Fuel gauge issues?

I'm going to tell you more than I know. Moisture-proof heat-shrink tubing is designed to be used on cars, and it is expected to be in the vicinity of leaking gas, oil, and coolant, so it has to be compatible with those products. We know it's okay to solder splices inside the gas tank because wires are usually soldered to the sending unit. (Some are just crimped or riveted).

The same holds true for the tubes I mentioned with the ring of solder inside. A number of people have been very happy using them, but I like to see the solder flow smoothly into the joint, so I'm not that comfortable using them yet. Also, it is a sign of good soldering techniques to make a strong, solid mechanical connection between two or more wires, THEN you make the good electrical connection with the solder. We're not making that mechanical connection first with those tubes.

Here's something totally different you might consider. Once the splices are soldered, seal them with a small ball of Silicone Gasket Sealer. Many years ago, my mother hit a large chunk of scrap metal in the highway with her '88 Grand Caravan. It tore off the rear heater and AC lines, and punched a 3" x 4" hole in the front of the gas tank. Hours later, I was able to drive it a mile at a time to leap-frog it home, with time to cool down as I walked back to get my car. After a few miles of that, I sanded the tank around the hole, then completely enclosed it by building up layers of Chrysler's black gasket sealer. Never smelled gas from then on. Once at home, it was going to take many days to get a new tank, so for a temporary patch, I covered the vulnerable gasket sealer with a sheet of very thin tin, then, to keep that from corroding, I added another layer of gasket sealer. That patch became hard as a rock over time, and that "temporary" repair lasted over 30 years until the tank rusted out on top.

At that time Chrysler offered two types of gasket sealer. That black stuff that I used cures more rubbery, and it will not bond and seal through any film of gas or oil. It has to be applied to clean, dry surfaces. Once it's in place and the parts are assembled, it can come in contact with any liquids, even before it cures. It's commonly used for valve cover gaskets. They also have a gray sealer that cures harder. It will bond through a light film of oil in case you overlooked it. It's also harder to remove next time compared to the black stuff. They may have other versions of that now, and there are plenty of similar products from other suppliers. I mainly mention Chrysler's products because I'm very familiar with them.

By the way, I've used those sealers in my other career, in sealing arcing high voltage transformers in TVs. Even repaired the arcing high voltage transformer in one of my alignment computers.

Inside your gas tank, you can use these sealers as a glue too. For example, if one of the wires has a chance of dragging along the float arm and preventing it from moving freely, use a rubber band, tape, or anything else to hold the wire out of the way, then add a spot of sealer to hold it there. In this case you'll want to wait for it to cure so it stays where you want it. Both of these begin to skin over within about 20 minutes, but give them a couple of hours to fully harden.

CARADIODOC isa one of our best! You want to use automotive grade sealant, some silicones with react with engine oil.

As far as I know, the color of the product has no meaning. As I mentioned, I'm very familiar with the two products Chrysler offered in the 1990s. Those were black and gray, with different characteristics and different suggested uses, although either could be used in any application.

One thing that did become an issue was for engine parts, valve covers, for example, some products were not recommended because they gave off fumes that could damage oxygen sensors. Many of them today specify "oxygen sensor safe" on their labels.

My friend uses Permatex products a lot. I've seen blue and dark gray stuff in his shop.

I think if I had to use a product I wasn't familiar with, I would apply it, then let it cure for a few hours, or overnight, before submerging it in gas or oil. I DO know Chrysler's products can cure after parts are assembled and filled with fluids, and I described how I "fixed" a hole in my mother's van's gas tank. Gas did hit that before it cured, but the whole idea behind these "RTV" sealers, (room temperature vulcanizing), is they need the humidity in the air, (moisture) to cure. To be totally submerged in gas might prevent proper curing

With epoxy, that doesn't take very long to cure, so I would wait with assembling the fuel pump to be sure the float arm moves freely, then finish the assembly.

Another reason to let any product cure overnight is there's a good chance the repair will get bumped as the pump housing goes back into the tank. Any glue or sealer will smear off, and possibly drop into the tank where it can get sucked into the fuel pickup screen. Hardened / cured chunks will get stopped there, but uncured product could make it through the screen and pump, then it could partially plug the filter. I can't say I've ever seen this happen, but every now and then we do get questions about foreign material such as sugar in the tank and all the problems that causes with plugged injectors. I'd feel better waiting a few hours before assembling the pump into the tank.