I am curious as to if my ignition system is still up to par after 220K miles. i am getting crappy gas milage and i am running lean most of the time. and i know i am getting plenty of fuel and compression is pretty good. but i am starting to suspect my ignition. i know they have those spark testers at autozone that u set the gap and see if it jumps it or not or something like that.. do those really work? I know that the BEST way to test the amount of spark is to hook it up to an oscilloscope, but i don't have one of those.. so what is the best way to test everything to make sure im getting enough spark?

 

Well, bad mileage could be caused by poor spark, but running lean? I would think it would run rich if the spark is poor and not getting a complete burn.

I have heard of testers that can measure the amount of energy present in the spark (joules), but haven't ever used one.

 

well by running lean what i meant was symptoms of running lean. backfiring, low power\milage, backfiring(?).. emissions readings say i am running really rich at idle. and the HC are really high at idle. see my other post

 

use a spark checker, if it sparks with that your spark is strong enough. make sure you get one for HEI and not points or lawn mowers.

 

id use a screwdriver in the plug wire, next to the head, just crank the car, and vary the gap, it should be a nice bright spark, if its not, something is wrong.

just my way, yes i might be crazy, no its not technical, and no dont do it while the engine is hot.


adam

 

Why not use a voltage tester?

http://www.actron.com/cgi-bin/web_st...=2901000_14715

 

screwdriver is cheaper and easier to find.


adam

 

Before tearng into the ignition system, check to be sure that the HEI is getting 9 volts at the absolute minimum. the lower the voltage going to the HEI set up the worse it will run, GM says 9 volts is absolute minimum for HEI, but I would want the full 12 volts and investigate if I didn't see it.

 

what gap are you using? i'm learning that gap isn't really all that important. one of the techs at work went to a nascar shop last weekend and he said our (Autolite) plugs were only using 9kV on their race engines, as opposed to a regular car which is probably 20-30kV. a larger gap forces the coil to charge more before there's enough charge to jump the gap, hence the increased voltage. if your coil isn't up to par it won't be able to jump a large gap and you will get a misfire. i would just check spark with a screwdriver, make sure the spark will jump a decent amount because one thing you don't have at this point is high ambient pressure which is present during combustion and also increases required voltage. i've been shocked at work by a coil from a couple inches so if you can get the spark to jump even an inch to a screwdriver then you're probably fine.

 

I pull a plug with the wire attached, then twist a length of wire stripped back around the threads and clip it to ground.

If it is yellow, then I hook the wire up to the battery, then if white, I will check ground to block and wire to back of heads etc

good luck.

Don

 

an HEI spark checker has at least 1" air gap for the spark to jump. the color and size of the spark is pretty subjective and not very easily quantified using the screw driver or old spark plug method. use a DVM and you'll fry it. spend 10 dollars and do it right with the right tools for the job.

 

just hold 1 plug in your hand while turning the engine over;

and follow this chart:

Medium spark: Jerks your arm slightly
Strong spark: Jerks your whole body
Weak spark: Tingles but doesnt really hurt
MSD ignition spark: Simultaneouselly tightens all the muscles in your body

 

Ohhhhh yeah.

 

Yea, but you will only do this test one time in your life.

 

otflmfao

Damn Kingtalon dont try to kill the poor guy.

Get a spark tester they are cheap and safer to use than open sparks around a gas engine. Incidently look for a white spark I hear yellow or orange spark are indicators of a week spark. Have you done any work on the distributor? like, replace the module if you did, did you put the heat sink material on the back of the module. Does your battery go dead? Weak spark could be an indicator of a weak battery or as in my case a non charging alternator

 

No, I've inadvertently done this test a number of times.

 

OTFLMAO

Some people never learn hey can I borrow you to check for spark from my 50,000 volt coil lol. Yeah that does work I did it once. I saw this guy do it once but he died. It through his pacemaker out of wack.

 

Yes. Engines with a lot higher compression than what we have today, and a plain Kettering ignition with ONE set of points used to do very well with an 0.030" gap. The POSITION of the spark is more important than the gap. As long as the spark is healthy, it'll get the job done. You might tend to get more deposits on a smaller gap plug, but some of that has to do with correct heat range as well.

 

I recently had a ignition issue with a '82 454 Chevy HEI ignition. The engine wouldn't run. But it would jump a spark across a conventional spark plug (spec gap .045). I invested $14.00 in a Wilmar W86553 Spark tester on ebay (it looks like a spark plug with the ground electrode removed) with a nice ground alligator clip so you clip it to a ground (thus no jolt to the user) . When I connected it to a plug wire it wouldn't jump a spark. (ie got spark on a spec plug in open air, no spark on tester plug in open air, presume conventional plug wasn't firing under compression in the cylinder either) Thus I started to work back in the ignition, first replacing the coil. It started right up on the new coil. (One of those pesky problems where its partially working)
Glad I now know the difference between HEI spark and points ignition spark and have suitable tester in my tool kit. good luck

 

Sounds like you have some worn-out parts ( spark plugs, wires, cap, rotor) to me.
"backfiring" is actually a mis-firing (no spark to that hole).
You would say the engine is "missing". Missing is clear sign you have a spark issue. Missing would increase HCs (unburned fuel)

I think you just need a basic tune up. When was the last time you did one? If don't know then the answer is simple, it is time to replace some parts.

You can test the coil with a multi-meter, if the coil fails the test you replace. If the coil goes bad typically you have no spark at all but it won't hurt to test it.

 

17 year old thread , I'll bet the OP has solved his problem , got married and had some kids , and has moved on to owning a minivan by now

 

I hope so...

 

Well, except for the minivan part.

 

correct !

 

I knew the minivan comment would bring out the reaction in people , and rightly so .