2G 6-bolt swap '95 TSi AWD with '97 ECU wiring

[Charger3100]

Hey yall. I am coming to the end (hopefully) of an engine swap. The donor car is my old 1997 Talon TSi. There was nothing wrong with the car when I began the swap. The donor '97 had a 6-bolt swap done years and years ago and has always run great. I recently acquired a 1995 Talon TSi AWD without an engine and early this fall began the swap.

I drove the donor '97 up to the '95 TSi AWD so the two cars were nose to nose and swapped everything over.

Where I am now is, I got everything connected and ready to go and gave it a crank and it just cranks and cranks. I have just over 40psi of fuel pressure while cranking but no spark. I tested for spark by connecting alligator clips from the spark plug to a known ground source and tested for ground at the spark plug before cranking. No spark.

So my question right now is, are the harnesses of a 97 and a 95 the same?

I am using the 1g 6-bolt engine and engine harness, the 1997 ECU, and the 1995 car harness. I was able to find all of the same color wires for the 6-bolt CAS conversion on the '95 harness as was on the '97 harness and connected everything to the same colors as was on the '97 donor car. Is something different that I am missing?

To summarize, A '97 TSi ECU in a '95 TSi AWD with a 6-bolt and 1g head. The '97 ran perfectly. Now with the same engine and computer the '95 has no spark. Any ideas before i go through the motions?
Thanks, Nick

 

[steve]

So my question right now is, are the harnesses of a 97 and a 95 the same?

They are close but not the same. MPI relay is one difference. There are others but I'm not up to speed on them.

Are you sure the ECU is powering up and running when you turn the ignition on? Engine will crank without an ECU but needless to say nothing interesting will happen.

 

[Charger3100]

i havent done any diagnostics yet. i spent the day getting fuel to the motor. another nightmare. the mpi is connected to the fuel pump as well correct? i am getting power to the fuel pump. i will check the ecu when it gets light out. is there any sort of wiring change i would need to do due to the mpi relay being different? the wiring at the motor was pretty identical. Pics of my sending unit. Thankfully these tanks are plastic

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[steve]

The MPI relay in a 95 is different that those of the later 2GT cars. At the ECU the interface is the same. If you only changed the engine wiring you wouldn't have touched it.

 

[Charger3100]

Thanks for replying. Im going to check for ecu power tomorrow. looking at the wiring chart i found online there should be power in at pins 12 and 25? and grounds at pins 13 and 26?

 

[motomattx]

Can you try using the 95' ecu in the car? The 1g cas outputs a flipped signal over the factory 95' sensors though, so spark plug wires would need swapped for it to run, if I remember right.

 

[Charger3100]

i could try the '95 ecu to confirm spark but the '97 ecu has the tune. i am running a gt3082r at around 420whp. would i still get spark without inverting the coil signals?

or are you saying that each individual two wire coil harness has to be flipped?

 

[motomattx]

You would still get spark, the 1/4 spark plug wire would need swapped with the 2/3 spark plug wires is all, this can be done right at the coil pack itself.

 

[Charger3100]

I appreciate it. so with the '97 ecu i would still need to do the inversion or no?

 

[motomattx]

I appreciate it. so with the '97 ecu i would still need to do the inversion or no?

No, but the 97' wont properly power up your mpi relay with 95' wiring/95' mpi relay, they worked differently slightly, you could wire them to be compatible by changing how the mpi is pinned though. This is how I seem to remember it being, anyone can correct me if I dont remember right, it has been a while now since I have messed with 95'-97' differences electrically, my 95' I did the 6 bolt swap on, I was using a 95' ecu though and simply tuned it by burning a chip for it that offset the cam sensor issue properly. Now that I think about it I eventually installed a flashable 99' ecu in the 95' and did not move any wiring for the mpi relay for the 99' ecu, I do know that the SPYDER had a different way to run the mpi relay vs the hardtops. If its an easy thing to try, plug in the 95' and see if you get spark, it wont hurt the ecu or the car to try it. Are you getting a check engine light for a few seconds when you flip the key on?

 

[Charger3100]

and that would cause a no spark condition you think? do you know how to repjn the mpi? is it easily reversible? my goal is to get the car running and drive it to the tuner after i have my eprom computer chipped so i can get an improved tune and maybe a little more hp

 

[motomattx]

and that would cause a no spark condition you think? do you know how to repjn the mpi? is it easily reversible? my goal is to get the car running and drive it to the tuner after i have my eprom computer chipped so i can get an improved tune and maybe a little more hp

If the mpi relay wont turn on the car wont start, the mpi relay powers everything fuel injection. Are you getting 12v at your coils with the key on?

 

[Charger3100]

ill be back at it in the morning and will test. i do have power to the fuel pump when i crank so that side of the relay is working for sure

 

[Charger3100]

So i followed steves thread https://www.dsmtuners.com/threads/2g-basic-ecu-mfi-mpi-relay-circuit-function.497188/ and thank you for writing it.

From Steves thread:

MFI Relay function:

The 2G ECU receives backup power on pin 80 from Dedicated Fuse #11 (room) in the relay box in engine bay. This is used to maintain the RAM in the ECU's CPU and allow the ECU to power itself up. It also provides power to the radio to maintain it's settings and to the cabin lights. Like MFI relay input pins the backup power on ECU pin 80 should be present all the time. In other words it's unswitched. Yes. i have constant power at pin 80

The ECU sits dormant in a powered down state waiting to see pin 82 (IG1 from ignition switch) go high (to battery voltage). When the IG1 from ignition switch goes high the ECU pulls pin 38 low (to ground). This causes the the MPI/MFI relay to activate and switches the MFI power from the input to the output pins providing power to the ECU on pins 12 and 25 along with various sensors, solenoids, injectors, ISC, and O2 Heater in the engine bay. I am receiving power at pin 82 when ignition is turned to on position however when i plug the harness holding pin 82 into the ecu and turn ignition on i am not getting a ground signal from pin 38 out of the ecu. does this mean my ecu is bad? It was fine before the swap. could i have done something to it during install?

Shortly after battery voltage shows up on ECU pins 12 and 25 the reset circuit in the ECU wakes the ECU up, the CEL will come on for about 5 seconds and then turn off, the boost gauge will display 0 (Stock ECU software on turbo cars) and the ISC on the throttle body will move in and out to rehome. I am not getting power at pins 12 and 25 with the ignition turned to the on position. My CEL will come on but it does not turn off after 5 seconds. it stays on for as long as the key is on

Can anyone confirm i should be getting a ground signal from the ecu at pin 38 with ignition in the on position. I cant see how the ecu could have gone bad just from moving it from one car to another. Thanks

 

[Charger3100]

Disregard that last post, my initial readings were off. When I back probe the harness at pins 12 and 25 I am getting voltage with the key in the on position. I guess my issue is elsewhere.

I also have power at the coils but it is reading just under 10v where everything else I've tested has higher readings. I don't think this is my primary issue though as I am getting zero spark

 

[Charger3100]

Solved... The CAS connector on the harness was broken allowing it to slide onto the CAS backwards. I flipped it 180° and she started right up.

 

[steve]

Glad to hear that it didn't fry the CAS being reversed.