Fusible Links... Where are they?

Mr.G

Mr.G

Club Member
Can't seem to find them anywhere in the engine bay.:conf2:

Previous owner of my 240Z had the L28 with the EFI loom installed but I have no idea where they put the fusible links, I cant even see a modern type fuse box in the engine bay.

Also trying to figure out the way the immobiliser was fitted, same time as efi loom was installed. I discovered that a yellow wire comes from the drivers side and enter the Loom plug and goes into pin 1 of the ECU. The original wire that had gone there has been cut and substituted for the yellow wire. What's the logic behind this?

Any ideas folks, appreciate any help.
 
Pin 1 is the "run" signal from the ignition coil -ve. Without this connected, nothing happens! Can't help with immobiliser, but a good ploy would be to get it to cut this run signal...??

On the original 280ZX, the fusible links serve the EFI relay. On the later 280ZX, these are in line direct from the battery +ve. Find your EFI relay and work back from pins 71 and 72 to see if fusible links have been used or if the relay is simply hard wired to 12V +ve.
 
The two fat white wires into the relay should be linked to the battery (or direct H/D 12V source) via two fusible links.
 
Will double check tonight thank you Mike.

Mike, does the relay i showed you above act as a Power Relay and Fuel Pump Relay?

And is it common practice to do what this guy did ie Cutting into Pin1 to make an immobiliser? I guess if he cut into the original wire for pin 1, replaced it with the yellow wire which goes to a switch and then fed the wire that would have gone to pin1 to a switch, then the switch would control the -ve coil signal.
 
I had a look and can now confirm that there are no fusible links in between, and as you said the Fuel Relay is hard wired to the +ve side of the battery.

Next thing I am trying to figure out is why this wire, NO.1 in the pic runs down the rad support and towards the main loom?
http://www.xiotis.com/EFI_files/image011.jpg
 
The yellow wire with the female bullet connector looks like the water temperature sender for the gauge. Would the other two be connections to B and C terminals on a 280ZX distributor?

Back to the EFI relay - this is only for switching the power circuits for the injection system and ECU. Output is to pin 10 of the ECU and secondly, power supply to the dropping resistor and on to the injectors themselves. The injectors are triggered by switching to ground within the ECU. The fuel pump should be controlled by at least one, possibly two, relays, separately powered and with some safety control regarding loss of oil pressure and the run signal from the alternator built in...

As noted earlier, immobilser interruption of the ignition "run" signal would be an effective anti-theft device as the ECU will not operate without this signal.
 
Mr.F said:
The fuel pump should be controlled by at least one, possibly two, relays, separately powered and with some safety control regarding loss of oil pressure and the run signal from the alternator built in...
Click to expand...

I will look for the Fuel pump relays, they are definately not in the engine bay. The FSM says that there is a FLAP in the AFM which when closes sends a signal to the Fuel Pump relay to close the power to the relay.

In theory then if I follow the connector of the AFM one wire should lead me to the Fuel pump relay. Or I guess there must be a +ve terminal leading to it.

Also where is the Tach signal and what is it for?

Sorry for the zillion questions!
 
As far as I can see, there are no direct connections between AFM and fuel pump relay control system. One relay links to the air regulator - I presume to its heater system when the fuel pump is running. Early EFI systems run two interlinked relays, later EFI runs a single relay.

I'm assuming you are dealing with the UK style EFI system rather than the ECCS version - there are some diversions with that system, including different distributor / crank angle sensor...?

The "tach" signal is the same as the "run" signal noted above which links to pin 1.
 
Thanks Mike.

That would mean that I most probably have a later 280ZX system, that's if we go by the single efi relay. And yes, it is a UK 280ZX System including Dizzy (for now).

With regards to my idea of following a +ve connection from the battery, I am assuming it should eventually take me to the fuel pump relay? There must be one, surely.

And lastly, is it normal to have the coolant terminal, B and C Wire, (which we mentioned earlier) coming off a seperate loom from the EFI loom? The loom they are on is part of the main loom situated on drivers side of the bay, runs across the rad support and then goes to the coil and the coolant sensor and dizzy.

Engine wiring, fun :) fun :unsure: fun :confused:
 
Don't confuse the EFI relay (a single unit in all systems) with fuel pump relay(s) - one or two relays in UK cars depending on age and modified implementation on your car.

