Fuel line to tank issue


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By B-rad - 2 Months Ago
I've been trying to put the tank back into my 54 lincoln but am having trouble connecting the fuel line. I didn't have an issue taking it apart but now it seems like the threads are stripped at the beginning of either the fuel line or tank. It's hard to see either side to know where the problem lies. I can't use a tap or die because the fuel line end is too big for the die to go over and the threads in the tank are not deep enough for the tap to connect right to the threads. I'm thinking about maybe using a dremmel tool to try to correct the threads in the tank but am not sure what tool to use.
My engine and tranny are rebuilt and connected and ready to go in. I just need to finish painting the engine bay and undercoating the tranny tunnel area first. I did scrape everything off the frame and underbody and am spraying undercoating on everything. So surprised to see how perfect everything looks under there. Just old undercoating and very minor surface rust. Just a quick wire brushing takes it off.
Once the engine is ready to install, I'll have to prelube the engine while it's out. Way easier I imagine.
I don't have any electrical in the car anymore so I'll be asking how to get her started and broken in. Then I will be installing a new wire harness. Expect updates.
By 57RancheroJim - 2 Months Ago
I wouldn't use anything like a dremmel tool or any other tool that can create a spark
By B-rad - 2 Months Ago
The tank hasn't seen gas since 1965 and I cleaned it out. So I think it's safe. Seeing if there's a way to fix the first little bit of threads
By paul2748 - 2 Months Ago
Is the fitting in the tank and inverted flare?  If so, it has a straight thread (not pipe).  Try threading a bolt of the correct pitch and size in the hole (don't thread it in too far and hurt the flare inside).  If it goes in ok, then it's the fitting on the line.  Sometimes its difficult getting something like that to start if the line is bent a little  so the threaded part is on a slight angle so it won't thread in.  Just a trial and error thing.  I've had this problem in the past if the angle is just a little bit off.
By Ted - 2 Months Ago
Another option is to use the same size inverted flair nut without the tube and use that to thread into the hole.  Using the correct nut will ensure that the threads are good all the way down to the raised bevel at the bottom of the hole.  As Paul mentions, the existing nut with the tube within it must be at the correct angle before being able to start within the hole.  It’s very easy to cross-thread those inverted flair nuts if not being careful with the angle when starting them into their respective threaded holes.
By B-rad - 2 Months Ago
It was suggested to me by a friend of mine that it would behoove me to change out the original fuel line for new. That way I could cut the fitting off the old lune and use that to try and fix the threads on the tank. I'm sure it would be difficult to completely clean all the crap in the old one so it would be worth it to put on a new line.
By Hoosier Hurricane - 2 Months Ago
A "bottom tap" might clean up the first threads of the tank fitting.  A bottom tap has no lead-in taper, full thread starts right at the end of the tap.  They are used to cut the threads all the way to the bottom of a blind hole.  If you can't find a bottom tap, you could grind the tapered part of a regular tap off.
By panel driver - 2 Months Ago
You may be able to use a thread file on the line side of the fitting. The bottoming tap is also a great idea for the tank side. . 
Hope this helps. 
By B-rad - 2 Months Ago
Excellent idea, bottom tap. I didn't know those existed. Thx
Isn't the threads a special type of threads? Straight threads vs pipe threads.
By Hoosier Hurricane - 2 Months Ago
If your line is 5/16 diameter (likely), the thread is 1/2-20.  If it is 3/8 diameter line, (unlikely), the thread is 5/8-18.  These are machine threads, not pipe threads.  You might be able to use a fine thread bolt with notches sawed or filed in the threads as a thread chaser if you don't have a tap available..
By B-rad - 2 Months Ago
If I was to grind the tapered part of the tap off, is there a way to know if it is done right? Like if you saw a bolt the start threads may not be cleaned out properly to screw a nut on and need filing. What should the starter thread cutters look like on the tap after grinding?
By paul2748 - 2 Months Ago
While using a tap seems like a good idea, if it doesn't start correctly you have very good chance of really screwing it up by cross cutting threads.  Cutting the end of a tap off if not straight can cause a misthread.
By B-rad - 2 Months Ago
I got a bolt with the correct thread count and it screwed right into the tank. I'm going to get a nut today and make sure it screws onto the line fitting. If it does, then why won't the two pieces screw together? I tried for 15 minutes under the car. Do I need to push them together really hard for them to start to thread together?
By patm - 2 Months Ago
After you have verified the thread condition with the nut, refer back to Paul & Ted' s articles 5 days ago; the angle is very important. Wiggle the line incrementally & slowly while turning the fitting with your fingers.

Pat in AZ
By B-rad - 2 Months Ago
So, now I'm wondering if I should replace the whole fuel line since it's been idle since 65. I did shoot a half a can if carb cleaner thru it and it seems to be pretty clean. If anyone has an opinion about this, I'd be happy to hear. I'll probably change out the rubber pieces of the line due to age but the remaining parts of the lune should be solid. Think a half a can oc carb cleaner would clean out the line sufficiently?
By paul2748 - 2 Months Ago
If you haven't got the line installed, try this.  Loosen the line from all things holding it to the frame. You will be able to move he line around more  and help get the fittings together.
By 57RancheroJim - 2 Months Ago
I may be way off base since I'm not familiar with your year and model but almost all my tanks seem to have a fitting hat goes into the tank the the line goes into the fitting??
By B-rad - 2 Months Ago
There's a male fitting on the end of the line that screws into the female threads in the tank.
By 1/8cavman - 2 Months Ago
   If you have a helper, try loosing the tank straps so the tank came be moved- wiggled to a neutral position to get the line taper end seated in the tank and then you might be able to start the nut by hand, of course. A little penetrating oil on the threads and line end may help. If you don't have some one to get under there with you, this too much of a balancing act. Good luck.
By Hoosier Hurricane - 2 Months Ago
Your picture may be deceiving, but it looks like the tank needs to be shifted to the left to align with the line, or the line shifted to the right.  Are your tank support straps in the proper indents of the tank?
By B-rad - 2 Months Ago
I removed the tank completely again to check out the threads on the tank. I will be putting the tank up with the straps barely secured so I can move the tank around, ensuring proper alignment
By B-rad - Last Month
Threads on fuel line fitting and in tank are both good. Verified using correct nut and bolt. Spent half hour trying to screw together and still spins without biting. Lubed both threads , moved tank and line around, verified angle bolt goes into tank. Frustrating