Hey guys, I just got a multimeter to help out with all the igniton system work I'm going to be doing.

Is there a way to use it to tell if current is flowing through a wire, and how strong it is?

IE, can I use it while I'm trying to crank the car to see if power is going to the coil, determine how strong the power is, and if there is power coming out of it? I'm sure there is a way, but the manual doesn't explain much worth a crap.

 

ttt

 

You never want to measure output of a spark coil or of a spark plug wire- that's over 45,000 volts, and it can kill you. Only way you can tell if spark is coming out is to put a screwdriver into a spark plug wire, lay the screwdriver so the metal shaft is close to metal, then take your hands off the thing, and crank the car, and watch for spark. Or you can spend $12 on this little sucker: http://www.eastwoodcompany.com/aspfi...0.asp?T1=46140

But you can take the wires off the car and measure them. Resistanace of plug wires goes per foot. My MSD 8.5mm wires are 50 ohms/foot. So if I have a 2 1/2 foot wire in good condition, it'd show around 125 ohms on my meter. If the wire showed 118 ohms, or 170 ohms, okay, no big deal. If the wire showed 8201 ohms, it's way off spec, so it's a bad wire.

You can also test the power at the spark coil harness connector. The gray connector powers the coil up. The pink/black wire runs right off your ignition switch- when you flip your ignition switch to the "on" position (right before crank), that pink wire gets +12 volts. (Same during cranking). The black connector on the coil is "bridged" to the gray connector. What I mean is, inside the coil, the gray connector's "A" terminal is connected right to the black connector's "A" terminal. And same goes for "B", gray B is connected to black B. All this is the "primary" ignition side. You never want to directly measure the output of the "secondary" ignition side, which is the high voltage side (spark coil, spark plug wires, spark plugs, distributor cap, etc). But you can remove these items and test them on the bench without killing yourself.

If you're going to get deep into diagnostic, the GM Helm Service Manual is the way to go; it tells you EVERYTHING. This is another one of those things that everyone should've bought by now. It was the first thing I bought for my car- I've had the book before I ever owned a Haynes!

 

Sounds like something I'll look into, but I have one more question, and pardon me if it sounds dumb.

You said there are 45,000 volts going through those wires; How does that come about from a 12 volt batt?

 

Your Ignition Coil is essentially a transformer. It has small wire inside that is wrapped around a metal rod thousands and thousands of times. This creates a magnetic field around the wire which multiplies Voltage in the wire. This turns 12 Volts into thousands of Volts.

Some newer cars with DIS are capable of 60,000 Volts....but a coil only produces enough Voltage to jump the spark plug gap so it's not pumping 60,000 all the time. More like 10,000 at idle, and a bit more under load.


Also, the ignition system is high voltage but low amperage due to the small wires. Because of this, you can get shocked by a regular distributor ignition system and it won't hurt that bad. If you get shocked by a DIS coil you might end up in the hospital though......

 

Thanks for the info!

 

Here's a link you might also find useful; didn't go through all of it, but it looks like it'll cover our HEI (high energy ignition) systems too. http://www.howstuffworks.com/ignition-system.htm

 

You can see if the coil is getting power with your multimeter though. The thing you want to watch out for is the power leaving the coil.

 

Cool, how can I check?

 

I'd be damned, but I coulda swore that I just mentioned how to do that, in my first message, above. I guess I type so much that nobody reads what I write, eh? (sigh) I -am- a bit long-worded... I'll change.

 

I meant checking it with the multimeter...something a little safer than putting a screw driver in there. I could (read: would) really hurt myself on that one.

Also, I know I am not getting spark...I want to check the power going to the coil to see if that is where the problem is. If there is no power getting to the coil, then I can backtrack from there.

I might just be misunderstanding you, I haven't touched any of this stuff before, except for the plugs.Bbut that website you mentioned, howstuffworks.com, really taught me a lot of stuff I should have learned a long time ago.

 

TomP,
You did.

 

Okay, cool, thanks Mike, good to know it was just "inexperience" (no offense meant!) instead of me "typing for nothing"!

Start reading my message up there from where I say:
The screwdriver I mentioned is the safe way to check for spark; this way, you're not touching a spark plug wire or spark plug at all.... you're 10 feet away from the screwdriver. And yeah that site is pretty cool; I wish I knew about it (or, haha, wish it was around!) when I first started with cars.

 

so, camaro89dude.... how'd it check out?

 

Tom , type alot ? Nah , you never type much Tom !


HEY GUYS ! ....I've missed you guys !!!! I've been pretty busy with school and exams this week . Today was my last exam!!!!!!! You'll start seeing me on here again now for a little while !

 

Haven't gotten to it yet...its been rainy, and I had finals this week. Hopefully I'll get to it soon, even though its so cold.

 

Had my last class yesterday, got two finals on Thursday. That'll be fun, switching from doing a math (numerical analysis) final to a computer (database systems) final. Funny thing is, I'm better at the math class (how to do interpolations within the limits of a computer) than the database class- I'm doing "real" stuff in the math class, but the database class is all damned theory. If I knew that, I wouldn't have taken it.

 

So sorry to hear about finals, guys. All I've got to do is go receive my degree tomorrow morning!

:lala:

 

<--Jealous I could've had a doctorate by now. (sigh) Congrats!