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Any Small Engine Experts Here?


AzRednek

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Does anybody know how to test a magneto coil?? I'm working on a Weed Eater brand hedge trimmer. I tested and re-tested the kill switch and it seems to be working properly. I can't get a reliable spark.

 

The trimmer quit, wouldn't start, about 3 hours later it fired right up on the first pull, then died after running about 2 minutes. This morning I tested it and got spark, re-installed the plug and it fired up. After a few minutes it quit again and I couldn't get any spark. After it sat and cooled off I tested it with a new plug, got spark, fired it up and it died after apx 30 seconds. I tried both new and old plugs and couldn't get any spark.

 

I took the coil to a mower shop and he said the only way to test it is try a new coil. Then he said no return on electrical parts and offered to fix it for 75-100 bux. Its tough being a cheapskate but no way will I give the mower shop any business.

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I had a trimmer with the same symptoms. The local shop said it was the magneto, said I was better off getting a new trimmer. I did. They are cheap.

 

I have no idea how to test a magneto. It has to be spinning, but not many meters can measure the output. I assume that the spark is like the heating ignition components I use in HVAC. Output ranges from 10,000 volts(gas) to 30,000 volts(oil.) No one buys meters for that. If the control has power, and the spark doesn't jump the prescribed gap, replace the control.

 

On your trimmer, if you have the proper input to the control (spinning), the plug wire is intact (low resistance), and the spark plug gap is right, and you don't have spark, get a new magneto. New magnetos come with new trimmers.

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Here's a test I've done before - its pass/fail and won't tell you much.

 

Take the spark plug out and get out a pair of thick gloves. Reconnect the spark plug wire and ground the spark plug out on the side of the jug. Have one of your buddy's pull the starter rope and see if it sparks. If it does, you've got fire. If is does not, toss the weed eater and buy a new one.

 

This test won't tell you if its sparking reliably; it'll only tell you if you're getting a spark or not.

 

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Chances are, if your trimmer has a few hours on it and its not working correctly, its probably time to cemetary the thing and buy another one. $150 buys lots of Weed Eater.

 

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Here's a test I've done before - its pass/fail and won't tell you much.

 

Take the spark plug out and get out a pair of thick gloves. Reconnect the spark plug wire and ground the spark plug out on the side of the jug. Have one of your buddy's pull the starter rope and see if it sparks. If it does, you've got fire. If is does not, toss the weed eater and buy a new one.

 

That is how I tested it last night and it sparked like crazy. After doing some net surfing I found out it is not always an accurate test. With no compression or resistance on the starter the engine rotates rapidly when cranked. I did get spark last night. Today I left the plug in, hooked the plug wire to another spark plug I grounded against the engine block. I got spark the first time, it started for a short time, engine died and when I repeated the test no spark.

 

 

This test won't tell you if its sparking reliably; it'll only tell you if you're getting a spark or not.

 

It does get spark but not necessarily at the top of every power stroke.

 

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Chances are, if your trimmer has a few hours on it and its not working correctly, its probably time to cemetary the thing and buy another one. $150 buys lots of Weed Eater.

 

You're absolutely right but it is hard being a cheapskate and trashing a tool for a bad part. Not worth the aggravation though to fool with it anymore. At least two stroke engines are not illegal in Phoenix yet so I best get a new one while the pickings are still good. I used a 4 cycle trimmer a couple of months ago and it was gutless. I returned it to Lowes, bought a cheapie 2 cycle Robyi for 20+ less. To Al Gore's dismay, it not only creates noise pollution and dumps hydrocarbons into the atmosphere. It cuts like they're supposed to.

 

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"At least two stroke engines are not illegal in Phoenix yet so I best get a new one while the pickings are still good. I used a 4 cycle trimmer a couple of months ago and it was gutless. I returned it to Lowes, bought a cheapie 2 cycle Robyi for 20+ less."

