So almost 3 years ago when I upgraded to a Walbro 450 fuel pump, I used one of those ATL wiring pass-thru glands to run 10AWG Tefzel wire straight to the pump to support its electrical demands. Reference this post here in my build thread for pictures: https://www.rx7club.com/build-thread.../#post12479854

Yesterday on the way home from the Rotary Spirit event at NJ Motorsports Park, about a 90 minute drive with ambient temps in the 97~98*F range, I was smelling the strong stink of raw fuel in the cabin. I had the A/C on with recirculate then, so I opened the windows to help my nose determine what was going on - the stink dissipated a bit, so with that little hint I suspected that fuel vapor/liquid must be wicking up the pump wires past the ATL seal and into the cabin. Pulled over, removed the hatch carpet and extra sound deadening mat that covered the fuel tank access panel, and sure enough, I could feel wet fuel wicking up the wires!

I know lots of you use these ATL bulkhead wire pass thru fittings without issue, so I'm wondering what the best course of action to repair this might be? Thoughts at present:

1. Perhaps I just got a bad ATL fitting - replace with a new one, try again, and hope it can handle the hot days better!

2. Maybe with the excessive heat I found the sealing limits of these ATL fittings - perhaps a simple stud & insulator pass thru like this one would solve the problem for good? https://www.racetronix.biz/p/bulkhea...on-ss/bhs-6mss Only downside I see is I'll need to drill 2x new holes in my pump hanger bulkhead, and seal up the hole that the now unused ATL fitting sits in.

 

We addressed this in our fuel pump upgrade video... you got a really good run out of it so you definitely installed and used it correctly. We advise potting the backside as well so should the sponge seal fail or lose its sealing qualities, there's sealant to block the wicking.

This would be the quickest, easiest and cheapest path to repair. You could also replace the fitting.

Our current method to this mod uses a similar fitting with no seal at all. We just pot the entire thing and have had 0 failures or issues so far so i can confidently say just potting your current fitting will solve your issue.

 

Thanks, good video!

I didn't use any potting on the backside when I installed it, so I think the best thing to do is just replace it and pot the backside this time around - what kind of sealant do you use to pot these? Obviously it needs to chemically resistant to gas/ethanol fuels and be able to deal with pretty high vapor pressures on a hot day.

 

We use Toyota FIPG and just pack it in. The nozzle helps a lot. Main thing, fill it and wiggle the wires around to create air pockets. Repeat until there are no more pockets. You want to let it cure fully before reinstalling it.

Im sure a "fuel" grade sealant would be the better option but FIPG comes from the gods so I would call it adequate.

 

Pete, any pics of the wiring? For 5years I ran that ATL bulkhead set-up with fuel safe 10-gauge wiring and never had the fuel wicking up.
Only switched it because I needed another pump and upgraded to the Radium surge tank

Steve

 

I didn't take any pictures of it after it leaked, but the wiring looks identical to what it looked like when I first installed it. See the 1st post here for direct link to my build thread with the pictures. Other than the wire insulation feeling wet/damp from the fuel wicking, there was no real visible difference - wire insulation was still looked like new & undamaged. The fuel never wicked up & leaked enough to pool up anywhere - instead the fuel was getting absorbed into that 1" thick sound proofing insulation that I had under my Garage Alpha rear hatch mat/carpet. Removed the mat & insulation, and the stink left the cabin.

The wire that I'm using is that expensive Tefzel insulated mil-spec 10 gauge wire, which I picked because it's rated for use submerged in fuel. What kind of wire are you using? TXL insulated automotive wire may also work; I'm not sure about it's fuel resistance, but since TXL typically has a thicker insulation OD than Tefzel for a given wire gauge, it might seal up better in the ATL bulkhead pass-thru.

 

https://www.summitracing.com/parts/a...BoCWZUQAvD_BwE

 

Well I just finished the repair, and so far it's good - no evidence of wicking/leakage after a short drive with a full tank of gas. I basically used a new fitting and took FDAUTO's tip of potting the back side of the fitting as an extra layer of sealing. For the potting/sealant, I used JB Weld 2 part epoxy, which claims to be fuel resistant when cured, and gave it the full 24 hour cure time before reinstalling it in the tank.

For a new fitting, I didn't want to wait a week for the real-deal ATL piece to arrive from Summitt/JEGS, etc., so I ended up purchasing this one from Amazon -
It's a clone of the ATL CFD-504 fitting; materials & construction appear to be identical to the ATL piece, and it fit my wires & the hole I had previously drilled in the bulkhead; much cheaper than the ATL one and I got it the day after I ordered it. We'll see how long it lasts, but honestly unless the materials it's made of turn to mush with gasoline exposure, it should last as long as the ATL one - should find that out soon enough.

 

These are poor solutions for street cars and will almost always wick fuel up to the point of smelling vapor over time either in the wire braid itself or around the sealing grommet. I much prefer bulkhead studs sealed with silicone on both sides to avoid any sort of wicking.

 

^You're probably right about this - I think what is going on is with stranded wire, there is space under the wire's insulation where fuel vapor/liquid can wick up into the wire, effectively bypassing the wire's insulation and whatever bulkhead sealing grommet you're using. So unless you're using a solid conductor wire (good luck finding that in a 10 gauge with Tefzel or other fuel submersible rated insulation), you'll always have this issue with stranded wire. I'll be keeping an eye (and nose) on this, and if it starts to stink/leak, I'll be switching to the bulkhead studs.