John Deere model “D” Magneto Problem – Wrong Diagnosis

(the photo above is similar to my Mag).

Tractor: Unstyled John Deere model “D” with Mag

Symptom: Wouldn’t start, not even a pop or hiss

I removed the cap and got spark at the coil BUT I used one of those inline spark testers that contains a neon lamp. Neon lamps require less than 100 volts to flash!

I suspected the rotor or cap because we have had very humid weather and the tractor sits for long periods without being started.

I temporarily jumpered the coil to rotor and impulsed the mag. Got spark again using the inline neon bulb tester.

Out of frustration and being in a rush, I bought a cap and rotor from JD. These parts didn’t fix the problem.

I finally did what I should have done in the begining. I carefully filed the points with a points fine – and it started right away.

Lessons Learned: -Check the simple, (and common) problem areas first. -neon spark testers tell you if there is anything, but not if you have a good, strong spark. -Correct diagnosis is 95% of the solution.

Now I will see if my contact at the local JD branch will re-stock the cap and rotor, which they stock because there are a number of antique JD collectors in our area.

Knock, Detonation, Pinging

(Photo courtesy of Hastings Manufacturing)

An interesting article on Wikipedia about engine Knock, Detonation, & Pinging located at:   http://en.wikipedia.org/wiki/Engine_knocking

Also, a great animation showing the four strokes of a 4 cycle internal combustion engine, very dramatic in full screen mode –  at the following link:   http://schoolbusmechanic.blogspot.ca/2008/07/animated-4-stroke-internal-combustion.html

“Mystery Fluid” smooths out engine after rebuilding the Carburetor!

(This is not the carb referenced in this blog – I didn’t take a picture of it – unfortunately)

We cleaned out a very plugged up carburetor using “Red Stallion Combustion Chamber and Carburetor Cleaner” spray – which seemed to do an excellent job. The bowl was green inside, and the float needle was stuck open with ‘varnish’.

We didn’t have a tank full of cleaning solution so our only option was to disassemble as much as we could; spray, blast with 160 psi air, spray, blast, repeat, repeat, etc.

The carb ‘looks’ very similar to the one Honda uses on their single cylinder engines on their generators but it had a Japanese name on the body, which I neglected to record.

The engine started immediatley but it ran very rough (on fresh premium fuel).  Changing the mixtures made no difference.

Then a helpful neighbour produced a can of “Sea Foam Auto Marine Fleet Motor Treatment” liquid – part number SF16C (UPC code 0 1881200001 9). He dumped an unmeasured amount into the fuel tank and within a few minutes the engine smoothed right out and ran beautifully.

We have not replaced the fuel in the tank to confirm that the engine runs smoothly on new untreated fuel, but we believe that it will.

DISCLAIMERS:

I have no financial interest in this product or in the company that makes and distributes it.

I am generally not in favour of  additives and “magic fixes” to solve engine and transmission problems. Some engine manuals discourage their use.  In this case it seems to have worked very well.