Fuel Sending Unit Screws too long and punctured top of fuel tank?
 

So, i've been chasing down a slight fuel smell since I inherited this car about a year and a half ago. It comes and goes, but is usually stronger when the tank is full or close to it.

With this being a boosted engine and i've been working with my tuner on knock sensor issues (a whole separate deal), I recently kept thinking that he just had it tuned really rich. However, I just got a notice in the mail for the EVAP Vapor Vent Tube warranty extension, and thought "that has to be it!".

I went into the local dealer here in Lafayette, IN and got some less than good news. He said he pressurized the fuel tank, and could tell there was a leak coming from the fuel sending unit hatch behind the passenger seat. Mind you, I'd actually just replaced the o-ring and the metal ring there thinking it might be the cause of the fuel smell. He told me the o-ring could have been pinched and that was the likely cause. I was frustrated as I'd just done the work, but really want to be rid of the smell so I said go ahead.

After he started to pull the ring off, they came back to me and said I need a new fuel tank. That someone had used non-stock small bolts instead of the oem screws that were a bit longer, and they had punctured the tank which was causing the leak.

I paid for the work that I'd already done myself earlier and left pretty angry in general. Now that i've had a bit more time to think it through, I'm not sure that I believe the punctured fuel tank thing? I'm hopping down to the garage shortly to see if I can grab some pics, but is this a realistic scenario?

Thanks for the sanity checks!

TLDR; if someone use longer screws to hold the fuel sending unit to the fuel tank, could those 'puncture' the tank causing fuel vapor and liquid leaks?

Here's a couple of pictures.
1st picture is of the cover. 4 nuts hold it in place.

2nd picture is with the sender removed. There is 6 bolts that hold it in place. The holes that they screw into is a blind hole. If the longer bolts broke through the blind hole. What you can do is use some rtv on the threads of the bolts to seal up the hole. Also wipe off the o-ring. Apply a thin coating of grease on it. The grease will let it slide into position easier. Making a better seal there.

Thanks!!! This was exactly the response I was looking for. Yes, it was the blind holes that were screwed through essentially.

I think I got so caught up in who would have swapped the screws to longer ones and why they did; instead of thinking through how to solve it.

Sent from my SM-G950U using Tapatalk

Thanks again Rusty. Went and got blue and black RTV. Ended up using the black, because the blue said to not use on applications that will come into contact with gasoline.

Confirmed all 6 screws had punched through. Used the RTV and swapped out for the stock screws. (Pic attached for reference of what someone had switched to at some point). Since the dealership just put in a new o-ring, i left it in place and switched out one a time.

Do you think I'll have to worry about this sealant corroding over time? Also, should I be concerned about the possible metal in the fuel tank?

Thanks again!https://uploads.tapatalk-cdn.com/201...b81723d368.jpghttps://uploads.tapatalk-cdn.com/201...51a58f03a8.jpg

Sent from my SM-G950U using Tapatalk

Nice Save, Rusty!

You're welcome. :tiphat:

Too late for you but I replaced those mini bolts with studs and nuts.
Loctited the studs in place and tightened the assembly with washers and locking nuts.
Neat and simple and never loose a small bolt down the abyss ...... a nut or washer ...... maybe but they are cheap

That is a pretty good idea!

Any fear that a nut will grab and want to thread the stud too far when tightening?

Maybe if your of the Hulk mentality and over torque everything.

SMASH!

Let me clarify.... if there are any imperfections, foreign object, etc in the thread of either - the nut may grab and you'll start turning the stud even if the nut has not threaded down to the mating surface. This would be difficult to perceive with such small fasteners, more so if you were using a socket over it. Not sure how much torque it would require to puncture through though... either way, just a thought. Still seems like a good solution.

I have seen (via email and phone) this several times. I have a warning about it in my 370z fuel pump mod PDF.

I usually recommend attempting a heavier coat of PTFE thread sealant. Tank replacement is the only true fix. But if you can get thread sealant (gasoline compatible) to stop the leak, then it won't matter until next time you have to service the pump and deal with it again.

Thanks phunk. I didnt smell gas anymore after an initial test, but then i think i ran into other issues and the tune or maf code caused a rich condition bringing fuel smell again. Ill try the PTFE thread sealant and see if i have any luck.

Wish i had the info on why someone switch the screws out to begin with!! :mad: :mad:

Sent from my SM-G950U using Tapatalk

Bet they dropped the little bolts when they was trying to install them, and lost them.