Anyone know how to set up a multimeter to check a spark plug?
#1
Teching In
Thread Starter
iTrader: (1)
Join Date: Oct 2002
Location: ORLANDO, FL USA
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
Anyone know how to set up a multimeter to check a spark plug?
just like the title says people. Anyone?
My plugs look fine, but I changed them, and seem to have gotten rid on my miss. I am thinking a plug is bad internally somehiw and want to see if there is a way to test them to see?
My plugs look fine, but I changed them, and seem to have gotten rid on my miss. I am thinking a plug is bad internally somehiw and want to see if there is a way to test them to see?
#3
TECH Veteran
iTrader: (19)
This is maybe the easiest test you will ever do in your life.
Put the meter on continuity (cont mode). If it doesnt have that look for the Omega symbol on there. Anything to measure resistance will work. Attach one lead to one side, the other lead to the oppisite side. So easy, right??
If it looks like a low resistance it is good. High it is bad. Some meters will say like 32K ohms when it is bad because that is the max it will show. Some beep when there is a conection. I mean if it is showing like less than 5 ohms you are ok.
This is like a 5 second test. Too bad testing diodes and chips isn't so easy!
Put the meter on continuity (cont mode). If it doesnt have that look for the Omega symbol on there. Anything to measure resistance will work. Attach one lead to one side, the other lead to the oppisite side. So easy, right??
If it looks like a low resistance it is good. High it is bad. Some meters will say like 32K ohms when it is bad because that is the max it will show. Some beep when there is a conection. I mean if it is showing like less than 5 ohms you are ok.
This is like a 5 second test. Too bad testing diodes and chips isn't so easy!
#5
Teching In
Thread Starter
iTrader: (1)
Join Date: Oct 2002
Location: ORLANDO, FL USA
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
thanks.
I already replaced the plugs. The car ran great. I just wanted to narow it down to which cylinder had the bad plug. And be positive it was a bad plug!
Especially now that I have my miss back on plugs that are less than a few hours old!
I am at a loss now. I think I may have a coil or a tps going bad or something. COuld still be O2's possibly, being that I haven't replaced em with new. I used the two rears. I can't belive that they are the problem after trying a different pair, extending the harness the right way. Now the car is pissing me off!
Anyone have any ideas?
I already replaced the plugs. The car ran great. I just wanted to narow it down to which cylinder had the bad plug. And be positive it was a bad plug!
Especially now that I have my miss back on plugs that are less than a few hours old!
I am at a loss now. I think I may have a coil or a tps going bad or something. COuld still be O2's possibly, being that I haven't replaced em with new. I used the two rears. I can't belive that they are the problem after trying a different pair, extending the harness the right way. Now the car is pissing me off!
Anyone have any ideas?
#6
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
You can't see all faults with a DMM. Only gross open
circuit, in a plug; however cracks in the insulation
will give you trouble at higher cylinder pressures
where the gap will present more arc standoff voltage
than sneaking out the crack and arcing somewhere
else. Similarly the wires, one pinhole and you can lose
spark under load (or all the time). Looking at the motor
in the dark is one thing to do, misting wires with water
and looking for worsening is another.
circuit, in a plug; however cracks in the insulation
will give you trouble at higher cylinder pressures
where the gap will present more arc standoff voltage
than sneaking out the crack and arcing somewhere
else. Similarly the wires, one pinhole and you can lose
spark under load (or all the time). Looking at the motor
in the dark is one thing to do, misting wires with water
and looking for worsening is another.
#7
On The Tree
iTrader: (1)
Join Date: Feb 2004
Location: Kentucky
Posts: 190
Likes: 0
Received 0 Likes
on
0 Posts
With apologies to Carroll Smith for adapting his bolt test to this thread, the best way to test a spark plug is to throw it into a lake. If it floats, it's good.
Pulling a plug to check for signs of the engine running rich/lean/hot, etc, is one thing, but if you have any reason to suspect the plugs themselves might be bad, just toss them and move on.
Pulling a plug to check for signs of the engine running rich/lean/hot, etc, is one thing, but if you have any reason to suspect the plugs themselves might be bad, just toss them and move on.
