The spark plug, such an inexpensive and small component but one that is tasked with a very important job.
In this tutorial I'll answer some of the most commonly asked questions about the spark plugs.
Contents of this tutorial at a glance:
APPLIES TO: This tutorial applies to the following vehicles:
- Ford E150: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
- Ford E250: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
- Ford E350: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
What Does A Spark Plug Do?
The sole purpose of the spark plug is to ignite the air-fuel mixture within its cylinder and start the combustion process.
It does this by having a spark jump from its center electrode to its side electrode.
This spark is produced by the ignition coil and arrives via the distributor and spark plug wire (the spark plug is connected to).
Symptoms Of A Bad Spark Plug
When one or more spark plugs fail in your Ford E150 (E250, E350), you'll see one or more of the following symptoms:
- Rough idle.
- Bad gas mileage.
- Extended engine cranking (engine takes longer than usual to start).
- A heavier than normal exhaust smell coming out of the tailpipe.
- The engine is not as peppy as it used to be.
- Hesitation when you accelerate the vehicle on the road.
What Causes A Spark Plug To Stop Working?
Quite a few factors can cause a spark plug to stop working.
The most common issues causing a spark plug to stop sparking are:
- Normal wear and tear. In other words, they simply wear out.
- Carbon deposits blocking the air gap between the center and side electrode.
- Spark plug is damaged during installation.
When the spark plug's air gap is blocked with carbon deposits, spark will not jump between the electrodes.
Carbon deposits blocking the air gap between the electrodes usually only happens on high-mileage engines that are burning oil within the cylinders.
You can tell these engines apart because:
- They burn oil and have blue smoke coming out of their tailpipe.
- These engine require being topped off with engine oil on a regular basis.
How Do I Know My Spark Plugs Need Changing?
What will usually tell you that it's time to replace the spark plugs is when one of the following conditions is met:
- You've removed the spark plugs and they are showing signs of heavy wear and tear.
- The spark plugs are causing an engine performance problem.
- You're following the recommended spark plug change interval laid down in a repair manual or owners manual.
There's nothing written in stone that says you have to change the spark plugs at a specific interval.
Which Spark Plugs Should I Buy?
When your Ford E-Series van left the factory, it came equipped with Motorcraft brand spark plugs.
In plain English this means that the Motorcraft brand spark plugs are the original equipment spark plugs for your Ford E150 (E250, E350).
To get the best performance, I recommend that you purchase the Motorcraft brand spark plugs.
Now, having said that, any spark plug that's specifically designed for your van (year, engine size) will work.
Should I Use 100,000 Mile Spark Plugs?
Spark plugs that are advertised as having a service life up to 100,000 miles have platinum or iridium tipped electrodes. Regular copper spark plugs, won't last as long.
Now the catch here is that if the engine is in perfect working condition (e.g. it's not burning oil) then you'll definitely see these spark plugs give a service life of about 100,000 miles.
But if the engine in your Ford E150 (E250, E350) is burning oil, you're not going to see anywhere near 100,000 miles on those spark plugs. Carbon buildup will eventually close the air gap between the spark plug electrodes and cause a misfire.
Important Tips And Suggestions
When replacing the spark plugs in your Ford E-Series van, keep in mind the following tips and suggestions:
TIP 1: Replace the spark plugs with a completely cold engine. If you don't let the engine coool down, you run the risk of damaging the spark plug threads of the spark plug holes in the cylinder head.
Stripping the threads of the spark plug holes is a nightmare that you don't want to experience.
TIP 2: Check the air gap of the new spark plugs with a spark plug gapper. I strongly recommend that you double check that the spark plug gap is correctly set to your vehicle's recommended specification when installing spark plugs.
Don't trust that they are gapped! I've solved many driveability problems that were due to incorrectly gapped spark plugs.
TIP 3: Label the spark plug wires with the cylinder number they belong to BEFORE replacing the spark plugs. This will keep your from losing the spark plug wires' firing order.
TIP 4: Use a torque wrench to tighten the spark plugs. If you don't tighten the spark plugs enough you run the risk of having them come out as you're driving down the road. This could also damage the spark plug hole threads in the cylinder heads.
If you over tighten the spark plugs, then you run the risk of damaging the threads of the spark plug hole.
The way to avoid any of these problems is to use a torque wrench to tighten the spark plugs. Now, it's easier said than done because some of the spark plugs are in very tight places (some just can't be tighten with a torque wrench). Still, you won't go wrong if you use a torque wrench on the ones you can.
More Ford E150, E250, and E350 Tutorials
You can find a complete list of tutorials for the full-size Ford E-Series vans here: Ford 4.9L, 5.0L, 5.9L Index Of Articles.
Here's a small sample of the tutorials you'll find:
- Manifold Absolute Pressure MAP Sensor Test (Ford 4.9L, 5.0L, 5.8L).
- Ignition Coil Test -No Spark No Start Tests (Ford 4.9L, 5.0L, 5.8L).
- How To Troubleshoot A No Start (Ford 4.9L, 5.0L, 5.8L).
- Testing A Blown Head Gasket (Ford 4.9L, 5.0L, 5.8L).
- How To Test Engine Compression (4.9L, 5.0L, 5.8L).
If this info saved the day, buy me a beer!
