Checking the engine compression on your Dodge Ram van with the 5.2L or 5.9L V8 might seem intimidating, but it's actually a pretty straightforward job.
In this tutorial, I'll walk you through the steps to perform a compression test —and just as importantly, I'll explain how to understand what the results mean.
Why bother with a compression test? Because it can help you figure out whether the engine is worn out. It's a valuable diagnostic step if your van won't start, or if you're chasing down a stubborn misfire that's been tough to pinpoint.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 1989-1994:
- Dodge Ram B150 Van 5.2L V8: 1989, 1990, 1991, 1992, 1993, 1994.
- Dodge Ram B250 Van 5.2L V8: 1989, 1990, 1991, 1992, 1993, 1994.
- Dodge Ram B250 Van 5.9L V8: 1989, 1990, 1991, 1992, 1993, 1994.
- Dodge Ram B350 Van 5.9L V8: 1989, 1990, 1991, 1992, 1993, 1994.
- 1995-1997:
- Dodge Ram B1500 Van 5.2L V8: 1995, 1996, 1997.
- Dodge Ram B2500 Van 5.2L V8: 1995, 1996, 1997.
- Dodge Ram B3500 Van 5.2L V8: 1995, 1996, 1997.
- Dodge Ram B2500 Van 5.9L V8: 1995, 1996, 1997.
- Dodge Ram B3500 Van 5.9L V8: 1995, 1996, 1997.
- 1998-2003:
- Dodge Ram 1500 Van 5.2L V8: 1998, 1999, 2000, 2001, 2002, 2003.
- Dodge Ram 2500 Van 5.2L V8: 1998, 1999, 2000, 2001, 2002, 2003.
- Dodge Ram 3500 Van 5.2L V8: 1998, 1999, 2000, 2001, 2002, 2003.
- Dodge Ram 1500 Van 5.9L V8: 1998, 1999, 2000, 2001, 2002, 2003.
- Dodge Ram 2500 Van 5.9L V8: 1998, 1999, 2000, 2001, 2002, 2003.
- Dodge Ram 3500 Van 5.9L V8: 1998, 1999, 2000, 2001, 2002, 2003.
Symptoms Of Engine Compression Problems
In most cases, engine compression issues lead to one of two main problems:
- Engine no-start: Either the compression is so low that the engine won't start at all.
- Cylinder misfire: The engine manages to start and run, but it does so with a noticeable misfire.
If a misfire is happening because of a compression-related issue (and your Dodge Ram van is equipped with OBD II) you're likely to see one or more of these diagnostic trouble codes pop up:
- P0300: Random/Multiple Cylinder Misfire Detected.
- P0301: Misfire Detected in Cylinder #1.
- P0302: Misfire Detected in Cylinder #2.
- P0303: Misfire Detected in Cylinder #3.
- P0304: Misfire Detected in Cylinder #4.
- P0305: Misfire Detected in Cylinder #5.
- P0306: Misfire Detected in Cylinder #6.
- P0307: Misfire Detected in Cylinder #7.
- P0308: Misfire Detected in Cylinder #8.
You might also experience these symptoms:
- Rough idle: The engine idles roughly, though no misfire code is triggered. Once you press the gas, the roughness fades.
- Misfire under load: The misfire only shows up when you accelerate the vehicle.
- Idle-only misfire: Misfire is felt while idling but disappears as RPMs increase.
- Poor fuel economy: Because some cylinders aren't contributing evenly, fuel efficiency takes a hit.
- Strong exhaust odor: A noticeable, heavy exhaust smell may come from the tailpipe when the engine is running.
Important Tips And Suggestions
TIP 1 –Always start with a cold engine: Make sure the engine has completely cooled down before you begin removing the spark plugs.
Taking spark plugs out of a hot engine can strip or damage the threads in the spark plug holes —something you definitely don't want to deal with.
TIP 2 –Use a proper spark plug wire puller: When it's time to disconnect the spark plug wires, a spark plug wire puller is the tool you'll want to use.
This simple tool helps prevent damage to the wires while you're removing them from the spark plugs. Specifically, it saves you the headache of having the metal terminal stays stuck on the plug while pulling the wire off.
To see an example of this tool, you can see it and buy it here: OEMTOOLS 25542 Spark Plug Pliers (at: amazon.com).
TIP 3 –Mark the spark plug wires: Tag each spark plug wire with the number of the cylinder it connects to. This ensures you keep the correct firing order intact when it's time to reconnect them.
Which Compression Tester Should I Buy?
There are lot of engine compression testers to choose from and many places to buy them. Here's the one I use and recommend: Actron CP7827 Compression Tester Kit.
TEST 1: Dry Compression Test
To determine whether low engine compression is behind a no-start condition or a misfire, it's important to check the compression in all 8 cylinders.
That said, you don't always have to test every single one —especially if you've already confirmed that one or two cylinders are "dead" (misfiring). Still, I highly recommend testing at least two additional cylinders so you have healthy compression numbers to compare against the faulty ones.
If you don't already have a compression tester, your local auto parts store sells or rents them. Want to save a little money? Check out my picks here: Which Compression Tester Should I Buy?
Alright, let's jump into the testing process:
- 1
Unplug the ignition coil by disconnecting its 2-wire connector.
This step disables the ignition system so no sparks are produced while cranking the engine. - 2
Pull the spark plug wires off the spark plugs.
NOTE: Make sure to label each wire with the cylinder number before disconnecting them. This will help you put everything back in the correct order. - 3
Take out the spark plugs.
Be careful not to drop them! Dropping a spark plug could crack the porcelain insulator, which might lead to a misfire later on. - 4
Screw the compression tester into the spark plug hole for cylinder #1.
Only tighten it by hand —don't use a wrench or any tools to secure it. - 5
Have a helper crank the engine until the gauge needle stops rising.
- 6
Write down the reading and note which cylinder it came from on paper.
- 7
Repeat steps 4 through 6 for each of the remaining cylinders.
Now let's break down what the compression numbers are telling you:
CASE 1: Most cylinders show 0 PSI. This usually means your Dodge Ram van's V8 engine has major internal damage. Common causes include:
- A broken timing chain.
- A thrown connecting rod.
Even if the reading isn't zero, any cylinder with a reading under 100 PSI indicates internal mechanical trouble.
CASE 2: All cylinders have compression, but the numbers are inconsistent. A little variation between cylinders is normal. But if the differences are significant, it can lead to a misfire or a rough idle.
To learn what to do next, head over to: Interpreting The Engine Compression Test Results.