NA6 VVT Swap Electrical Issues
02-07-2021, 01:32 PM
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NA6 VVT Swap Electrical Issues
Hello All,
For some background, I bought this car several months ago, it's a 1990 with a 2002 VVT swapped into it. It ran well when I bought it, although it idled like crap. It had several electrical issues like the IAC was somehow not receiving a signal from MS3 and I could not test the injectors properly via Tuner Studio, although everything seemed to run fine when making power as I was able to achieve good power on the dyno. However, I was not making proper torque and my VVT Solenoid was also not operating.
The car's wiring from the previous owner looked like a mess of wires and improper soldering all over the place making it impossible to reverse engineer, so with reluctance, I bought a used wiring harness off of eBay. This was also under the recommendation of a couple local community experts. I swapped the existing harness for the one I bought and now I'm having several odd issues that I cannot explain, so I'm asking for your advice. I closely followed the instructions of the Definitive VVT Swap thread, from the local Megasquirt reps, and others.
The first issue: The trigger for the Main Relay is not receiving power. This is the BLK-WHT wires from the Engine Fuse/Cooling Fan Relay. On the driver's side fuse box, I am measuring 12V at the Engine Fuse. However, the the fuse box in the engine bay on the passenger side, I am not getting 12V. I used some long probes and tested for continuity, got nothing. According to my wiring diagrams and the eye test, this wire does not terminate anywhere from the driver's side to the passenger side all the way through the fire wall. It simply follows other wires in a loom all the way through. I can't imagine a break any where, as the rest of the wires around it seem fine all the way through. I was able to run a wire to prove the relay itself worked, but now once I have power to the red/white wires (for ECU, injectors, etc) the throttle body is making a buzzing sound, super weird. My local MS3 rep says this is normal, but it did not do this before I swapped the harness. Any suggestions?
Second issue: I ran a wire from Engine Fuse to the Main Relay trigger and it worked. So the relay itself is not the issue. However, once I was able to operate the Main Relay, I found my fuel pump was no longer running. I was able to jump the F/P and GND wires in the diagnostic port in the engine bay and the fuel pump continuously primed, as expected. I believe the purple wire that triggers the fuel pump relay is also not receiving power as it should be.
Third Issue: The starter cranks when you turn the key and press the clutch, so the clutch switch and the starter are getting power. Out of the ignition switch, all wires have 12V that should. So when I got the fuel pump to prime, I tried to get it to fire up. No luck. I opened Tuner Studio and tried to test the coils and injectors. I was able to test both coils just fine. When testing the injectors, InjA made a loud noise but I don't know where it came from exactly. It sounded like the fuel rail, which is worrisome. No other Inj tests yielded a noise except InjG, which shouldn't have made a noise. This one was significantly more faint and I could not tell where on the injector harness it was coming from. I put a voltmeter to the fuel injector wiring harness to test for signal, I got 12V on the red/white wire that powers each injector, but the only 5V signal I was able to measure was for the ECU temp sensor. So that means none of the tests should have worked and I have no 5V signal to any of the injectors. I have no clue what's causing this.
I took the dash completely off again to check for any grounds I may have missed. I found 1 that I missed, but had no better results once we put everything back together.
I hope I explained the full context and some of you can help. I'm open to try anything and I'm thankful for any of those that are willing to spend their time.
For some background, I bought this car several months ago, it's a 1990 with a 2002 VVT swapped into it. It ran well when I bought it, although it idled like crap. It had several electrical issues like the IAC was somehow not receiving a signal from MS3 and I could not test the injectors properly via Tuner Studio, although everything seemed to run fine when making power as I was able to achieve good power on the dyno. However, I was not making proper torque and my VVT Solenoid was also not operating.
The car's wiring from the previous owner looked like a mess of wires and improper soldering all over the place making it impossible to reverse engineer, so with reluctance, I bought a used wiring harness off of eBay. This was also under the recommendation of a couple local community experts. I swapped the existing harness for the one I bought and now I'm having several odd issues that I cannot explain, so I'm asking for your advice. I closely followed the instructions of the Definitive VVT Swap thread, from the local Megasquirt reps, and others.
The first issue: The trigger for the Main Relay is not receiving power. This is the BLK-WHT wires from the Engine Fuse/Cooling Fan Relay. On the driver's side fuse box, I am measuring 12V at the Engine Fuse. However, the the fuse box in the engine bay on the passenger side, I am not getting 12V. I used some long probes and tested for continuity, got nothing. According to my wiring diagrams and the eye test, this wire does not terminate anywhere from the driver's side to the passenger side all the way through the fire wall. It simply follows other wires in a loom all the way through. I can't imagine a break any where, as the rest of the wires around it seem fine all the way through. I was able to run a wire to prove the relay itself worked, but now once I have power to the red/white wires (for ECU, injectors, etc) the throttle body is making a buzzing sound, super weird. My local MS3 rep says this is normal, but it did not do this before I swapped the harness. Any suggestions?
Second issue: I ran a wire from Engine Fuse to the Main Relay trigger and it worked. So the relay itself is not the issue. However, once I was able to operate the Main Relay, I found my fuel pump was no longer running. I was able to jump the F/P and GND wires in the diagnostic port in the engine bay and the fuel pump continuously primed, as expected. I believe the purple wire that triggers the fuel pump relay is also not receiving power as it should be.
Third Issue: The starter cranks when you turn the key and press the clutch, so the clutch switch and the starter are getting power. Out of the ignition switch, all wires have 12V that should. So when I got the fuel pump to prime, I tried to get it to fire up. No luck. I opened Tuner Studio and tried to test the coils and injectors. I was able to test both coils just fine. When testing the injectors, InjA made a loud noise but I don't know where it came from exactly. It sounded like the fuel rail, which is worrisome. No other Inj tests yielded a noise except InjG, which shouldn't have made a noise. This one was significantly more faint and I could not tell where on the injector harness it was coming from. I put a voltmeter to the fuel injector wiring harness to test for signal, I got 12V on the red/white wire that powers each injector, but the only 5V signal I was able to measure was for the ECU temp sensor. So that means none of the tests should have worked and I have no 5V signal to any of the injectors. I have no clue what's causing this.
I took the dash completely off again to check for any grounds I may have missed. I found 1 that I missed, but had no better results once we put everything back together.
I hope I explained the full context and some of you can help. I'm open to try anything and I'm thankful for any of those that are willing to spend their time.
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