snoz

I think at this point I'm going to start disconnecting things one at a time and retesting each time between what should be 12v+ and ground. I believe the only thing I have connected to that harness under the hood currently is the CPS. I'll start there and then start disconnecting it inside the car.

Landseer

So that harness, into which cps connects, also contains the ground wires for the engine electronics. Those are anchored at base of valley, right and left sides, bolted with 10mm bolts through their ring terminals,
correct?

snoz

It does, yes.

PorKen

I think the white and shield wires may be reversed (in the Audi style connector).

snoz

Apologies to everyone. I had what I was measuring switched around in my head. I wasn't measuring resistance between the injector wire that should be 12v+ and ground. I was measuring it between that wire and the battery post. I don't believe resistance between those two points is all that important.

The CPS is functioning properly. When I connect my noid light between the injector connection that should get the ground pulse from the LH and the battery post, the light flashes when I crank the engine. It wouldn't do that if the CPS wasn't functioning. The issue is that I'm not getting the constant 12v+ on the other wire in the injector connection. Is that voltage supplied by the LH?

FredR

As per the wiring diagram for your model year the voltage to the injectors comes from the battery to the central electrics via the fuel pump relay.

snoz

I feel like an idiot. I didn't know that the fuel pump relay had to be plugged in to for the injectors to activate. It makes sense that it does though. I had that relay out because I don't have the fuel rails and injectors on yet. I've tested with the relay in and things look good. Thanks FredR. That did the trick and thanks everyone else for the help. It's much appreciated.

Mrmerlin

based on your pictures the shielded wire appears to be on the opposite end of where it should be the ground goes to the center position

snoz

Thanks Stan. I'll get that switched around.

FredR

Ethan,

I get the impression that you may have inadvertently sown some seeds of confusion here.

The photo you submitted is a female connector as attached to the loom and one presumes it is the connector that fastens to the CPS. I have a feeling that our friends may have misinterpreted this as the connector for the CPS that your wording tends to imply and therein maybe the "confusion" I perceive [rightly or wrongly].

The junior power timer connectors have a terminal numbering convention for purposes of clarity on the wiring diagrams. For whatever reason the connectors built into our 928's do not show the terminal numbers and thus have to be inferred in line with some visual convention whatever it may be. Ironically on the wiring diagrams for the 1986 model even Porsche does not appear to use the terminal numbers of the connectors as they do for my model year.

The convention that Porsche seemingly uses for these cables appears to be terminal 1 for the measured variable [white colour cable], terminal 2 for earth [brown] and terminal three for shield. Your photo clearly shows that the shield is on the end terminal that corresponds to terminal 3 [as I can tell] the brown core is in the middle position and that leaves no scope for error- I submitted a photo to confirm the same layout to eliminate the notion that the mid terminal was the shield.

I am assuming that you have access to the wiring diagrams - the info that you need to know is that on the EZF plug terminal 7 is the white cable, terminal 19 is the brown cable and the shield is terminal 20.

I had a CPS that was working perfectly and i have a male junior powertimer connector to revamp it but unfortunately as I pulled the thing apart the male connector literally disintegrated and I was left with three terminals- the shield was obvious - the other two wee off-white and black but I have no clue as to which is which or how to test [if anyone happens to know?].

Bottom line- it is very easy to confuse cable orientation if one think one is looking at a male connector when in fact it is a female connector given the way they interact.

It gets even better for my model year- that has a Hall sensor and terminals 1 and 2 are inverted compared to the CPS and knock sensor convention and the cable colours are not labelled correctly [for the Hall sensor] on the wiring diagram!

Mrmerlin

well you should be able to find the ground wire might be black, it goes to the center pin,
the shield wire as,
Fred suggested should go to pin 3 location,
look on the connector the slots are labeled

FredR

The slots are labelled on new after market connectors like the ones I have been using but I could not find any markings on the connectors I took out.

I think the CPS male connector assignments you mentioned with black on pin 2 and white on pin 1 are the most likely- if they were the wrong way round one wonders if such could damage the EZF unit?

Mrmerlin

well if you have a picture of the old plug use the slotted connector rib as a guide