Noobie here needs Fuel pump help!

[JRSGTS]

YES! It has to be a ground...I think.. When I ground 72 I get FP...I will make sure I get feed on 76. But I did cont. check on 20. There is no open between the relay and the ECU, so where am I losing ground? Ran a fresh ground to the pump, the engine, the ECU case ( Just in case ) As far as the Christmas bulbs go, should I be using a whole string? Cause the one little bulb blows real easy when it hits 12V!

Love the colored schematic! Wish my stupid printer would communicate! It's on holiday. Guess that's what we should all do. Have a great turkey day! I'll check in with progress on Friday. Thanks again! JR.

[FastWoman]

Sounds promising!

I have no idea how literal the schematic is, but if you take it at face value, the ground runs all the way back to the battery and is the same branching ground system that grounds the ECU. That could be your smoking gun right there.

I'd first check the connections off the battery for obvious reasons. However, the branched connections in the wiring harness are crimped and wrapped over and are possibly also subject to corrosion. You might want to unwrap the wiring harness enough to find all these branch points and verify they are clean/good.

Don't worry about the fact that 12V will blow a bulb. A straight 12V will melt down an injector the same way. Remember that you have drop resistors wired in series to limit the current flow! Just use a single bulb, and you'll be fine.

Have a great Thanksgiving, JR!

[superlen]

JR.

FYI, you can stop worrying about pin 20 going to the ECU. It's not even connected inside the ECU. My thoughts on why are that Bosch engineers were planning ahead to control the FP relay at some point via the ECU, but for your year model, they didn't. If you look at the ECU connector (Not the harness, the ECU itself), most likely there won't even be a pin installed in location 20. (Some do, but most of the 75-77 ecus I have taken apart don't have pins there). And, even if the pin is there, it's not connected to the circuit board inside.

The ONLY ground you need to worry about on the relay is pin 72 on it. Both internal coils ground through this connector. If you have good gnd there, the relay will be satisfied. Here's the path for the fuel pump to turn on via the flap.

1. Bat + at pin 70. (all the time regardless of key pos)

2. You turn key to ON. This first one coil inside the relay block and connects p70 to P43 (dropping resistors), & P39(one side of AFM switch) P43 and P39 are connected inside the relay.

3. Now move the AFM vane. This runs the +12v back to the relay onto to Pin36 which fires the second coil in the FP relay. That relay will then close and connect P73(+12 via fusible link) to P74(the pump).

If I were troubleshooting I would do these in order.

1. GND pin 72, hot wire +12V to pin 36. (This should FIRE fuel pump by connecting p73 & p74)

2. If that works, then your problem is with the signal getting to Pin36 by way of the AFM switch.

3. If that doesn't work, then you either don't have +12v reaching pin 73 via the fusible link or the relay it'self isn't passing the signal to p74 or the wire from p74 to the FPump is open, or the pump doesn't have ground.

Another way is to work backwards with a +12V jumper wire.

1. With the key OFF.

2. Jumper +12V to P74 (pump should run - as P74 is the actual wire going to + side of pump)

3. Jumper +12V to P36 (pump should run ) - tests one of internal coil/contacts of relay

4. Jumper +12V to P39 & Move AFM flap off idle (pump should run) - tests AFM contacts

5. Now turn key ON & Move AFM flap off idle (pump should run) - tests the second internal coil/contact.

I'll be heavily involved in fuel pump relay wiring & general purpose ECU testing Friday. If you are working on it then, PM me and I can give you contact info to call me. With a diagram in front of you and some quick conversation I bet we can figure it out. The Z's relay scheme isn't quite straightforward, but once you wrap your head around it, it makes sense.

Happy Turkey Day!

Lenny

[JRSGTS]

Wow!! Thanks so much Lenny And Sarah!(I checked your profile so I didn't keep calling you Fast:) Some really great info, and lots more tests to run! I'll dive in fresh and well fed fri. AM. If I'm still head scratching Lenny I'll PM you.

I'm wishing you and yours a very happy Thanksgiving!

[FastWoman]

You're quite welcome, JR!

I think once you get this Z running, you will fall in love with it and have to own one yourself.

