Finding the failed spark plug?

[82ColEd]

Hey Gang,
am after a fouled spark plug again, but instead of taking each one out and checking it, i wanted to see if there is a smart way of determining the one fouled one. I have changed #5, but no change in the idle issue. I know the symptoms of the fouled plugs, and all wires are ok. Am just lazy to check each one, let the car sit to cool down and try again. :ugh

Anyone got a smart way of finding the one fouled plug?

Thanks for any advice..


Stefan

 

[bill81vette]

Stefan,is it not firing?or just getting fouled up to where it wont fire?

 

[LLC5]

Hey Gang,
am after a fouled spark plug again, but instead of taking each one out and checking it, i wanted to see if there is a smart way of determining the one fouled one. I have changed #5, but no change in the idle issue. I know the symptoms of the fouled plugs, and all wires are ok. Am just lazy to check each one, let the car sit to cool down and try again. :ugh

Anyone got a smart way of finding the one fouled plug?

Thanks for any advice..


Stefan

If you have headers you can spray a stream (not a spray) of water on each individual header tube while the engine is running and see which one does not evaporate quickly, a temperature meter will do the same thing. If you have the OEM manifolds you can disconnect each plug wire individually (one at a time) with the engine OFF, start the vehicle and see if it runs the same or worse. Worse means the cylinder was firing, the same means the cylinder is dead, for what ever reason. Do NOT disconnect a plug wire with the engine running as HEI systems can potentially kill you if you become the ground source of a good spark path. Good luck with it.

 

[82ColEd]

Stefan,is it not firing?or just getting fouled up to where it wont fire?

Bill: Not sure if it doesn't fire at all or it's just fouled. I am thinking fouled up, as the car still runs, but it shakes from side to side. And the "Computer" is trying to correct it and adds RPMs. Am thinking fouled.. :ugh

If you have headers you can spray a stream (not a spray) of water on each individual header tube while the engine is running and see which one does not evaporate quickly, a temperature meter will do the same thing. If you have the OEM manifolds you can disconnect each plug wire individually (one at a time) with the engine OFF, start the vehicle and see if it runs the same or worse. Worse means the cylinder was firing, the same means the cylinder is dead, for what ever reason. Do NOT disconnect a plug wire with the engine running as HEI systems can potentially kill you if you become the ground source of a good spark path. Good luck with it.

No headers, good ole OEM manifolds. So, ok, I'll unplug the wire from each and fire her up. Good idea. And yes, I'll be careful, i know the HEI can spark you to another world.

Appreciate the tip.


Stefan

 

[Hib Halverson]

If you have headers you can spray a stream (not a spray) of water on each individual header tube while the engine is running and see which one does not evaporate quickly, a temperature meter will do the same thing. If you have the OEM manifolds you can disconnect each plug wire individually (one at a time) with the engine OFF, start the vehicle and see if it runs the same or worse. Worse means the cylinder was firing, the same means the cylinder is dead, for what ever reason. Do NOT disconnect a plug wire with the engine running as HEI systems can potentially kill you if you become the ground source of a good spark path. Good luck with it.

You also can use an IR thermometer and the engine doesn't need to have headers for that to work. Just aim the laser sight at the joint betweeen the exhaust port in the head and the exhaust manifold. If you find one that's a lot cooler than the others that's likely your miss.

As for pulling plug wires. It's unlikely an HEI will injure you because the current is so low, but no doubt, if you are grounded and you touch a plug wire end with the engine running, you'll get shocked. The solution? There are several plier-like tools with rubber coated "jaws" on the market designed specifically for pulling off plug wires. I have a set in my tool box and use them in situations like you have.

That said, if you already know the engine is fouling plugs, rather than spending a lot of time finding out which plug is fouling, why not spend some time trying to find the cause.

Is the engine using a lot of oil?
Exhaust smoking? If so, is it blue or black smoke.
If you've had a fouled plug before, was it oil fouled or wet with fuel?

