Kevin in Atlanta

No start after replacing head gaskets and top end refresh and injector harness end replacements.

Current status:
Followed Rich Andrade's testing steps. Everything passed.
Tach bounce - yes.
Noid and spark plug tester fail. So, no spark and no injector click. At one point the noid and spark plug tester blinked once on the initial engine crank.
Fuel pump does not run - I have a pressure gauge. Will pressurize when jumpering the FP relay.
New Porsche relays for FP and LH in stalled.
Fresh CPS sensor

Swapped known good EZK and LH computers - no change.

I can feel the LH and EZK relays click when I turn the key on. The FP may be clicking, but it is very faint if it is.

It may be a dodgy CPS harness connector - having it repaired shortly.

Kevin

Mrmerlin

tach bounce means its getting a signal,
O scope is needed to see what that signal is.
Some questions .
Did you connect the ground wires at the rear of the V?
Have you made absolutely sure that you dont have a relay placed in the wrong socket.
Did you use a Bosch CPS?
What parts on the intake refresh were not Bosch.
NOTE only use Bosch parts for the electric system
Put the computers into another car to verify they work.
NOTE if your not sure about the wire harness then replace the harness.

Kevin in Atlanta

Thanks for responding, Stan.

Did you connect the ground wires at the rear of the V? Yes. One on each end of the throttle wheel assembly and one secured a 10mm bolt.

Have you made absolutely sure that you don't have a relay placed in the wrong socket. Yes XX and XXV are correctly populated.

Did you use a Bosch CPS? Yes - 944 version (long)

What parts on the intake refresh were not Bosch. None

Put the computers into another car to verify they work. - I can do that in the AM.

Like I said everything tested correctly per Rich's write-up.

The only thing I do differently is I use studs to hold down the throttle wheel assembly - can't imagine that could be a problem.

Kevin

Mrmerlin

SwayBar

My guess is that your harness is shorted for the injectors.

Check the ohms at the connector to the LH for the injectors.

ador117

see my next post!

Kevin in Atlanta

Why would that take out the spark?

But, I'll circle back to the injector test.

Koenig-Specials 928

Also confirm that you did not mistakenly swap the CPS & TPS leads.
They look the same and if swapped it will never fire

Mrmerlin

This is a good point ^^^
FWIW I suggest to always label every connector you take apart when doing an intake refresh,
after a month or more away from the wires,
things can get put back in a swapped position

ador117

Hello,
I don't know what your check procedure contains but if you have no spark and if you check with a known good EZK, the easiest would be to verify the resistances of your ignition coils :- Resistance between terminals 1 et 15 : 0,4 – 0,7Ohms,- Resistance between terminals 1 et 4 : 5,0 – 8,7 kOhms

with ignition on you may have over 10 volts at terminal15. If you want to go further to check the signal of the 944 606 170 02 in case it could help you, this is the screenshot I get while cranking on an oscilloscope between terminals 6 and 23 of the EZK plug, in case one day I need it (with a 1/10 probe):


And you could also check your ignition system from the T45 connector behind the fuse panel :



12V brief contact to terminal 1 will generate a spark on the bank of cylinder 1 and the other pin to the bank of cylinder 8. If not and if your coils are good you may have a fail first ignition stage failure.

Good luck,
Raphaël

SwayBar

You stated that the Noid light failed which is injector related.

Kevin in Atlanta

Having done that before that was the first thing I checked. Visually, the wire going to the TPS is black. The wire to the CPS is grey.

If that is not good enough, Rich's test steps includes continuity to the CPS connector - this passed as did all his steps.

I'll have the CPS connector replaced this week and see if that resolves the issue.

Thanks to all.

Mrmerlin

O scope will tell you if your getting a solid signal to the computer

Kevin in Atlanta

So, you are saying I can get a tach signal bounce and still not have the LH and EZK inform the relays to close?

Kevin in Atlanta

For giggles I moved the MAF out of the way and attempted to start it - no start and no tach bounce. Then I moved the CPS connection down toward the 'U' fuel hose, tried again and no start with the a tach bounce.

Need to repair the CPS connector before I do anything else.