Key switch to starter ??

[Big Paul]

I have a Standard ( clutch system) C10 1/2 ton P/U.

I replaced my key switch starting wires from just past the fire wall plug to cab on the engine side. I hooked wires to solenoid, starter, alt and the junction that bolts down wires on fire wall. When hooking the Batt. back up to the truck it started turning the starter on its own to try to start the truck. Now I put one of the key switch wires on the starter and when I use the key it acts like it not getting fire to to the plugs in the start sequence to start immediately. It bumps or Coughs only when the key position is back to the regular key position on, and if I miss that initial bump or cough I have to wait a about 1-2 min before I can try again to start the truck. After running and going down the highway 2-3 miles it looses power. I have put 2 new distributers in the truck thinking module, but continues doing the same.

Please !! Any suggestions or schematics on how to run the wires ? Or why the truck is acting this way ???

 

[89Suburban]

We need to get you a schematic. Go to the advanced search box and search the word "starter" under all posts by member "chengny". I am on mobile so I am useless right now.

 

[gpmorgan]

I think you should have a purple wire coming from the clutch switch to the "S" terminal on the starter solenoid. This should be the only wire on the "S" terminal.

 

[89Suburban]

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picture share

 

[jux]

Very nice!

 

[89Suburban]

I didn't have time to clean them up, crop them and rotate them and such. I don't have time for a ******* thing anymore. my job is kicking my ass.

 

[chengny]

I replaced my key switch starting wires

Why?

Was there a problem with the starter-solenoid/ignition switch that required re-wiring the circuit?

For obvious reasons, providing the whole story is critical to solving problems via the internet. It is especially important to include the reason for doing the last thing you did before the issue arose.

Anyway, it's probably not the wiring job that you did in the engine compartment. It's sounds like you just replaced the regular wires - nothing really difficult there. Here is how the solenoid is connected:

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B Terminal - Positive battery cable. Some vehicles also have an additional wire or two (usually red and protected with a fusible link) connected to this stud to feed power to various other circuits.

S Terminal - Wired to the ignition switch "SOL" terminal. This connection is often made with a purple colored wire. On many vehicles, the connection runs through a clutch safety switch (manual trans) or a park/neutral safety switch (auto trans).

R Terminal - Used to bypass the ballast resistor (or resistance wire) to feed full battery voltage to the ignition system for a hotter spark during engine cranking. This terminal is not needed with HEI ignition systems since they do not use a ballast resistor or resistance wire. As a result, many 1975-up solenoids do not have an "R" terminal.

M Terminal - Connected directly to the motor via a screw. See low/high torque motor differences above.

So, apparently -if the solenoid was pulling in and cranking the starter - the purple wire that is on the "S" terminal was seeing 12VDC even with the ignition switch in the off position. Sound right?

That purple wire runs alongside near the other, big hot leads (that connect the battery to the starter, then go to the alternator and junction block). It is possible that there was/is a cross connection from an always hot lead over to the purple wire which should only become hot when the ignition switch is in the "start" position.


Now I put one of the key switch wires on the starter and when I use the key it acts like it not getting fire to to the plugs in the start sequence to start immediately. It bumps or Coughs only when the key position is back to the regular key position on

I kind of lose you at this point. What does "one of the key switch wires" mean. As mentioned above (other than the big black wire from the battery and the pair of reds with the fusible links) the only other lead connected to the solenoid is the purple.



If I had to guess, I would take a good look at your ignition switch.

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That is really the only place where the battery voltage can inadvertently leak over to the "SOL" terminal (yellow wire that changes to purple after the clutch safety switch). There could also be a short to ground in that area, that is sucking down the required 12 volts that the ignition coil requires in order to fire the plugs.

 

[Big Paul]

Why : My key switch wires were burned and melted. So I replaced them with new wire from the auto parts store and used a bigger wire for lower resistance reasons. I thought this was the reason why the truck would`nt start during the start sequence, but would bump when you let the key switch go back to the on position. It`s like it`s not getting any fire when starting until you let the key go back to on, then when you do get it running the truck loses power about 2 miles then you you let up on the gas pedal to get to 40 mph and it catches up and runs great up to 60 mph and it starts all over again Not sure where to go from there ??

 

[chengny]

My key switch wires were burned and melted.

Something caused those wires to melt, and it wasn't the wires themselves. What ever problem made them get hot enough to burn the insulation off is probably still there.

You might want to read this; it is from a previous post. It is me talking in the text below and it sounds very similar to what you are currently experiencing.


I'm always sympathetic to this scenario - it happened to me 3-4 years ago, and figuring it out just about killed me.

New complete distributors (3), gear engagement with the cam verified, new plugs, new wires, new rotor and cap, timing checked again and again, valve binding and preload checked. Always got 12.4 volts at the B+/pink wire terminal. This was all checked by many people, all of whom know stuff about stuff. Never got more than the weakest little yellow spark that could barely jump across the electrodes.

Went so far as to clamp a distributor by the shaft housing in a vise, attached one plug wire and a plug to a post, applied 12VDC to the B+ and spun the shaft with a 1/2" drill motor.

That made a spark - OH BOY did it make a spark! I had my hand near enough to the posts that didn't have wires and when I pulled the trigger on the drill - I lit up like a Christmas tree. Took about a week for my heart to return to it's normal rhythm.

But put that same distributor back in the truck, crank it over - NOTHING!


One night after about 50 tries I started to notice that the only time the engine seemed to fire (and only for a brief moment) was at that instant when I would give up and let the key snap back to the run position from start.

Long story short: Went to the corner of the gar gage found a beat up old starter. Wired it up, bolted it on and turned the key. Not only did the test plug that was laying on the engine make a big, bright blue spark , but the engine fired up before it had made 2 revolutions!