 

[LLC5]

You also can use an IR thermometer and the engine doesn't need to have headers for that to work. Just aim the laser sight at the joint betweeen the exhaust port in the head and the exhaust manifold. If you find one that's a lot cooler than the others that's likely your miss.

As for pulling plug wires. It's unlikely an HEI will injure you because the current is so low, but no doubt, if you are grounded and you touch a plug wire end with the engine running, you'll get shocked. The solution? There are several plier-like tools with rubber coated "jaws" on the market designed specifically for pulling off plug wires. I have a set in my tool box and use them in situations like you have.

That said, if you already know the engine is fouling plugs, rather than spending a lot of time finding out which plug is fouling, why not spend some time trying to find the cause.

Is the engine using a lot of oil?
Exhaust smoking? If so, is it blue or black smoke.
If you've had a fouled plug before, was it oil fouled or wet with fuel?

The IR thermometer is actually the temperature meter I was referring to, and if you have one then yes definitely use it. As for HEI, yes it has killed people (GM training in the '80's was very clear about this) but luckily it is rare. Less than 1/4 amp can kill a human and HEI at 60K plus volts can push it through you if you are perfectly grounded. I will admit to being "bit" may times by HEI just by being near a connected high tension lead that is bad, and it doesn't just wake you up, it hurts.

As a side note to the OP, I forgot to mention to ground the unplugged spark plug wire if you check the vehicle in this manner, as leaving the plug wire circuit "open" can potentially carbon track the ignition coil. I use a 16 gauge wire with small alligator clips at both ends to accomplish this, but any way that you can properly ground the wire will be safer than not grounding it. Good luck with it.

 

[HammerDown]

Harbor Freight and other parts stores sell a cheap tester.


Harbor Freight and other parts stores sells cheap spark plug testers.
One lead goes to the battery and the other sits on the SP wire...if the plug fires, the led on the tester lights.

 

[82ColEd]

You also can use an IR thermometer and the engine doesn't need to have headers for that to work. Just aim the laser sight at the joint betweeen the exhaust port in the head and the exhaust manifold. If you find one that's a lot cooler than the others that's likely your miss.

As for pulling plug wires. It's unlikely an HEI will injure you because the current is so low, but no doubt, if you are grounded and you touch a plug wire end with the engine running, you'll get shocked. The solution? There are several plier-like tools with rubber coated "jaws" on the market designed specifically for pulling off plug wires. I have a set in my tool box and use them in situations like you have.

That said, if you already know the engine is fouling plugs, rather than spending a lot of time finding out which plug is fouling, why not spend some time trying to find the cause.

Is the engine using a lot of oil?
Exhaust smoking? If so, is it blue or black smoke.
If you've had a fouled plug before, was it oil fouled or wet with fuel?

Hib: Now that you are saying it.. Yeah, an IR Gun should do the trick.. That' awesome. (And i wasn't even thinking Temp Meter = IR Gun, LLC5, but yes).. That sounds like the lazy man's tool i need.. Already asked neighbors, no one has one handy.. As it's Sunday and all shops are closed in Germany, i'll buy one tomorrow and check the temps. Thank You Guys!

Hib, as to the cause: A comination really of the engine oiling some cylinders (#5 and #6), the car never really warming up properly due to the little i drive her (3 miles to and from work each day). The mechanic set her a bit higher, temperature wise, so she warms up in about 5 minutes, but once a year a spark plug fouls up. To properly fix it, i would have to have the engine pulled and either honed or over sleeved (Mechanics terms, obviously not mine) and would be something i'll do when i get to do a frame off resto.

The IR thermometer is actually the temperature meter I was referring to, and if you have one then yes definitely use it. As for HEI, yes it has killed people (GM training in the '80's was very clear about this) but luckily it is rare. Less than 1/4 amp can kill a human and HEI at 60K plus volts can push it through you if you are perfectly grounded. I will admit to being "bit" may times by HEI just by being near a connected high tension lead that is bad, and it doesn't just wake you up, it hurts.

