the_tool_man

I haven't updated in a while. But I've been researching chelating chemistry for de-rusting the tank instead of more destructive methods like acid or bead blasting. When Evap-O-Rust was $12/gallon, I wouldn't have balked at the cost. But now it's $30/gallon. I found some info on using EDTA mixed with citric acid to form a DIY, pH neutral chelating agent. Here's one guy who made an instructional video: He claims $0.75/gallon, but the cost of EDTA has skyrocketed in the last few years, driving the cost of a DIY chemical to about $15/gallon. Then I found something called Rust911, which is a concentrated chelating chemical you just add to water. One $75 gallon makes 16 gallons. That's what I'm using. With that sorted, I needed to strip off the rubberized undercoating on the bottom half of the tank. I ended up using a propane torch to soften it so I could scrape it off with a narrow spatula. It was tricky, because too little heat and it wouldn't budge, but too much and it would smear around. And if I let too much collect into a glob, it would catch fire. It became a balancing act to move the flame around with one hand while scraping with the other. Here's what I started with: After scraping off what I could: There was still a lot of coating in the concave areas, so i followed up with more heat and a wire brush: It took some paint off, too. But I plan to strip and repaint most of the outside anyway. I ran out of propane at this point. Overall, while it was a nasty process, it worked pretty well. I only burned one of my fingers. And what's left on the tank should come off with stripper, or if I use the bead blaster. I pity the person who tackles removing this undercoating from the body. I have no plans to do it. Next, I'll set up for de-rusting the inside. Stay tuned.

I think a tank sealant would plug the screen. It's quite fine. I plan to leave it uncoated. I may remove it, since I've installed an external filter before the pump.

Now for some questions. What's the small tube sticking up out of the screen for? It's open at the end, and doesn't connect to anything. What's your favorite coating? In my case, I'll need something that can be brushed on, and later thinned enough to slosh inside the seam. So it has to be able to stick to itself as well as it sticks to steel. What's the easiest way to remove the old tar-based undercoating from the outside of the tank? I'm thinking propane torch and a spatula. Is there a better way?

During the latest round of EFI issues with my 77, with some help from @Patcon we isolated the fuel delivery problem to the fuel tank. I had cleaned and treated the tank for rust a few years ago. But that apparently didn't work. After dropping the tank I got a few cell phone photos of the inside for confirmation. Lots of rust. We suspected the primary issue is a rusted through pickup tube. Fast forward to yesterday. I took it to a buddy who is a master with a cutoff wheel so he could help me cut it open. We cut just inside the factory weld on the flange, leaving plenty of material to weld it back together later. After getting it open, it's clear that I did the right thing. Everything is rusty. Even the brass screen inside the fuel baffle is corroded. I'm posting pics for anyone who wonders what these look like inside. Bottom half from passenger side: Bottom half from driver side: Top half: Borescope photo of screen: The plan is to bead blast this clean and thoroughly coat it, leaving a strip for welding. Then I'll slosh more coating over the completed weld seam. More to come.

Oh, I have. At ~$800 shipped to the US, I'm looking at repair options first.

Anyone have thoughts on the tank coating options? Looking at how complex the inside is, I doubt very seriously that I can slosh something around and get it all coated. As evidence, my previous effort failed miserably. I'm thinking with the tank cut open, I could coat the internal baffles, leaving a band of uncoated metal near the heat-affected zone of the weld, and then slosh coating in the welded tank to get those areas. Some parts would get double-coated, but maybe that's okay. My employer sends components to a few vendors in our area for hard chrome plating and anodizing. I may reach out to them to see if they could galvanize the tank, either as halves or whole. I think OEMs have tanks stamped and welded from galvanized sheets. I would imagine the galvanize is affected locally by welding, but it still protected anodically by the remainder of the zinc. If that's the case, having the halves galvanized might work great. I'll report back what I find.

Bosch OEM replacement, purchased 6 years ago. The price has tripled since then. https://zcardepot.com/products/electric-fuel-pump-fuel-injection-oem-280z-280zx-75-83?_pos=21&_sid=289a78e44&_ss=r

Tonight @Patcon and I switched the car back to the fuel tank to test it, or tried to. I think we had issues getting the fuel pump to prime. More on that in a minute. Skipping ahead, I had already made up my mind to drop the tank and inspect it. When we did, we found rust, and lots of it. I guess my cleaning and rust prevention work didn't do the job. I'm glad I followed my instinct and looked. Even if the car had run, it would have eventually clogged the filter or failed in some other way. At this point I'm going to enlist help from a friend who can help me cut the tank open and get it properly cleaned out and welded back together. We'll get a close look at the pickup tube and baffles, repairing what needs it. What's the best coating to use afterwards? I plan to run ethanol-free gas, but can't necessarily guarantee it. Back to the testing: I had the tank hooked up when Charles arrived. When the pump ran, it wouldn't build pressure. We tried just running the pump and it got to 11psi. We started the engine and it sputtered and shut off. Our assumption was that the pickup in the tank was perforated or clogged (we put only 2-3 gallons in it). We switched back to the jug, just to confirm it would run again...BUT IT DIDN'T. It behaved exactly the same. After some head scratching we unhooked the pump discharge and dumped it into a bucket to test the pump. It flowed strong. We hooked it back to the car and it built proper fuel pressure. The car started right up. Clearly the pump needed help priming. But why? We were sucking out of tanks that were higher than the pump. In the case of the jug, it was lifting a foot or so to the neck of the jug, and then downhill to the pump. If the pump builds 35psi it should push air or fuel past the FPR. I can only speculate that the pump has too much clearance allowing air to backflow (at around 11psi). Does that mean the pump is bad? FWIW it is almost new, with maybe an hour on it. I'm curious to hear what you think.

I can't take credit for the tank, and you know it. That was all you, my friend.

Not yet. Gonna mess with the VR first.

Yes. I'll investigate adjusting te VR. I didn't have time today because I WAS TOO BUSY DRIVING THE CAR!!! It runs strong and pulls to 5k. The hesitation and backfiring from before is completely gone. Of course I've got a new list of issues now; restoring the fuel tank, adjusting the voltage regulator, the brake booster inoperative, and after driving for a while the tachometer has developed a mind of its own. For now I'm extatic.

Thanks @SteveJ. I've already got one in my cart, with the connector on my Amazon list. Reading all I can find on the wiring changes needed for my 77.

It idles well and revs when parked. I won't know more until I can drive it.

Or I could unhook the alternator and run off the battery. It wouldn't be the sketchiest thing, considering the 5-gal gas can in the back for a fuel tank.

Thanks for that info. I assume https://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html is a good how-to (though it uses a 60A 280ZX alternator instead of the Frontier 70A). I'd planned to drive the car this weekend to do more diagnosis. Is there any risk to driving it before correcting the voltage issue? I don't plan to drive it much, just up the road and back a few times to see if my fuel delivery issue under throttle comes back.