Injector, Opti, or ECM?
Thread Starter
Instructor
Joined: Feb 2001
Posts: 117
Likes: 1
From: Acworth Ga
Injector, Opti, or ECM?
Here's where I'm at:
'92 Roadster - Stock LT1 - 6 Speed
Engine died going about 15 MPH.
Checked spark - nice white arc.
Checked fuel pressure - 45psi
Checked Fuel Filter - bypassed for now, will replace later
Ohmed Injectors - 12.4ish Ohms
Checked power to the injectors - 12.8 volts
Checked ground to the injectors - 0.03ish ohms
Here's the question: When I put the Noid light across the injector lead and don't get a pulse, what is the fix?
I'm guessing ECM replacement but does the Opti send a signal to the ECM?
And if I get a pulse then what?
'92 Roadster - Stock LT1 - 6 Speed
Engine died going about 15 MPH.
Checked spark - nice white arc.
Checked fuel pressure - 45psi
Checked Fuel Filter - bypassed for now, will replace later
Ohmed Injectors - 12.4ish Ohms
Checked power to the injectors - 12.8 volts
Checked ground to the injectors - 0.03ish ohms
Here's the question: When I put the Noid light across the injector lead and don't get a pulse, what is the fix?
I'm guessing ECM replacement but does the Opti send a signal to the ECM?
And if I get a pulse then what?
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
The low resolution pulse from the opti which is the main clocking pulse drives the ECM. The ECM then determines the injector firing and drive to the ICM. So if the opti was not working, you would not have spark.
The potion of the ECM that drives the ICM and hence the coil is working since you have spark. So you can forget about the ICM and coil.
The portion of the ECM that fires the injectors (or grounds the return wire from the injector) seems to be the problem. If the noid light is lighting on starting but then later does not light, then the ECM would seem to be the root of the problem.
This is not an un-common fault with the 92-93 ECM units. It would seem like you would need to get that one repaired or get another one.
The potion of the ECM that drives the ICM and hence the coil is working since you have spark. So you can forget about the ICM and coil.
The portion of the ECM that fires the injectors (or grounds the return wire from the injector) seems to be the problem. If the noid light is lighting on starting but then later does not light, then the ECM would seem to be the root of the problem.
This is not an un-common fault with the 92-93 ECM units. It would seem like you would need to get that one repaired or get another one.
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
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St. Jude Donor '12
FUSE!!!!!!!
Check the 10 and 20 amp ignition fuses, fusepanel accessable by opening the passenger door.
Mine was running like crap - noid was no pulses on driver side, replaced 20 amp fuse and all is well!
Helps if I read everything, still think it might be a fuse, there is one for the ECM.
If you want to try a different ECM I have a spare for a 6spd, I need it back though. They are rarer than hens teeth.
Just down the road in the Stone Mtn / Duluth area.
Check the 10 and 20 amp ignition fuses, fusepanel accessable by opening the passenger door.
Mine was running like crap - noid was no pulses on driver side, replaced 20 amp fuse and all is well!
Helps if I read everything, still think it might be a fuse, there is one for the ECM.
If you want to try a different ECM I have a spare for a 6spd, I need it back though. They are rarer than hens teeth.
Just down the road in the Stone Mtn / Duluth area.
Last edited by jaa1992; Oct 15, 2009 at 09:49 AM.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Since you indicated you have voltage on all of the injectors, this would preclude of having a bad fuse and it is probably good.
Jaa1992, you had a solid constant problem
The fuse for either bank 1 or 2, or the main fuse for the ECM are probably good as fuses once they open don’t correct themselves.
Bad ECM fuse = no spark at coil.
C92 - Take the offer and try the ECM.
FUSE!!!!!!!
Check the 10 and 20 amp ignition fuses, fusepanel accessable by opening the passenger door.
Mine was running like crap - noid was no pulses on driver side, replaced 20 amp fuse and all is well!
Helps if I read everything, still think it might be a fuse, there is one for the ECM.
If you want to try a different ECM I have a spare for a 6spd, I need it back though. They are rarer than hens teeth.
Just down the road in the Stone Mtn / Duluth area.
Check the 10 and 20 amp ignition fuses, fusepanel accessable by opening the passenger door.
Mine was running like crap - noid was no pulses on driver side, replaced 20 amp fuse and all is well!
Helps if I read everything, still think it might be a fuse, there is one for the ECM.
If you want to try a different ECM I have a spare for a 6spd, I need it back though. They are rarer than hens teeth.
Just down the road in the Stone Mtn / Duluth area.
The fuse for either bank 1 or 2, or the main fuse for the ECM are probably good as fuses once they open don’t correct themselves.
Bad ECM fuse = no spark at coil.
C92 - Take the offer and try the ECM.
Thread Starter
Instructor
Joined: Feb 2001
Posts: 117
Likes: 1
From: Acworth Ga
Here's an update. Noid light pulses during attempted start. I have spark at 2 different plug wires. Fuel Pressure is 45 psi dropping to around 25 right before I crank the engine and then it returns to 40 psi during cranking. When I let off the starter a cylinder fires once, twice, maybe three times before stopping. Pulled a fuel rail up and checked to see if fuel was squirting through a bank of injectors. I realize this isn't the safest thing to so I only turned it over a few revs. Got fuel out of all 4 injectors this way and the engine sputtered once or twice again. Anybody got any ideas?
Last edited by c92vette; Oct 18, 2009 at 12:56 PM.
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From: Woodstock Georgia
