Want to check spark plugs - how?

The spark plug wrench in the factory tool kit makes changing the forward bank relatively easy. If you are going to the trouble of pulling the plugs, you might as well just replace them if they have many miles on them - fouled plugs are notoriously hard to un-foul, and fresh plugs will give you a clean sheet to see what is going on in the engine.

You may want to practice pulling and replacing a plug on the family truckster or lawn mower first, just to get a feel for it. About the only bad thing you could do is to cross-thread the plug (not very likely), or strip the threads by using gorilla-force on the wrench (possible).

 

Using the spark plug wrench in the tool kit is by far the easiest way to go . I agree--if you suspect any fouling at all, replace the plugs. In some cases unburnt fuel will glaze the plug over and it will not fire at all after this happens.

 

You can't tell anything from just looking at a plug. You need to do what we used to call a plug chop. Take the car out on a striaght road, get it in 3rd or 4th, get the rpm up, full throttle. Then turn the ignition off, push in the clutch, coast to the side, then pull the plug.

You want to see a light brown color on the plugs. When you look into the plug, you should see a slightly darker color at the base of the electrode. If you see dark small spots that sort of shine, you've got detonation, and you've got to adjust your timing. If the plug is oily, then you've got bad rings, or bad valve stem seals. There are books on reading your plugs.

Hope this helps.

Art

 

Your description sounds like you fouled a plug. That means in short it quit firing. When you pull them out I bet you will find most if not all are black with the exception of the fouled one, it will be somewhere from black and wet to washed clean and wet.

You have new cats so on the smog test they are working so well that it masked the fact that the carbs are not all that in tune or you have a combination of carb and ignition problems.

In the old days we tolerated and even expected carbed cars to do that. There isn't really a reason for it. Your car should be very happy driving slow a reasonable percentage of the time and idle happily in traffic. If it does not some tuning work needs to be done.

For the time being get yourself a set of NGK BP6ES plugs, set them to .025 or so and put them in.
I do not believe in just fiddling with carburators. They are the last of a succession of things that are called a tune up and if all is done right the previous time they should be the last to deteriorate into trouble. You need a good foundation to build upon before fooling with them if for no other reason than just confirm it is a carb only issue.

 

5's are hotter than 6's (less prone to fouling) so for the time being you might want to go with them again and start the process straightening out the tune.

Give NAPA a try. Those used to be some of the most popular import plug numbers but times change and they may not be a stocking item.

 

Autozone and Pep Boys have sporadically stocked BP6ES's in the past, but the last time I went to buy some I could not find them anywhere. I have now stocked up via www.ngk.com aka www.sparkplugs.com .

I found one of the best articles on reading plugs on wikipedia of all places:
http://en.wikipedia.org/wiki/Reading_spark_plugs_for_racing

another good article:
http://www.strappe.com/plugs.html

One interesting thing these articles say is that a tan/brown color means nothing, as it comes from the gasoline additives and thus means nothing as far as the combustion. The only 'color' that matters is the black carbon soot.

 

Since you've never replaced a spark plug, here's a few tips:

Label the wires, or only do one at a time!

Put anti-seize on the threads before installing.

Get one of those gap disks and make sure it's right. Out of the box may work; most *seem* to be .025 which is what was mentioned. I gap to .032 on my Lotus because I have a new, strong coil and it likes a larger gap; your car may also (but ask someone who knows!)

Now, when you install the new plug, tighten it down so it's "pretty tight" but not snug. Then loosen it up and then torque to spec. This is a really important step!

Ken

 

These are all good tips in my experience. I might add one more, I always like to treat the new plug threads with a shot of WD40 which will lube them, and also act as a starting fluid. Just a little squirt. Then, I always thread the plug with my finger tips and make sure that it spins freely in and out a few times before threading them in. You can spin them in the rest of the way with your spark plug tool. Snug them down, then back up a bit and apply your torque wrench. I have cross threaded plugs into blind holes I could not see and it is a pain in the butt to fix a crossed thread, so avoid at all cost of being careful.
Ed

 

Aaron, I know you are new at this so just remember far more things are screwed up from overtightening than from being left loose.

