Captain Obvious

Yes, the click coming from the area near the passenger feet is probably the ignition relay. But it's a non-problem. The B/Y jumper across the starter relay takes all that out of the equation. in other words... With the starter relay bypassed (by shorting the B/Y wires), the ignition relay does not have any effect on the starting circuit. You should be able to completely remove the ignition relay from the car and it should still crank. So what next? I'd go upstream... Next time it acts up, I'd hotwire directly across the ignition switch and see if you can get the starter to engage. I know you said it's a new switch, but who knows. Jumper from White/Red to the Black/Yellow and the starter should spin. If it still won't crank under those conditions, I'd wiggle your fusible links around and try again. Failing that, it's time for a meter and really start digging into things.

So thinking about projects that still need attention... I still am am looking for a front spindle. Anyone got something laying around?

Yeah, there are a bunch of mistakes in the early wiring diagram. Another example is that the wire colors on your car are not the same as the diagram. The diagram indicates that both TEMP and OIL use yellow/white, but your car uses yellow/black for one of them. So a while ago I worked up (what I think is) a better version of the diagram and fixed some mistakes as well as cleaned things up a bunch. I've not uploaded my latest version, but here's the thread where we talked about it: https://www.classiczcars.com/forums/topic/69026-1970-wiring-diagram/ Which of the gauges uses the Y/B wire? Does that go to the TEMP, or the OIL? I'll change that on my diagram. And let us know how the bench testing goes.

So Zedhead posted a good pic of the starter relay earlier... it's up in the engine compartment in front of the battery. If you disconnect the starter relay and short the two black/yellow contacts together (on the car side of the harness), it will take both the starter relay and the transmission inhibitor switch completely out of the starting circuit. In other words... With the two B/Y wires shorted together, when you turn the key to START, the starter should spin even with the transmission in drive. If it still fails to crank even with that jumper in place, then it's something other than the starter relay or the transmission interlock.

The diagram (created by @wal280z , not Eurodat) says the dashed line is for Canada. And there's still no link between the seat belts and the starting of the car. They just changed how the belts and warning light and buzzer get connected.

Gotcha. You probably already mentioned that somewhere. And I hope the under load fuel pressure testing provides some clues to what's going on.

The wiring diagram says the sender units connect to a yellow/white wire (not straight yellow), but that may be on the chassis side of the gauge connector. Sometimes they changed wire colors at the connector right there at the gauge. So if it's as simple as Y on the gauge side and Y/W on the dash harness side, then yes... Your bench test connection plans should work out fine. No, you do not have to have the sender unit (either of them) hooked up. It won't cause any damage, but the needle will just rest way down at the bottom. So you can let the oil pressure connection hang open while you are messing with the temp side testing. Can you snap a couple pics of the gauge? Some of the connector leading to the gauge, and maybe something of the corresponding connector on the dash side. So we can confirm the color change there at that connector? Also, can you snap a pic of the inside of your gauge so I can see the wiring and the adjuster (if there is one). The pics I've been posting are from 280 cars. I assume the 240 stuff is the same, but I've never been inside the early 240 gauges to confirm.

That all sounds normal. The gauges should move off their seats when you turn the key to ON. Bench testing should be relatively easy. Only complication is that you will not be able to directly measure the resistance of the sender unit while the sender is being used in the circuit. I would suggest connecting everything up, heating the sender to temp, note the gauge reading, and then quickly disconnect the sender and measure it's resistance before it has time to change temp dramatically.

I'm not sure that is related to the issue you've been working on or not. Next time you try to start the engine from cold, pull the small B/Y wire off the starter first and turn the key to START. You should hear the fuel pump run and prime the system. I'm thinking that your first start of the day difficulty may simply be that your fuel pressure has leaked down since the last time the motor ran. And yeah... Do the longer fuel line thing and let us know how the fuel pressure looks while driving.

Confusing diagram. I think they are trying to show "this is how it looks while in use". I think you are correct in that the nomenclature for normally open and normally closed is wrong in that diagram.

