Salvage 993 Cab won't start. No Spark.

[BR Racing]

Hello! I purchased a 1996 993 Cabriolet from a salvage auction. I want to use the engine for another project. The 993 has both crash and water damage. The engine cranks but I am not getting spark.

I have done the following:

1. Removed the Motronic and set it to Specialized ECU Repair. It was unusable from water damage. I purchased a replacement with the Immobilizer Bypass.
2. Installed the starter jumper relay in R61.
3. Removed the immobilizer.
4. Jumpered the wires in the immobilizer connector to allow the OBD port to work.
5. Tested ECU with Durametric software. ECU seems to work -- i.e. I can turn on the fuel pump through the software, etc. I got the attached graph when cranking:

6. I confirmed 12v on terminal 15 of the coils.
7. I confirmed 12v on terminal 86 of DME relay.
8. I do not get continuity to ground on terminal 85 of DME relay (not sure why I should as recommended based on my review of the wiring diagram) Maybe this is a problem?
9. The alarm module is still plugged into the harness (but the immobilizer is not).

Bottom line - I would like to get the engine running with no immobilizer or alarm module.

I'm thinking my next steps are to:
1. Learn to use an oscilloscope and see what the patterns are on terminal 1 of the coils.
2. Study the wiring diagrams to trace and confirm all connections from the coil back to the ECU.

All help and advice are welcome!

Thank you.

[porschyard]

Do you have injector pulse ?
Richard

[BR Racing]

No injector pulse. Here is an updated list of steps I have performed:

1. Removed the Motronic and set it to Specialized ECU Repair. It was unusable from water damage. I purchased a replacement with the Immobilizer Bypass.
2. Installed the starter jumper relay in R61.
3. Removed the immobilizer.
4. Jumpered the wires in the immobilizer connector to allow the OBD port to work.
5. Tested ECU with Durametric software. ECU seems to work -- i.e. I can turn on the fuel pump through the software, etc. I got the attached graph when cranking.
6. I confirmed 12v on terminal 15 of the coils.
7. I confirmed 12v on terminal 86 of DME relay.
8. I do not get continuity to ground on terminal 85 of DME relay (not sure why I should as recommended based on my review of the wiring diagram) Maybe this is a problem?
9. I removed and jumpered the alarm module
10. Checked Terminal 15 power to ECU pin 56 when the key is on by testing 12v at pin 10 of X4/1. Passed.
11. Checked AC volts at pin 9 of ODB connector. Observed around 5v. Passed.
12. Made DME jumper and jumped 3-5 and 3-7. Fuel pump turned on when battery was connected. No start. Failed.
13. Put a noid on one of the injector leads. No light.
14. Put a scope on Speed sensor - Passed (I assume it should have based on the AC test on OBD previously performed)
15. Put a scope on the hall effect sensor in distributor - Passed.

[Grotch]

Studying the wiring diagrams in detail is crucial; focus on the ignition circuit and trace connections from the ECU to the coils. Using an oscilloscope to check the signal at the coils will provide insights into whether the ECU is sending the correct signals.

[Kevin Stewart]

I remember there being a similar problem on my 3.6 to SC conversion. The first engine harness I used did the same thing, I changed the harness on the advice of Timmins and it fired. I still have the harness and I believe there is a bad wire in the harness. Not sure this helps but pull the harness and check for shorts. Have you checked the ground strap.

[BR Racing]

Thanks. I will test it.

[BR Racing]

Originally Posted by Grotch

Using an oscilloscope to check the signal at the coils will provide insights into whether the ECU is sending the correct signals.

I will put a scope on the injector and ignition signals on the ECU. I opened the connector so I can get access from the back. Thanks.