On a plug a light to medium sinch will do, you ain't launching a space shuttle its just a spark plug.

 

I always blow out the spark plug wells b4 pulling a plug.
Ciao
Bill

 

My 308qv could use a set of plugs too- any suggestions for the best plug for injected 308's (normal driving, NOT track) ?
Is there a torque spec for plugs ?

 

It does sound like you may have some issues either in the ignition or the carbs but one of things that hasn't been touched on here is what you do (specifically with the gas pedal) when you are trying to start the car. You say this is your first carb'd car - starting a carb'd car requires a different technique from starting an injected car - there's no clever ECU's etc to help you do it.

So, at the risk of "teaching my grandmother to suck eggs (!)"

There will be a routine that it "likes" best in order to get it to start.

For example, it may be that when starting from cold what you need to do is to switch on & wait for the fuel pump to build some pressure & then pump the gas pedal to the floor 2 or 3 or 4 times before you crank it. Once its cranking you then need to "catch it" carefully with the pedal. If it doesn't go, stop cranking, pump the pedal a couple more times & try again.

When its hot you may well find it'll start easier if you just hold the gas pedal to the floor & crank it - obviously releasing the pedal as it fires (but still working with it to keep the thing running).

When you pump the gas pedal there are accelerator jets in the carbs that squirt neat gas into the cylinders - this is good for cold starting hence you give the thing two or three pumps before you crank it when cold.

When its hot, holding the pedal to the floor opens the butterflys right up & helps clear out any vapour locks that may have developed from sitting with a hot engine.

One thing that generally doesn't help (especially when hot) is to sit there cranking the thing & working the gas pedal up & down - every time you pump the pedal you are squirting gas into the thing & that's when it will "flood". If you can smell gas the likelihood is you've flooded it. Let it sit for 10 minutes & try again.

Try different methods & see what works best but the above are good general "rules of thumb" for starting carb'd cars

I.

 

Yup, good point, that has always worked for me, just a light "snick" to seat the plug with one hand on the end of the rachet and the other to cradle it. One more thing I learned the hard way......make sure the neoprene cushion is inside the plug socket, otherwise you can apply side torque and snap the plug off.

 

Forgive me for going slightly off topic, but I did not get a tool kit when I got my car. Most of the tools I allready have (just not the Ferrari brand). I really would like a factory plug wrench though. Anyone have a spare they would be willing to sell me? Or advice where to get one. I suppose an aftermarket one would be fine if it was in some way far superior to the origional. Anyone?

Cheers

DT
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There is nothing like a Ferrari, there never has been and never will be!

 

The tools in Ferrari tool kits are garbage so I wouldn't bother.

 

True, except for the plug wrench. The length and position of the u-joint are made for the car. What do you use that is better?

 

The Snap On I have been using for over 30 years has exactly the same dimensions.

Seems to work fine.

Only difference is it is cheaper, easier to get and still works.

Can't seem to think of any other attributes I really care about.

 

If you have never changed plugs before get a small torque wrench especially with an aluminum head, the sure sign that an amateur worked on one is stripped plug threads.

 

The way to "properly" check a spark plug takes a little more effort that just taking them out in the garage. If you do not have access to a dyno, you will need to first warm up the engine to the factory specified normal operating temp. Then,drive the car at a moderate rpm for several miles...then turn off the engine while moving and depress the clutch and coast to a stop...note that you do not want the engine to drop to idle speed...then you remove the plug. If the tip is a coffee tan/brown color you're OK...if the tip is a black/sooty color, you're too rich, if the tip is a white/chalky color, you're too lean. If you have a dyno you do the same thing, except on the dyno so you do not have to remove the plugs on the side of the road or have the car flatbedded back home before checking the plugs.