The background:

The HEI system needs a minimum of 10 volts on the primary side in order to produce the 20,000 volts required on the secondary side.

As you noted above, there is sufficient power (12 volts) available at the coil input with the key in the "RUN" position.

But, from what I gather while looking at the previous posts, this is specifically a "non start" condition as opposed to a loss of ignition while running.

While a voltage check at the coil input with the key in RUN is a helpful diagnostic, it tells you nothing about coil supply voltage while the engine is being cranked over by the starter.

Get a realtime voltage value while the starting circuit is energized. Use a couple of jumpers attached to your test leads - long enough to allow you to read the meter while reaching in and turning the key. Or have a helper crank the engine while you monitor the voltage at the coil input.

Note whether the supplied voltage at the coil remains above 10.5 VDC while cranking or drops under the 10 volt minimum.

If voltage is stable and above 10.5 while in the static condition, but suddenly drops dramatically when the key is moved to the start position, you have a short to ground in the ignition switch/solenoid wiring circuit or within the starter/solenoid itself.

Inspect the purple wire that runs from the ignition switch to the S terminal on the solenoid. Pay extra attention to where it enters/leaves the L shaped conduit.

It is rare, but occasionally, the starter and solenoid with develop internal shorts to their casings (which are grounded). Buy a new one or, if you have a spare, change it out and see what happens.


One way to determine if the starting is causing a system wide voltage drop (one that is severe enough to prevent ignition) without pulling anything apart or buying anything, is to provide an external 12 volt supply to the coil.

This is easy enough; use a battery charger or a separate, independent battery and run a jumper from the positive to the coil (be sure to disco the installed wire or the independent supply may be pulled own as well) and ground the negative to the frame.

 

[89Suburban]

Good stuff there

 

[Big Paul]

My key switch wires were burned and melted.

Something caused those wires to melt, and it wasn't the wires themselves. What ever problem made them get hot enough to burn the insulation off is probably still there.

You might want to read this; it is from a previous post. It is me talking in the text below and it sounds very similar to what you are currently experiencing.


I'm always sympathetic to this scenario - it happened to me 3-4 years ago, and figuring it out just about killed me.

New complete distributors (3), gear engagement with the cam verified, new plugs, new wires, new rotor and cap, timing checked again and again, valve binding and preload checked. Always got 12.4 volts at the B+/pink wire terminal. This was all checked by many people, all of whom know stuff about stuff. Never got more than the weakest little yellow spark that could barely jump across the electrodes.

Went so far as to clamp a distributor by the shaft housing in a vise, attached one plug wire and a plug to a post, applied 12VDC to the B+ and spun the shaft with a 1/2" drill motor.

That made a spark - OH BOY did it make a spark! I had my hand near enough to the posts that didn't have wires and when I pulled the trigger on the drill - I lit up like a Christmas tree. Took about a week for my heart to return to it's normal rhythm.

But put that same distributor back in the truck, crank it over - NOTHING!


One night after about 50 tries I started to notice that the only time the engine seemed to fire (and only for a brief moment) was at that instant when I would give up and let the key snap back to the run position from start.

Long story short: Went to the corner of the gar gage found a beat up old starter. Wired it up, bolted it on and turned the key. Not only did the test plug that was laying on the engine make a big, bright blue spark , but the engine fired up before it had made 2 revolutions!


The background:

The HEI system needs a minimum of 10 volts on the primary side in order to produce the 20,000 volts required on the secondary side.

As you noted above, there is sufficient power (12 volts) available at the coil input with the key in the "RUN" position.

But, from what I gather while looking at the previous posts, this is specifically a "non start" condition as opposed to a loss of ignition while running.

While a voltage check at the coil input with the key in RUN is a helpful diagnostic, it tells you nothing about coil supply voltage while the engine is being cranked over by the starter.

Get a realtime voltage value while the starting circuit is energized. Use a couple of jumpers attached to your test leads - long enough to allow you to read the meter while reaching in and turning the key. Or have a helper crank the engine while you monitor the voltage at the coil input.

Note whether the supplied voltage at the coil remains above 10.5 VDC while cranking or drops under the 10 volt minimum.

If voltage is stable and above 10.5 while in the static condition, but suddenly drops dramatically when the key is moved to the start position, you have a short to ground in the ignition switch/solenoid wiring circuit or within the starter/solenoid itself.

Inspect the purple wire that runs from the ignition switch to the S terminal on the solenoid. Pay extra attention to where it enters/leaves the L shaped conduit.

It is rare, but occasionally, the starter and solenoid with develop internal shorts to their casings (which are grounded). Buy a new one or, if you have a spare, change it out and see what happens.


One way to determine if the starting is causing a system wide voltage drop (one that is severe enough to prevent ignition) without pulling anything apart or buying anything, is to provide an external 12 volt supply to the coil.

This is easy enough; use a battery charger or a separate, independent battery and run a jumper from the positive to the coil (be sure to disco the installed wire or the independent supply may be pulled own as well) and ground the negative to the frame.

******** Ok so let me get this straight ***** I need to clip the positive side of cap where coil wire goes in with a volt meter and and my other lead from volt meter to the red supply wire itself, crank the engine and if it falls below 10 volts direct current ( VDC ) side of meter the starter may have a ground ?

 

[chengny]

Red probe from the meter connects to the wire (pink I think) that goes to the B+ terminal on the distributor cap.

Pull the clip from the distributor and stick the probe in between the tabs. It doesn't need to be attached to the distributor for this test.

The black probe needs to go to a good ground.

Turn the key tothe "RUN" position and see battery voltage - about 13 VDC.

Then, while some cranks the starter, watch the meter and note the voltage.

Expect to see a drop in voltage - but not lower than 11 volts.

The battery must be fully charged and the terminals clean/tight.