Ford 800 no spark

Ed M

Member
My 800 has been sitting for the winter.Always ran fine.Now no start.Have 12 volts on ballast resitor and 51 ohms across resistor.No spark at points with key on and manually opening points.But have spark at points when jumper wire is put on from battery and bypassing reistor.So I assume my coil is good.Do not know what voltage is suppose to be at coil.I have a 12 volt conversion also.Rotor bad ? Thanks to anyone you makes a post. Ed
 
Rotor bad? May bee tires too? Wtf??

51 ohms.. really?

Why a ballast resistor on a 12v system, and not a real 12v coil

Oh, and clean those points and jump out possible bad wire connections to test.
 
Try this simple no brains test. Run a hot wire from the battery to the ignition side of the coil. If you have a good spark when you do that then the problem is from the coil back to the battery. If still no spark problem is in the distributor and likely toi be corroded points
 
Well the tractor was my fathers and he had it switched over to 12 volts back in the 80's.I just got the tractor from my mother a couple of years ago.Don't ask me why there is a ballast resistor.It was there and this is the first problem with the tractor in 40 yrs.Like I said I have 12.71 volts on the battery side of the resistor.No spark when I manually open the points but if I run a wire from the battery to coil and manually open the points I get a spark.I am not a parts replacer but am trying to troubleshoot his logically.I wonder if my coil is weak.Since I am running a ballast resistor I assume I have a 6 volt coil.Am I right about this ?
 
No way to know what coil you have, unless it has writing on it or you can precision test it.

No way that is a 51 ohm resistor either.

If it was me, I'd start over with a Napa ic14 SB coil and ditch the resistor, gap and clean points and go
 
It's not the rotor.

Do you have spark when shorting the points out with a screwdriver?

If so, burnish the point contacts with an IBM card or piece of brown paper bag. Do not use a point file.

Dean
 
What voltage do you read at the coil's primary distributor terminal to ground? With the points open, this should be 12 volts to ground. With the points closed, it should be zero volts. Once you've made these two simple measurements, you should be able to figure out the rest.
 

When you bypass from the battery you are bypassing a number of other possible culprits. Another good possibility is the key switch.
 
Get one of those 12v test lights put it on the moveable side of the points with the points closed if it lights up bad points. If not open points and check it should light if not keeping working your way back to the switch.
 
After reading some of the reply's
might be key switch
run this jumper wire and check
clean the points
ect..........
I might be the dumb one here so lets review what you said.

Have 12 volts at resistor but no spark at points.
Bypass resistor with jumper wire now you have spark at points.

Hummmmmmmmm.
Could it be the resistor is bad?

I'm with soundguy.
Go to napa and get you a IC14SB coil for $25 and do away with the resistor all together.
 
UPDATE : My bad.I have an electrical degree and work on postal equipment and am not a dummy but sometimes lazy especially when its getting late and darkness is very close.Kinda laid meter lead on battery when checking----1st mistake.Did not know what ballast resistor should have been but should have known 50 ohms was too much.Got my fancy test light out this am and methodically went start to finish.Ballast resistor bad---the 50 ohms must have been coming from contamanents on the nylon string through the center of it.Because when I looked at it in daylight I could clearly see it was broken.But guess what ? After jumpering around it,still no start......Gotta remember to put coil wire back on distributor cap.Heading to autozone for temperary ballast resistor then during the week to NAPA for a 12 volt coil to do away with ballast resisitor.
On a side note while bush hogging in late fall tractor was shutting off as driving.I would giggle key on and off and would sometimes work,so I thought ignition key was bad.I bet resistor was already bad the last time I used it and the bouncing would make contact till finally parked.
Thank you to all who gave me support.....Ed
 
Save the money on the resistor and just get a 12v coil. You can get whatever parts store to cross the Napa number for you.

No need to spend more

If the key switch is suspect, test or jump it out.

Your electronics degree should make all this easy.. easier than it is looking so far..
 
New resistor is .6 ohms.Voltage at coil is 6.55.All is good.New resistor looks just like my old one which is about 1980 vintage.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top