DNS question

[zrfast1]

Ok gurus…here we go. I have the dreaded no start syndrome. What I have learned so far is the early ones suffer from this condition. I have a 91. I have all the prints (schematics) for the system but what I don’t have are the so called, “fixed by GM in the later models” prints to see what was done. Is there any truth to that statement and if so, can anyone please post a print for me?
Or, has anyone just bypassed the CCM by splicing the ground wire off the starter relay and create a solid ground for it? Assuming all other components are functioning, that looks like a good fix.
Thoughts?

[-=Jeff=-]

I found my 90 to have a similar by-pass done.. but I still had a no start.. I think the final fix was replacing the starter contactors.. I also found my clutch switch to be bad whichi is why it was bypassed when I got the car..

[zrfast1]

Hey Jeff
Starter was rebuilt 3 weeks ago. Car ran fine until today when I just warmed it up because its in bed 15 miles away. Turn it off after 40 min. of idling. When I returned 15 min later, dead. Walked away pissed and returned 20 min later....its alive again. WTF

[-=Jeff=-]

yeah it could be that relay, or vats..

My other final change was a new relay grabbing power from the battery. I have not had any issues in a while now.. I see you are local to many of us too

[zrfast1]

Correct me if I'm wrong but vats reports to the CCM and when and only when the entire security system reports its good, then the CCM will provide a ground for the starter relay. Bypassing the CCM ground....imho should eliminate the delay due to heat in the CCM. I suppose with the heater on today for a long time and it lives in the dash and its 24 years old, circuitry could be getting a little tired....per say...I don't know!! All I know is when the weather turns, I don't want this to happen again.....yes in Palatine. Have we met? I did go to MM and the pizza night in Addison.

[Paul Workman]

Here are the two schematics:

The 90-92 MY...



The 93-95 MY...



The common problem with the 90-92 circuit is with the switch(*ed.) at the clutch pedal: it carries ALL of the starter solenoid* current. And, if the ignition switch is turned to START prior to the clutch pedal being fully depressed (closing the clutch interlock switch in so doing) OR releasing the clutch pedal from the fully depressed position while the ignition switch is yet in the START position...will hasten the eventual failure of the switch.

Eventually, the starter will need servicing; the internal solenoid contacts, primarily. If there is a strong "CLICK" sound at the starter when the key is turned, but there is no start, chances are the high-current contact ring and/or the brushes need servicing (replacement). There are other potential issues with the starter too, but with the (loud) "CLICK" one can usually be sure there is a problem with the starter IF all the battery connections are or have been cleaned, of course.

Going back to the clutch pedal safety switch: The issue on the pre-93s is current load at the clutch pedal safety switch: it is relatively high, and it results in arching - especially if the (clutch) is not fully engaged when the key is in the START position. Always making sure the pedal is fully depressed before turning the ignition switch to START will significantly reduce internal arching/failure of the (clutch pedal) safety switch.

This problem was addressed in the 93+ MY cars (see schematics). However, the 90-92 MY cars can be retro'ed by inserting another relay between the clutch pedal switch and the starter (see below), OR eliminating the clutch safety switch altogether (by-pass).

Auxiliary clutch solenoid relay:

[-=Jeff=-]

Originally Posted by zrfast1

.....yes in Palatine. Have we met? I did go to MM and the pizza night in Addison.

We might have. I was unable to go to MM but may have met at HRI

[zrfast1]

Originally Posted by Paul Workman

Here are the two schematics:

The 90-92 MY...



The 93-95 MY...



The common problem with the 90-92 circuit is the relay at the clutch pedal: it carries ALL of the starter current. And, if the switch is turned to START prior to the clutch pedal being fully depressed (closing the clutch interlock switch in so doing) OR releasing the clutch pedal from the fully depressed position while the ignition switch is yet in the START position...will hasten the eventual failure of the switch.

Eventually, the starter will need servicing; the internal solenoid contacts, primarily. If there is a strong "CLICK" sound at the starter when the key is turned, but there is no start, chances are the high-current contact ring and/or the brushes need servicing (replacement). There are other potential issues with the starter too, but with the (loud) "CLICK" one can usually be sure there is a problem with the starter IF all the battery connections are or have been cleaned, of course.

Going back to the clutch pedal safety switch: The issue on the pre-93s is current load at the clutch pedal safety interlock relay: it is relatively high, and it results in arching - especially if the (clutch) is not fully engaged when the key is in the START position. Always making sure the pedal is fully depressed before turning the ignition switch to START will significantly reduce internal arching/failure of the (clutch pedal) safety switch.

This problem was addressed in the 93+ MY cars (see schematics). However, the 90-92 MY cars can be retro'ed by inserting another relay between the clutch pedal switch and the starter (see below), OR eliminating the clutch safety switch altogether (by-pass).

Auxiliary clutch solenoid relay:

Thanks Paul those prints are a big help!! I see what was done now!

[Paul Workman]

Originally Posted by zrfast1

Thanks Paul those prints are a big help!! I see what was done now!

BTW, if you opt to do the clutch pedal switch by-pass, then adding the relay is MOOT and only ads unnecessary complexity. (Just thought I should point that out...)

FWIW, I don't fault those that make a big deal out of the "safety" added by the clutch (safety) switch. But, I was taught to fully engage the clutch before cranking the motor when I was 12 years old, and I've never unintentionally cranked a motor with the clutch engaged. So, for the likes of me it is JMO, but it is just one of those things some government idiot cooked up to justify his job. Your mileage may vary.

[zrfast1]

Ill get into it when I return home if its not too cold. Car is in an unheated garage 15 miles away. Ill report back. Have a wonderful holiday.