Fellas,
I've been chasing a No Spark/Surging Idle/Stall, Buck, Backfire problem for quite some time now. I have worked though most of the tech notes I've found on the online, studied the systems using the Helm manuals, as well as the diagrams by jrichker, tmoss & joel5.0, and Tom Cloud's Technical Notes on the EEC-IV MCU--all GREAT trouble shooting guides/learning materials. I think I am just now beginning to understand how the different systems work together.
Here's what I'm struggling to understand at the moment:
1. How can higher current circuits be isolated from the circuits that power the sensors? I am particularly confused about isolating grounds.
On one hand, Tom Cloud writes...
"As with any instrumentation and control system, poor or improper grounding of sensors can should be avoided. The TFI module seems to be the most susceptible to problems -- and especially when making a new or modified installation. The largest source of current-induced voltages in the grounding system is the starter current, with the alternator being the next, so every care should be taken to isolate the engine management circuit grounds from the starter current path."
On the other hand, jrichker notes at the end of his tech instructions on grounds...
"The best plan is to have all the grounds meet at one central spot and connect together there. That eliminates any voltage drops from grounds connected at different places. A voltage drop between the computer ground and the alternator power ground will effectively reduce the voltage available to the computer by the amount of the drop."
2. Are Cloud and jrichker talking about different grounding issues?
I got to thinking about this, in particular, because I pulled the starter wire off my starter solenoid and it had 0 resistance with other grounds. I did this following solenoid-troubleshooting advice on another forum where the expert said:
"If you are getting power on both sides of the relay withe the ignition wire off and the starter wire disconnected, the relay has failed and will need to be replaced. The wire from the starter should not be grounded. If it is, the starter is bad and should also be replaced. The starter may have caused damage to the relays. Replace the relay and the starter."
3. Is that guy's advice sound? If so, could the fact that my starter wire has 0 resistance with ground (due to a bad starter) also account for my Surging Idle/Stall, Buck, Backfire problems problems, i.e., starter circuit interfering with sensor circuit grounds?
I've been chasing a No Spark/Surging Idle/Stall, Buck, Backfire problem for quite some time now. I have worked though most of the tech notes I've found on the online, studied the systems using the Helm manuals, as well as the diagrams by jrichker, tmoss & joel5.0, and Tom Cloud's Technical Notes on the EEC-IV MCU--all GREAT trouble shooting guides/learning materials. I think I am just now beginning to understand how the different systems work together.
Here's what I'm struggling to understand at the moment:
1. How can higher current circuits be isolated from the circuits that power the sensors? I am particularly confused about isolating grounds.
On one hand, Tom Cloud writes...
"As with any instrumentation and control system, poor or improper grounding of sensors can should be avoided. The TFI module seems to be the most susceptible to problems -- and especially when making a new or modified installation. The largest source of current-induced voltages in the grounding system is the starter current, with the alternator being the next, so every care should be taken to isolate the engine management circuit grounds from the starter current path."
On the other hand, jrichker notes at the end of his tech instructions on grounds...
"The best plan is to have all the grounds meet at one central spot and connect together there. That eliminates any voltage drops from grounds connected at different places. A voltage drop between the computer ground and the alternator power ground will effectively reduce the voltage available to the computer by the amount of the drop."
2. Are Cloud and jrichker talking about different grounding issues?
I got to thinking about this, in particular, because I pulled the starter wire off my starter solenoid and it had 0 resistance with other grounds. I did this following solenoid-troubleshooting advice on another forum where the expert said:
"If you are getting power on both sides of the relay withe the ignition wire off and the starter wire disconnected, the relay has failed and will need to be replaced. The wire from the starter should not be grounded. If it is, the starter is bad and should also be replaced. The starter may have caused damage to the relays. Replace the relay and the starter."
3. Is that guy's advice sound? If so, could the fact that my starter wire has 0 resistance with ground (due to a bad starter) also account for my Surging Idle/Stall, Buck, Backfire problems problems, i.e., starter circuit interfering with sensor circuit grounds?