 |
|

12-04-2018, 07:41 PM
|
 |
350 Buick
|
|
Join Date: Aug 19, 2003
Location: mi
Posts: 956
|
|
How to troubleshoot a GM OBD1 ignition
I know this is the fuel injection forum but I have a GM OBD1 system controlling fuel and spark in my 82 J10 with a Ford 460. I had trouble with my IAC and found that the stock wiring pinout was wrong for my new Holley Tbody. I reversed the wiring and corrected that issue but ended up with no spark. I have an MSD 6A ignition box and jumped the test terminal and got a very strong spark out of the coil. With the key on I have no voltage at the coil + terminal but I understand that is normal with just the key on. My issue is I don't know the sequence of operation between the ECM and Ignition Control module and coil. I disconnected my ecm to troubleshoot the IAC so I could have disturbed a connection there. I replaced the Ignition Control Module no luck. So does anyone know with the key on what voltage I should be reading at the wiring harness connection to the ICM? My module has a 2 pin and 4 pin connection on one side and a two pin (input?) connection on the other. I believe if I knew what 8 terminal should read voltage wise with the key on I could track the issue down. This system came out of a 91 Camaro if that helps and I a standard billet dizzy with the computer controlling spark. This link has a ICM similar to mine. http://www.fieros.de/en/v6help/code42.html
Thanks in advance for any ideas
__________________
82 J10 SOA 6" SPRINGS D60-D70 W/DETROIT LOCKERS 38x15.5 TSL'S on 12" M/T CLASSICS 460 V-8 C-6 CUSTOM EFIS EFI AND HYDROBOOST
|

12-05-2018, 07:24 AM
|
 |
out of order
|
|
Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,811
|
|
Maybe it's early and I need more coffee but the diagram you posted shows you the module power pin.
__________________
Tony
|

12-05-2018, 05:34 PM
|
 |
350 Buick
|
|
Join Date: Aug 19, 2003
Location: mi
Posts: 956
|
|
Quote:
Originally Posted by babywag
Maybe it's early and I need more coffee but the diagram you posted shows you the module power pin.
|
As helpful as the pinout appears it does not tell me what to anticipate and test for with the key on. Given that I am not familiar enough with the sequence of operation I need to know where to expect the switched 12v current to show up when you turn the key on. Usually, it would be at the + terminal of the coil? Or in this case does the ignition key send 12v to the MSD? What comes from the ECM when the key is on? There are 6 pins on one side of the module as you can see in the picture. When the key is on what Voltage should these terminals be outputting? There are 2 pins on the other side of the module what voltage should they be outputting when the key is on or cranking? Maybe I am making this harder than it needs to be but I it appears to me that's the info I need to troubleshoot this one.
__________________
82 J10 SOA 6" SPRINGS D60-D70 W/DETROIT LOCKERS 38x15.5 TSL'S on 12" M/T CLASSICS 460 V-8 C-6 CUSTOM EFIS EFI AND HYDROBOOST
|

12-05-2018, 06:47 PM
|
 |
out of order
|
|
Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,811
|
|
Module should get power key on/crank "+" on diagram you linked.
MSD would need same on ignition wire.
ECM would also need same on ignition wire.
There is a voltage check sheet for ecm probably find it on thirdgen or gearhead-efi.
Also full wiring diagrams.
__________________
Tony
|

12-06-2018, 07:13 AM
|
 |
350 Buick
|
|
Join Date: Aug 19, 2003
Location: mi
Posts: 956
|
|
Exactly what I needed thanks alot.
__________________
82 J10 SOA 6" SPRINGS D60-D70 W/DETROIT LOCKERS 38x15.5 TSL'S on 12" M/T CLASSICS 460 V-8 C-6 CUSTOM EFIS EFI AND HYDROBOOST
|

