Troubleshooting Outboard Motor Magneto Ignitions Application Note

Coil 23 SERIES II MULTIMETER

kΩ Introduction Flywheel 10 20 30 40 OFF V Your outboard motor won’t start. V 300mV Yes, its been in storage for awhile but it was running well when you

Primary

Secondary A A left it. Should it go to the repair PRESS RANGE

AUTORANGE 1 SEC shop? The shop will do a good job TOUCH HOLD 10A V but they’re always busy and the ! 100V 300 COM mA 750V repair will probably take two FUSED weeks —remember your out of town guests want to go fishing tomorrow. Isn’t it time you learned how to Breaker fix it yourself? You suspect the igni- Points tion since that’s what went bad last time. Will you need the special test equipment called out in the repair Condenser manual? NO! This application note will show you, in a few simple Engine Block steps, how to pinpoint magneto ignition troubles quickly. All you will need is a few mechanics’ tools and a good quality digital multimeter. Won’t start scenario Troubleshooting procedure You can justify the multimeter Now let’s get down to cases with We will assume you have already because it will do double duty for the dead engine. In order to start, tried the normal starting procedure, your other electrical troubleshooting the engine needs three critical i.e., turned the engine over a num- tasks, including the battery and items: a) proper amount of fuel/air ber of times, first with choke closed charging system, trailer lights, mixture, b) properly timed spark and then open. corrosion protection system, and and c) some compression. If it won’t other electrical systems in either start, chances are that one or more Spark plug check your house or boat. of these is missing. The trouble- The ignition troubleshooting Remove the cowling (if necessary) shooting logic is straightforward: procedure that follows can be used to gain access to the spark plugs. find out which critical items are for any small one or two cylinder For a twin cylinder engine, label missing and why. gasoline engine that employs a the spark plug wires so that they Before getting into the actual breakerpoint magneto ignition; for can be replaced in the correct procedure, verify that the fuel tank example your lawn mower, order. Pop the wires off and has sufficient quantity of fresh fuel chainsaw, generator, pressure unscrew the spark plug(s). Keep mixture and if your engine has an washer etc. track of which plug came out of electric starter, use the dc volts each cylinder. function on your multimeter to Now, examine each plug care- check the battery voltage and the fully. This is like palm reading; the ohms function to check the cables condition of the plug tip can tell a for loose or corroded connections. story about what is going on in With reference to the ignition each cylinder. If the plugs are wet system, here is a list of the critical with gasoline, fuel is undoubtedly components listed in the order of reaching the cylinders. their likelihood of failing: If the plugs are dry, the opposite Spark Plug, Breaker Points, Coil, HV is true. Look for a blockage in the Wire, Condenser and fuel system or a bad fuel pump in a Flywheel Magnet remote tank configuration. If the plug(s) are fouled with and coil to the engine block. This Coil carbon and/or oil, several things can be checked without taking 23 SERIES II MULTIMETER could be wrong: The spark to the apart the magneto as follows: Set kΩ Flywheel 10 20 30 40 Ω OFF V plug(s) is weak or nonexistent, the the multimeter into the ohms ( ) V spark plug heat range is too cold, function. Use the range button to 300mV or the engine has been run for long manually select the 40 kΩ range.

Primary

Secondary A A PRESS periods of time at low speeds (Auto ranging may not work here RANGE AUTORANGE 1 SEC TOUCH HOLD possibly with an incorrect fuel or due the inductance of the coil). 10A V

! 100V 300 COM fuel/oil mixture. In the case of Now, touch one probe tip to the mA 750V FUSED multi-cylinder engines, if only one engine block and the other to the plug shows difficulties, the problem metal connector inside the plug Breaker is likely to be a weak spark from wire cap. The meter should read Points the ignition system. the resistance of the coil and HV In any event, the next step is to wire in series. Good readings will Condenser check actual spark plug operation. range from 3 kΩ to 15 kΩ. Higher If new plugs are available, use readings mean a poor connection, Engine Block them for the next test. If not, clean which typically occurs either where the old ones as follows: using a the HV wire connects to the coil or Figure 1: HV wire resistance/continuity test sharp object such as the point of a at the other end where the HV wire Coil safety pin or a straightened fish connects to the spark plug clip SERIES II MULTIMETER 23 hook, scrape off the deposits on the inside the cap. A reading of OL kΩ

10 20 30 40 insulator that surrounds the center means an open circuit or break in OFF V V electrode. Dig down between the the electrical path. If a bad reading 300mV insulation and sidewall and remove is indicated, double check to make

Primary

Secondary A A PRESS as much carbon as possible. Now, sure you are making a good con- RANGE AUTORANGE 1 SEC TOUCH HOLD wash out any remaining oil or nection with both test leads. 10A V

