SNOWMOBILE TECH TIP: Diagnose weak spark or lack of spark

July 30, 2010
A gasoline engine needs three things in order to run: fuel, compression and spark. No fuel or compression? Those are easier to track down because they’re usually due to a mechanical problem like a dirty carburetor. Low compression is also a mechanical issue a technician can actually see and wrap his or her head around. But lack of spark often throws people for a loop because the problem can’t be seen — a bad stator, for example, looks no worse than a good one — and it could be from multiple sources. Start diagnosis and repair with the simplest and least expensive culprits by working through the following inspections.
1. Make sure the engine has the correct spark plugs and they’re gapped correctly. This might seem silly and really elementary, but seemingly big problems are sometimes caused by the simplest failures.
2. Check connection of the spark plug cap to the spark plug wire. Also check the spark plug wire condition.
3. Disconnect the main electrical connector coming out of the engine, and then check for spark again. This unhooks the kill switch, ignition switch and wiring for those switches. If the spark improves, the problem is within wiring from one of those switches or a switch itself is to blame. Now you’ll need to disconnect each switch (one at a time) to trace it to the failed part.
4. Test the stator resistance to make sure it’s within the manufacturer’s specification. You can get the specs from a dealer or try a search online.
Keep in mind that most dealers don’t accept returns on electrical parts, so be sure the part you order is to blame, otherwise you could be stuck with a brand new $300 ignition part, such as a CDI box, and a sled that still won’t run. Think of your friends and riding partners who have the same or similar snowmobile. You might be able to borrow parts from their machines to diagnose the problem.

One thought on “SNOWMOBILE TECH TIP: Diagnose weak spark or lack of spark

  • You failed to mention spark plug caps. Can’t tell you how many times, I have replaced these things.

    Reply

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