drilled through the firewall.

Vehicle Fitment:
Universal Product

(1) Fitting with o-ring and nut as pictured

Install Notes:
Typically we use 14 gauge wire, but 12 gauge with a thin sheath will also work.
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Customer Reviews

Based on 7 reviews
Greg Dean (Wake Forest, NC, US)
Do Not Use For Fuel Bulkheads

Performed testing using this style of bulkhead and found a massive issue with its use that makes it extremely dangerous to use these as fuel bulkhead fittings. I notified STM of this issue on the phone when returning the items and on the return form. No follow up on their end. Video of test -

Testing done with fuel safe 14awg PTFE wire, sealed jar half full of gasoline.

The root cause of the issue is not necessarily the fitting itself, but that the fitting allows the wire to pass straight through. When the wire passes straight through, where one end is submerged in fuel and the other end is open, the wire will act as a straw. As the pressure in the fuel tank increases naturally from the fuel evaporating, the fuel will be forced up and out of the wires, traveling through the strands between the insulation. Same way a conventional spray gun works. Once the pressure inside the container is released then the "wicking" issue stops. Seeing as all fuel tanks/cells will always be under some pressure "higher than atmosphere" this issue will always occur. Correct method to prevent this is to not allow the wire to pass through, either by using some sort of hermetically sealed stud or connector.

From the video you can see that the red unsoldered wire is flowing fuel out and bubbling, this is the pressure from the evaporated fuel forcing itself out of the container through the wire. The black wire is soldered on both ends, this was a test to see if converting the multi strands into a single solid core stopped the "wicking" from occurring. While this did slow down the wicking issue a lot compared to the non-soldered wires, there was still fuel coming from the wire and you can see it slowly starting to form a drip. YouTube video placeholder
Richard Freborg (Bismarck, ND, US)
STM 4 wire bulkhead fitting

This was a good fix for my Holley Sniper CJ7 fuel pump module. I was able to eliminate the cheap pass through connection that it came with my Holley in tank fuel pump module. It burnt up within a year and less than 3000 miles of use leaving me stranded and frustrated for spending $400 on Holley’s junk module that somehow makes it out of warranty but not much further. Thanks to this I was able to salvage my fuel pump module.

Jesus Figueroa (Weslaco, TX, US)
Great dual pump bulkhead fitting!

Bought it for my custom twin fuel pump setup. If you need to pass through 4 wires this bulkhead is perfect. I am using 4x PTFE 14 gauge wires and they fit nice and snug

Abel Flores (Brooklyn, NY, US)
Good product

Save me after stock plug got fyed

Michael lopresti (Marlboro, NY, US)

STM Wire Bulkhead Fitting

Cancer and Reproductive Harm