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Maybe you could use a needle taped to test lead into 34 wire as close to the ecu connector as possible to check for voltage from ecu before unwrapping more harness.
 

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Discussion Starter · #42 ·
How hard is it to work on the ecu connector? I cut and tested wire 34 about 6inches away from the connector and still no power.
 

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Well, you traced it back to ecu 34 no power. Are you in cranking mode when you check this?
EF-15 tells you the fuel pump is to run in the Start, cranking position; after running the air flow meter enters the picture to keep the pump running.
I admit I'm not experienced with the intracies of Zs, but trying to help where I can.
 

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Discussion Starter · #44 · (Edited)
Yeah I tried with the key turning to start. Ecu pin 34 is still reading good. But the wire leading to the air regulator just isn’t getting power, like I said I tested it about 6 inches away from the ecu connector and no power there. So I’m assuming something is wrong with the base of the wire connecting to the ecu connector. I’m just not sure how daunting it would be to work on the ecu connector. Once again, thanks for all your help, it’s really appreciated.
 

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They make (or you can) "lockpicker" tools with small, fine tips that can be inserted into the "cavern" that the wire terminal is in.
Key will be whether the terminal is held in by a mini plastic tab(s) that snap into a notch in the metal terminal or whether the terminal has tab(s) that snap into a notch in the plastic ECU connector.
With great care they can be removed. Tugging on the terminal to get a little movement helps to remove the "tension" on the tab as the mini tool is inserted.
As an example of the type of tips a removal tool might have:
None of these may be right for you, but .........
Sometimes one of the smallest flat blade screwdrivers in a dollar store set can be used effectively. Again one or two tabs is key.
Examples of typical types of terminals:
https://www.mouser.com/Molex/Connectors/Automotive-Connectors/_/N-1ehb5?P=1z0zlewZ1z0xaraZ1z0jmic
They come in round and rectangular/square.
A Jewelers Loupe can with backlighting, opposite the loupe, thru the connector body can be handy to try to ascertain the tab location and type.
 

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Discussion Starter · #46 ·
Thanks for the tips. Yesterday was actually the first day I’ve had a chance to work on the Z since my last post. But I took apart the ecu connector and can now confirm that wire 34 isn’t getting power at the base of the terminal. And that wire 72 is feeding power all the way through to the ecu, now I’m just waiting for a set terminal removal tools to arrive like the ones in the link, because I couldn’t seem to remove that terminal with anything else. Looking inside the terminal I can’t see any corrosion or anything that would look like it would prevent power going through, guess I won’t know for sure until I get it out though
 

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Thanks for the tips. Yesterday was actually the first day I’ve had a chance to work on the Z since my last post. But I took apart the ecu connector and can now confirm that wire 34 isn’t getting power at the base of the terminal. And that wire 72 is feeding power all the way through to the ecu, now I’m just waiting for a set terminal removal tools to arrive like the ones in the link, because I couldn’t seem to remove that terminal with anything else. Looking inside the terminal I can’t see any corrosion or anything that would look like it would prevent power going through, guess I won’t know for sure until I get it out though
Hold on - before you start yanking out wires from the ECU connector, where does that wire terminate/what does it control. There could be a corroded connector along the way which is why it isn't getting power to the computer...
 

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Discussion Starter · #48 ·
Thanks for the tips. Yesterday was actually the first day I’ve had a chance to work on the Z since my last post. But I took apart the ecu connector and can now confirm that wire 34 isn’t getting power at the base of the terminal. And that wire 72 is feeding power all the way through to the ecu, now I’m just waiting for a set terminal removal tools to arrive like the ones in the link, because I couldn’t seem to remove that terminal with anything else. Looking inside the terminal I can’t see any corrosion or anything that would look like it would prevent power going through, guess I won’t know for sure until I get it out though
Hold on - before you start yanking out wires from the ECU connector, where does that wire terminate/what does it control. There could be a corroded connector along the way which is why it isn't getting power to the computer...


It’s the wire that goes to the air regulator. As far as I can tell it just runs straight from the ecu to air regulator. I pulled the whole wire through to firewall to examine it. I followed the figure on EF-49 in the fsm. If I bypass that wire and just run a lead straight to battery, I can get the fuel pump to run.
 

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Discussion Starter · #49 ·
Does anyone have any tips or tricks they could share on how to exactly pull a terminal free from a connector? I bought removal tools like the one dumbestone linked (much obliged), but unless I’m just clueless, I can’t figure how to free the darn thing. The terminals have a little maintenance slot that I gather you’re supposed to insert the tool into and lift up, and that frees the terminal. But I’m beginning to suspect that after 40 years, the metal terminal is just stubbornly set. Unless I’m missing some tabs or locks that can’t be seen
 

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When you insert the tool, you should (maybe) feel some resistance and then a slight give as the tool pushes the tab down. If the tools are too wide or too thick, you may have to make a tool out of .016 brass with a tab about 3/32" wide for a start. Local hardware stores, like Ace, should carry brass stock for a couple of $$.
Have you tried pushing the tab in and out while the tool is in there. It can take some force if you can get your finger and thumb on the wire/terminal. Or a small set of needle nose pliers held snugly but not over-tightly on the terminal, which gets a better grip.
 

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Discussion Starter · #51 · (Edited)
Thanks for all your help dumbestone. Wouldn’t have figured it out without you guys. I started to damage the terminal so I just gave up. I’ve bypassed wire 34 for now, and taped up the harness, it’s good enough for now to get the car running. Fortunately there’s a couple of shops near by that specialize in old nissans. So once I’m completely road worthy im taking a trip to there, a buddy who takes his 240 there says they do excellent work, so I’m sure they’ll be able to sort out wire 34 no problem. Well onto replacing the blown water pump now, and the giant rust hole under the battery tray ?, do all Datsuns have rust in the same place? My friend and I both have rust directly under the battery tray.
 

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Of course, it's just one man's approach, but some time ago I adopted the practice of mounting all batteries in marine battery boxes. Haven't had an issue since.
 

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I vote bad oil sending unit. Read the FSM. I have fought this before. Made in Japan is the best. But are getting hard to find. Generic ones do not work properly. Small items can cause Large issues.
 

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Seems to me that if the engine is running, you have no problem between the fuel pump and the join under the seat...
 
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