Trending Topics
#8
Originally Posted by jimmyblue
You can't see all faults with a DMM. Only gross open
circuit, in a plug; however cracks in the insulation
will give you trouble at higher cylinder pressures
where the gap will present more arc standoff voltage
than sneaking out the crack and arcing somewhere
else. Similarly the wires, one pinhole and you can lose
spark under load (or all the time). Looking at the motor
in the dark is one thing to do, misting wires with water
and looking for worsening is another.
circuit, in a plug; however cracks in the insulation
will give you trouble at higher cylinder pressures
where the gap will present more arc standoff voltage
than sneaking out the crack and arcing somewhere
else. Similarly the wires, one pinhole and you can lose
spark under load (or all the time). Looking at the motor
in the dark is one thing to do, misting wires with water
and looking for worsening is another.
In reality it's probably best to just replace it, plugs are usually $2 at the most.
#10
TECH Regular
iTrader: (16)
Join Date: Jun 2004
Location: michigan
Posts: 483
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 2002_Z28_Six_Speed
This is maybe the easiest test you will ever do in your life.
Put the meter on continuity (cont mode). If it doesnt have that look for the Omega symbol on there. Anything to measure resistance will work. Attach one lead to one side, the other lead to the oppisite side. So easy, right??
If it looks like a low resistance it is good. High it is bad. Some meters will say like 32K ohms when it is bad because that is the max it will show. Some beep when there is a conection. I mean if it is showing like less than 5 ohms you are ok.
This is like a 5 second test. Too bad testing diodes and chips isn't so easy!
Put the meter on continuity (cont mode). If it doesnt have that look for the Omega symbol on there. Anything to measure resistance will work. Attach one lead to one side, the other lead to the oppisite side. So easy, right??
If it looks like a low resistance it is good. High it is bad. Some meters will say like 32K ohms when it is bad because that is the max it will show. Some beep when there is a conection. I mean if it is showing like less than 5 ohms you are ok.
This is like a 5 second test. Too bad testing diodes and chips isn't so easy!
acctually if you buy yourself a nice fluke brand dvom they have a diode test built right in em now
#11
Originally Posted by 2002_Z28_Six_Speed
The DMM supplies it the power for the cont test. You are not going to put the DMM inline and test it in amperage mode.
#13
TECH Fanatic
iTrader: (4)
Join Date: May 2002
Location: Fairview Heights Illinois
Posts: 1,851
Likes: 0
Received 0 Likes
on
0 Posts
I've had about 80% luck showing faults using the DMM.
Set the ohm setting to 20,000 ohms for the test.
Depending on the plug type you may see between 4000 and 5000 ohms on most of them. If one is way out of range then it's suspect.
If the insulator is cracked the ohm test will likely not show a problem.
I've also seen where the resistor inside the plug is cracked, but shows good on the ohmmeter when cold. The problem only showed on the meter after warming the plug.
If the plug has the screw-on tips, the meter will not show a problem with that either.
If the plug is misfiring then you can usually see it as a difference in plug color. It will simply appear to be burning cooler in that cylinder.
HTH
Set the ohm setting to 20,000 ohms for the test.
Depending on the plug type you may see between 4000 and 5000 ohms on most of them. If one is way out of range then it's suspect.
If the insulator is cracked the ohm test will likely not show a problem.
I've also seen where the resistor inside the plug is cracked, but shows good on the ohmmeter when cold. The problem only showed on the meter after warming the plug.
If the plug has the screw-on tips, the meter will not show a problem with that either.
If the plug is misfiring then you can usually see it as a difference in plug color. It will simply appear to be burning cooler in that cylinder.
HTH
#14
Testing a spark plug with a multimeter is one of the most important things you can do to maintain your vehicle. By doing regular maintenance checks, source you can catch any potential problems before they become bigger issues. In this article, we will answer some common questions about how to test a spark plug with a multimeter.
#15
TECH Senior Member
Testing a spark plug with a multimeter is one of the most important things you can do to maintain your vehicle. By doing regular maintenance checks, source you can catch any potential problems before they become bigger issues. In this article, we will answer some common questions about how to test a spark plug with a multimeter.
Besides, did you see how OLD this thread is??
#16
TECH Enthusiast
The following 2 users liked this post by grubinski:
G Atsma (11-05-2022), Old Buzzard (11-06-2022)