280z efi to weber electrical issues

[Classic Z]

Hi

I have a 1977 280z which I am converting to triple webers.

I am having difficulty with the wiring and hoping someone who has been through this could help or point me in the right direction.

My 1977 280z has been fitted with a 280zx distributor and was installed by the previous owner. I have removed all EFi from the car including the wiring loom for the efi and ECU.

I am installing the mangoletsi manifold with triple webers and low pressure fuel pump. My question is, if I install the low pressure fuel pump in the back where the old pump was and wire it up there will the car start or do I have to rewire in the engine bay? The efi wiring loom seemed to connect to the coil I believe. Can anyone tell me what is needed. I a wondering if I have Brocken the circuit somehow or now that the ecu is missing if that would effect the fuel pump or ignition system.

Many thanks

 

[jonbills]

I dont think you should need any rewiring in the engine bay.
whether it will start or not is a different question...

 

[moggy240]

Before you start, test the fuel pump wires to see if you are getting power first.

 

[Classic Z]

Before you start, test the fuel pump wires to see if you are getting power first.

Good idea. Will check that first then install the low pressure fuel pump and see if it works. Thanks

I think what I will do, is once I install it and get everything working I will produce a step by step guide of what I did and post it on the forum so that others can benefit.

I have found it very difficult to find a guide of what to do online.

 

[johnymd]

Looking at the basics.

Replace the pump at the rear with a low pressure pump and check you have ignition power. If you don’t the trace the wire and connect with an in-line fuse, as the 240z does.

The coil need ignition/start power (via the tachometer on 240z) to its + terminal (no ballast resistor). Piggy back off this terminal to the + on the distributor. The - on coil goes straight to the - on distributor.

That should be it I think.

 

[moggy240]

The ecu wiring is totally separate to the rest of the car wiring so you should not have any problems. You should be able to turn the car over on the key with the ecu wiring removed.

 

[peter_s]

The ecu wiring is totally separate to the rest of the car wiring so you should not have any problems. You should be able to turn the car over on the key with the ecu wiring removed.

Not fully, the fuel pump is controlled by the relay that is connected to the ECU. There is one connector connecting that ECU harness to some other things, on the steering rack.

I would put in a new relay and fuse for the pump. You can use the existing wiring going to the pump. It's connected along the steering rack close to the ignition switch.

 

[johnymd]

Yes, but will the coil and distributor wiring be part of the egi/engine loom? I think it is part of it so the engine will turn over but not start until you wire up the coil and dizzy.

 

[peter_s]

Yes, but will the coil and distributor wiring be part of the egi/engine loom? I think it is part of it so the engine will turn over but not start until you wire up the coil and dizzy.

That connector also goes to the transistor ignition unit and the ignition coil. That is controlled by the same double relay. I can't answer exactly how it is on this exact car doe to the alterations with the 280ZX parts. But on mine, that connection would be critical if you were to use the stock ignition parts.

I'll dig up the wiring diagram!

 

[peter_s]

Here is the wiring diagram. Look at the connector just above the Door switch (L.H). All the green cables goes to the relay controlled by the ECU.

If you trace on the other side of the connector you'll even find one going to the starter. I have never understood why (I think it's so you can't engage the starter above a certain speed)... It should be safe to remove that one.

 

[peter_s]

The connector is on the bottom close to "1977"

 

[moggy240]

I found this diagram in the Haynes manual.

 

[peter_s]

Yeah, that's a good overview!

The one I uploaded is the correct with the color codings, for the whole car. You can find it at www.classiczcars.com

Here is how I did, I cut off the connector with wires from my ECU harness. If you connect a 12V source (with a relay and fuse) straight on to the cable there going to the fuel pump you'll have the direct cable going to the pump. It's the greenish one on the other side (going up under the dash). That relay should be controlled by a source that has voltage after after ignition.

Since you have ripped out the ECU I don't know if you need any other connectors there. Can you still use the transistor ignition unit? If not I would switch to an MSD electronic ignition system or similar.

 

[moggy240]

That is spot on!!!
If the wiring is missing from the distributor and coil I wonder if you can wire it up as if you was fitting a 280zx dizzy to 240Z conversion

 

[peter_s]

If the wiring is missing from the distributor and coil I wonder if you can wire it up as if you was fitting a 280zx dizzy to 240Z conversion

I think that wiring is almost fully in the other harnesses. But the ECU still send power via that double relay to that circuit, "arming" it after ignition has been switched on. That's the only connection between the ECU harness and the other harnesses. You can trace the connections in the wiring diagram I uploaded.

I would just connect another relay to those parts via a fuse the same way as the fuel pump I described above. If you haven't altered anything else, you shouldn't need any other wiring than that. But I'm not 100% about what the ECU controls here when it comes to that double relay. I don't think you need anything else though:

1. One relay and fuse to control the fuel pump
2. One relay and fuse to control the ignition relay

That should be it (but I might have forgotten something)

Thing is, I have just wired up my car regarding these parts, but I'm going EFI, so the only cable I need here is for the fuel pump. My ECU controls the pump, ignition and injectors. So not exactly the same as this problem, but the carb setup should only need power to the fuel pump and ignition system.

 

[Classic Z]

Thank you to all for your help. Appreciated.

I will be looking at the wiring today and will let you know how it goes.

With regards to the fuel line: I plan on running the main fuel line into the Webers and then out the back into the return line as seen online. I am only using a low pressure fuel pump in the back and no fuel pressure regulator in the engine bay. Do any of you know if its essential to use a fuel pressure regulator or not. The company who I bought the Webers from said that I could simply use the low pressure pump with no fuel pressure regulator is that correct?