vapidorg

my friends girlfriend called me today to say her Civic wouldnt start, but would just turnover. I'm sort of a Mr. Fix-It to all my friends and have a decent amount of automotive repair experience so I said I would take a look after I got off work.

So, I checked the fuel pressure and it was fine. Then did the screwdriver in the plug wire to check for a spark and got nothing. I removed the dist cap and the nodes as well as the rotor were pretty corroded, but everything else (igniter/coil) looked fine. Everything was clean, no dampness, no oil, no corrosion. Then I checked the fuse panel and found a blown 15a fuse on the ignition circuit. So I replace the fuse, cap, and rotor but still get no spark. I checked the coil to see if power was going to it and found there was (this was done with a light bulb) then had the engine turn over and had the light pulse, but no spark coming off the spring. It's like the power is there but it's just too weak.

They aren't that fiscally set so to say. So buying a new igniter or coil could be done, but I don't want to buy them if they aren't the problem. I've read a lot of posts, looked at vids, and looked at trouble shooting guides but cant find anyone mentioning this specifically.

Can anyone shed any light on maybe why the fuse was blown, or why, even after replacing the fuse, (plus the cap and rotor) still no start? Or, why I'm getting power, but no spark at the source?

Thanks

ezone

Did you try this same trick right at the coil?

Will the coil make a 1/16 inch long spark?
Will it make a 3/4 inch spark?
If it can make any spark at all, but not a 3/4 inch spark or longer, the coil is just bad.

When you pull it out of the distributor, remove the metal shield from the side of the coil. There should be a burned spot in the side of the coil where the sparks have been leaking out.

The WHO??



A short........could be anywhere. The harness that runs under the intake manifold is a good place for intermittent shorts, the harness rubs insulation through against the brackets.



Explain further here. You had 12v on the pos side of the coil.....what were you doing to see the test bulb flash?

OMFG someone that might be able to use a test light! No effin way!

The correct way would be to use a dwell meter, but a test light may suffice.

You have batt voltage on the pos side of the coil.
You have a pulse on the negative side of the coil when cranking, so the igniter is working. (If I guessed your post right)
No spark when doing the screwdriver trick while someone cranks the engine.
You have a bad coil. (Again: If I guessed your post right)



It takes more than just a power source to make any electrical load work. It must have a return path to ground.
The coil has a constant 12v on one side of the primary winding.
The ground side here is controlled by the igniter.
If there was no control signal (pulse) coming from the igniter, then I would work backwards through the system. If a component has the proper signals on the control side, but no output, then the component must be bad.
Spark happens when the ground is removed from the neg side of the primary winding. Spark happens as the magnetic field collapses across the secondary windings. Look up how a transformer works.

vapidorg

thanks for the reply.

I did try the screwdriver trick @ the coil, but could get no spark of any length. I put a new coil on last night, but had the same results. Meh.

The bulb was tested on the neg side of the coil (as per a vid I found). With the key in the 'on' pos it lit up and then pulsed when the key was moved to 'start' as the engine turned over.

THANKS for that explanation of the igniter/coil relationship. Really helped me understand what was going on under the cap.

So, I am getting the control signal but no spark meaning the ignition module is good? But since I have tried a new coil and wound up with the same results I'm still guessing. I would note that the new fuse I put in has maintained. I'll have to check for a short under the manifold as you said.

The only other thing I can think of (based off what I've read) was that the new coil being an off brand (generic parts house only thing open late last night) could be the culprit as most people say use OEM parts. Just wondering if people have problems with generic parts out of the box. I'll have to check for the burn marks, unfortunately the cars at a friends house and I have to work.

Thanks a ton for the insight. I really appreciate it.

ezone

Put a dwellmeter on the coil neg/batt gnd, use 4 cyl scale, crank it. If there is any reading at all, then the igniter is trying to fire the coil. I see about 2-5 deg when doing this test and the igniter is good.


Your screwdriver was grounded when you checked the coil for spark?

When I see bad coil, most will still spark just a teensy bit (1/16"). Any time the gap gets larger, it leaks spark out of the hole in the side, since that plate becomes the closest ground for the spark to jump to.

Spring missing from coil? (Carbon rod? Whatever bridges the gap between the coil and the cap? I can't remember.)

vapidorg

so, turns out it was a bad coil. i went to an imports parts house and got a new one instead of the one i had bought from the generic parts house and put that in, started right up.

thanks for the input. you gave me a much better understanding of the system, what to look for (there was a burned spot on the old coil), and most importantly, how to fix it. i appreciate it.

ezone

Good to hear it. Thanks for the update.

Did the bad coil come from ChinaZone?
Is it any wonder that I really hate cheapo parts? I have to guarantee my work, and that doesn't cut it.
YW.

I have never ever seen one before in my life. LOL

It's a pattern. When they burn through, that's where they do it.


The fuse problem is probably still lurking in the darkness, ready to jump out at the worst possible time.

vapidorg

yep, the bad coil came from the zone. i miss the old Hi/Lo (I'm in Texas) auto parts when all the people working there had some useful knowledge and tried not to sell you something that wasnt reliable.

i checked the wiring leading up to the dist, esp around the manifold, but found no wear. everything looked good. i would note that there was a very significant amount of buildup on the rotor and tabs inside the cap. i wonder if that had anything to do with it...

now if i can just get them to spend the cash to do a tune-up. leaking valve cover gasket, everything is dirty, ugh, and still original (plugs, wires, fuel filter) since it was bought back in 2000.

ezone

The cap and rotor can't make a fuse blow.




NGK, ZFR5F-11, standard plugs. Pretty darn cheap.
If they are original, and the gap is worn to like .080"+ then you could point to that as a cause of the coil failure. Firing across a larger than spec gap makes the coil work harder.
(It probably wasn't really the cause, the coil would have eventually failed anyway. They just fail like that.)

gwlindq

Thanks from another Civic owner. This one ran, then sat for a week, then w/n start... After I used my 94 Accord book to find wire colors, had 12v, had ignitor interruption, so went around the corner to Honda Dealer (Heard that loud and clear, but cost $120) bought a new coil and Voila! It Lives! Also changed and gapped new plugs I had around, and the best part is Wife is happy... FYI, can see burn mark on housing
Thanks again for diag tips and your knowledge...billl

gwlindq

...Now that the spark is fixed, it has a 'hunting' idle... idles high for a few seconds, then momentarily drops 'nothing', the immediately goes back to high idle... so what did I mess up changing the coil?
billl

ezone

Knock vacuum hose off?
Drained coolant?
Make sure the radiator is completely full and the cooling system is bled. Make sure the FICV (I assume it has one) gets hot with coolant temperature. Make sure it isn't stuck.