As a side note to the OP, I forgot to mention to ground the unplugged spark plug wire if you check the vehicle in this manner, as leaving the plug wire circuit "open" can potentially carbon track the ignition coil. I use a 16 gauge wire with small alligator clips at both ends to accomplish this, but any way that you can properly ground the wire will be safer than not grounding it. Good luck with it.

I looked at those, but that would involve me pulling the wires off and grounding and all that. I think i'll prefer the aim, shoot, replace with the IR Gun.. Thank you though, learned something again by checking the Spark Plug testers out.

Harbor Freight and other parts stores sell a cheap tester.


Harbor Freight and other parts stores sells cheap spark plug testers.
One lead goes to the battery and the other sits on the SP wire...if the plug fires, the led on the tester lights.

Hammer: Yep, defo would do if i still lived in the States. But nearest Harbour Freight Store is 4000+ miles away. I'll go to my local automotive store on Monday and get me an IR Gun..

Thanks y'all. Helpful as always..
-Stefan

 

[Barry08]

Stefan,
Change one plug at a time and drive for a day or two till you find the right one.
If I recall #6 is usually the culprit on a sbc.



Barry

 

[HammerDown]

Hammer: Yep, defo would do if i still lived in the States. But nearest Harbour Freight Store is 4000+ miles away. I'll go to my local automotive store on Monday and get me an IR Gun..

Thanks y'all. Helpful as always..
-Stefan

Regardlessof what country you live in, I would imagine most any auto parts store will have the tool I described. Here in the states, I believe it's under $10.00
And again, when it's placed on a spark plug wire a LED/diode lights/flashed every time the spark plug fires. If the light/tool light has a 'miss' your SP isn't firing all the time. If the tools light doesn't strobe...the plug or SP wire is bad.
This is the one I have...
http://www.ebay.com/itm/Spark-Plug-..._Automotive_Tools&hash=item58abebe659&vxp=mtr
Good luck

 

[TimAT]

A safer way to force a cylinder to drop out with an HEI is to use a sharp point testlight. Ground the lead on the light and stab each wire at the cap. - 2 problems with this- it will kill the light bulb, and it will also leave a hole in the wire that moisture will get into and fail the wires early.

As far as HEI- be careful. It hurts.

 

[Hib Halverson]

If all you do 3-mi a day, you're going to cause a lot more problems than just fouled plugs.

Short trips, from an engine wear and comtaminants perspective, the second-most severe duty to which you can subject an engine.

You're better off is you drive the car farther each time you use it.

If you can't do that and you're not going to fix the engine, I'd put hotter plugs in the cylinders which foul.

 

[82ColEd]

If all you do 3-mi a day, you're going to cause a lot more problems than just fouled plugs.

Short trips, from an engine wear and comtaminants perspective, the second-most severe duty to which you can subject an engine.

You're better off is you drive the car farther each time you use it.

If you can't do that and you're not going to fix the engine, I'd put hotter plugs in the cylinders which foul.

All good tips Guys, much appreciated..

I finally got the IR Gun, had to wait a week as the stores only had a Celsius one, but i knew i would have to report back so i wanted one that can do both C and F and save me the math (Can you tell i am lazy? :L).

So, here is the report (Not as i easy as i though it would be, there is still a lot of stuff in between me and the point i am aiming at, but i think it got enough info for now):
Cylinder 1 = 181F
Cylinder 2 = 159F
Cylinder 3 = 171F
Cylinder 4 = 135F
Cylinder 5 = 171F
Cylinder 6 = 167F
Cylinder 7 = 190F
Cylinder 8 = 152F

So i am thinking it's Number 4, that's not behaving. The most difficult one to of course ad. I'll let the car cool off and swap the plug for a new one tomorrow (Wife and i going away overnight, so no chance getting that sorted today).

