Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 2:30 pm

Ok, so this guy's Cub I am working on trying to get wired correctly will not run. He told me he couldn't get it to crank after installing new points, etc. That is one reason I was to check the wiring besides checking to see if alternator charged. We have installed a NEW set of points, and I wired the ignition correctly. We are getting fire EVERYWHERE and a good spark at that; but there is no fire coming from distributor cap to spark plugs. We have tried a couple other distributor caps, a couple other rotor buttons, and another set of New wires; and still NO FIRE.

We are scratching our heads!!!! Please HELP. THANKS .

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 3:00 pm

It is a distributor or magneto? Either way though it sounds like the cap or the rotor needs to be replaced.

DUH! didn't see the last statement. Is there anyway the rotor could have gotten out of time and is in between terminals when the spark is generated?

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 3:04 pm

Has the timing been messed with. If you have spark from the coil and the cap is good, the timing must be off. This means the rotor is not in line with the post at the inside of the cap when the coil fires.

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 3:09 pm

I am pretty sure he checked the timing, and said it was good. I will double check though.

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 4:06 pm

Wrong post

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 5:08 pm

Huh??? I'm confused.

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 5:12 pm

rtr wrote:Huh??? I'm confused.

Mule Boss, meant to post a message in another thread but posted here by mistake. He edited his message here.

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 5:31 pm

New here but I am wondering about the following.

Was the governor removed and reinstalled? Did you set the point gap right for his cub?

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 5:39 pm

Not sure what you mean by getting fire everywhere but from the distributor cap to the plugs. AFAIK (and I have been known to be misinformed) the only place to check for spark is at the coil wire and at the plugs. The first questionthat comes to mind from your description, though, is have you replaced the plug wires?

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 5:54 pm

If the distributor was removed when the points were changed the rotor got out of time. Set the engine on TDC on #1 and make sure the rotor is pointing at the #1 tower location on the cap.

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 7:13 pm

Ztr,

This is going to sound wild, but bear with me. These tractors are old. Most of the parts on this tractor are metal and even they show some wear.

Inside the distributor is a plastic block your points attach to and then to a metal post.

Many times we tighten up the points lead so much it cracks the plastic insulating block. When this happens, the spark arcs on the side of the distributor and no fire to the coil or plugs happens.

It is very hard to see if that plastic block is cracked too. Get a good light and with the distributor cap off, look that post going through the distributor on the side real good. Make sure your plastic block isn't cracked.

If it is, replace it. Tom at TM used to have those things.

Don't ask how I know about this. BTW, the top of my head is pretty slick these days too. (balding)

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Wed Dec 15, 2010 8:10 pm

YTmag
First of all, we have tried just about everything you all have mentioned (as far as trying other parts). The best we could get was a VERY TINY BIT of spark out of the plug wires at the plugs. When the guy wanted us to work on it, he came to the house with the distributor with him (oh no!!), so there is NO TELLING if the timing is correct or not. Who knows, he could have taken the governor off too; BUT we should still be getting spark!! We have not tried another condensor yet, but have a couple extra used ones we can try.
I believe you are going to earn that $100-.

YTmag
2nd while the head is off, we are gonna check timing
Time the distributor to the engine and then static time the distributor. Also check to see if the mechanical advance is working.

The correct firing order is located on the side of the engine block.

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Sat Dec 18, 2010 5:54 pm

UPDATE:

We got the new head gasket on and torqued down to 45 ft-lbs. While it was off we found that the timing was 180 degrees off, and fixed that. Once everything was back together again, we tried to start the tractor. Still having the same problem. No fire through the spark plug wires. It is getting lost somewhere between the rotor button shaft on the distributor and the plug wires themself. The coil is firing excellent, therefore the plastic piece shouldn't be cracked. We also checked the rotor to see if it was turning, and yes it is. We have tried new wires, new distributor cap, and a new rotor. Still no luck. What is next?? New distributor??

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Sat Dec 18, 2010 6:36 pm

It is out of time! period, If the information you are giving us is correct. Bring # 1 cylinder up on compression stroke. align pointer to mark on the front pulley , then align rotor to # 1 terminal on distributor cap. MAKE sure firing order is correct 1 3 4 2 . You will now have spark to the plug wires. Most likely you have gas fouled the plugs by now and they will need to be replaced.

Boss

Re: Cub Engine WILL NOT FIRE AT SPARK PLUGS!!!

Sat Dec 18, 2010 6:39 pm

Let me recap. You have a distributor - battery operated ignition system. You have hot spark coming from the coil to ground when cranking over the engine. No spark from a distributor cap connected plug wire to ground. Correct so far?

That means the points are opening and closing. The spark is going some place.

New distributor - no. You need to locate and correct the problem.

Is the mechanical advance hooked up and working? Grasp the rotor and gently turn it. It should turn a bit in one direction and not turn in the other.

Did you time the distributor to the engine and then time the distributor to the correct firing order? This is actually a multiple step process?

I think your distributor is not properly timed. OK. Roll the engine over until the pointer and TDC timing mark are lined up. The rotor should be pointing exactly at either the #1 spark plug tower on the distributor cap or the #4 spark plug tower.