Fuel Tank Diagnosis, Your Opinion?

[TacoJonn]

Hey all,
You may have seen my other threads about my fuel system woes. Got my new to me 76 a couple of weeks ago. It died on me, I replaced two fuel filters, got it going again, then it died on me again. Since I have taken ownership of it I have maybe driven 25 miles on it, and have added at least 10 gallons of fuel via Jerry can (fuel gauge does not work).
I have been chasing the issue upstream of the fuel filters (PO had two on there) and decided to tear into the gas tank. I tried to pull the fuel drain plug but no surprise, it was rusted pretty tight. I then tried to siphon the fuel out and noticed there was ZERO fuel in the tank. At this point I decided to tear into the tank. No surprise, it was bone dry inside, I was expecting at least a few gallons to be sloshing around there.
That being said I have a few questions. I am relative n00b, but am learning by doing, so be gentle:

1. Does this look like an OEM tank?
2. Does this look rusted enough to be causing fuel filter clogging issues and/or potential leaking issues?
3. What are 1, 2 and 3 in the image with yellow text? Is 2 the drain plug from the inside? What is 1 and what is 2?
4. Does this tank look like a candidate to be restored or replaced? Wondering if I should just pull it off and see what can be done to it.

Thank you very much for your information. I have really enjoyed working on this old girland am excited to get it on the trail soon.

 

[spotcruiser]

Certainly looks like a stock tank. #1 in the photo should be the drain plug. There should only be one, and it should line up with the hole for it in the tub. #2 looks to be corrosion. #3 looks to be a screen trapped under a baffle. I don't believe there is a screen anywhere in there originally, so maybe that came from a fuel nozzle somebody was using. I'd remove the loose screen. Overall, the tank looks very good inside. It never hurts to clean the tank thoroughly and seal it. There are kits for sealing tanks. Because of what looks like a corrosion spot inside, I'd look carefully at the outside bottom of the tank, take care of any rust, and then paint it with something that will prevent future corrosion. I'd also get rid of any stock "carpet" or foam that's cushioning the tank and replace it with something that will not hold moisture against the tank.

 

[TacoJonn]

One more thing I forgot to mention is that this new-to-me 40 basically does not have gas cap. It jiggles, has no gasket and nowhere near air tight. Wondering if one these hot summer days some fuel might be escaping from the gas cap?

 

[spotcruiser]

You can still get new gas caps for a 76. I just got one myself.

One more thing I forgot to mention is that this new-to-me 40 basically does not have gas cap. It jiggles, has no gasket and nowhere near air tight. Wondering if one these hot summer days some fuel might be escaping from the gas cap?

 

[thebigredrocker]

I posted part#’s of couple vented caps Need a Vented Fuel Cap 76 FJ40

At this point you might as well seal your tank. I’ve used both sealer kits that Summit sells. No idea if either is better. I run dual servieable filters in both 40’s. I found a couple tiny chunks of the POR15 sealer in first cleanout on my 76 40’s 100micron pre-filter. None since.

 

[TacoJonn]

I posted part#’s of couple vented caps Need a Vented Fuel Cap 76 FJ40

At this point you might as well seal your tank. I’ve used both sealer kits that Summit sells. No idea if either is better. I run dual servieable filters in both 40’s. I found a couple tiny chunks of the POR15 sealer in first cleanout on my 76 40’s 100micron pre-filter. None since.

View attachment 1774215 View attachment 1774217 View attachment 1774222

Wow your tank was looking pretty gnarly but much better now. Thinking I might as well seal it to be sure. Everything is already off and no cross country trips currently planned in this rig

 

[Tancruiser]

Por15 is a great product it takes some time but worth it.

 

[TacoJonn]

As far as vented caps go. Wouldn't you not want a vent to keep gasses from escaping? Or does it work like a one way valve?

 

[thebigredrocker]

Wow your tank was looking pretty gnarly but much better now. Thinking I might as well seal it to be sure. Everything is already off and no cross country trips currently planned in this rig

Yeah yours looks better inside. I’ll be curious how it looks when you yank it and flip it.

 

[TacoJonn]

Yeah yours looks better inside. I’ll be curious how it looks when you yank it and flip it.

I will for sure post up here with detailed pix after I flip it. Hopefully I can do it tomorrow.

 

[thebigredrocker]

I had to go with a vented cap cause the OEM charcoal venting stuff was missing. You probably just need a stock non-vented cap.

 

[TacoJonn]

Well I pulled the tank. The backside does not look *that bad*. I noticed something is rattling around in there and sound sizable, but haven't fished it out yet.
I still think that while I have it off I might as well seal the tank with Por 15. Wondering if I should paint the tank with Rustoluem or another product while I am at it? Also, what do you all recommend (if anything) to put between the tank and fuel cover. From the pix above, it looks like the PO used astro-turf or something along those lines.

 

[Martyt]

I would use rust converter (like Black Star) on the exterior then I would sand the exterior and powder coat. Finally, I would use Line-X on the bottom (where it can’t be seen once tank is mounted)

 

[Dizzy]

I'd identify a leak first, or, just buy a new one.

I suspect the drain plug, or the seam next to the door because it gets the most exposure. To me, it seems that there is not enough access to the three chambers to do a visual or a repair.

I inadvertently did a pressure test on mine when rinsing the internals with fuel (the cap was missing for years, and it had wasp nests in it) by removing the sending unit and capping it off with a plate, and plugging the vapor vents and sending and return lines on a sunny spring day. I noticed fuel leaking out the slightly compromised drain plug gasket and when I loosened it, it was like pulling the core out of my bicycle valve.

I used bungee strap (about 1/4") with the ends cut off to cradle the tank and the tank cover. I applied a combination of Boeshield and auto wax on my surface rust and factory finish.

 

[lone gunman]

I used rust mort on any surface metal after sanding to stop the rust. SEM Products Rust-Mort SEM-69504

a buddy of mine who does body work and paint for a living swears by the stuff. he coats all bare metal surfaces with it before painting to stop any rust from forming. I then coated the tank with cheap rattle can bed liner.

and as far as the tank goes the POR15 fuel tank coating works great. I used diluted muriatic acid on the inside of the tank to remove the rust and then the POR15 kit. youtube is full of videos of how to do it and the muriatic acid is available at Lowes. I did this over ten years ago and no issues yet. but I would put it on a couple saw horses fill it with water and check for leaks first. if no leaks do the kit.

I had the same issues as you with my 76 40 I could drive a while and then the rig would die. or it would drive fine around town (low rpm) but once I got on it it would die. I got a couple cheap clear inline fuel filters and used them to verify it was a plugging issue and sure enough, the filters would fill with chunks of rust and either completely plug the filter or at least restrict fuel flow. if I let it sit for a while it would start up and run till the filter sucked enough chunks back up to plug it again.

 

[DylanZ]

Mate, I had the same problem, kept clunking out and dying even after fresh fuel and filters. I ended up dropping the tank to only find rust just like yours ..... mine was worse though. I used the POR15 tank repair. It worked a treat and coated all the inside. Its a lengthy process but it ensures no more holes and more importantly no more rust. I found that the small "dust" like rust was what was clogging all my filters. So far, Iv had no more issues.

I also put a kit through my carby just to make sure, drives like a new car.

 

[DylanZ]

Also, I installed a new fuel pump, sender, and cleaned thoroughly my pickup. Blowing air through your lines helps get all the dust out too.