Here are pages from the 1981 current flow diagram:




Power supply/starter, Ignition, and Fuel pump.





Fuel Injection System.



If I understand correctly, all the injectors are tied to pin 87 of the AFC relay (relay XVI). Pin 30 of the AFC relay is tied to B+ (battery +) Meaning one side of all the injectors is hot with 12V. To fire the injectors, the fuel injection control unit grounds them in banks of two.

The fuel injection control unit is powered by wire 50 from the fuse/relay (CE) panel via:
-wire 50 through Starter Blocker Relay via pins 30 and 87
-junction past pin 87
-Plug W, pin 7 on the CE panel
-bk/gn (black wire with green tracer) wire to pin 4 on the fuel injection control unit

Now, I am a dolt and don't really understand where wire 50 gets is power in the CE panel. I want to say it is constant power. However, I believe wire 50 is good in your CE panel because the engine starts and briefly runs.
Note that wire 50 through Starter Blocker Relay is used to energize the starter solenoid via the yellow wire through pin 14 of the 14-pin connector. As well, it powers the thermo time switch for the cold start valve.
Find the connector on the fuel injection control unit, find pin 4, look for 12V on it when the key is in the 'START' position.

OK, to further muddy things a bit, the fuel injection control unit is also powered from the ignition control unit:
-pin 16 on the ignition control unit to green wire (not THE green wire) to Plug O, pin 7 on the CE panel
-Plug W, pin 6 on the CE panel
-bk/gr (black wire with gray tracer) wire to pin 1 on the fuel injection control unit
Find the connector on the fuel injection control unit, find pin 1, look for 12V on it when the key is in the 'RUN' position.


I am sorry if this is confusing, as I don't yet fully grasp Porsche wiring diagrams.
Good Luck!!!

 

 

WOW!
Thanks for the detailed description. I have some sleuthing to do. Good news is that I do have a set of factory manuals and some friends that actually understand how to read them.
Here goes!

 

Why do you even have a relay in VIII? I don't believe VIII is used on an 81. Fuel injection relay is XVI (928.615.119.00)

Check your relay in XVI for correct part number and remove whatever relay is in VIII and let us know.

This is the relay I pulled out and I bought a new one from Roger even though I bench tested it and jumped it.

 

Okay, but you posted that you replaced relay #8. There should be NO relay in that spot-just an empty space for a relay.

 

When cranking, do you have power coming from the 3rd wire at the starter?

 

Relay #8 (VIII) is the 4th spot on the top row from the left. That spot should be vacant on your car.
Relay XVI is your fuel injection relay. It is located 4th from the right on the top row. That's where you need that new fuel injection relay from Roger.

Not trying to be patronizing, but some folks stick relays in empty slots and it can cause unwanted results

 

Here is a pic of the relay in the #8 position. I went by the relay guide. You are saying it should be in the #4. Why do you think #4 was empty?

 

Okay. I see where you are coming from now. There are actually little Roman numerals made into the white plastic of the CE panel that show the relay numbers (I - XXII)
What you are calling relay position 4 is actually relay position VIII (8).
What you are calling relay position 8 is actually XVI (16).
So by the numbering systems that you are using, relay positions that should be WITHOUT relays are : 1, 2, 4, 15, and 16

I think most folk use the factory numbering for the relays. You can see that on 928 Specialists' website, (www.928gt.com). Just go to the fuse/relay charts area on the left side and click the year of your car.
Or here is a shortcut thanks to 928 Specialists
https://www.928gt.com/t-81fuse.aspx

 

My next step is to verify power to the injectors. I just hope the injector loom is not bad, Although this car is a lot easier to work on than my 32v

 

Van, have you put a fuel pressure gauge on the fuel rail yet. If not that is where I would go next. Please excuse me if you have I just didn't see it in the thread.

 

My next step is to ues a stethascope on the injectors to hear if they click. There is lots of corosion everywhere and I'm slowly sorting thru it and cleaing everything as I go.
This car sat in a barn with little or no protection for 22 years. It's a good thing that I enjoy cleaning...It came from Flordia or at least it had 1994 Florida plates on it .
The most problematic issue was that the car was wired for a phone ( huge phone brick in the rear quarter) along with an Ungo alarm system. I think I have taken 10#'s of wire out of it. It had wires runing up the A pillar. Other than that the car is in pretty good shape, at least it's all original

 

Van --

Your thread title mentions "fuel pressure?". Have you verified fuel pressure with a gauge yet? It's typically among the first things to check with your symptoms. Other Stupid Stuff like low or no fuel in the tank has bitten certain community members whom I know personally. (... Asking for a friend ...)

 

Thanks Dr. Bob...Funny, I woke up in the middle of the night thinking about enough fuel. I'm going to put another 5 gallons in it and get a fuel pressure gauge

 

I added another 5 gallons of fuel...not much difference. check that box.
Note that is will run on all 8 but only for about 5 seconds and only after its been sitting for an hour or so. It appears to and smells like it's flooding. Should I replace both fuel pressure units that are against the fire wall?