How To Test The Fuel Injectors (1998-1999 2.7L V6 Chrysler)

How To Find The Bad Or Clogged Fuel Injector

In the hope of helping you save time, money and frustration in diagnosing a bad fuel injector on your 2.7L Intrepid (Concorde), in this section I'm gonna' offer you a simple diagnostic strategy to find the bad fuel injector.

The main idea here is to first test the most obvious (and common) components that usually cause a misfire.

This specific troubleshooting method/process has saved me a lot of time and frustration and that I think will also help you:

1. Find the 'dead' cylinder first.
   • This is the most important first step and the one that will speed up your troubleshooting efforts.
   • This requires checking for specific misfire codes (P0301, P0302, P0303, P0304, P0305, P0306) or doing a cylinder balance test.
2. Once the 'dead' cylinder has been identified, the next step is to make sure it's getting spark.
   • You must use a dedicated spark tester to check for spark.
   • It's important that you check that the spark plug boot and spark plug wire are not damaged, cut, or burned.
   • Make sure that the spark plugs and spark plug boots ARE NOT swimming in motor oil from a leaking valve cover gasket (this is a very common cause of misfires).
   • You should also remove the spark plug and check it for cracks or carbon tracks (this is SO important).
     • Here's a real life case study on carbon tracks and how they can cause a misfire: Carbon Tracks Are A Common Cause Of Ignition Misfires.
   • The key here is to eliminate the ignition coil (COP coil), the spark plug wire and the spark plug as the cause of the cylinder's misfire.
3. If spark is present, then the next step is checking that that cylinder has good compression.
   • This is one of the most overlooked tests when diagnosing a misfire or rough idle condition. You can find the test here:
     • How To Test Engine Compression (2.7L Chrysler).
4. Check the fuel injectors.
   • This now involves removing the upper intake manifold plenum to access all of the fuel injectors (if applicable).

5. Swap the fuel injector with its neighbor on the fuel injector rail.
   • I'll swap out that fuel injector with its neighbor if I have confirmed:
     1. The ignition system is not at fault.
     2. That the cylinder's compression value is good (compared to the rest of the cylinders).
     3. The fuel injector resistance is good.
     4. I think the fuel injector is clogged.
     If the misfire now follows that swap, I now know that fuel injector is clogged (or bad) and needs to be cleaned or replaced.

The most important thing to remember is to first identify the misfiring cylinder. Once you've identified it, keep in mind that either air, spark or fuel is missing and keeping that cylinder from producing power.

Precautions To Take When Removing The Intake Manifold Plenum

As mentioned at the beginning of this tutorial, the intake manifold plenum has to be removed to get to the fuel injectors beneath. Removing the plenum isn't hard but it does require you to keep in mind the following precautions:

1. Buy or borrow a repair manual (preferably a Haynes Repair Manual -Chilton manuals suck) so that you can have the intake manifold removal process explained in detail.
   • The manual will also give you the torque specifications for the bolts.
2. Be careful that foreign objects (like a bolt, a nut, or any metal piece/part) do not fall into the open manifold port runners.
3. Once the plenum has been removed, place a clean rag or rags on the open intake runners. This will keep things from falling into them.
4. As you're removing bolts, nuts and stuff from the intake plenum to remove it, place them in a container and away from the engine compartment.

Anything falls into the open intake runners, without you knowing, and the engine is started, you are going to be in a big world of hurt! Since it may require the removal of the cylinder head to retrieve the part that fell in. So be alert and be careful.

NOTE: Once you're done and are re-installing the plenum don't use any type of sealant on the plenum gaskets. Using a sealant like RTV Silicone is not needed or recommended and could cause vacuum leaks down the road.