These are some of the most common signs that you have a glow plug or relay failure:
- If there is a problem with your glow plugs, the glow plug dashboard light may flash or the check engine light may illuminate when you try to start your automobile. You’re undoubtedly used to seeing the glow plug dashboard light come on for a few seconds when you start your car in colder-than-normal conditions to warm up your engine. If the light does not turn on or begins to flash, this is the first clue that anything is amiss.
- You’re having trouble starting your car. On a frosty morning, if your car takes longer to turn over than usual, this could be a warning sign.
- Until the engine heats up, there will be white smoke. This could indicate a problem with injection timing or an issue with the injection pump, both of which would affect the glow plugs and the relay. If the white smoke clears up as soon as your car warms up, it’s probably not a coincidence. Normal condensation is not to be mistaken with this white smoke.
- After your automobile has started, there is rough idling or hesitation. This could potentially indicate a problem with the glow plug, relay, or injector.
If you have any of the problems listed above, you should have your Mercedes serviced as soon as possible. Even if your car is having minor problems, you should have it diagnosed as soon as possible. If left unchecked for an extended length of time, most automotive difficulties can swiftly escalate into severe problems or full engine failure.
Testing glow plug resistance:
- Connect the power wire to the glow plug and disconnect it. If you don’t do this, you’ll be measuring the resistance of all the glow plugs at the same time, rather than just the one you’re interested in.
- Connect one multimeter test lead to the engine’s ground (preferably near the glow plug).
- Connect the other end of the other lead to the (power supply) terminal on the glow plug’s top.
- Take a look at the multimeter display for the outcome. A resistance of less than 6 usually indicates that the glow plug is in good working order.
What exactly is AIH relay?
The AIH is controlled by the PCM through a relay next to the glow plug relay. This intake heater, which is located on the cold side of the intake manifold, protrudes straight into the air stream and blocks approximately 20% of the intake path.
Will a diesel engine start if the glow plugs are bad?
With defective glow plugs, you can’t start a diesel engine. A faulty glow plug will not provide sufficient heat to preheat the cylinder and ignite the fuel. It may take multiple attempts to start the vehicle if it can’t generate heat quickly enough.
What’s the best way to test a relay?
A multimeter is the sole tool needed to inspect a relay. Check for 12 volts at the 85 position in the fuse box where the relay plugs in with the relay removed from the fuse box, the multimeter configured to measure DC voltage, and the switch in the cab activated (or wherever the relay is located). Check to see whether the proper fuse has blown if there isn’t one. Check that the switch is allowing current to flow to the relay if the fuse is intact.
Set the multimeter to continuity mode and check to see if the 86 slot has a good ground connection once you’ve confirmed there’s voltage at the 85 position.
If voltage can flow via that side of the relay, proceed to the 87 connecting point and check for battery voltage there. If it isn’t, a blown fuse or circuit breaker is likely.
What is the ideal ohm value for a glow plug?
Step 1: Determine the resistance of the multimeter. You must first determine the resistance value of your digital multimeter before testing the terminals. To do so, turn on the multimeter and set the display to Ohms.
- The omega sign, or a symbol that appears like an upside down horseshoe (), is used to represent ohms.
Touch the two leads of the multimeter together and study the resistance reading that appears once the multimeter is set to read in Ohms.
If the multimeter reads zero, try increasing the sensitivity setting to a higher one until you get a reading.
This value should be written down on a piece of paper because it will be used to calculate the resistance of your glow plugs later.
Step 2: Locate your engine’s glow plugs. The majority of glow plugs are mounted in the cylinder heads and have a heavy gauge wire attached to them, similar to a typical spark plug wire.
Remove any coverings that may be impeding access to the glow plugs, and if necessary, use the flashlight for extra lighting.
Disconnect the glow plug wires in step three. Disconnect any wires or caps attached to the glow plugs once you’ve found them all.
Step 4: Make a connection with the negative terminal. Connect the negative leads of your multimeter to the negative terminal on your vehicle’s battery.
If feasible, tuck the lead inside or underneath the clamping mechanism of the post to attach it to the terminal.
Step 5: Make a positive contact with the positive terminal. Take your multimeter’s positive lead and connect it to the terminal on your glow plug.
Step 6: Measure the resistance of the glow plug. Record the resistance reading on the multimeter while both leads are touching the terminals.
If you don’t get a reading after touching the glow plug, double-check that the negative lead is still connected to the negative battery terminal.
Step 7: Work out how much resistance there is. Subtract to get the true resistance value of the glow plug.
By subtracting the resistance value of your multimeter (recorded in Step 2) from the glow plug resistance value, you may determine the true resistance value of the glow plug (recorded in Step 6).
Step 8: Determine the resistance level. Compare your glow plug’s computed real resistance value to the factory specification.
The glow plug must be replaced if its resistance exceeds the specification or falls outside of the permitted range.
- The genuine resistance value for most glow plugs is between 0.1 and 6 Ohms, which is the permitted range.
Step 9: Repeat with the remaining glow plugs. Continue with the remaining glow plugs until all of them have been tested.
It is suggested that the complete set of glow plugs be replaced if any of them fail the test.
If the resistance values are too far apart, replacing just one or a few glow plugs may produce engine troubles comparable to a damaged glow plug.
Testing the resistance of a glow plug in most automobiles is a fairly easy technique, provided the glow plugs are in an easily accessible area. If they aren’t, or if you don’t feel comfortable doing it yourself, any expert mechanic, such as one from YourMechanic, should be able to do it swiftly and efficiently. They may also replace your glow plugs if necessary, allowing you to start your automobile normally.
On a 2000 7.3 Powerstroke, where is the glow plug control module?
Next to the AIH relay, just above the passenger side valve cover. It’s the rectangle box with two square plugs in an aluminum color. A GPCM is only seen on CA emissions trucks.
Is there a relay on glow plugs?
A glow plug relay is used by the glow plug control unit to turn on and off the current to the glow plugs. The circuit will require greater current as the number of glow plugs monitored by a control unit increases. Glow plugs are frequently divided across two circuits, with two glow plug relays, to reduce the amount of current required. This is a common configuration in earlier glow plug systems.
The ignition process of a diesel-powered car
Here’s what occurs when you start a diesel-powered car to put this idea into practice:
- The glow plug control unit analyzes the ECU’s input to determine the glow plugs’ timings, electric current, and duration requirements.
- Fuel is sprayed directly onto the hot tip of the glow plugs after the intake air is compressed.
- When the injected fuel interacts with the compressed air in the heated cylinder, combustion begins.
- To ensure optimal fuel combustion and decrease emissions, the glow plug control unit keeps the glow plugs on for a short time after the engine begins.
On a 7.3 Idi, how do you replace the glow plugs?
- With the connector removed, thoroughly spray the base of each glow plug with your favorite penetrating lubricant (WD-40, PB Blaster, etc.) and let it sit for 5 minutes to assist loosen any seized threads.
- To loosen and remove the glow plug from the cylinder head, use a 3/8″ deep socket.
- Replacing one glow plug at a time, install the new glow plug in reverse order. A small amount of anti-seize can be sprayed to the threads of the new glow plug if desired.