Arcing to engine block

[Kettler]

Is it OK to arc the spark plug to the engine block to test for spark?

 

[iwombat]

Re: Arcing to engine block

It's OK, but doesn't really test much. For a proper spark test you need to simulate the plug under load. For that, you need to create a 7/16" or so air gap and test that way (w/ no plugs involved).

 

[Joe Reeves]

Re: Arcing to engine block

No, not really. That tells you that there is a spark of sorts but it's best to have a regular spark tester. You can make one for next to nothing if you wish.

(Spark Tester - Home Made)
(J. Reeves)

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:


..........X1..........X2

.................X..(grd)

..........X3..........X4

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

 

[jtexas]

Re: Arcing to engine block

yup. check for spark or no-spark by holding it against the engine block.....a better test is with a spark tester set at 7/16" - that distance gives you a better indication of whether its firing under compression.

Guess if it jumps 1/2" with the plug attached, that'd be a good sign........

 

[Kettler]

Re: Arcing to engine block

Thanks for the info. What if I get no spark at all on the top cylinders spark plug testing like this?

 

[HighTrim]

Re: Arcing to engine block

Check the DVA output on the orange wires from the power pack while connected to the ignition coils. You should have a reading of at least 150V or more. If the readings are low, disconnect the orange wires from the ignition coils and reconnect them to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad power pack.

 

[Kettler]

Re: Arcing to engine block

What if I switch the orange wires from the powerpack to the coils and then get an arc on the top cylinder,still a bad coil?

If I don't get an arc on the top plug but then switch the orangre wires from the powerpack, top to bottom coil and vice-versa and then get an arc on the top plug wouldn't that mean the top coil is OK?

 

[HighTrim]

Re: Arcing to engine block

When you're getting no spark on one cylinder, that is usually the power pack or ignition coil. Rare cases include a weak trigger magnet in the flywheel or a timer base. Rule out the coil first. Switch coil wires. If the problem follows the coil, replace it. If it doesnt, switch the power pack. If the problem follows, replace the power pack, or test its DVA as stated above if you have access to the meter. Unlikely but check the plug springs inside the plug boots. If they are rusty or rotted, you will get weak or no spark. If you find it highly corroded, get a new boot kit. Cut the old plug wire back, allowing enough to reach the plug, cut back a bit of the insulation, fold the exposed wires over, insert the new plug spring, spray with wd 40 to ease with installation of the boot, then slide the new boot over. Let us know what you find.

 

[Kettler]

Re: Arcing to engine block

I only tested the top cylinder after switching the orange wires on the coils and when I got an arc never bothered testing the lower plug to see if IT arced, will retest and let you know,if it doesn't I'm assuming powerpack?
Will also build spark plug tester.
Thanks.

DVA? can I test this with my multimeter?