A Guide to Replacing the Ignition Coil on Your 1951 GMC P252
Keep your classic GMC's engine firing reliably with the right new aftermarket ignition coil.
- You must use a 6-volt ignition coil designed for a system without an external resistor.
- Symptoms of failure include no-start, hard starting when hot, misfiring, and stalling.
- Premium brands like NGK and Standard Ignition offer higher quality and durability for improved reliability.
- Replacement is very simple and can be done in under 30 minutes with basic hand tools.
Is Your Ignition Coil Failing?
On a classic truck like the 1951 GMC P252, the ignition system is relatively simple. The coil is a common wear item that can cause frustrating problems when it starts to fail. Because these parts can degrade slowly over time or fail suddenly, knowing the symptoms is key.
Common Symptoms of a Bad Ignition Coil
- No-Start Condition: The engine cranks over but never fires up. This can happen if the coil has failed completely and isn't producing any spark.
- Hard Starting: The truck takes a long time to start, especially when the engine is warm. Heat can increase the internal resistance of a failing coil, leading to a weaker spark.
- Engine Misfires or Stalling: The truck may run rough, hesitate during acceleration, or stall unexpectedly. This can be caused by an inconsistent spark from a weak coil.
- Visible Damage: Check the coil for cracks in the housing, oil leaks, or burnt terminals. Any physical damage is a clear sign it needs replacement.
Choosing the Right Aftermarket Ignition Coil
Since "new old stock" (NOS) or original 1951 OEM parts are nearly impossible to find, your only option is a new aftermarket coil. For your P252, quality and correct specifications are more important than brand loyalty. The most critical spec is voltage: your truck uses a 6-volt, canister-style ignition coil. Do not use a 12-volt coil unless you have converted the entire vehicle's electrical system.
Aftermarket Brand Tiers
Not all aftermarket brands are created equal. They generally fall into a few quality tiers:
- Premium Brands (NGK, Standard Ignition Blue Streak): These brands are known for high-quality materials and manufacturing standards that often meet or exceed original specifications. NGK is respected for its OE-level engineering, while Standard's Blue Streak line often includes design improvements to fix common failure points of older parts. For a vehicle you depend on, spending a little more on a coil from these brands is a wise investment in reliability.
- Standard Brands (Spectra, Global Parts, Skyward): These brands offer a balance of affordability and function. They are designed to be direct-fit replacements and can be a good value. However, user reviews for brands like Spectra are sometimes mixed, with some reporting shorter lifespans. They can be a suitable choice for a budget-conscious repair, but may not have the same long-term durability as premium options.
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Ignition Coil | $23.02 - $38.58 |
| Shop Labor | $50 - $100 |
Pro Tip: Check Your Wires
While replacing the coil, inspect the small primary wires connected to its terminals and the main high-tension wire going to the distributor cap. If the insulation is cracked, brittle, or oily, replace them to ensure a strong connection and prevent voltage leaks.
Frequently Asked Questions (FAQ)
Do I need a coil with an external resistor?
No, a stock 1951 GMC P252 with its original 6-volt system does not require an external resistor. You need a standard 6-volt coil designed for systems without a resistor. Some coils made for 12-volt conversions do require a resistor, so be sure to buy the correct part for your system.
How do I test my old ignition coil?
You can perform a basic test with a multimeter. Disconnect the coil and measure the resistance between the two small primary terminals (+ and -). Then, measure the resistance between the center high-tension tower and one of the primary terminals. You will need to find the correct primary and secondary resistance specifications for a 1950s GM 6-volt coil to compare your readings. If the readings are far out of spec, the coil is bad.
Are there any recalls for the 1951 GMC P252 ignition coil?
No. There are no open recalls or technical service bulletins (TSBs) on file with the NHTSA for this part on this vehicle. This is normal for a vehicle of this age.
Is this a difficult part to replace myself?
No, this is a very easy job for a DIY mechanic. The coil is typically mounted to the engine or firewall with a simple bracket and held on by one or two bolts. It involves disconnecting the battery, removing two small wires and the main coil wire, unbolting the old coil, and installing the new one in reverse order. The entire process usually takes less than 30 minutes.
Technical Specifications
Voltage: 6V, Style: Canister, Construction: Oil Filled, Primary Terminals: 2 (Stud type).
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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.