checking for sparks at the cylinders

[prebordao]

What's the best way to quickly check for sparks at the cylinders ?
Unplugging a socket and getting it close to an intake runner, for instance ?

[David]

Pull the plug wire off a spark plug, plug a spare spark plug into it, hold the plug tip against the engine to ground it, crank the engine, and look for spark at the spare spark plug tip.

[Superman]

Today's ignition systems pack a punch. Ignition systems used to be 15,000 volts. Today, 30,000 volts is weak. If you've ever experienced becoming a conductor in one of these systems, it makes you very cautious. DO NOT pull a spark plug wire off the spark plug on a running engine. Those volts will look for a path to ground. A better method is to pull the wire off the top of the distributor cap. The spark will jump from the cap to the wire, as you separate them. You can see and hear it. Use insulated pliers if you can, but this can usually be done with bare hands without trouble. Usually. On the other hand, conventional wisdom is that you never put your hand anywhere near the distributor of a running engine.

If you have the time, David's method is good. Actually, if you have a timing light, put it on each of the ignition wires. If it flashes, there is a spark happening.

[prebordao]

That's good ! I have a timing light.

[Steve@Rennsport]

Originally Posted by David

Pull the plug wire off a spark plug, plug a spare spark plug into it, hold the plug tip against the engine to ground it, crank the engine, and look for spark at the spare spark plug tip.

IMHO, this is the best way to assess spark continuity as well as quality (you want a nice fat blue one).

[Superman]

Originally Posted by Steve@Rennsport

IMHO, this is the best way to assess spark continuity as well as quality (you want a nice fat blue one).

Agreed. A nice, fat, blue, snappy spark. But you know.....weak sparks tend to fail when under the pressure of a cylinder. I've seen situations where the timing light flashes when hooked to a spark plug that is lying atop the head, but doesn't flash when connected to the spark plug screwed into the cylinder. The pressure in the cylinder makes the spark more challenging, apparently. If you pull a wire from the top of the distributor and it arcs a full inch or so to jump the gap between the distributor cap terminal and the wire, while the engine is running, without missing, then you can have confidence in the spark. You can also tell whether that cylinder is running well. When the wire is held too far away, the engine should run more poorly. But again.......touching the distributor of a running motor can be VERY exciting. Some might say "electrifying."

[john walker's workshop]

especially with MSD.

[ischmitz]

I use a spare spark plug - quick and easy on the road.

What you should never do is remove a spark plug from the engine and use it instead. Two issues here. First, you un-necessarily stress the thread and second you might get a mighty bang when the combustible gas coming out of the open cylinder ignites......

[47silver]

this plugs into the wire, and to the spark plug so you can tell if it is getting a good ground etc..

10 bucks.

[prebordao]

Originally Posted by Superman

Actually, if you have a timing light, put it on each of the ignition wires. If it flashes, there is a spark happening.

Where's the best place to get 12V for the timing light ?
In one of the wires going to the coil ??

[T77911S]

im not HOLDING any plug wire while the engine is running. im certainly not pulling one out of a dist cap. ive been knocked on my butt before from a 911, and not because i was holding it. i did even hold my lawn mower plug wire the other day when it would not start.

[47silver]

if you have an msd or cdi do not use the wire to the coil. It is high voltage not 12.

use one of the red wires under the fuse cover.

[911pcars]

Disconnect any spark plug wire from a convenient spark plug. Insert longish Phillips screwdriver or equivalent into the connector, then position the exposed SD blade about 1/2 from a metal ground. Crank engine and observe the spark. Cost: Free.

Do not hold spark plug cable while engine is cranking or running unless you're prepared for a potential 6,000+ volt shock. If you want to be sorta high tech, purchase a plastic pair of pliers (just one) from an auto tool store.

Sherwood