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2g full engine wiring harness help

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GloriousDSM

15+ Year Contributor
271
2
Feb 9, 2006
Sterling Heights, Michigan
Hi all.

Where to start....
The car is a 98 Gst. Car was running a few years ago and now it won’t start. It has some work done to it after motor has been rebuild and some bolt on upgrades. Engine is 7 bolt. All work done and now it won’t start :(

The car initially fired up for a few seconds when put back together and then cut off. Cylinders 1 & 4 no spark. All cylinders have fuel.

I’ve replaced Cas, coil packs, power transistor. No luck starting. The wiring harness is hacked up at the power transistor so I believe this to be the culprit. Some poor connection/ ground etc. 1 & 4 won’t fire at all.

I have since purchased an entire engine wiring harness for 98 gst fwd (manual transmission.)

I have not had much luck with electrical and was wondering if any pros are located in the SE Michigan area and can lend a hand with this sometime in the next few weeks? *When things start to reopen etc. Car has been sitting for 3 years since the last time tried to fire it up and troubleshoot.

I have taken the car to two general mechanic shops over the years and no dice. Looking for someone who is a pro or really knows these cars and could trouble shoot or potentially help with a rewire if needed. Stock engine harness replacement if necessary.

If someone can help out let me know, I can pay for time troubleshooting.

thanks in advance for any advice.
 

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Sigh...if only I lived in the Midwest, I could just be a mobile DSM mechanic.

And WTF was happening with that wiring...if you have a complete spare harness in good shape, just swap that in. I can recall if any engine wiring is going to be different between 97 and 98 (I know certain things changed but not an expert on what exactly) but swapping the engine harness is a viable option to eliminate issues.

Another option would be repairing what you have, but it also seems that may be beyond your skillset at this time.
 
Thanks for responding!
I’m not sure if the harness I have is a 97 or 98, I didn’t know they were possibly different

I’ll see if I can find a receipt for it.

yes, I hacked that part up to move it since I installed a cyclone intake manifold and needed to relocate the coil pack, it was a wrong move for sure. Lol.

also I wired up the slimline fans so I’m not sure if I did that correctly.

Worthy mention: ever since this engine install there is now a parasitic battery drain I cannot find also :/
 
Pulled the plugs to check for spark? swapped plug wires?

Do you have a multimeter?
Yes only 2/3 get spark, even if switched. Wires are good, plugs are new and correct temperature and gap -Ngk bpr6es. Swapped plugs/wire combos and retested few times. Tried another coil pack that was working before also.

No meter at the moment.

I’ll be possibly looking for someone to assist with the rewire soon if it will be necessary. Bought a new complete harness said to be in good working condition from online.
 
- Normally the power transistor should be mounted in it's bracket TO THE HEAD for 1) a heat sink and 2) because the bracket gives a much better high current ground than does the black ground wire. It also should be close to the coils. But it sounds like you had to move them for space? If you're going to leave the PT there at least bolt its bracket to the firewall so it has a better ground and heat sink. Where did you put the coils?

- PT pinout: https://www.dsmtuners.com/threads/ptu.340317/#post-151903320

I recommend testing continuity of the PT wires (while jiggling each) to make sure they still have full electrical connection to their destinations. Also a PT test.

- PT test: https://www.dsmtuners.com/threads/how-to-test-the-power-transistors.229419/

- 98-99 has a fuel tank diff pressure sensor and evap emission vent solenoid where 95-97 doesn't have either.
 
Last edited:
- Normally the power transistor should be mounted in it's bracket TO THE HEAD for 1) a heat sink and 2) because the bracket gives a much better high current ground than does the black ground wire. It also should be close to the coils. But it sounds like you had to move them for space? If you're going to leave the PT there at least bolt its bracket to the firewall so it has a better ground and heat sink. Where did you put the coils?

- PT pinout: https://www.dsmtuners.com/threads/ptu.340317/#post-151903320

I recommend testing continuity of the PT wires (while jiggling each) to make sure they still have full electrical connection to their destinations. Also a PT test.

- PT test: https://www.dsmtuners.com/threads/how-to-test-the-power-transistors.229419/

- 98-99 has a fuel tank diff pressure sensor and evap emission vent solenoid where 95-97 doesn't have either.

I’ll look into it once I reconnect the battery soon.

I swapped out to a Cyclone Manifold and had to move a few things around. This was probably not the best idea since I ended up cutting the transistor up, I bet since I extended the wires to reach a bit this is a high chance of issue. I don’t have much experience and should not have done this without more research. Rest of setup looks like this.
 

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