Ignition Contact Set Guide for 1955-1959 GMC PM153 Trucks
Keep your classic GMC's engine firing correctly with the right set of ignition points.
- The ignition contact set (points) is a regular maintenance item on your PM153 and should be replaced every 10,000-15,000 miles to ensure reliability.
- Always replace the condenser at the same time as the points; a bad condenser will quickly ruin new points.
- Standard Ignition is a reputable aftermarket brand; their premium 'Blue Streak' line is recommended for longevity.
- Properly setting the point gap with a feeler gauge after installation is critical for correct engine timing and performance.
Signs of a Failing Ignition Contact Set
Ignition points are a normal wear item. The rubbing block that rides on the distributor cam wears down, and the electrical contacts can pit, burn, or corrode from the constant sparking. When your GMC PM153's points start to fail, you'll notice clear signs that shouldn't be ignored, as a complete failure can leave you stranded.
- Hard Starting or No Start: This is the most common symptom. Worn or incorrectly gapped points can't create the clean electrical break needed for a strong spark, making the engine difficult or impossible to start.
- Engine Misfires and Rough Idle: Pitted or burned contacts deliver an inconsistent spark. This can cause the engine to shake at idle, run unevenly, and misfire or stumble during acceleration.
- Reduced Power and Poor Acceleration: A weak or poorly timed spark from worn points leads to inefficient combustion. You may feel a general lack of power or a hesitation when you press the gas pedal.
- Engine Stalling: As the points degrade further, they may fail to deliver a consistent spark at low RPMs, causing the engine to stall at idle or when you come to a stop.
Choosing the Right Aftermarket Ignition Points
For a classic truck like the PM153, original equipment Delco-Remy parts are no longer in production. The market now relies on aftermarket manufacturers. Fortunately, brands like Standard Ignition have been making quality ignition components for decades and are a trusted choice.
Aftermarket Brand Assessment
| Tier | Brand(s) | Assessment |
|---|---|---|
| Standard Aftermarket | Standard Ignition | A well-regarded brand in the classic car community, known for making reliable ignition parts that fit and function correctly. The 'Blue Streak' line is their premium offering, often featuring better materials for longer life. Given the critical role of the points, opting for the premium version is a wise investment for reliability. |
Pro Tip: Always replace the ignition condenser when you replace the contact set. The condenser absorbs excess voltage to prevent the points from arcing and burning out prematurely. A faulty condenser will cause a new set of points to fail very quickly.
Frequently Asked Questions (FAQ)
What are ignition 'points'?
"Points" is the common name for the ignition contact set. They are a mechanical switch inside the distributor that triggers the spark from the ignition coil. This technology was used for decades before being replaced by modern electronic ignition systems.
How often should I replace the ignition points on my GMC PM153?
As a standard tune-up item, points should be inspected annually and typically replaced every 10,000 to 15,000 miles. Since they are a mechanical wear item, regular maintenance is key to keeping your classic truck reliable.
What does 'gapping the points' mean?
Gapping refers to setting the correct maximum distance between the two electrical contacts when the points are opened by the distributor cam. This is done with a tool called a feeler gauge. An incorrect gap will alter the ignition timing and dwell angle, leading to poor engine performance.
Can I upgrade to an electronic ignition?
Yes, many owners of classic trucks choose to replace the original points and condenser with an electronic ignition conversion kit (like a Pertronix unit). These kits eliminate the need for regular point adjustments and can provide a more consistent spark. However, a properly maintained points system is very reliable, and many owners prefer to keep the original factory setup.
Are there any recalls for the 1955-1959 GMC PM153 ignition system?
No. The National Highway Traffic Safety Administration (NHTSA) recall database was established in 1966, long after this truck series was produced. There are no official recalls or Technical Service Bulletins (TSBs) for the ignition system on these vehicles.
Technical Specifications
OEM Part Numbers: 1954557 D108P
Mechanical ignition contact set with one-piece breaker arm and rubbing block. Designed for use with a Delco-Remy style distributor and an external condenser. Requires manual gap adjustment upon installation.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.