12-15-2018, 11:55 AM
|
 |
350 Buick
|
|
Join Date: Aug 19, 2003
Location: mi
Posts: 956
|
|
Quote:
Originally Posted by babywag
Module should get power key on/crank "+" on diagram you linked.
MSD would need same on ignition wire.
ECM would also need same on ignition wire.
There is a voltage check sheet for ecm probably find it on thirdgen or gearhead-efi.
Also full wiring diagrams.
|
Thanks alot for the info. The guys at thirdgen were great and had the details I needed. My beast is starting and running great. It turns out I damaged the ICM while rewiring the IAC. I had suspected that and replaced the ICM but I did not actually mount it but rather just plugged it into the wiring harness when I tested the new one. I thought the wiring harness would ground it but it does not. Once I ran a test jumper to ground it she started right up and then I bolted it down and all was good.
__________________
82 J10 SOA 6" SPRINGS D60-D70 W/DETROIT LOCKERS 38x15.5 TSL'S on 12" M/T CLASSICS 460 V-8 C-6 CUSTOM EFIS EFI AND HYDROBOOST
|

12-15-2018, 12:15 PM
|
 |
out of order
|
|
Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,811
|
|
It should be grounded via the harness, if you have to add a jumper something isn't correct.
Very unusual for an ecm to actually be bad, 95% time it's a wiring issue and frequently poor grounds.
This is a resource for a TBI wiring diagram I modified for folks.
http://www.ifsja.org/forums/vb/showthread.php?t=169223
__________________
Tony
|

12-15-2018, 12:25 PM
|
 |
350 Buick
|
|
Join Date: Aug 19, 2003
Location: mi
Posts: 956
|
|
Thank, I will check it my harness out
__________________
82 J10 SOA 6" SPRINGS D60-D70 W/DETROIT LOCKERS 38x15.5 TSL'S on 12" M/T CLASSICS 460 V-8 C-6 CUSTOM EFIS EFI AND HYDROBOOST
|

12-19-2018, 02:10 AM
|
258 I6
|
|
Join Date: Nov 11, 2006
Location: Oak Harbor, Wa
Posts: 360
|
|
ICM must be mounted on a heat sink and bolted to ground. Preferably, directly to the engine, not the firewall or inner fender.
The module grounds thru the mounting screws.
There is a low ref signal gnd wire but that does not provide the ground for the high power transistor used to fire the coil.
It's all been covered on binderplanet.
__________________
Bill USN-1
Fuel Injection Moderator at BinderPlanet
Hamilton Fuel Injection
75 scout XLC 345/727/JPD300/3.73's/33's/4wdisc/hydroboost/EFI/OBA/OBW
1977 Innocenti 1001 (Italian Mini)EFI 1275/DIS
|

12-19-2018, 07:45 AM
|
 |
350 Buick
|
|
Join Date: Aug 19, 2003
Location: mi
Posts: 956
|
|
Quote:
Originally Posted by Bill USN-1
ICM must be mounted on a heat sink and bolted to ground. Preferably, directly to the engine, not the firewall or inner fender.
The module grounds thru the mounting screws.
There is a low ref signal gnd wire but that does not provide the ground for the high power transistor used to fire the coil.
It's all been covered on binderplanet.
|
Thanks Bill!
__________________
82 J10 SOA 6" SPRINGS D60-D70 W/DETROIT LOCKERS 38x15.5 TSL'S on 12" M/T CLASSICS 460 V-8 C-6 CUSTOM EFIS EFI AND HYDROBOOST
|

12-19-2018, 08:39 AM
|
 |
out of order
|
|
Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,811
|
|
Quote:
Originally Posted by babywag
It should be grounded via the harness, if you have to add a jumper something isn't correct.
Very unusual for an ecm to actually be bad, 95% time it's a wiring issue and frequently poor grounds.
This is a resource for a TBI wiring diagram I modified for folks.
http://www.ifsja.org/forums/vb/showthread.php?t=169223
|
Apologies...my brain saw/read ECM. Bill is correct, ICM must be mounted properly.
__________________
Tony
|
Thread Tools |
Search this Thread |
|
|
Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 08:43 PM.
|