ramcram

My April 86 build 5.0l Australian delivered 928S has just had the engine out and pretty much everything that can be renewed has been. Coils, caps, rotors, plug leads plugs, fuel regulator, fuel dampers, injectors, hoses just to list a few.

My query is the Green and White shielded wires that run from the EZF unit to Ignition Trigger units 1 and 2, plug into the EZF loom by the CE Board with a 2 pin plug. My car has a 4" [100mm] aprox extension piece plugged into this connection joint. It is just like an extension but it certainly doesn't need one because the wires are too long if anything.
I has a Porsche tag on the extension piece with 928.612.033.00 on it. PET says it is an 'adapter' and lists it 4 times, one of which is M28.45/46 Australia 86.

What does it do?
TIA

ramcram

My April 86 build 5.0l Australian delivered 928S has just had the engine out and pretty much everything that can be renewed has been. Coils, caps, rotors, plug leads plugs, fuel regulator, fuel dampers, injectors, hoses just to list a few.

My query is the Green and White shielded wires that run from the EZF unit to Ignition Trigger units 1 and 2, plug into the EZF loom by the CE Board with a 2 pin plug. My car has a 4" [100mm] aprox extension piece plugged into this connection joint. It is just like an extension but it certainly doesn't need one because the wires are too long if anything.
I has a Porsche tag on the extension piece with 928.612.033.00 on it. PET says it is an 'adapter' and lists it 4 times, one of which is M28.45/46 Australia 86.

What does it do?
TIA

ramcram

The reason i'm asking for this advice is that it started and ran as sweet as, even drove around the block but now, a couple of days later it refuses to start and i'm stumped as to why.

Mrmerlin

pictures are a great way to add detail.
do some simple tests.
Put the engine at TDC look for the timing marks to align.

Pull a plug is it wet?
if so try cranking with the foot to the floor till it runs.

Spray some ether into the intake and crank it,
if it runs then your missing fuel.

Pull a plug wire add a plug and ground the electrode crank look for spark.

ramcram

Thanks Merlin.
The engine has just been put back in. It was removed to rewire [partially] the engine bay because of an engine fire [I bought it like this].
While it was out I took the opportunity to do as much as I could to the hard to get at bits. This included cam seals, sump gasket, timing belt and water pump.
Cam timing was checked with Porken's 32Vr tool.
As the wiring was repaired [my mate and I did this work and we are both qualified auto electricians and this is my 5th 928], we tested each system and sub system with the trusty multimeter and an external 12v 30A power supply.
The in-tank pump was removed to check it and its filter, it failed and was replaced. As part of the fuel tank/lines flushing process, we did a delivery test and it exceeded specs.
Haven't yet done a fuel pressure test as just haven't got there yet and it started and ran absolutely perfectly first time. Even a quick drive around the block was very pleasing.
Went on doing some of the other thousand things that have to be done with a motor replacement, new bonnet cable, new trans cooler hoses etc. Then tried a start and to our surprise, it refused.
It does fire but seems to load the starter motor as if the ignition timing is too advanced. This of course is not adjustable and the firing suggests that spark and fuel are present.

John Speake

In the WSM it shows a test connector for the output stages near the fuse/relay panel. It's an in line series connector between the CE panel and the lines going to the output amps.

It's for testing the output amps. There are two wires White and green. If you touch either to 12v then it will trigger the output amp. I think this may be what you and seeing ?

See Vol 1A Page 28.63. This is for the 16v Euro, but the '86 has the same ignition system.

ramcram

Yes, these are the wires John, they are shielded and run from the ezf unit to the 2 trigger units.
Mine has a connection piece [adapter 928.612.033.00] plugged into this joint. All it seems to do is make it longer but under the insulation I can see that the shielding must be open circuit because I can see a distinct reduction in the wire diameter.
What does it do? And why is it there?
What happens if it is removed?

John Speake

If you mean it is just an extender in a series connection with the feeds to the output amps, then you could remove it if there's enough cable to reconnect the original connections. If it's just a spur off then you could also remove.

I have no idea what the lead assembly was designed for, never heard of it before !

ramcram

It is an extension in series, that's the mystery. there is already excess cable, it certainly doesn't need more length.
Why would Porsche make this part, assign it a part number and list it in the PET?
It bothers me!

Mrmerlin

This thread....

John Speake

Maybe it needed an extensive to able to connect into some test set ?

ramcram

We have spent a good bit of the day testing stuff to see why it won't start. Everything tested so far says it's ok. Didn't have my oscilloscope though, so didn't do some things.
Tried to start it with and without the mystery green/white extension wire and it made no difference.
It fires on crank, telling me it has spark and fuel but loads the starter as if it is too advanced. Bridging the fuel pump relay with a switched bridge, so the fuel pumps can be turned on and off shows that firing stops as soon as the pumps are turned off and begins again as soon as they are turned back on. This tells me it is not flooded.
Some times during cranking, the tacho needle swings erratically across its scale like low voltage but we have checked the cranking at 9-10 volts.
All this and it ran superbly a few days ago?

John Speake

It sounds to me that the EZ-F may be having problems synchronising to the gap in the timing gear teeth. This is the usual cause of EZ-F failure. I assume the car only runs briefly and then cuts out ?

I suggest you borrow a known good EZ-F from another owner, or Matt Nicholson will probably be able to offer you one on a sale or return basis.

ramcram

No, it doesn't run at all now, just fires during cranking, trying to start as if a bit too advanced.

John Speake

Swap the EZ-F..... could save you lots of time chasing other possibilities.