8n with weak spark

[waterman74]

Got an 8n w/ 12v side mount dist. that has a weak spark. Just replaced the points and condenser. Ran strong until it got warmed up, then it didn't want to run under a load....this has gotten worse until now it just won't crank. Got weak spark, getting good fuel flow. compression is 125,125,100,115. Where to start? Coil?

thanks

 

[souNdguy]

weak spark.. was good. now won't crank? where to start? BATTERY

sound slike dead battery.

retest once battery is charged.

after that .. check charge system.

Now.. if you meant to say that it DOES crank.. but won't start.

check wireing to coil.

is this a 12v coil? what type? any resistros used?

hotwire the coil.. could be bad switch.

post back with more details.

coil type. resistors.

more info on battery state of charge.. etc.

did you doube check points? etc

 

[waterman74]

Battery is good, will crank won't start.

Not sure what kind of coil

 

[souNdguy]

allt hose questions I asked.. and you chose to answer only 2 of them?

when you answer some of the others.. get back to us.

can;t help you unless you provide some basic info.

ie.. the wire bypass test at least.

and even a basic ohm value via meter on the coil primary.

resistor info too. ( if present )

 

[Bruce (VA)]

" Battery is good"

How do you know that? Did you check it w/ a hydrometer and load test it? Put it on a charger over night?

Trust us on this one......until you confirm that the battery is good, a weak battery is a likely cause of a weak spark.

You need a strong battery to:

1. Close the solenoid

2. Spin the starter

3. Engage the bendix

4. Provide voltage to the coil.

As the battery gets weaker, the first thing to fail is your spark. If the battery is almost totally dead, all you will hear is the solenoid clicking.

The more current you use to spin the starter, the less you have for the ignition. The fact that the starter spins does not mean you have a strong battery.

Put it on a charger.

" Not sure what kind of coil "

Does it have a resistor in-line or not?

After you fully charge the battery, pop the distributor cap off & check your point gap; .025. Then, bump the starter until the points open. Get out your multimeter, turn the key on & measure the voltage across the open points. What is it?

Post back; you will get plenty of help here to get it running.
75 Tips

 

[waterman74]

Battery was charged and tested good on charger. Here is a pic of what the coil looks like. More findings to come.

 

[Bruce (VA)]

Good, we're making progress.

But........

We know it's a round coil. What we do not know is if it has a resistor in the circuit or if it's a 6v or 12v coil. Measure the internal resistance to find out.

Plz post back w/ the other info & test results.
75 Tips

 

[waterman74]

sorry I have been out of town. I spoke to a friend who used to work on tractors and he said it was most likely the coil. I bought a new one (12 volt, no resistors). I also rewired the key switch because it was looking bad. The tractor still will not start, it just doesn't seem to be turning the starter over fast enough. I even took my battery out of my truck, and the same thing, slow starter spin. The negative battery cable is getting hot... Do you think I should replace that... It seems to be some sort of wiring issue. Were to start?

Thanks

 

[waterman74]

update..I just found out that my guy has not tried the new coil yet. i need some help

 

[Royse]

Battery cable getting hot is a problem, but maybe not "thee" problem.
Check the connections at both ends of both cables to make sure
they are clean, free of rust, corrosion and paint and are tight.
Battery cannot crank well or charge well without good connections.
If the cable is swollen anywhere, or has corrosion showing then I
would replace it, those are obvious signs. They don't always "look"
bad when they are bad though.
If the connections and cables are all good have the starter tested.
Most good parts stores will test them for free.

 

[Bruce (VA)]

" Were to start?"

That's easy.

Start by re-reading all the advice you have gotten here and either do what has been suggested or tell us you've done it.

For example....you say the battery cable is hot & ask if you should replace it; Royse has already told you to do that.

Soundguy told you to run a wire directly to the coil, Did you do that or not?

I asked you "Does it have a resistor in-line or not?"

I also said: "After you fully charge the battery, pop the distributor cap off & check your point gap; .025. Then, bump the starter until the points open. Get out your multimeter, turn the key on & measure the voltage across the open points. What is it?"

And you do not need to pull your truck battery out; see tip # 43.

 

[waterman74]

ok, will work on all of above. If the normal place for the resistor is between the coil and the distributor , then no it doesn't have one...

also, can you explain further "running a wire directly to the coil"

thanks

 

[Royse]

Normal place for the resistor is between the key switch and the coil.
As for the wire, you have a 12V negative ground system, so you
would connect a wire from the positive side of the battery to the
key side (not distributor side) of the coil. You will have to pull that
wire off to shut the tractor off, so alligator clips would be a good idea.

 

[waterman74]

Ok here is more info.

I have run a wire from battery to the coil (no resister between key switch and coil),and measured what I think you are talking about on the points. One lead on the open point and one on the tractor frame results in 12.6 volts.

Tractor still will not start.

Also, a new wire ground wire was installed from the battery. The one that was getting hot.

 

[Bruce (VA)]

Ok, we're making progress.

Put the battery back on the charger.

Remove the jumper wire & check the voltage at the distributor. If it's the same w/o the jumper wire, you can assume the ignition circuit is good to the distributor.

" measured what I think you are talking about on the points"

No. That's not what I said.

Measure the voltage across the open points AFTER you check the gap.

So, in order:

charge the battery.

Check voltage at the distributor w/ & w/o the jumper

Remove the jumper.

Dress the points by running a piece of card stock or brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant.

Check the point gap (.025)

Make sure you have voltage across the open points, as in past the insulator on the side of the distributor. That is a very common failure point on sidemounts, along w/ the attached copper strip. It's hard to find a short there because it is usually an intermittent . So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. If you find the short there, the Master Parts catalog lists everything you need on page 154. You can make the strip and you could also make the insulators as well. But, somethings are just easier & in the long run cheaper to buy. Get the strip, 12209, screw 350032-S, 12233 bushing & 12234 insulator & just replace it all. If you just replaced the rotor & lost spark, put the old one back in. Insure that the rotor fits firmly on the shaft & that the little clip is there. Make sure the distributor cap is not cracked & doesn't have carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. In fact, replace it temporarily w/ a plug wire. Next, remove the secondary coil wire from the center of the distributor cap, turn the key on & crank the engine while holding the end of the wire 1/4" from a rust & paint free spot on the engine. You should see & hear a nice blue/white spark. If not, you have a bad coil or condenser. Just put the old condenser back in to eliminate that as a possibility.

Post back w/ results; I'll be interested in what the problem was.

 

[waterman74]

We did gap the points first, before we checked the voltage. I'm just wondering if I measured correctly( placement of leads) is why I worded it that way, we did it separate from jumping the coil. So, we will measure both with the jumper and without. after gaping.

I'll follow these step by step, but may need some clarification when it comes to some steps involving the distributor.

Thanks

 

[waterman74]

Well, today we decided to try to crank it after adjusting the points again. It just seems to struggle to turn over the motor, but it seems like it wants to start , but just can't, almost like it has too much compression or something. After it almost fires, the starter spins for a few seconds, and now, I just found out the starter will not engage at all. I'm ready to go at this thing with a match and a gas can.

 

[waterman74]

Well the bindex on the starter has completely disappeared. Turning the flywheel with a screwdriver seems difficult and there is a squeak coming from inside the motor when its turned. It appears that a bearing inside the motor is starting to seize and I believe that the added resistance has destroyed the bindex. It's inside the motor somewhere. Looks like this thing will have to be split. I just might sell it for parts.