Chrysler Plymouth, Dodge, Imperial, Chrysler, DODGE TRUCK 1973 Diagnostics Manual

When a 1973 Chrysler product rolls in with a no-start, or a miss that won’t clear, the first thing most guys do is throw a scope on it and start guessing. I’ve been turning wrenches since before most of you were born, and I can tell you that guessing costs time and money. This 16-page factory diagnostics manual is what the dealer techs used when these cars were new. It covers the electronic ignition system across the entire Chrysler lineup: Plymouth, Dodge, Imperial, Chrysler, and even the DODGE TRUCK. No third-party rehash – this is the original OEM document.

TESTING THE ELECTRONIC IGNITION – Factory Procedure

The heart of this manual is the step-by-step diagnostic sequence for the transistorized electronic ignition. You get two main sections: ON-THE-CAR TESTING (page 8) and BENCH TESTING (page 12). The onboard section walks you through voltage checks at the control unit, pickup coil resistance measurements, and spark output verification – all with the distributor still in the engine. The bench section tells you exactly how to isolate a suspected control unit or coil with the parts on a workbench, using a standard 12V battery and a DVOM. No fancy break-out boxes required.

ON-THE-CAR TESTING: What It Covers

If you’ve ever chased a Chrysler electronic ignition problem armed with aftermarket wiring colors, you know the frustration. This manual gives factory wire colors, connector pinouts, and expected voltage readings at each test point. It even explains the transistor switching function so you understand why the voltage drops when you crank it. The manual explicitly warns you not to ground the tachometer lead to the coil negative terminal during testing – a mistake that fries the control unit instantly. That kind of safety detail is missing from generic guides.

BENCH TESTING: When the Unit Comes Off

Slow cranking? Intermittent spark? You suspect the control unit, but you don’t want to fork over cash for a part that tests good. Page 12 lays out a bench test procedure using a spare spark plug, a 12V bulb, and a jumper wire. You simulate the pickup coil signal and watch the unit’s response. If the bulb doesn’t flash, the control unit is bad. Takes about ten minutes. The manual also includes the internal schematic for the transistor switch – not just a block diagram, but actual component-level detail. That’s rare in a dealer-level publication.

Why OEM Documentation Matters

I’ve lost count of how many times a tech has shown me a reprinted manual with torque values off by 20 ft-lb or wire colors swapped. This manual is a direct scan from the original 1973 Chrysler publication. It matches the On-board Diagnostics (OBD) systems of its era – long before OBD-II, when you needed actual logic and a meter. The testing procedures are written for a technician who can read a schematic and operate a voltmeter, not someone expecting a plug-and-play code reader. If you own a 1973 Dodge Dart, a Plymouth Satellite, an Imperial LeBaron, or a Dodge pickup with the 400- or 440-cubic-inch engine, this is the diagnostic reference your shop manual shelf is missing.

For earlier models with breaker points, see the Chrysler Plymouth Dodge Radio Sound System Troubleshooting manual if you need audio system help – but for ignition, this 1973 booklet is it. Pair it with the Chrysler Torqueflite Transmission 1973 Diagnostics Manual for a full drivetrain reference, or the Chrysler Electrical Circuit Troubleshooting Reference Book for lighting and starter circuits.

Who Should Use This Manual

Home garage guys restoring a B-body or a Mopar truck. Vintage racers keeping a 340 or 426 Hemi alive. Any shop that still sees 1970s Chrysler products. The manual assumes you know how to set a dwell meter and read a voltmeter – it doesn’t hand-hold the basics like what a ground is. If you can follow a logical test sequence, you can diagnose an electronic ignition in under an hour. If you can’t, get a Manual Transmission clutch job – this manual won’t bail you out of beginner incompetence.

Does this manual cover the 1973 Dodge Truck electronic ignition?

Yes. The manual covers all Chrysler-built vehicles for the 1973 model year, including DODGE TRUCK.

What tools do I need to perform the bench test on page 12?

A 12V test light or multimeter, a jumper wire, a known-good spark plug, and a 12V battery. The manual shows you how to connect each lead. If you don’t have the right pickup coil resistance specs, they’re listed on page 8. Do not skip the step that disconnects the control unit from the coil – I’ve seen guys blow a transistor because they left it hooked up.

Download the Factory Manual and get the real test data Chrysler printed for its dealers. No aftermarket speculation – just the original 16 pages of diagnostic logic that kept Mopars on the road in the 70s.