The ignition side of the system is part of the main loom on the UK EFI set-up - a loop runs all the way to the back of your tacho, for example, to a pick-up on the rear of the gauge. There is no ignition control from this EFI system, only fuel - the ignition advance is handled in the old-fashioned vacuum / centrifugal weights manner by a standard (albeit electronic) design distributor. On the ECCS system, the crank angle sensor distributor provides input to the ECU and allows for control of advance / retard via the signal to the power transistor and coil, i.e. the distributor internals are fixed and the ECU adds delay into a pre-advanced system. Automatic retard for the turbo system is incorporated in the relevant ECU for that model.

We didn't have ECCS systems in the UK, so if you are trying to integrate such a system into your car, then you will have more work to do and the standard UK distributor will be obsolete...

For UK EFI, fuel pump and fuel pressure control are completely separate from the ECU whereas on ECCS, fuel pump has additional control via a modulator unit which changes the voltage applied to the pump, reducing noise at low speed operation and power consumption. In many ways the 280ZX ECCS shows the early development of the systems common to Z31 and Z32 models.
 
Cheers Mike, educational as always.

No, I'm not trying to integrate the ECCS system in my car, I have the intention of using some form of Standalone EFI system and my intentions are to get to grips with understanding my system before undertaking the installation of a completely foreighn one.

I am aware that I can rip most of the loom I have out, but I hope by knowing how existing things are wired will help to eliminate some problems that may haunt me later.

Any tips for hunting down the fuel pump relay? Would it have a +ve power source to it? Would there definately be a fuel pump relay or could it be hard wired in?
 
On your type of conversion it is common for the installer to have skipped over the complexity of wiring in the fuel pump relay(s) and their associated protection against the fuel pump continuing to run even if engine stops or oil pressure is totally lost.

On the two relay (UK) system an ignition controlled feed switches in the direct battery feed for a few seconds to energise Relay 2 to prime the system and then cuts off. If the engine is started (and has oil pressure), the system restarts. Relay 1 is a normal single ON-OFF relay, but Relay 2 has two coils and a "flip/flop" temporary ON mechanism which energises or switches off Relay 1.

On single relay (UK) EFI systems - late '81 to '83 - the relay is again a "flip/flop" type, but gets its switching signal from the ECU via pin 13. Without the signal, fuel pump is off; with the signal, the direct power IN from BATT source is switched to ground, the relay flips and the fuel pump is ON. The ECU automatically grounds for a few seconds on power up to prime the system.

So...first identify which type of ECU and EFI system was used to implement the conversion in your car and this will tell you what sort of fuel pump control should be there. Give me a call with the part number off the ECU and I can identify for you.

Aftermarket wiring will not necessarily have been part of the EFI loom, but added separately.
 
That's smashing info Mike.

I am surprised there is not a write up in the UK of a 280ZX EFI conversion into a 240 or 260Z.

Information on back of ECU is as follows:

22611 P6600, A11-000 42L, 8Y24, L28MT
 
22611-P6600 is early type EFI (no integral fuel pump switching) suitable for manual transmission. Dated 10/78 to 09/79.
 
Brilliant detective work there! You are wasted on us Mr.F, you would have had a very prosperous and succesful career at NASA HQ.

So in summary, for a layman like myself what does this all mean?? No integral fuel pump switching, does that mean there is no fuel pump relay?

Thanks for your patience.... :)
 
It means that the original installer could have direct wired the fuel pump to th eignition with no effect on the EFI system. In UK cars this early system would have had the twin relay system in place with connections to alternator and oil sender.

This should help:

EFI scan.jpg
 
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That is awesome!! :bow: Just what I need! :)

I've printed it on A3 paper and it looks fairly straightforward. What do the numbers mean though? I know what the ones relevant to the harness connector are, but what about the others?
 
Most of the devices will have the relevant numbers cast onto them alongside the contacts. Otherwise, the numbers relate to the pins on the ECU or the equivalent contact on th enext device in line.
 
Mike, on further investigation of the wires coming from the main loom and going to the dizzy, I observed the following:

I have a GREY wire which goes to the B terminal of the ignition module on the dizzy, I can tell that it is new and has been formed by joining a WB Wire and a GW wire from the main loom. I think this wire is the Key on 12V positive.

Could you tell me what those two wires do and why they were joined together? I can't seem to find a relevant wiring diagram of this area. I did do some digging on the net and there may have been a ballast resistor to drop the voltage to the coil but since i cant see one it may have been removed to get the full 12V going to the coil.

There is also a BW wire going to the (+) pole of the dizzy, i think this is also a Key on Positive. Do both my new GREY wire and the BW wire do the same thing. So in theory I can change my GREY to (+) side of the coil and the BW to B side of ign. module?
 
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