! 100V 300 COM mA 750V carbon particles with a nonconduc- FUSED tive solvent such as paint thinner or Coil and HV wire continuity unmixed gasoline. Allow the plug to test for two-cylinder engines air dry; blow on it if necessary. If you are testing a 2-Cylinder, Next, gap each plug by tapping 2-Cycle engine (mixed fuel) then or bending the outer electrode. If perform the test as above for each you don’t know what the recom- cylinder individually. Look for a mended gap is, use 0.025" (a bank correlation between a bad reading credit card is typically .030"). Test Figure 2: Resistance/continuity test for 2-cylinder, (OL) and a fouled spark plug on the each plug and HV wire combination 4-cycle engines same cylinder. by connecting the wire to the plug If the engine is a 4-Cycle model and laying the plug on the engine (unmixed fuel) such as a Honda or Coil block where the gap can be seen. Onan, the test is performed slightly The plug outer body needs to make differently as shown in Figure 2. electrical contact to the engine Here we will be looking for conti- block as it does when it is screwed nuity from one spark plug clip to in place. the other since there is only one Now, turn the engine over at secondary coil which is not normal cranking speed and watch

Primary connected to the engine block. An Secondary for a spark. If you are in bright sun, open spark path will kill the spark you may have to shade the plug to to both cylinders. see the spark. If this test shows no spark or a weak spark, troubles HV circuit repairs with the breaker points or coil inside the magneto are likely. A break in the HV circuit can occur in several places as shown in Coil and HV wire Figure 3. resistance/continuity test If the poor connection or open Figure 3: Possible locations of breaks in for one-cylinder engines circuit occurs at the spark plug clip, secondary HV circuit you may be able to repair it without The next test checks for a continu- taking anything else apart. If the ous path for the spark through the problem is located inside the mag- HV wire and the ignition coil. Refer neto, it will probably be necessary to the electrical diagram in Figure 1. to remove the flywheel. Note that for a one cylinder engine there is a direct electrical path from the plug cap through the HV wire,

2 Fluke Corporation Troubleshooting Outboard Motor Magneto Ignitions Coil The preferred cleaning method 23 SERIES II MULTIMETER is to scrape the contact surfaces with a sharp carpet-layer’s knife, 10 20 30 40 Flywheel OFF V followed by a wiping with solvent V

300mV on a clean cloth. Filing will sometimes work but there is a risk of

Primary

Secondary A A PRESS damaging the underlying metal RANGE

AUTORANGE 1 SEC TOUCH HOLD 10A V which will shorten the life of the

! 100V 300 COM mA 750V contacts. In any event do not use FUSED sandpaper. The grit will imbed itself in the contact metal, render- Breaker Points ing the points useless. If you want a quick fix to get the engine running, try the “old-timers Condenser Engine point cleaning trick” as follows: Block With the crank shaft positioned so that the points are closed, pry the Figure 4: Breaker point contact resistance test breaker arm open and insert a clean business card between the Breaker point test Measure the contact resistance contact surfaces. Release the breaker arm so that the points grip The breaker points on a magneto as follows: place the multimeter in the end of the card and then drag ignition are often located under the the Ω function and hold the probe the card through its width, wiping flywheel. Remove any parts that tips tightly together to obtain a the contacts in the process. The might interfere with the flywheel reference reading with the tips card has two properties which removal. Hold the flywheel in a shorted. The reading should show make it work. It is absorbent stationary position with a strap between 0.0 and 0.3 ohms, note enough to remove oil and gently wrench and remove the large nut the value. This is the reference abrasive enough to remove surface that holds the flywheel to the reading. contamination. crankshaft. Now place the probe tips on When you think the cleaning is Use a puller to loosen the fly- opposite sides of the point contacts complete, verify the results by wheel and lift it off the crankshaft. when the points are in the closed repeating the electrical resistance Locate the breaker points and position. The meter should now test. Before leaving the points, examine the contact surfaces. read no more the 0.1Ω greater than make a visual inspection of the gap (Caution here: when rotating the the reference reading. Higher read- in the open position. A typical crankshaft, turn it in the forward ings indicate contamination on the specification would be 0.020 inches. direction only to prevent damage to contact surfaces. If the contact surfaces are pitted, the best choice the water pump impeller). Condenser test For proper operation the breaker would be to replace the points. If point contact surfaces should be you can’t install new ones, then Next check the condenser as clean and shining. Make an electri- carefully clean the ones you’ve got. follows: Disconnect the condenser cal resistance test with your digital The object here is to remove all lead, then place the multimeter in multimeter before attempting to contamination without damaging the capacitance function and hold clean the contact surfaces. This will the underlying metal. one test lead to the capacitor case allow a before and after indication. and the other to the terminal. (See Refer to the diagram in Figure 4. Figure 5). Note that the points are in parallel with the primary coil. When the points are open the resistance 23 SERIES II MULTIMETER across the coil and points in paral- 10 20 30 40

OFF V lel will be about 1.0Ω (the coil’s V wire resistance). When the points 300mV (with clean contacts) are closed the

A A PRESS RANGE resistance will fall to a value of 0.1 AUTORANGE 1 SEC TOUCH HOLD to 0.2Ω. Any oil or corrosion on the 10A V

! 100V 300 COM mA 750V point contact surfaces will raise the FUSED resistance and reduce the primary coil current, which subsequently weakens or kills the spark.

