8n Ford Tractor

Jim Shimp · Feb 23, 2010

I have a 8n Ford Tractor, side distribtor. I have replaced almost everything electrical on it, distributor cap, points, condenser, wires, coil, wires to coil, battery, battery cables. My problem is that it will start every once in a while and run like it is brand new, but after about five or ten minutes it will just shut off like someone turned the key off. Then it will not start again maybe for two or three days. It will start right up again run for awhile then shut off again. Does anyone have a idea what is going on?

MurrayE · Feb 23, 2010

Hi, Could be in your fuel supply. Might be clogged somewhere's along the line. You will have to check everything along from inside the tank, through to the carb. Cheers, Murray
There will be other information from people with more knowledge then myself.

Anonymous-0 · Feb 23, 2010

Can only be 2 things. Fuel or electric. If your filter is good and lines are not plugged, I'd say a bad coil. Or a resistor somewhere.

Dave

Paul from MI · Feb 23, 2010

I'd do a little diagnosis. Check for a good flow of fuel to the carb. Let it run at least a couple of quarts of gas to test. Does it have spark when it quits? If so, the problem likely is fuel related maybe a sticking float. If no spark, bypass the igntion switch, see if that fixes it. Before you spend any more money you need to find the culprit. Good luck with it.
Paul

ericlb · Feb 23, 2010

since youve repaced everything else it can only be the ignition switch, and 8 n's are famous for having bad ignition switches, and when they do, they'll run just the way yours is now, try a new switch next

Jim Shimp · Feb 23, 2010

I have already drained the fuel tank and put in new fuel. I also forgot to mention that I did replace the ignition switch. I have bought three new coils, I have also bought and tried a electronic ignition that didn't work either. I replaced the float in the carb. Nothing has worked.

El Toro · Feb 23, 2010

When it quits pull off a plug wire ASAP before the engine cools and see if you still have fire to your plugs. You will probably need a helper.
Be sure to have the ignition switch in the on position.

If there's no fire you need to check for battery voltage to your coil. With the points open and the ignition switch in the on position you should have battery voltage on both small terminals on the coil. If there's no voltage present check the switch. To bypass the switch run a separate wire from the battery to your coil and then see if the engine quits after 10 minutes of running. Are you using a ballast resistor between the ignition switch and the coil? They're known to fail. Hal

Dean · Feb 23, 2010

Bingo!

Replacement ignition switches (new or otherwise) for vintage Ford tractors are of notoriously poor quality. Often the tractor will start and run properly for 15 or 20 minutes until the switch contacts heat sufficiently to increase contact resistance enough to diminish coil primary current such that ignition secondary voltage is unsufficient to properly fire the spark plugs.

This condition is very difficult to diagnose because the switch contacts begin to cool down immediately when the engine stops if the engine stops with the point contacts open. Often the spark will appear OK when one attempts to restart the engine leading one to look elsewhewre for a problem.

Tey this: Prepare s short jumper lead with an alligator clip on either end and carry it with you in the toolbox. When the tractor next stops unexpectedly, use the jumper wire to connect the two contacts on the ignition switch and attempt to restart the engine. If the engine now starts, replace the ignition switch.

Alternatively, simply replace the $10 ignition switch.

In either case be prepared for the same problem in another 3 or 4 years.

Dean

Anonymous-0 · Feb 23, 2010

(quoted from post at 07:07:59 02/23/10) I have already drained the fuel tank and put in new fuel. I also forgot to mention that I did replace the ignition switch. I have bought three new coils, I have also bought and tried a electronic ignition that didn't work either. I replaced the float in the carb. Nothing has worked.

I replaced 3 starters on an old car once with rebuilt ones.......... Nothing electrical is sacred, maybe forget you have an 8N (or anything specific) and troubleshoot the problem itself??

Dave

R.D.F. · Feb 23, 2010

Get yourself a spark plug tester, $10, will save a lot questions about tractors that won't run, narrow down some of the speculation.

Anonymous-0 · Feb 23, 2010

If I recall correctly, there is a resistor on the back side of the dash. If it's bad, either the engine won't run worth a flip or it won't run. May want to check or replace it also if you haven't done so yet.

Bob · Feb 23, 2010

Side-mount distributor 8N's did NOT use a ballast resistor (as they were set up as they left the factory).

If it is a 12 Volt conversion and a voltage-dropping (converting) resistor has been added, that is another scenario.

old · Feb 23, 2010

Well as Dell would say down on the N forum replace your weakter ignition switch. The factory ignition switch are known to be weak and run time for a bad one is around 5 minute and will not start for hours some times days. One way to be sure on that is to hot wire it. If 6 volts go right to the coil from the ignition side of the battery. If 12 volts and you have a ballast resister in line with the coil hook the wire to the igniti0n side of that resister and start it up. If it runs like it should and doesn't shut down then you know you have a bad switch

smallercrawler · Feb 23, 2010

Chased similar problem for quite awhile-found small piece of insulating paper in distributor IIRC at condenser connection was cracked allowing connection to ground occasionally due to vibration. Replaced with milk bottle plastic insulator-no problem for several more years till sold. HTH.

ben brown · Feb 23, 2010

i had one show up at my shop run sometime and sometime not i had over hauled it my self the guy came pick up motor took it home and installed it in tractor it stated right up run great for a few day . it was front dist. i had put a 12volt coil on it for some reason it split open . he went got a new one local place told him he needed a resister in the power line to cut the voltage it run some time and sometime not brough it to me i fought that thing for several day . he had installed the resister and had not mounted it to the frame. witch left it ungrounded, not sure why but a reister must be mount to frame to work proberly. mounted it still running like a dream, so check your resister if you have one make sure it is mounted.

Bob · Feb 23, 2010

"but a reister must be mount to frame to work proberly."

BULL "puckey"!

souNdguy · Feb 25, 2010

As an engineer for quite a while now, having had electronics education back since the late 80's.. I can tell you that a resistor does not need to be mounted to function.

it's a restive element that opposes current flow plain and simple. mounting it is a good idea to prevent the wires from being damaged due to vibration, and to keep it from shorting out to chassie.. but that's it.. electrically it only needs the incoming and outgoing wire connection.

google a resistor on wiki for easy to read 'small words' definition for the layman.

soundguy

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