Yeah, I think it's a naming problem. I've looked the diagrams over and even though they call that thing a seat belt relay, I cannot find any connection between the seat belts and that relay. The switch in the seat belt buckle only actuates the buzzer. There is no interaction with the starter at all. And the inhibitor switch is on the transmission. It is closed only when the transmission is in PARK (and probably NEUTRAL). In other words, if the transmission is in reverse or a drive gear, the starter will not crank. You have to have the trans in "P" to start the car.

There is mention of a click when the key is turned, even when the starter does not engage. Can we get some clarification of the location of that click? In the original post, it was said "I just hear a click at the starter" and then later it was described as "click heard under the passenger side relay panel". Can we narrow that down to either a) at the starter itself, or b) over by the passengers feet?

This is a no crank situation when hot, on an automatic. Other than the obvious (wires, fuses, and connectors, etc) here are the components involved: Ignition switch Ignition relay Starter relay Inhibitor switch Starter The starter and ignition switch have been replaced recently. Doesn't guarantee that it's not the problem, but hopefully unlikely.

Yup. Slight pressure and move the tumblers around. Each tumbler should click over the wall and then move to the next one. Keep doing that one wafer (tumbler) at a time and the cylinder comes out.

I don't know if the heating and cooling over the years has an effect. The change in needle location before and after the work you did is a little puzzling other than the possibility that you cleaned a bunch of connections between the two ends of the system. So do you know if your oil pressure gauge is anywhere near accurate? Ever put a mechanical gauge on it? If the oil pressure gauge IS correct, it's still puzzling. But if your oil pressure gauge is reading inaccurately high, you're back to adjusting the gauge. And... It would be good to know if you've got lower oil pressure than you thought you did.

That is correct. The lower resistance, the higher the gauge reads. So yeah... One possible explanation is that maybe with the work that has been done to the car, including cleaning connections, may result in a higher reading than before that work had been done.

I think the complication may be that the compensation section is shared by both the gauges in the housing. it's in there, but not obviously attached to the TEMP gauge. Those pics I posted above are from the fuel gauge which shares the housing with the ammeter (or voltmeter depending on the year). And since the operation(s) of the ammeter/voltmeter are very different than the other gauges (fuel/temp/oil), they do not use a compensator stage. Here's a pic of the guts for the TEMP/OIL gauge. Note that there is only one compensator stage located down by the OIL gauge section. (in the lower right). That compensator is shared between both TEMP and OIL: So the bottom line is that if you adjust the compensator, it will affect both TEMP and OIL. If you're OK with that, then that's where you should focus your effort. If you DON'T want to do that (because you like where your OIL gauge reads and don't want it to change), then yes... I'd just tweak the bimetallic strip on the TEMP gauge and call it a day.

Yeah, once you know what you are working with, it's easy to get it apart even without the correct key. Been a while since I've been into the locks and I don't remember which direction the tumbler springs push with respect to the "walls" inside the barrel, but it may be as simple as using an uncut key? If not that, then some rudimentary lock picking would be the trick.

Phoned a friend! Haha!! Glad to help.

Sorry, but I can't view that attachment. Whatever format that is, my system can't deal. Can you post a .jpg or a .pdf?

This worked great for me. Both with loosening, and then re-tightening with engine out of the car: I'm not sure if all the flywheels had these holes along the outside edge, but I used a tight fitting punch (8mm or 5/16) in the hole and then blocked rotation with a bolt threaded into the block: This may be old hat to you engine guys, but it worked great.

Well it sounds like you have narrowed the issue down to an ignition electrical issue, and not fuel. That's a big step. So it may be temperature related, but at least we know it's not (directly) related to the fuel supply. Can you post a pic of your thermostat housing?

So the unusual nature of this issue has me intrigued. I know you said you were going to have the combo switch thing rebuilt, but in the meantime, I had a question. Are you running an old style single screw mount ignition switch, or has the whole assy been replaced sometime over the years with the newer two screw style? Here's a hoovered pic of the difference. Older single screw mount on the left, newer two screw mount on the right:

Yeah, that temp gauge is a little disconcerting. Even if your logical mind knows that it's an instrumentation issue and not a real temperature issue, just looking at that thing would drive me nuts. So while you are in there, are you happy with the location of the oil pressure readings? Because if you're going to be into the guts of the gauge, that would be the opportunity to adjust the OIL as well.

I figured. But it was worth a look!