steps to test spark

DBLD

Seaman Apprentice
Joined
Dec 19, 2002
Messages
41
Hi. 1994 Johnson 88hp. Couldn't get it to start yesterday. Turn the key and it cranks, starter engages flywheel and spins it, but it won't turn over. It doesn't cough, smoke, nothing. So, I am thinking either there isn't any fuel in the cylinder to combust, or there isn't any spark to fire. I want to test the spark, and I have read alot here on the boards about testing it, but could someone lay out the steps on how it is done.<br /><br />I could really use the play by play - that is, do I pull just the plug wire, the whole plug, when do I turn the ignition, etc. I understand the idea behind it, but I really don't know the steps on how to do it.<br /><br />Also, some thing leading up to this (that may or may not be related) are: two weeks ago, I couldn't get it going at full throttle. The throttle was all the way down, but it seemed sluggish. The plugs were a little old (about 40 hours on them), so I bought new ones. That seemed to help a little, but not completely. Also, I added some fuel stabilizer and ran the motor for a good 2 hours last week to get the stablizer through it before laying it up for winter. I don't think that would have anything to do with it, but I figured I'd mention it. That was the last time I ran it before this happend, now I can't get it to turn over.<br /><br />The primer bulb in the fuel line is firm, so I think the fuel is getting there - unless there is something wrong, clog, etc. in the fuel pump or maybe in the carbs to deliver the fuel?<br /><br />Don't know yet, but I thought testing the spark would be a good first step. If anyone has any thoughts or could help with how to test spark, that would be greatly appreciated. <br /><br />Thanks!
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: steps to test spark

(Compression & Spark Test)<br />(J. Reeves)<br /><br />1st - Regardless of what problem one might encounter, always start with the basic troubleshooting procedure. Check the compression which should be in the range of 100+ psi (somewhat less on the smaller hp engines) and even on all cylinders.<br /> <br />2nd - With the spark plugs removed, rig up some type of spark tester whereas you can set a gap to be jumped. On magneto ignition systems.... and also the Battery Capacitance Ignition system OMC engines from 1968 to 1972, set the gap to 1/4". On the solid state OMC ignition systems from 1973 to the present, set the gap to 7/16". The spark should jump the gap with a strong blue lightning like flame.<br /><br />If there was no change in the spark, disconnect the main electrical plug at the engine. Remove the s/plugs. crank the engine via the starter solenoid (jumper bat term to small 3/8" term nut, not the ground nut) and observe spark. If spark is now okay as stated above, the usual cause is a shorted ignition switch.<br /> <br />If the above checks out as it should, and the engine dies out when throttle is applied, it is usually due to one or both of two things. The carburetors are fouled, in which case the cure would be to remove, clean, and rebuild them..... or the timer base under the flywheel is sticking which would result in a retarded spark.<br /> <br />To check the timer base for sticking (Engine Not Running), spin the prop to align the shifter dog with forward gear and while doing so, put the engine into forward gear. Now, while watching the timer base, slowly apply throttle clear up to full throttle. The timer base should move smoothly all the way up against the black rubber cap that is atached to the end of the full advance spark setting screw. If the timer base sticks, find out why and correct that problem.
 

DBLD

Seaman Apprentice
Joined
Dec 19, 2002
Messages
41
Re: steps to test spark

Hi Joe,<br /><br />Thank you for your reply. I think I have seen your response in a post when I was looking for an answer, and I think I have a question - sorry to be a pest.<br /><br />So, to test the spark, do I remove the spark plug from the cylinder, leave it connected to the spark plug wire, and then turn the ingition to see if the spark plug fires? <br /><br />I am learning my way around outboards slowly, but the last thing I want to do is have this thing fire with gasoline in the cylinder and cause some sort of fire or anything that would harm the motor. <br /><br />I appreciate your help. Thank you!
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: steps to test spark

Your latest question of "Do I remove a spark plug from the cylinder etc etc??"<br /><br />You're skipping over my post without reading it. To quote myself.....<br /><br />"2nd - With the spark plugs removed, rig up some type of spark tester whereas you can set a gap to be jumped. On magneto ignition systems.... and also the Battery Capacitance Ignition system OMC engines from 1968 to 1972, set the gap to 1/4". On the solid state OMC ignition systems from 1973 to the present, set the gap to 7/16". The spark should jump the gap with a strong blue lightning like flame."
 

DBLD

Seaman Apprentice
Joined
Dec 19, 2002
Messages
41
Re: steps to test spark

Hi Joe,<br /><br />Thank you for your reply, I appreciate your help. I should have written what I meant - I apologize. I guess I mean, do I put another plug in the cylinder just to seal it off so the plug that I am testing doesn't ignite any gas that may be around the cylinder? Also, I didn't know if I should leave the spark plug attached to the plug wire, or am I looking for the end of the wire to send out a blue flame?<br /><br />Sorry, I know these are real basic questions, but I haven't done this before and am trying to learn without screwing it up. I figure, if I do it wrong, then the results of the test won't tell me anything.
 

93bronco

Ensign
Joined
Nov 11, 2001
Messages
962
Re: steps to test spark

if you do not do all four at the same time, make sure the other three are grounded. <br />also make sure you dont have that spark checker too close to the open plug hole.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: steps to test spark

Leave the/plugs out to obtain the highest available rpm. The engine must turn at least 300 rpm in order for the stator to generate the power (approx 300v AC) to energize the powerpack properly.
 

Hooty

Rear Admiral
Joined
Oct 2, 2001
Messages
4,496
Re: steps to test spark

Here's what a spark gap checker looks like. You can either buy one of these or build your own.<br /><br />c/6<br />Hooty<br /><br /> Spark Gap Checker
 
Top