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Discussion Starter #1
Ongoing problem with the 69 Z28.
Replaced the ignition switch, and neutral safety switch.
Took the car for a ride, got back home, key on ignition energized, no starter engagement(it has done this numerous times after cooldown it starts) and after cooldown this time no start. Pulled bulkhead connection underhood, purple wire to starter good connection. red to horn relay bus good connection (wrings good with my Radio Shack multimeter continuity check). Pulled battery and rang connection to voltage regulator(VR-70) and hornrelay no open connections?
Anyone have any idea where to go next. If I drive the car with a starter switch underhood it starts, although I think my stalling issue after its hot might be low voltage to ignition(I haven't checked that yet). Car is on jacks seats pulled to troubleshoot. I also have my original starter rebuilt to reinstall, but the starter in there is a unit I rebuilt recently.

Todd
 

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When hot you get crank but no start or no crank-no start? Could be heat soak of the starter.
 

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Starter might be fine but the attached solenoid may be the issue.
 

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Todd, I would change out the starter, and use the mini type. I have the mini with a heat blanket on it....no problems even with headers running by it. and nice ride:D
 

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Discussion Starter #6
I've got a refurbished unit ready to go in, its the original 1108367 rebuilt starter. I rebuilt the one in the car now its a 1108367 unit as well, maybe my garage refurbishment of the solenoid didn't work so good, it's an original delco remy solenoid looks correct.
Todd
 

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Hmm, per chance did you check the voltages at the solenoid at the no start condition? Hard to imagine that you would have heat soak yesterday as it was pretty cold here in SoCal.

I was having a similar issue, not as pronounced. Had the starter gone thru by an automotive starter shop (they replaced the solenoid with a new one). They cured it for me.

alan
 

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you mean you don't have continuity from the starter to the ingnition switch on the purple wire?
 

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With the above Post 6 symptom and being a '69 Z/28, clutch switch can be a problem if not an open circuit elsewhere.
Ign sw replaced/adjusted on column and still hot start problem, I offer the following:
1. Move ground cable to the block as the present return path back to battery from starter case is through the block, the head, intake manifold, upper alt bracket, and finally, the cable. Shorten the path.
2. Check battery voltage during cranking or no crank. Battery voltage below 9.5 VDC, low charge on battery, either a too small battery, not enough recharge time, or too low of recharge voltage. Also, check voltage between solenoid stud and battery post, not on the terminations. Same goes for the return path, motor case to negative post. Measurement should be less than 1 volt during cranking. This measurement tells you the amount of voltage dropped across the current path. Do the same for the purple wire at the solenoid - stud to post measurement. Count the connections in this one circuit.
3. Battery cables too small of gauge/size. GM in their design to price thinking, installed the smallest cable size to get the car through warranty. Min size wire is 1/0 gauge with molded post clamp.
4. All the connections are low resistance as they cannot be accurately measured by the typical ohmmeter, one needs a low-ohmmeter to measure the resistance. Suggestion here would be disconnect each connection from battery positive post through the start circuit, through the starter and the ground path and wire brush the terminal rings and the item the rings are attached. This cleaning for the slip-on connectors of clutch switch would be a shot of contact cleaner.
5. Solenoid, the plastic end piece can come off as you know and one can rotate the copper bolts and the mating disc providing a 'new' contact surface.

As I stated about resistance, heat is its natural enemy. More heat, the higher the resistance, more current given up at the junction(s) or lack of wire size as heat, less current available for the starter motor.
 

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Yes, voltage puple wire at solenoid "0 volts" ignition switch @ start position. Disconnect battery and run continuity nothing shows up.
When in this predicament, check voltage at every connection you can think of between the batt and the starter. Going from memory - accessory wire (fusible link) at pos batt terminal, junction block ahead of battery, horn relay bus, bulkhead connector, ign switch in & out, NSS in & out....Hopefully you will find good voltage up to the point of failure, then nada after that.

Also is your wiring new? Not unusual to see an original purple wire look good on the outside but be full of crud when you peel away the insulation

A wire can show good continuity and also be incapable of carrying required current

the fact that you can run a hot from the batt to the R terminal and it cranks normally tells me that the solenoid is fine and that the problem is in the wiring
 

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Discussion Starter #13
Yes, no voltage at purple wire, when it won't start. This time when it failed hard (wouldn't restart even after cool down). I removed bulkhead harness connector to starter and contiuity to the starter was good. Continuity check was with my multimeter which reads open unless resistance is less than 50 ohms. Removed battery connections, battery terminal, horn relay terminals, voltage reg connector all passed 50 ohms check. Checked dash harness red power in to purple wire out to starter good. Thought maybe an intermittent fuse link when hot.
 

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Did you check the voltage at the bulkhead connector? At this point, I'd be check for voltage along the path from the column harmonica connector to the purple wire at the solenoid.

alan
 

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Keep in mind that a continuity check with a DVM may not reveal a bad connection. A DVM puts all of 1 micro-amp of current through the circuit to check continuity. Seems like the start solenoid draws more like 8amps. A bad connection will probably test good with a 1uA continuity check and fail at 8amps.
 

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When I took autoshop in 1968, the first thing we did was to construct a test light made out of an 1157 bulb and an alligator clip. I still have it and still use it to this day!!! It is great for seeing if I do indeed have voltage where I want it.

If you are testing ECU's, you will want a tester with an led as a filiment bulb can draw enough amps to damage a micro circuit.

alan
 

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Discussion Starter #20
Yep I'm going to dig into the underdash connectors/wiring and do a few more continuity checks. After that I'll put everything back together and put power to the circuits and perform checks. I thought for sure i'd find the "smoking gun" issue. But its probably a burnt wire somewhere under the insulation or at a connector where I can't see or test for failure.

Todd
 
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