But Hib, i think i am getting what you are saying, though i am not very technical when it comes to cars: A "Hotter" plug would combust easier/hotter and basically mean i get rid of the fouling once a year? You have me intrigued. Currently i am running the OEM Plugs, AC Delco R45TS. And why should i change only 1 plug not all 8 to your recommendation of plugs (Am all ears)?

I'll report back once i've changed #4 and let you guys know..

Thanks for all the input!

Stefan

 

[82ColEd]

Alrighty..
I swapped #4 and after warming her up she idles fine again. So, the IR Gun, pointed at the right spot does the lazy man's trick. Thanks for the suggestion!


The plug was completely oily and looked like it had crud on the arc (the bend piece going over the point; sorry don't know what that's called)

Hib: Am very keen to hear about using a different plug in the car that would eliminate looking like i had my yearly fight with 3 cats at once.

The CAC rocks!


-Stefan

 

[Vettehead Mikey]

You're already running a 45 plug which is about the hottest that GM used in a Corvette. I suppose going to a 46 might help, but doesn't fix the root cause. Why not take the car out in in a while to just burn off the accumulated crap instead.

 

[TimAT]

You might also try using AC Delco R45TSX plugs- same heat range, just the "X" denotes extended tip. Gets the end of the plug out into the chamber a little more and may help burn off the goo.

 

[Hib Halverson]

You're already running a 45 plug which is about the hottest that GM used in a Corvette. I suppose going to a 46 might help, but doesn't fix the root cause. Why not take the car out in in a while to just burn off the accumulated crap instead.

An AC45 may be the hottest plug use in a Corvette under normal circumstances, but here we have an engine which sees only short trips and uses oil, so either an extended tip 45 or a 46 would be a good solution...or, at least put a hotter plug in the fouling cylinder.

Now once the engine is repaired or the duty cycle changes to one that has some high-load and high-rpm use, then I'd swtich back to a colder plug.

 

[82ColEd]

An AC45 may be the hottest plug use in a Corvette under normal circumstances, but here we have an engine which sees only short trips and uses oil, so either an extended tip 45 or a 46 would be a good solution...or, at least put a hotter plug in the fouling cylinder.

Now once the engine is repaired or the duty cycle changes to one that has some high-load and high-rpm use, then I'd swtich back to a colder club.

Ok, cool.. Thanks for the info Gang..

I will get some AC Delco R45TSX or AC Delco R46TS (am guessing here at the proper name?) at the local shop, next time i stop in. Just to have in case #4 is fouling again.

But i guess i am hearing you loud and clear...
Now that the weather is better, i should make it a weekly staple in my house to take the car out and run her on the Autobahn for a bit, burn off the gunk of the week and put her away until Monday..

I shall put that in my regular to do (Not that it takes much convincing to run her).

Thanks Guys, you all helped me out as always!


Stefan

 

[Wayne robson]

fouled spark plugs

If you have a car with lower compression or another problem that makes one or more spark plugs foul,
i never start that car unless it gets driven at least 5 or 10 miles minimum, and with alot of our older classics
that means parking in your garage to alloy getting it out.not while it is idling,while you move another car,thats a no no with me
as thats when it is running on choke,etc and really not good for your car.spark plugs are critical for smooth running of your classic
so when doing my tune ups,or if you have never checked them correctly,with new spark plugs ,remove each plug one at a time engine cold
mark each box with the number of which plug,doing this you can really inspect all the plugs properly when they are beside each other.
the plugs can tell you a lot about the condition of your engine,should all be light grey colour,but some may be darker and even black.
Over the years different brand of cars recommend there brands like AC Delco for our corvettes,European, is Bosch or NGK or Nippondenco,
Ford is Autolite ,Chysler and english cars is Champion ,GM Autolite.My years with GM i always had a spare set of Autolite ,but use ac Delco.
I personally think that Autolite is a real good spark plug,i dont think i have ever had to gap them from new,seem to be correct out of the box
but always the correct heat range or one slightly higher for a bad cylinder.