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1G 90 AWD won’t run, ground problem?

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Ssm90gsx

Probationary Member
17
1
Jan 6, 2015
canton, Ohio
Car cranks, will eventually fire up but there is zero consistency in it firing up. When it does run, I can keep it throttled to 2500-3k rpm, and then eventually it’s just dies all together.

ECU pins 101/106 to any ground point with key off have zero resistance. When the key is turned on, the same pins test at 50 ohms to ground. This car had a MPI relay short internally and ever since then it’s had weird issues starting. I swapped the engine harness with a mint 90 harness, thinking this could be an issue, and it seems the problem has only continued to get worse. I have a log of the car running, but I doubt it’s of any use. Simply what I’m wondering if these resistance values on pin 101 and 106 with the key on are Normal.

My multimeter won’t even register continuity between pin 101/106 and any other grounding location on the car with the key on. Key off there is zero resistance. I have added grounds and replaced my battery/alternator with new terminals as well recently. I’ve swapped every spare sensor/component that would possible cause the car to not run, I’ve verified timing, and this has convinced me that this is something wiring related.
 

steve

DSM Wiseman
15,575
2,290
Feb 3, 2002
St Charles, Illinois
Once you turn the key on, assuming that you then get battery voltage at 102/107, you will have the return current flowing on 101/106 making your multimeter measurements invalid.
 

Ssm90gsx

Probationary Member
17
1
Jan 6, 2015
canton, Ohio
Any ecu codes being flagged? do you know how to test for codes?
Car has ECMLink and there are no codes unfortunately..

Once you turn the key on, assuming that you then get battery voltage at 102/107, you will have the return current flowing on 101/106 making your multimeter measurements invalid.
This is the thought process I was thinking but needed verification. I don’t know where to turn with the car. It has some incredibly weird issues and my options are very limited to correct the issue. Money is not a problem, but getting on the path to correcting the issue has come up blank through everything test I do.
 

steve

DSM Wiseman
15,575
2,290
Feb 3, 2002
St Charles, Illinois
I doubt this is a ground issue. Please post a log of you attempting to start and when the car just dies out.

Double check the fuel pressure quickly comes up to spec and tracks manifold pressure. I didn't see injector size or fuel type in profile.
 

Ssm90gsx

Probationary Member
17
1
Jan 6, 2015
canton, Ohio
I doubt this is a ground issue. Please post a log of you attempting to start and when the car just dies out.

Double check the fuel pressure quickly comes up to spec and tracks manifold pressure. I didn't see injector size
Here is a log of both the car cranking over like it wants to start, and finally starting up and dying after. injectors are 1250cc FIC. Fuel pressure is consistant.
 

Attachments

  • log.2023.05.23-01.elg
    213.5 KB · Views: 7

Ssm90gsx

Probationary Member
17
1
Jan 6, 2015
canton, Ohio
I went out today and got 2 logs of each individual issue. One of it trying to start. One is it starting up and then dying down.
 

Attachments

  • start and shutoff.elg
    13.7 KB · Views: 5
  • trying to start.elg
    14.4 KB · Views: 6

talon749

15+ Year Contributor
101
18
Sep 19, 2004
Peoria, Illinois
Just throwing this out there but your injbatteryadj dead times look low for those injectors. Something is wonky with your voltage for sure, you're only at 11.9 when its running. How is the cable from the fuse box to the battery? Mine was jacked up once and caused all sorts of issues.
 

steve

DSM Wiseman
15,575
2,290
Feb 3, 2002
St Charles, Illinois
I only got a chance to quickly look at the first log, maybe things changed since.

He's not using direct access map for injbatteryadj, the using a global deadtime adjustment.
The injector pulse widths look pretty large for those sized injectors when it's trying to start.

His battery voltage doesn't really start to climb until the car starts running.
 

Ssm90gsx

Probationary Member
17
1
Jan 6, 2015
canton, Ohio
Just throwing this out there but your injbatteryadj dead times look low for those injectors. Something is wonky with your voltage for sure, you're only at 11.9 when its running. How is the cable from the fuse box to the battery? Mine was jacked up once and caused all sorts of issues.
I had my alternator unplugged during this startup and completely forgot about it. (Just repinned a new alternator connector). Cable from the fuse box to better is actually brand new. I previously had a battery relocated in the trunk, but recently made a low mounting bracket to bring it back into the engine bay (did this due to thinking this was part of the problem but this made zero difference in the cars ability to start up). The car seems like it wants to live. It’s a brand new motor and brand new speed density conversion. To my knowledge, everything is correctly pinned in the ecu. All the conversion harnesses came from reputable companies.
 
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