Figure 5: Checking condenser leakage Check for leaking condensers with the Ohms function. As the condenser charges up, the resistance should increase to infinity. Any other reading indicates that you should replace the condenser.

Troubleshooting Outboard Motor Magneto Ignitions Fluke Corporation 3 Do not touch both leads simulta- fingers. Watch the meter reading as Reassembly and final check neously with your fingers because the capacitor charges up. A reading Once you’ve checked out and the resistance through your body of OL in the ohms function means repaired the ignition system, reas- will cause reading errors. A typical the capacitor is not leaking or semble the engine and repeat the range of good readings would be shorted, i.e., it’s probably good. spark plug test. If the spark looks .015 µF to .030 µF. A reading of OL Now reverse the test leads and good, install the plug(s) and try (overload) in the capacitance func- repeat the test. The results should again to start the engine. If troubles tion means the capacitor is shorted. be the same. persist, look to the fuel system. A very low capacitance reading Carburetor cleaning may be probably means the capacitor is Flywheel magnet test required. Remember that most open. Capacitors are not normally Flywheel magnet failures are rare engine manufacturers recommend repairable so a bad reading will but sometimes do occur. You can the addition of fuel stabilizer for likely mean a trip to the parts store. verify the strength of the magnet long periods of storage. If your multimeter does not have with a simple test. Locate the inside the capacitance function, use ohms surface of the flywheel that travels instead. This test is best performed near the pole pieces of the coil. You with the capacitor removed from will find some magnetic material the engine. Start by shorting the (typically laminated steel) in two capacitor by touching the lead to places separated by a gap of non- the case. Now, touch one probe to magnetic material (typically alumi- the lead and one to the case with- num). Lay a hacksaw blade on the out touching the probe tips or laminations near the gap. If the exposed capacitor parts with your magnet is good it will exhibit a strong pull on the hacksaw blade.

Fluke Multimeters for Marine Applications The following Fluke Digital Multimeters are recommended for use in marine applications.

26 TRUE RMS MULTIMETER

73 MULTIMETER 27 MULTIMETER VAC MIN

k 30 0 10 20 30 0 102030 OFF V RANGE HOLD CAT 600V 600A V 40 CAL 1000A

V mV RANGE REL MIN/MAX HOLD H 300mV MAX Hz 20kHz Hz V 1kHz RESET 40 MIN MAX OFF 200A V 600A V V 1000A 200

OFF A mV mV 200V

600V A A OFF PRESS mA/A mA/A MANUAL RANGE A ZERO DC / AC AUTORANGE TOUCH HOLD A A

36 CLAMP METER 10A V OFF ! 40 V A 10A MAX V DC 600V CAT mA ! 600V CAT 1000V MAX 300 FUSED COM 1000V CAT TRUE RMS mA ! mA COM 10A FUSED COM A 320 mA MAX 600V

COM V

Fluke 12B Fluke 73 Series III Fluke 26 Series III Fluke 27 Fluke 36 Put basic tests ® ClampMeter • Touch Hold Same features as • Fully sealed, Fluke. Keeping your world on automatic captures stable Fluke 73 Series III, waterproof case • True-rms • VCheck™ auto- readings plus: • Touch Hold® responding up and running. matically • Auto and manual • Rugged, overmolded captures stable AC current to 600A switches from ranging case readings • measuring ohms/ • DC current to 1000A Fluke Corporation continuity to ac • Holster with Flex- • Tough, electrical test • Volts, ohms, amps, Stand™ included lead set with continuity, diode • AC and DC voltage PO Box 9090, Everett, WA USA 98206 or dc volts to 600 Volts Volts ac and dc silicone insulation test Fluke Europe B.V. Capacitance, to • and alligator clip • Current with ranges • Max Hold PO Box 1186, 5602 BD 10k microfarads • Resistance • µ • True-rms ac voltage from 320 A to 10A • Continuity beeper Eindhoven, The Netherlands • Continuity • Diode test/ capture locates continuity beeper • AC/DC current with For more information call: intermittent ranges from 4.0 mA • AC/DC current with to 10A U.S.A. (800) 443-5853 or opens and shorts ranges from 32 mA Fax (425) 356-5116 • Min/Max record- to 10A • Lo Ohms Europe/M-East (31 40) 2 678 200 or ing with relative Fax (31 40) 2 678 222 time stamp Canada (905) 890-7600 or Fax (905) 890-6866 Other countries (425) 356-5500 or Fax (425) 356-5116 Other marine application notes available from Fluke: Web access: http://www.fluke.com Troubleshooting Marine Engine Electrical Systems • ©1998 Fluke Corporation. All rights reserved. • Testing Corrosion Protection Systems Printed in U.S.A. 11/98 B0271UEN Rev B Printed on recycled paper.