Ignition & starting

The S30 ignition system has two distinct generations: a points-and-condenser setup on the 240Z and early 260Z, and a transistorized system on the 280Z. The starter circuit is essentially unchanged across all years — ignition switch "Start" energizes the starter solenoid, which both engages the pinion and switches battery + onto the starter motor.

Wiring topology

Points-and-condenser ignition (240Z, early 260Z)

The original Z ignition is a textbook Kettering system: the coil primary is fed through a ballast resistor during run, and grounded through the distributor points. When the points open, the collapsing magnetic field induces high voltage in the secondary, which the rotor distributes to the appropriate spark plug. (Specific ballast resistance varies by year and FSM revision — measure your own or check the FSM rather than relying on a published "typical" value.)

The condenser (capacitor) across the points absorbs the inductive spike and prevents the points from arcing themselves to death. A bad condenser will burn fresh points in a few hundred miles.

Tach signal: on 240Z and 260Z, the tach is a current-loop design — the coil primary wire physically passes through a sense coil on the back of the gauge. This matters when swapping to electronic ignition or a different ECU; see the gauges page.

Why the ballast resistor?

The coil is rated for ~7–9V continuous. Running it at full 12V would overheat it, but starving it during crank (when battery voltage sags to ~9V under starter load) would give a weak spark. The fix: drop voltage through a ballast resistor during run, then bypass it during crank with the "ST" output of the ignition switch. The result: full coil voltage when you need it most, reduced voltage when you don't.

Transistor ignition (280Z, some export 260Z)

The 280Z uses a Hitachi transistor ignition module. Some export-market late 260Zs are also reported to have transistorized ignition similar to the 280Z module — verify against the FSM for your specific market and year before assuming. The distributor still has a mechanical mechanism (centrifugal/vacuum advance), but instead of points there's a pickup coil generating an AC signal as the reluctor passes it. The ignition module amplifies that signal and switches the coil primary.

Key differences from the points system:

• No ballast resistor — coil is fed direct 12V from the ignition switch.
• No condenser, no points to gap or replace.
• Tach signal: 280Z tach is voltage-sensing off the coil negative — fundamentally different from the 240Z current-loop tach.
• Module is heat-sensitive. The early "matchbox" module in particular has a poor thermal-failure record. The later E12-80 module (from 280ZX and similar) is the popular replacement.

Starter circuit

The starter circuit has just three current paths:

1. Heavy battery cable from battery + to the starter solenoid main lug. Always live.
2. Solenoid trigger wire (B/Y) from the ignition switch "ST" position. Energizes the solenoid only while the key is held in Start.
3. Engine ground — the engine block grounds back to the battery negative. The starter motor itself grounds through the bell housing and engine block.

Auto-trans cars have a neutral safety switch in series with the trigger wire that only allows starter engagement in P or N.

Wire colors used in this circuit

Diagnostic procedure

Engine cranks but won't start

1. Confirm spark. Pull a plug wire, hold the metal terminal ~5mm from a clean ground point, crank. You should see a fat blue spark. Yellow/weak = ignition issue; no spark = either coil, distributor pickup/points, or trigger.
2. Coil + voltage, key ON. Should be ~7–9V on points cars (through ballast) or ~12V on transistor cars. No voltage = bad ignition switch IG circuit, blown fuse, or open ballast.
3. Coil − voltage. On points cars, key ON with points closed = ~0V (grounded); points open = ~12V. Stuck at one value = points stuck or contaminated, or shorted/open condenser. On transistor cars, expect a low duty-cycle pulsing voltage during crank.
4. Plug condition. Pull a plug. Wet = flooded (fuel issue, but ignition might be weak). Dry = no fuel or no spark at the plug. Cross-reference.

Click but no crank

1. Battery voltage under load. Voltmeter on battery posts, key to Start. Should not drop below 10V. Below that = battery, cables, or starter draw issue.
2. Trigger wire at solenoid. Backprobe the small spade on the starter solenoid (B/Y wire), key to Start — should read ~10V. No voltage = ignition switch contact block, neutral safety switch, or harness open.
3. Bypass the trigger. Carefully jumper from battery + to the solenoid trigger spade. If it cranks, the issue is upstream (switch, NSS, harness). If it still doesn't, the starter or its main cable is the problem.
4. Voltage drop on heavy cable. With key in Start, measure between the battery + post and the starter main lug. Should be <0.5V. More than that = corroded cable terminals or a bad cable.

Common failures

Ignition switch electrical block

The plastic switch block behind the lock cylinder cooks itself from years of carrying coil and starter current. Symptom: intermittent no-start, dies under bumps, accessories cut out. The electrical block is a separate part from the lock cylinder and can be replaced without keying issues. Reproduction parts are widely available.

Worn distributor advance

Centrifugal advance weights and vacuum advance diaphragm wear out. Symptom: ping under load, sluggish acceleration, hard hot-starts. Pull the cap and check the weights and springs visually; pinch off the vacuum advance line and see if idle changes (it should).

Transistor module heat failure (280Z)

Original matchbox module lives on the side of the distributor and bakes. Symptom: stalls when fully warm, restarts when cool. Tap the module while warm and listen for it to come back. Fix: upgrade to the E12-80 module relocated off the engine to the inner fender for better cooling.

Bad ground at engine block

If the engine-to-body ground strap is corroded, starter current finds alternate paths — through the throttle cable, the speedo cable, the EFI ground (on 280Z), anything metal touching the engine. Symptom: hot wires, melted accelerator cable, bizarre EFI behavior, starter clicks but doesn't crank well. Refresh the strap; it's a 10-minute job.

Ballast resistor open

The ceramic ballast resistor on 240Z occasionally opens. Symptom: starts on the key but dies the instant you let go (because ST→IG transition cuts coil voltage). Quick test: jumper around the ballast and see if it runs. Replacement is cheap and standard.

Sources & verification

Claims on this page should be cross-checked against:

• Nissan FSM — Engine Electrical (EE) and Body Electrical (BE) chapters for your specific year. Free PDF scans at xenons30.com.
• Atlantic Z Car Club — E12-80 conversion guide and ignition tech articles.
• classiczcars.com — forum archive, "will not start" diagnostic threads, ballast / coil compatibility threads.
• hybridz.org — for ignition swaps, megasquirt, standalone ignition.
• s30.world / Parts & Tech — part history and version differences.

Spot something incorrect or missing a citation? Drop us a note.