Dave WM

yes.

you should have a large neg battery cable terminated at the starter mount bolt. you should have a large Pos battery cable terminated at the starter solenoid. that same junction should have a medium sized (guessing here maybe 5 to 6 gauge) wire that go back in to the wire harness (and ends up a one of the fuse link boxes). of course you should have a spade connector that plugs into the solenoid to activate the starter (I can see that).

I also don't see the neg connection to the bolt on the starter for the main ground.

disconnect the battery positive. switch to continuity, check to see if that red wire that is loose has continuity to any of those fuse link connections.

I don't see the shared positive connection on the starter. why is there a loose red wire done there?

confirm you are comparing the chassis (negative) to all the fuse link connections under the plastic housing under the hood. NONE show 12v? is there TWO fuse link boxes or just one, I know my early 75 only has one box. you should post of a pic of what you are doing.

do you have the starter motor hooked up? the fuse link gets it power from a shared positive on the starter.

just make sure it will gravity feed out of the tube before you reinstall the tank. Or just hook up a hose and see if you can pour gas thru a funnel INTO the tank thru that now cleaned hose. what ever you do you need to make sure it flows freely. You should take your time and make sure it works, no rush, this will fix the car. one more thing when you do re install use a SINGLE G3 see thru fram filter as a prefilter (tank to pump). Make sure you have a NEW fuel filter under the hood. when you get the car running again check ALL the hose fittings for leaking gas, esp under the hood. Use FI rated hose after the pump, before the pump not under pressure. I use FI for all just to make it simple. I had a bit of a hard time getting the right size fuel lines IIRC down around the tank/pump area. check for leaks several times, after every drive, at least for a several cycles. ALWAYS carry a fire ext with you rated for gas fires in the car.

the short tube from the tank hard line to the CC. The 1st time I attempted to clear the plugged hard line I just fed in my cleaning wire thru the hose, it struck this restriction right off. I could then feel it and you can see it if you straighten out the hose (the hose is maybe 6 inches long).

again that follows. I was only thinking of a system that is active. they had to design for the inactive state. This is one of the reasons I get hung up on all the deleting of stuff, I am sure that a lot of thought went into the total system design and deleting one thing may upset something else not thought of I think its often called "unintended consequences". It is also why I tend to try and qualify most of my statements. Example why is there the small restriction in the rubber hose from the CC to the hard line? perhaps a way to limit the rate of flow? its in there but I did not see it mentioned in the FSM or could it be a remnant of something on my care only. You can feel/see it if you look closely at the short piece of hose (assuming it original and has not already been replaced).

sounds plausible good thinking there CO, a backup plan for extended non use.

IIRC my 280 has Wht and Wht/black stripe for speaker, bullet connectors.

I don't know why the tank is plugged, but it needs to be fixed. My SWAG is you should try to work some kind of snake in and out of the metal tubes that are plugged. I am lost as this thread has gone on so long. Did you do something to the tank and then the problem started? one of those sealers? if so did you blow the lines out after using? If the sealer is the problem you may try to position the tank is a way that will allow a funnel to be attached and then find out if there is a solvent that will attack the sealer and pour a little of that in to the funnel. I really don't know what to tell you at this point to fix it, but it clearly is the problem. I had a professional do my tank, which involved cutting the tank open and clearing out the internal screen and rewelding. It was expensive.

no prob you just need to use the multimeter and work the problem is a systematic way.

fuel tank. you need to fix the tank. all the other items are ok. as it turns out item one was the prob all along.

NO you need to fix the tank, get the tank so it will flow fuel by gravity, do this with it out as it will be much easier to fix the tank. see my next post.

its working as it should fix the tank

goose the engine if it was running, the fuel pressure will respond if the FPR is working right.

think the engine is running fan looks to be turning

ok then try checking the fuse links under the hood. see if there is voltage on one side but not the other. You cant tell by looking if they are good.

BTW, I would say the tank is good when fuel will siphon out of the fuel line. If it will not come out by siphon (gravity) then you have an issue.

only IF you need to. you need to get the car running with a good battery and then test the alt for output. if there is no or low output it could be a VR issue or an alternator issue. Too soon to go down that rabbit hole, you need to get the car started and the alternator turning before do any checks.

hold up no volts at all, you stated you have power at the fuse box, on side of the fuse will have power, if the fuse is good then the other side will as well. this is for the HEADLIGHT fuses, should be 2 of them.

Well there you go the problem is a plugged up tank, congrats, now all you have to do is clear it.

no headlights and you have 12v on both sides of the head light fuse?