My Plymouth 'Cuda cranks but has no spark. What should I check?

Short answer: With a test light, trace power from the ignition switch to the ballast resistor, coil and ignition box. Owners say the box fails most often, even new ones, so carry a spare. If the car fires on Start but dies when you let the key go back to Run, it's the ballast resistor. If no power reaches the box at all, look at the ignition switch and wiring. Don't bypass the ballast on a stock coil.

Symptom: The engine cranks normally but there's no spark, or it fires while cranking and dies as soon as the key goes back to Run.

What to check first

1. Key on: test for 12 volts at the ballast resistor, coil and ignition box connector.
2. If no power, check the ignition switch and wiring back to it.
3. Swap in a known-good ignition box.
4. Check the ballast resistor and coil.
5. Check the ground at the ignition box mounting.

Likely causes

1. Failed electronic ignition control box. Mopars of this era use an electronic ignition box (ECU) that switches the coil. Owners say it fails often, even brand new.
2. Ballast resistor burned out. The ballast resistor lowers voltage to the coil while running. If it fails, the car may run while cranking but die when you let the key go back to Run.
3. No power to the ignition circuit (switch or wiring). If the box isn't getting 12 volts, the ignition switch or the wiring is the problem.
4. Coil. A weak coil can also cause no spark.

What it usually costs

Owners in these threads didn't post prices. Ignition boxes, ballast resistors and coils are inexpensive parts.

Is it safe to keep driving?

A car that may die at any moment shouldn't be driven in traffic. Fix the ignition first.

DIY or shop?

Very DIY with a test light and a wiring diagram.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists 9 recall(s) for the Plymouth Barracuda in these years, and none match this problem. Check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• Plain words: The complaint count below shows how often owners reported problems that mention these words to NHTSA. A count is not proof of a defect.
• NHTSA complaints: 0 keyword-matched complaints for Plymouth Barracuda / Cuda 1970–1974 (of 1 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-31; keywords: spark, ignition, stall, start) (NHTSA returned no data for 16 model-year queries). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Plymouth 'Cuda 1973 that cranks but doesn't spark on Reddit r/mopar, owners of a 1973 'Cuda 340 that had been sitting found it cranked fine with no spark, even after changing the ignition box twice. Others said the box is the culprit most of the time, even new ones, to check the coil and use a test light to trace 12 volts through the circuit. The owners found no power reaching the box. Several said to check the ballast resistor, and noted a bad one lets it run with the key at Start but die when you let go.
• In Ballast resistor hack ? on E-Bodies.org, owners discussed bypassing the ballast resistor with a jumper wire inside a stock-looking housing. Members pointed out that the stock coil isn't designed to run on a full 12 volts, which is why the ballast is there, and that you should only remove it if you've switched to a coil or ignition designed for 12 volts.

Quick tip

Keep a spare ignition box and ballast resistor in the glovebox. On these cars that's cheap insurance.

Vehicle focus: Plymouth Barracuda and 'Cuda, 1970-1974.

Safety / mechanic note

A stall in traffic is dangerous, and old wiring can overheat. Verify with a mechanic.