 

Az,

 

I bought a new stil 110 weedeater here about 3 years ago. It was one of those new fangled 4 cycles that everyone raved about. Started it up and thought, man this thing sucks! I was wrong, its the best darn weedeater i've ever run. Its a lot easier on the hands than the big 250 i usually run, better fuel econmony, and quiet, and it will just about cut anything the 250 will. In the summer time, i run a weedeater alot, alot of 12 hour non-stop days. That little 4 stroke is the ticket. I'm kinda partial to the 4 strokes now.

 

Brenden

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AZ, I was a service manager at a lawn & garden, snowmobile, motorcycle shop for nearly 10 years, in my younger days.

 

There is generally no fixing the electronic ignition coil problems without replacing it. Keep your eyes open for a junker WeedEater like you have, that has spark, as they are usually all over the place with bad motors and such. It's good to have spare parts as Horsefly said.

It is not difficult to replace the coil as most now are in a non-adjustable fixed position.

If you can build a rifle, you can fix a weedeater.

Pop the covers off and check for wires rubbing on the magneto to the kill switch. It's most likely the coil heats up and shorts out due to a crack in the coil housing somewhere.

Good luck.

 

Spiris

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When you are looking for old ones keep the following in mind.

 

A friend of mine was having trouble with his and when he took it to the shop

the guy gave him some free advice.

The guy said that they were only built to run 100 hrs., after that things start to

come apart.

 

So my friend took the free advice and saved the $35/hr charge.

My friend took the thing back home and found that the head screws had loosened

and this is why it wouldn't start ( not a spark issue, a draw in fuel issue ).

My friend tightened the loose screws and Viola the thing started.

 

Tinker

 

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Thx Spiris!! I have the coil off, it was fairy simple getting to. I was just hoping there was a way to bench test it before I purchase one. I learned many years ago from the School Of Hard Knox, while working on cars, not to replace a part unless I'm certain it is bad.

 

Can you recommend an online source for small engine parts? I lost my connection to small engine parts. My neighbor was working in a warehouse that stocked small engine parts. Employees were allowed to purchase parts dirt cheap for their own use. The business closed the doors of their Phoenix and Tucson operations and my neighbor was left with the option of transferring at his own expense to the Midwest or be layed-off.

 

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AZ, there's possibly an ohm's test for the coil available in the factory service manual but I've seen coils with the right range of #'s and still be bad. If you haven't yet, disconnect the kill switch to eliminate it from the equation. It's usually a spade connector from the coil and make sure the connector doesn't ground out being disconnected.

I usually buy parts local because of the outrageous shipping charges that some places get these days.

 

Here's a place in WI that seems to have anything you want. Just follow the menus to get a price.

Not knowing your model, I did a random price check on a couple Poulan/WeedEater hedge trimmer coils and it was $25-28 for them + shipping. If this works out, see if you need anything else for the unit such as the recoil pulley or other wear items to make the shipping worth while.

Sometimes the same coil will be used on multiple models and types, but it takes time to research this. I only mention this if your able to pick up a junker for parts.

It's hard to believe that there isn't any place in Phoenix and Tucson that doesn't wholesale parts.

 

http://www.smallenginepartswarehouse.com/home.asp

 

 

Spiris

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I'm going to throw in another thought here for you. A bad, as in shorted, condenser can do the same thing. It can be usable until it starts to heat, then go to short and kill all spark. The condenser is only a few dollar part and worth the time to try before replacing the mag coil. If it is not the condenser then I would say without doubt it is the coil. Dave

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we stopped working on weedeaters because they are so cheap unless there a stihl or echo its not cost effective to work on.the no.1 reason most 2 cycle motors dont run is the exhaust ports are carboned up take the muffler off and check to see there open.we buy most of are parts from stens.

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swamp_thing, thanks for the suggestion, and I often wish that these small engines still used the points and condenser. Diagnosis was easier, and cost of repair was much less. They've all gone to pointless ignition with everything contained in the ignition module(coil) including the timing trigger, and diodes for voltage enhancement all sealed in epoxy. Vibration and heat sometimes takes its toll on the sealed components. It's possible that's what happened to AzRednek's trimmer.

 

Spiris

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