Testing the fuel injectors on the 1995-1999 3.1L V6 Chevrolet Lumina or Monte Carlo can seem an impossible task, considering that the fuel injectors are underneath the intake manifold plenum.
Thankfully, the intake manifold plenum does not need to be removed to test them and in this tutorial I'll explain how.
You'll be able to easy find out if you've got a bad one causing a rough idle problem or a misfire problem.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar Los Inyectores De Combustible (1995-1999 3.1L Chevrolet Lumina, Monte Carlo) (at: autotecnico-online.com).
FUEL INJECTOR CIRCUIT WIRING DIAGRAMS:
- Fuel Injector Circuit Diagram (1995 3.1L V6 Chevrolet Lumina, Monte Carlo).
- Fuel Injector Circuit Diagram (1996-1997 3.1L V6 Chevrolet Lumina, Monte Carlo).
- Fuel Injector Circuit Diagram (1998-1999 3.1L V6 Chevrolet Lumina, Monte Carlo).
Symptoms Of A Bad Fuel Injector
A fuel injector is an electro-mechanical valve that opens and closes thousands of times as you drive your vehicle from point A to point B. Eventually, they're going to wear out and stop injecting fuel into their cylinder.
When this happens, and if your vehicle is OBDII equipped, you're going to see one of the following trouble codes lighting up the check engine light:
- P0201: Injector 1 Control Circuit.
- P0202: Injector 2 Control Circuit.
- P0203: Injector 3 Control Circuit.
- P0204: Injector 4 Control Circuit.
- P0205: Injector 5 Control Circuit.
- P0206: Injector 6 Control Circuit.
In the majority of the cases, you won't see a fuel injector trouble code but a cylinder misfire trouble code. When this happens you'll see one or more of the following:
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
- P0305: Cylinder #5 Misfire.
- P0306: Cylinder #6 Misfire.
Besides a fuel injector or cylinder misfire trouble code, you're also going to notice one or more of the following symptoms:
- Rough idle.
- Bad gas mileage.
- A heavier than usual exhaust gas smell coming out of the tailpipe.
- Lack of power when accelerating the vehicle under load.
Location Of The Fuel Injector Harness Connector
As mentioned before, all 6 fuel injectors are underneath the intake manifold plenum. Thankfully we don't have to remove it to test their internal resistance.
We'll be testing the internal resistance of all 6 fuel injectors through the fuel injector harness connector that is located at the back of the intake manifold next to the alternator.
If you take a look at photo 1 of 3, in the image viewer above, the orange arrow points the location of the 10 terminal fuel injector harness connector.
If you disconnect the 10 terminal fuel injector harness connectors, you'll notice that the connector that belongs to the engine wiring harness has female terminals (see photo 2 of 3).
The connector on the fuel injector side, has male terminals (see photo 3 of 3). Our fuel injector resistance test will all take place on this connector.
Where To Buy The Fuel Injectors And Save
The following links will help you comparison shop for the fuel injectors:
Not sure if the fuel injector will fit your particular GM vehicle? Don't worry, once you get to the site, they'll make sure it fits. If it doesn't, they'll find you the right one.
TEST 1: Testing The Fuel Injector Resistance
On the 1995-1999 3.1L Chevrolet Lumina and Monte Carlo, the fuel injector resistance specification is: 11.4 - 12.6 Ohms with a cold engine (at 50-95° F).
If any of the fuel injectors is internally damaged or defective, then its internal resistance will not be within the specified 11.4 - 12.6 Ohms.
These are the test steps:
- 1
Place your multimeter in Ohms mode.
- 2
Disconnect the fuel injector harness from the engine wiring harness connector.
NOTE: All tests are done on the fuel injector harness connector which has male spade terminals. - 3
Probe terminals A and D with the multimeter test leads to test injector #1.
Your multimeter should register 11.4 - 12.6 Ohms. - 4
Probe terminals B and D with the multimeter test leads to test injector #2.
Your multimeter should register 11.4 - 12.6 Ohms. - 5
Probe terminals C and D with the multimeter test leads to test injector #3.
Your multimeter should register 11.4 - 12.6 Ohms. - 6
Probe terminals K and D with the multimeter test leads to test injector #4.
Your multimeter should register 11.4 - 12.6 Ohms. - 7
Probe terminals J and D with the multimeter test leads to test injector #5.
Your multimeter should register 11.4 - 12.6 Ohms. - 8
Probe terminals H and D with the multimeter test leads to test injector #6.
Your multimeter should register 11.4 - 12.6 Ohms.
Let's examine your resistance test results:
CASE 1: The resistance of all 6 fuel injectors is within specification. This is the correct and expected test result and confirms that the fuel injectors are not defective internally.
CASE 2: One or more fuel injectors' resistance value is not within specification. This lets you know that that fuel injector or fuel injectors whose internal resistance is not within the specification is bad.