Patto

I'm trying to problem-solve here and I'm a little stumped. This one uses the older coil-sensor ignition module.

I bought this slightly used 3W 70 off RCU's classifieds, and I can't seem to get a spark. There is current going through the ignition I found, but the plug just refuses to ignite. The seller insists it worked when he shipped it, so I'm going to give him the benefit of the doubt and assume I'm doing something wrong.

Has anyone else ran into this problem and if so how did you fix it? I'm using a 4.8V NiMh 2100 mah pack, (yes, it was charged!). I tried using a different battery, bypassed the switch and all that before testing for current. My guess is the sensor is either malfunctioning or is not picking up on the red dot when it passes under it. Does anyone know of a way to test the sensor, say by using some other stimulus to simulate the one on the hub?

-Pat

wjvail

My Feedback: (3)

Are you SURE it's not sparking? The older 3W ignition systems had a very weak spark and their instructions even said you may not be able to see the spark.

I assume you are asking these questions because you've tried starting the engine with no luck?

Bill Vail

Ih82crash

I have a 3w-70 and it is VERY cold blooded. If it is cold, I have had to choke it 12 times before I could get it to fire. On a good day I only have to choke it 8 times. I have the old style inition also. Try giving it full choke and flipping it over with the ignition on. When it pops unchoke it and it should start within two or three flips.

Antique

My Feedback: (4)

Older 3w plug caps were bad, the spark would jump inside the cap before it got to the plug..
Take both plugs out...Put the plugs back into the caps, spin the engine fast and look for spark at the gap in the plug..No need to ground the plugs to the engine, the shield on the wires is the ground...The thing on the engine is not a hall sensor, it's a little coil and needs faster rpm to trigger the ignition....
The caps are replaceable....

Patto

RCIGN1 hit the nail on the head when he said the coil needed a faster movement to get it to spark. It turns out that was exactly the problem. I got it running today and had NO problems with it at all!!

Thanks for the help guys.

-Pat

helitom

My Feedback: (12)

I just finished going through this about 10 min ago. I too bought a used 3W 70i. It absolutely would not do anything. I, like you, could not see a spark when I put the plug against the engine case. After I figured out that most of the case is painted (duh.....) I finally found a spot that showed the weakest spark I've seen on a gas engine. Since I actually could see the spark, I put it back together and found if I choked the **** of of it, it would fire, but would not run. I then disassembled the carb and it was filthly inside. $10 later after a trip to the chain saw shop, the carb was cleaned and a overhaul kit installed. Still nothing but occassional pops....no runnning. Then I tried to find the 3W recommended spark plug gap. It is nonexisant. I have all the docs for the engine, searched the web, etc, so I guessed .028. Same results.

Last night I read on RCU where some guy uses the thickness of a #11 Xacto blade with good results. A little while ago I took the plug out, slammed it down to the gap of a #11 blade. The engine fired right up and runs great. I tweaked the carb for a good idle and transition....I'm goin' flying tommarrow.

Hope this helps.

Tom

Patto

For awhile I was having all sorts of trouble getting the darn thing to start. It would take about 30 flips. I figured I must have just not been flipping it fast enough given that it seems to need a fast flip to get the spark at all.

Well, I took apart the fuel system eventually and found out that there was a pinch in the line where I had wrapped it around the fuel tank, (to avoid draining out the vent line). After I resolved that problem, it started on the 3rd to 5th flip very consistently. It has run very well ever since. I put a new spark plug in it recently and did not change the gap at all and it gives the same easy-starting results.

-Pat