How to Install New Truck Spark Plugs

White Ford truck with hood up in a shop
What You'll Need
A small wrench
A socket wrench
Silicon based lubricant
A small cloth
Tension tester tool
Replacement spark plugs
Feeler gauge

Truck spark plugs will need changing at regular intervals due to the general wear and tear of travel and use. It is important that you know how to install new truck spark plugs in case you need to replace them quickly. This process can be completed by following a few simple steps.

Step 1 - Disconnect the Battery

This step is arguably the most important. Disconnect the truck battery by removing the black battery cable. This will cut power from the battery to all parts of the truck. You also need to disconnect the battery in order to cancel out the chance of electrical shock as you work.

Step 2 - Locate and Access

removing a spark plug from an engine

Locate and access the truck spark plugs by lifting the hood and removing any plastic covers that house the engine. This is standard in new trucks and the spark plugs should be visible once the cover is gone. Make sure you can access the spark plugs with enough room to carry out a replacement. Easy access should make installing new truck spark plugs reasonably simple.

Step 3 - Disconnect Wires

Disconnect the spark plug leads. Treat them carefully as they are integral in creating the initial engine ignition. Gently move the boot to the left and right until it becomes loose and comes away. The boot is a small cap which you should be able to fit two fingers around easily. If you cannot move the boot yourself, use a small wrench to do the job for you but take great care not to damage the leads. If you are removing all leads simultaneously, number them so they can be put back in the correct positions after. It’s better to work on one boot and plug at a time so there is no risk of mixing them up.

Step 4 - Remove Spark Plug

Use a socket wrench to gently loosen the spark plug. When it is loose enough, unscrew it with your fingers and remove it from the engine. Do not be afraid to use a little extra physical force if you need to as the items are actually being replaced.

Step 5 - Install New Spark Plug

four spark plugs

Clean the wire boot and body of the new spark plugs with silicone based lubricant before you install them. You will also need to check that the plug gaps are consistent by measuring them with a feeler gauge. The lubricant should help the spark plug fit nicely into position. Place the new spark plug into position and screw it in with your fingers until it feels firm. Take a tension tester tool and test the tension of the new spark plug. Make sure the reading is similar to the one recommended on the spark plug packaging. If the readings are not similar, loosen or tighten the screw until the desired result is reached.

Step 6 - Reconnect Wires

Replace the spark plug leads back into their original positions. It is vitally important that the leads are attached in the same positions as they were before they were before. If they are not, the engine will struggle to run or may not even run at all.

Step 7 - Finish

Finish by putting the plastic cover back over the engine and reconnecting the black cable to the battery. The engine should start the first time if you have replaced the truck spark plug correctly. Repeat the process for all spark plugs.