Starting a new thread was my last option, as I've tried tor research this on my own on this site and have even consulted the FSM. I believe I'm onto the root cause, but I welcome any further feedback. This is for a 78 280 with no modifications on the engine nor fuel system. I've been going through aftermarket fuel pumps (Delphi) every 5 to 6k since 2022. I'm now on my third pump. This would quiet down the pump, help with starting, and provide all the expected benefits of having a new pump. I also inserted a Fram G3 inline filter between the tank and pump. Unfortunately, the filters didn't last anywhere near what they're supposed to. So, my best guess is the fuel tank is dirty and needs to be treated. How fun! heh.

Right now the car drives, but after a while in SoCal heat and with the A/C on (R12), I hear the sounds and feel the vibrations of a pump that sounds strained. After a while of cooling down, she'll drive fine on the way home, as the ambient temperature seems to take the edge off. I switched out the inline filter with a Wix one the other night and drove her again the next day under similar conditions, AC on, etc. After driving for about 30 minutes, by the time we park, the noise is there around the fuel pump, not as bad, but definitely not a healthy sound. On the way home, she sounded fine again, as the outside temperature had cooled down.

I know these aftermarket pumps can be questionable, but I don't think they are the problem. The filters have only been a band-aid until those get clogged, and then consequently the pump is starved, thus gets prematurely worn out, and so I'm back to square one. The warm weather and the added load from the AC doesn't help. I'm looking at the gas tank as the culprit, as I feel everything after the pump that's under the hood is probably not the issue. Perhaps I'm working backwards here, but I'm open to any suggestions. Regardless of the cause (or causes), I think getting the tank out and taken care wouldn't hurt at all. After that I can warranty another pump. Any thoughts? Thanks!

Edited 3 hours ago3 hr by AndysPlit
details

Removing the tank and cleaning / coation it sounds like a good step. I did my 280Z a number of years ago using the POR 15 tank cleaning system. It worked well but I decided to cut 2 "flaps" in the top of it so that I could get inside it to better clean and coat it. Then I welded them back in place. My tank was in good solid shape at the time. If yours is rusted and thin in places it probably needs to be replaced instead of being repaired.

2 minutes ago, mayolives said:

Removing the tank and cleaning / coation it sounds like a good step. I did my 280Z a number of years ago using the POR 15 tank cleaning system. It worked well but I decided to cut 2 "flaps" in the top of it so that I could get inside it to better clean and coat it. Then I welded them back in place. My tank was in good solid shape at the time. If yours is rusted and thin in places it probably needs to be replaced instead of being repaired.

Hey, thanks for your reply. Alternatively, I was looking at a tank for sale for $350 that has allegedly been cleaned and coated. It looks good on the outside, but I've asked if they have any pictures of the inside of it. No reply yet. FB Marketplace is a weird place. Anyway, I may inspect my tank before considering a replacement. I would hate to waste my current one that could be salvaged, but we'll see.

Edited 2 hours ago2 hr by AndysPlit
correction

Please don’t waste your money on a near 50 year old tank. There’s a screen assembly inside at the pickup that’s been known as a major culprit. I went the route of acid cleaning and red coat before. 3 months later pin holes developed around the seams of the tank. Do yourself a huge favor and order a new tank from S30.World. These tanks are an amazing duplicate to the factory spec. Check them out. I highly recommend it after wasting $300 on getting my 78 cleaned.

16 minutes ago, Yarb said:

Please don’t waste your money on a near 50 year old tank. There’s a screen assembly inside at the pickup that’s been known as a major culprit. I went the route of acid cleaning and red coat before. 3 months later pin holes developed around the seams of the tank. Do yourself a huge favor and order a new tank from S30.World. These tanks are an amazing duplicate to the factory spec. Check them out. I highly recommend it after wasting $300 on getting my 78 cleaned.

Oh, I didn't know about this site. After shipping it's $830. Might be worth it. I'll mull it over. Thank you.

Edited 1 hour ago1 hr by AndysPlit

They drop ship from a warehouse here in the US. You can re-use the rubber pads off your original tank by cleaning them up and re-gluing them back onto the new tank.

I have some pics somewhere, I’ll see if I can find those and post them here.

2 hours ago, AndysPlit said:

I've been going through aftermarket fuel pumps (Delphi) every 5 to 6k since 2022. I'm now on my third pump. This would quiet down the pump, help with starting, and provide all the expected benefits of having a new pump. I also inserted a Fram G3 inline filter between the tank and pump. Unfortunately, the filters didn't last anywhere near what they're supposed to.

Do you mean the filters are getting clogged? I think that makes the pump work harder, electrically, and might even cause cavitation, which can wear things out faster. It might even do that before getting clogged, I think that those filters are designed for carburetor flow rates.

I've had the thought that if I had a dirty fuel tank but didn't want to replace it or clean it that I would use a larger filter with a high flow rate between the tank and pump inlet. I'd probably look at using a filter like the one in the engine bay. I don't know if it's a high flow filter if used on a low pressure side though. Easy to test though, just fill it up and see how fast it drains.