I've been wondering this myself, and I've seen other people report doing it on forums and on youtube, and none of them blew up. But there is always a first time I guess.

 

A borescope from the filler neck is pretty common to investigate fuel tank issues, and is certainly easier than removing the metal shields on the front and sides before removing the straps, and dropping the Fuel Tank. Additionally, you don't risk damaging the rubber connections for the filler section, either. Might check to see of the borescope manufacturer has any hints, but I'd just be aware of sparks, and do this out in the open where there's airflow. Would be interesting to see what 30yrs of oxygenated fuels have done to our tanks,...

 

Congrats!!

 

There is a cone filter in the pump/ filter area that gets clogged. also the sock filter in the tank. Scope the tank and see if you have rust into the lines.

 

I'll be getting to the cone filter and in-tank filter sock/screen when I get the tank cleaned/relined and replace the fuel pump.


I drove the car 30 miles today and added 6 gallons of ethanol free gas along with 4 ounces of Idemitsu pre-mix (the tank already had 2 gallons in it without pre-mix in it)
Everything is running great on the car now, I'll make sure to be driving it more often so this doesn't happen again. I'll be adding this pre-mix in the future along with Sta-Bil to help reduce corrosion and hopefully extend engine life.

New fuel system related issue: While I was driving, I noticed the fuel light was just barely lit, very dim. It was almost impossible to see in the sunlight, and could barely be seen in the shade. I took a picture after pulling into my dark garage, you can see how dim it is compared to the brake light, and it is on despite about 7 gallons being in the tank.




After turning the engine off, I turned the ignition back on to see how bright the light gets when it is 'supposed' to be lit, here is another picture of that.


What could cause the low-fuel light to light up very dimly despite there being plenty of gas in the tank, and the fuel gauge indicating just over half a tank? I'm not sure how this circuit is wired in, so maybe the fuel sender part that triggers this light is going bad?
As noted above in a previous post, when I pulled into my driveway after first getting the car to run again, the low fuel light came on when there was indeed about a gallon or less in the tank, but it was night and I don't remember if the light was dim or bright.
Also in the video I posted that same night, the fuel light was not lit at all, even dimly, while I was driving. Either the light came on when the fuel level indeed got low and got 'stuck' on, or it came on sometime today while I was driving.



Also, funny side note, every time I start my RX-7 or pull into the garage with it, I get this notification on my phone, LOL

 

Wanna know something funny? I have never - for the life of me - seen that gas pump light come on outside of the pre-startup Christmas tree. Not once.

Here's what I'm thinking; your tank internals are rusty. As that rust advances progressively, it's getting into everything, just like it got into your Fuel Filter and even into your Fuel Injectors. Your fuel level sending unit is probably gunked up with rust, as well. There's likely a circuit switch on the fuel level mechanism that closes when he arm drops to full extension inside the tank (*empty), and that switch has gotten rusted up or gotten rust in it, resulting in the light coming on. Heck, the switch itself may be rusty and why it's lighting dimly... you won't know until you get it out and start cleaning up the tank.

In the meantime, I don't buy into the Fuel additives like Sta-Bil and the like. I especially don't believe in pre-mixing for street cars, but I can be talked into some Seafoam or MMO in the Fuel Tank from time to time. These additives aren't going to prevent rust progression or even help to keep your gas fresh, but I suppose it couldn't hurt.

Can't wait to see pics from when you drop the tank, though. Your phone must have some kind of sensor array to warn you like that, too!

 

The in tank sending unit can go bad and that light will start to do that. The gauge can work with the intake float, but the low fuel can be bad. This can be tested when you take the tank out. There are a couple of measurements you can make once the sending unit is out of the tank. There are ohm values for empty for the gauge and then another for the low fuel.

Fuel level sending unit- full=6 ohms / 1/2=31.5 ohms / empty=80 ohms.

 

Looks like its time to bite the bullet on removing the tank. I've got service manual access, but any tips for removing the tank with only jack/stands, and trying to avoid breaking anything? Do the lines on the top of the tank have enough slack to drop the tank down?

By the way, that phone notification comes from my smart thermostat upstairs above the garage, and notifies me any time we make smoke while cooking or I start the RX-7. Just something funny I noticed.


Might be time to start a new thread specifically for the gas tank?

 

Tank removal isn't too bad. I did one on jackstand a couple of years ago. One it's up on stands as high as it can go, take pics of the hoses and label them as good as possible. I'd suggest just replacing them all, they are 6mm and 8mm in size. I always use gates fuel injected hoses and clamps. Even on a carbed engine. I'm sure I'm missing something but here goes.

1, Put up on jack stands.
2. Drain tank with drain bolt.
3. pics and label. I'd put two labels on each hose and then cut the ones that connect on the top you can't reach.
4. Now the tricky part. Support the tank with cribbing. I've used a floor jack and it was less then optimal. The tank wanted to tilt off. Next time I'll use a couple of my wheel dollies and some wood.
5. Remove the fill neck bolts from within the filler door.
6. Remove the filler neck hose clamp.
7. I forget if the inner side or outer strap bolts need to be removed first.

 

I've removed the tank twice, and I've only removed the bolts at the rear of the car.

Make sure you get the correct screwdriver and don't strip the screws. I'm sure they're on tight.