6.0-928S

Thanks I'll check that too. But I did try to supplement the fuel by adding some ether into the intake in case it was lean but it made no difference.As soon as the key returns to the run position it shuts off. I had tried it over & over to the point that the valve covers were warm from all the fire ups.

John Speake

Are you sure there isn't a vital running circuit that has been wired to the "cranking" position of the ignition switch ? Sounds rather like it.....

Lizard928

Send me an email with how you wired up the brains. Running the 87+ in 85/86 it's best to make a change to the CE panel.

john gill

I may have missed this , but have you checked that there is correct fuel pressure at the injector rails , if it fires and wont run sounds to me like there is no fuel pressure .
I would remove the fuel pump relay , and bridge the connection enabling the running of the pump , you should here the pump running .

Hope this helps

6.0-928S

I have a fuel pressure gauge inline at the adjustable pressure regulator under the hood. I have plenty. Thanks.

Hammer

john gill

OK wont run , saying that the injectors are not firing , they are turned on after the ecu detects that there is a crank pulse , is there are crank pulse, you may need a cro to determine this , unless the ST will detect pulse width or crank angle, it has been a while since I have used the ST so I cannot remember , JS should be able to answer this , fronm what I remember the diagnostics are quite good in determining what is not happening .

Lizard928

The problem likely lies with the wiring that has been done.

Hammer has stated that the 88 harness has been plugged straight in without any modifications. This doesnt work.

So here is the information needed.
1985-86
W11 - tach and electric kickdown
W12 - from EZF to fuel consumption guage.
W13 - power from fuel pump relay for switched +12V signal to injectors, and heater for O2 sensor.
W14 - EZF power from relay
W15 - fuel pump activation

W21 - LH relay activation signal from EZF +12V
W22 - power to LH while cranking. <-- Diagram shows this to be ground, but I am 99.9% positive it is +12V, this is also activation line to the starter, output Q13.
W23 - LH power from relay.
W24 - LH pin 16 to instrument cluster (low pressure switch, and thermoswitch. Possibly to shut down the engine when low oil pressure, or overheats)
W25 - timing belt tensioner system

These are the pinouts on the 1988 fusepanel.
1988
W11 - tach and electric kickdown
W12 -
W13 - Power from LH relay to fuel injectors +12V
W14 - EZK power from relay.
W15 - fuel pump activation

W21 - LH relay activation signal from EZF +12V
W22 - Constant +12V to both LH and EZK
W23 - LH power from relay
W24 -
W25 - timing belt tensioner system

So with this information you can clearly see that the LH/EXK are ONLY getting power while cranking.
To fix this, remove the W plug from the panel, you will have a yellow piece on it with some ridges, this is what ensures it only gets plugged into this location. It is on the right. just to the left of this piece you have 5 wires, W21 is bottom, W25 is top.
the 5 wires to the left of that is W21 (bottom), to W25 (top).

You need to either separate the plug and remove W22, or just cut this lead, and make an attachment. This lead will then need to be bolted to the top of the fuse panel where the battery cables come into the car.

Once this is done, the car will run.

terry gt

this may not be relevent... , but if you have a scat crank , the first batch had the front pulley keyway 180 deg out .

Lizard928

Terry,
If that was the case the swapping of the two wires would have made things worse as they would have actually been correct.

GregBBRD

When I've done these conversions ('85/'86 using later motronics), I've had to add relays to the fuse panel and change some wiring. I've got lots of notes regarding how to do this, but as I recall, there was an issue (on the '85/'86 relay board) with one of the relays only getting triggered when the engine was cranking and I had to change the wiring so that the relay had power after the key was "released" to the "run" position.

Lizard928

I just converted my car to VEMS, I just used an output from the brain to activate the LH which I use to supply power to the coils and injectors.

GregBBRD

I went back into my notes. Very expensive!

Although it has been a few years since I had to do this, it looks like the W22 wire on the '85/'86 vehicle is powered only when the starter is turning. From there, it goes to the #4 connector on the LH....which is not connected on the '85/'86 car.

For the '87 and later brains, there has to be constant "30" power to the #4 connection to the LH computer. Therefore, W22 has to have full time power.

My notes tell me that I changed this W22 connection to have "full time "30" power.

This seems to make sense with what you are saying is happening? Runs only when the starter is engaged?

6.0-928S

You are correct! The car now runs! I spoke to Colin & he said the same thing. I just went to my shop & ran a feed wire to W22 & it's up & running. I posted an update with pics. I appreciate your time & trouble without you guys we'd still be scratching our heads. (I hired a Porsche tech but he doesn't see any 928s anymore & wasn't familiar with them) Thanks again!

Regards, Hammer

Lizard928

Excellent news Hammer!

Glad we got it running. Now where is the YouTube video and pictures of the car/engine.

Landseer

Wow, you guys are good. Really good.

Congrats on getting it running, Hammer!