[JRSGTS]

You are quite right Sarah! Though I would likely drop a small block chevy in it An early 240 with about 350 Hp could be one helluva ride!

Sorry I couldn't give an update today... Between getting the step daughter to emergency dentist appt. and all the other things to do, I got about a 1/2 to look at the car... I had a used starter to try for the fun of it to see if it changed my cranking problem...Yah..fun..easy swap. just had to try it. I'll have a new one tomorrow.

Did a real quick run on your tests Lenny. Post results tomorrow...Yup something's real wrong...I'll be in touch.. JR.

[FastWoman]

Nooooo! The Z doesn't need a small-block V8! The L28 is a beautiful engine. You'll see. But of course I'm a sucker for a nice inline-six.

[sblake01]

An early 240 with about 350 Hp could be one helluva ride!

That's true. There's one right up the street from me. A very nicely done 280 with an LS1. Somehow, though, it still just doesn't seem right to me........

[JRSGTS]

NICE!!! Good to know...

Here's the latest..Fighting a lingering tryptofan (sic) hangover. I went to the shop..12 degrees here, Toasty in the shop. Just another excuse to be lazy. I saw the starter was dropped off so I had to go to work.. Installed the starter, YAY cranks normally now! Even acts like if it had fuel it would run. Sputters a little and smells like the plugs are burning whatever they can find.

Lenny I did your tests. It failed the first one. went to ground P72, started letting the smoke out of my jumper wire! There is Battery voltage there...That's not right. Moved on to your backwards trouble shooting. 12V to P74=got pump.but, 12V to p36=no pump. and 12V to p39and move AFM flap+ still no pump. I also rechecked again for inj. pulse now that I have normal cranking= Nothing. tried to start it while p72 was grounded and pump running, Nope. didn't expect it to, had to try it.

Obviously 12V at 72 is a problem,Hopefully you can give me a direction. If it's not wiring I'm still leaning towards the ECU because of the no INJ. fire. The owner tells me it was running fine, drove into his drive way, and it never started again.

I've got to go to the neighbors for their printer to get the Schematic printed. My printer is still on holiday.

BTW, I posted some pics of my shop on my profile if you want to see some of my work.

[JRSGTS]

That's true. There's one right up the street from me. A very nicely done 280 with an LS1. Somehow, though, it still just doesn't seem right to me........

I get it. I respect the purist mentality completely. I ALSO love the dare to be different, and the right of choice with customizers. Lots of Ford people hate seeing Chevy's in Hot Rods. I say if it works for them, go for it. Besides, the LS1 is an amazing engine! Bet that car is way cool and makes more HP than that Z ever imagined. Of course it opens a whole can of worms for other issues. Congrats to him on his bravery!

[JRSGTS]

https://scontent-a-ord.xx.fbcdn.net/hphotos-prn1/p480x480/524047_691384690881200_1355525336_n.jpg Here is the little gem...Hope this works...Not very Forum tech savvy

[superlen]

JR,

Something definitely not right here. P72 should be connected to GND already in the harness. If you are seeing +12V there, we have an issue already. P72 is the ground side of both coils in the relay. This would also explain why (12V to p36=no pump.) as the coil gets +12V from you on p36 via jumper wire, but the other side of the coil isn't grounded. The following tests would be of no use until we figure out why P72 is showing power.

This same ground is the ground for the ECU as well, so that might also explain why the ECU is not firing injectors.

One thing I might bring up is that Datsun did some crazy color schemes on the FI harness power supply. Such as the ground wire (The same one I'm talking about) where it connects to the battery is a large 8awg or so "RED" wire. Sometimes its Black, but I have seen them RED. Where it connects to the battery is just a big spade connector (stock) but might have been changed over the years, but someone could have mistook it for a power connection and have it connected to +12V instead of gnd. It runs right up to the battery & looks like it should be tied to +12V because its' red.

To find out, pull the connector off the ECU and measure the voltage at pin 35. It should be GND. Actually pins 35,17,16 & 5 at the ECU connector are all tied directly to GND. If one of these is gnd all should be.

Lenny