n4n

I got in too much hurry while doing a compression test on my car and left the dizzy connected while turning the engine over w/o plugs connected. Now the car won't start - checked for spark first and it's bad. Don't turn your motor over without plugs connected or you can fry your coil and/or igniter! It's an expensive mistake.

To troubleshoot, I looked in my manual, and performed searches on google and several forums. Here are some of the links I found most useful:
https://honda-tech.com/zerothread?id=1430824 - pretty good link if you can get through the verbal diarrhea and improper ohmmeter use. His coil was likely just fine, BTW.
http://autorepair.about.com/cs...b.htm
http://www.askmehelpdesk.com/c....html
http://www.autozone.com/az/cds...1-1-1

My question is does fuse No 39 (50A) all these sources refer to *really* exist under the dash? I don't see anything even close to that in size under the dash. There is no fuse #39 and nothing labeled ignition or anything related under there, either.

I *do* see a 50A fuse labeled IGN (probably ignition) in the box on my firewall on the passenger side of the engine bay. That's got to be it, right? Can anybody confirm or tell my exactly where under the dash I'm not looking?

instructor74

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by n4n &raquo;</TD></TR><TR><TD CLASS="quote">I got in too much hurry while doing a compression test on my car and left the dizzy connected while turning the engine over w/o plugs connected. Now the car won't start - checked for spark first and it's bad. Don't turn your motor over without plugs connected or you can fry your coil and/or igniter! It's an expensive mistake.

</TD></TR></TABLE>
Never heard of that before.

pdiggitydogg

i always do it with plugs disconnected.......
i dont see how it would make any difference, unless it grounded out somehow

n4n

You should have the plugs disconnected and removed from the engine. However, the Chilton manual instructs you to *also* disconnect the high tension lead from the ignition coil. I can't remember which online source I read that indicated operating the ignition system without a load (spark plugs) can burn out your coild and/or igniter. In the past I have just disconnected the entire dizzy using the connectors.

My theory on why turning the motor over without plugs is an issue is that under normal use the spark plugs terminate the high voltage energy from the secondary coil. When the plugs aren't connected, the energy isn't terminated in the plug and the energy therefore reflects back through the coil an fries igniters and coils. Seems reasonable to me. You can probably get away with it for a while, but it will stress things more than designed during normal operation. Regardless, operating your ignition system without a load doesn't seem like a good idea from an EE (Electrical Engineering) perspective.

Something happened to my ignition during the few minutes I performed my compression test. Here's the proceedure I followed:

* Run the engine up 'til the fan started kicking on to ensure full temp.
* Shut off the car and remove the plugs. Leave plug wires hanging to the side. They weren't shorting on anything.
* Unplug the injectors.
* Install compression checker in each plug hole and turn the motor over to get readings.
* Reconnect injectors.
* Install plugs and reconnect to wires.
* Try to start the car again - no go. Have fuel but no spark.

I checked my coil and it's okay. Still need to check the igniter. My guess is that's what's bad. My engine has 170K miles on it. AFAIK, the igniter is OE; maybe it was on the fragile side after so much use.

Any ideas on my original question - how 'bout that fuse location? I have a '94 Civic EX. Seems like it's probably a misprint that everyone keeps passing on as gospel?

n4n

My car is running again. It was the coil. My igniter is fine. I had another dizzy that I canabalized to try things out.

A couple of interesting points: the coil seemed to pass the ohmmeter test but was still bad and the No 39 50A fuse is in the engine compartment on my car.

I replaced the ingitor and things still didn't work. I started getting nervous because my coil measured 1 ohm on the primary and 15K ohms on the seconday; which seemed good. The manual states that the primary should be 0.6 to 0.8 ohms and the secondary should be between 12800 to 19200 ohms. 1 ohm seemed plenty close to .8 ohms. I would expect a dead short (0 ohms) or an open if it were bad. The secondary measured 15K ohms or something, which in range. After checking the ignitor with an oscilloscope and realizing it was good, I replaced the coil and it fired up again. Ironically enough, the replacement coil measures 1.2 ohms across the primary and obviously works fine. The moral of the story is to replace the coil if in doubt.

My car was made in Canada. Maybe that has something to do with the placement of fuse 39? Either way, it does appear to be in the engine compartment and not under the dash like the manual and other references I have indicate.

I'm quite certain that turning my car over without plugs and without disconnecting the high voltage paths is what fried my coil. A couple of sources indicate that you shouldn't do that, and it seems obvious to me that doing so caused my coil to fry. It makes sense from a theoretical perspective, too. Hope somebody learns from my mistake.

postman

firing the car up with coil hooked up and wire not on plugs is a bad thing. seen a few coils get busted this way.

n4n

NOW you tell me. j/k. Hopefully my stupidity will save someone else some $$$.

I've done compression tests in the past without issue - but I followed the directions completely. I just got in too much hurry and didn't think it would matter much to leave one step out. I was wrong.