Ignition Coil questions

My buick chasis manual says

Primary reistance should be 1.28 to 1.42 ohms
Secondary resistance should be 7200 to 9500 ohms
Resitance Wire ohms 1.8


I tested my coil as such.

multimeter 200 ohms
primary - red to + black to - 1.6 ohms
multimeter 20000 ohms, secondary red to inside coil, black to -, 6.7 ohms

Then i tested a new coil and got 1.9 ohms and 11.2 ohms respectively



my question is this
why does a new coil only come up at 11.2 when it should be 7200 to 9500?
and what is the resistance wire ?


is my coil good or bad?

cheers

Gary

 

Gary, are you using a digital Ohmmeter? If so, the 6.7 reading is likely 6.7KOhms, or 6700 Ohms. The scale on a digital Ohmmeter adjusts automatically and you should see this in the units designation.

Devon

 

yes im using a digital multimeter. Ok i see now thanks!

so my coil is a bit low in ohms but not too bad. The new one is out of range too its too high in ohms. Should I replace it or not? $22

 

ya it still works. Daily driver. Just read that they dont just die, they get progressively weaker and weaker until the car runs like crap. I think the car runs good over all. I do have a detonation problem only when I floor it from a dead stop. I dont know if weak spark can contribute. I would think so since it affects burn rate and how quick the fire gets lit ..

It was suggested to me it may be carbon deposits on the valves and pistons too. I wonder if there is a SAFE way to get rid of that without taking the heads off and physically cleaning them.

 

Get the engine up to temp, and when it's running, very slowly pour about 1/2 gallon of water into the carb's primaries. You'll have to work the throttle a bit to keep it running, but the water will steam clean the combustion chambers. Just make sure your tailpipes aren't pointing toward anything you want to keep clean. Go slow with pouring the water.

Devon

 

Yes to both!

Devon

 

Well the car wasnt taken care of and it is still 37 years old. It doesnt have any smoke coming out of it. No blue smoke at start up and no smoke ever. It used to pour black smoke out when I would floor it with the two barrel, but it doesnt do that anymore now that I put the Q jet on. But still there may be some carbon. I havent doen a compresion check yet but i have a gage and will do it soon. I use 87 pump gas. In 1973 i dont know what the octane was but pobably better than 87 pump gas piss water. The radiator is corroded and does leak, thats an age thing not a miles thing. Im gonig to change oil and filter on the tranny next week. .. my carb bushings are coming tomorrow, im going to do it a secret way and then reveal it to you guys if it works. Im optimistic. Thats got to be what makes it idle so fast. It makes a high pitched whistel too, then if i lift up on the throttle linkage it stops... I spray but get no idle change so IDK.

 

The resistance wire is built into the engine wiring harness, and is the wire that supplies power to the coil. The section of wire with resistance connects to the engine side of the bulkhead connector (behind the fuse block), and has a spice (near the coil) to the yellow wire that connects to the S terminal on the starter solenoid before proceding to the coil. This bypasses the resistance wire while the starter is engaged. You could check the voltage on the positive post of the coil and it should be between 9 and 10 volts.

If the engine runs fine and you are not burning up points the resistance wire is within tolerance. If you change to an HEI this wire should be changed out.

Hope that helps

 

You want to put something better than 87 in it. Probably the highest octane you can get.

 

If it's not preigniting or detonating, more octane is a waste of money.

Devon

 

He said he was having a detonation problem.

I thought the older cars were supposed to have higher octane anyways because of the lack of lead in the gas now.

 

X2

 

Sorry, in one of his other threads we were looking at timing and his advance curve to get that variable out of the way first...not sure how far he is with that yet. I wouldn't think with his compression ratio that there should be an octane problem unless it's carboned up quite a bit.

Devon

 

In this thread i was trying to fix an intermittant miss that goes on every 10 seconds or so.. just thought I might have weak spark if my coil was getting tired and needed replaced but ive since learned the spark is spark and it either fires or it doesnt, not intermittant. So ill keep the coil. I wil check the wires witht the strobe. ihave not done this yet. Radiator should come today, if the lines come off easy, the rest should be cake. Then I can drive it and tune it with confidence and not worry about cooking my engine.

That miss bugs me but Ill wait till the car runs cool so I can do some tests and tuning without it overheating in the driveway.

thanks eeryone for you input