8N rough running

[cathead]

I lean towards fuel too. One thing one can use when checking for air leaks is a small propane tank.
You crack it open and wand it over hoses connections to diagnose ill fitting lines.

 

[Barncat]

Quit replacing parts and check things one at a time.
Firing order
Fuel flow- pull plug out of bottom of carb, should fill pint jar in less than minute
Adjustable gap spark tester, 1/4” gap, should have good blue spark
Those all good probably your new Chinese carb is junk

 

[Gnpenning]

^^^.

Every new part you add with out testing first can mask or increase your problems. New doesn't mean good in todays parts world. Many examples of multiple bad parts in a row happening.

Had something similar with my 66 bronco. Simple rebuild and runs like a champ now. A carb that simple I would not put a new one on unless the old one has major damage. I had small black pieces that some how made it through the new fuel filter in the carb bowl. Ethanol fuel is hard on old fuel lines. Upgraded all the fuel.

After doing what barncat and others suggested you can also use a ohm meter to check the plug wires. A cheap $15 multimeter will do everything you need if you don't already have one.

You can use a gray TF module from a early 90s Ford which will give you much better spark and can be wired in with your point system. Not sure if it will work with a 6v system if you haven't converted to 12v yet.

 

[tq60]

TROUBLESHOOT WHEN ACTING UP!

Most things stay broken, so given it runs smooth then acts up points to something variable.

When it is running rough is when you need to test things.

Carry a spark plug.

Pull choke, that tests fuel.

What does it sound like?

Shut off and pull one of the plug wires at a plug and attach to the spare, set it on the engine and start it.

Poor or hot spark?

Does this have a resistor between coil and key?

You are shotgunning and going nowhere, checking things for function.

Sent from my SM-G781V using Tapatalk

 

[Jake M]

I have a beautiful restored 8N tractor. It started running rough last year. Over time, I have replaced EVERYTHING with no success. It will idle fine for a minute, then almost die, then take off again. Can not drive it around, it will stall and die.

So it's not constant.... You can rule out a lot by that. Compression, head gaskets, worn out rings, vacuum leaks, stuck main bearings, plugged radiators, and leaky tires don't recover and "take off again". They "might" recover to some degree with heat soak/cold soak situations, but they don't come and go in steady state operation.

I though it was fuel and replaced a rusty gas tank - no help. BTW, I bought a Chinese one an it was slightly larger than original. Had an AWFUL time shoe horning it in. Then installed a new carb - no help.

True for anything, but ESPECIALLY for low production repro parts... New from china doesn't mean it's going to work right out of the box. They often introduce more troubles than they solve, even if the original was faulty. They are best used as a last resort, AFTER the problem has been thoroughly and acccurately proven.....

Decades ago my dad told me its always the ignition. So even though the parts were not that old I put in (over time and many trials) entire new distributor, new coil, new wires, new plugs. Its ALL new still no joy. Timing is spot on 4 degrees BTDC. No dwell meter but point gap is 20 thou. Visually can see plenty of contact and break time.

Decades ago, depending on how many, he might have been right. Times have changed. Ethanol or non-ethanol, gasoline has changed. And by "changed", I mean it has changed A LOT in the last 30 years. Gasoline (not to be confused with ethanol issues), Gasoline is not capable of being left in open vented systems without treatment, and it leaves deposits that plug up fuel systems. Hold on to your Dad's advice, these old ignition systems are not nearly as reliable and trouble free as today's systems are, but the fuel system is also highly suspect.

Double checked compression, its good and does not leak down so the rings and valves are good.

I thought last night, just maybe there's an intake air leak. But I do not know how to check for this. Ideas?

Or any other suggestions. I am about to give up and scrap it out.

Any of the parts you have recently replaced, if you've still got the ones that were present on the tractor BEFORE the issue started.... Put them back. I'm not joking. Chinese repop stuff is really that bad. It's worth doing.

After that, diagnosing an issue doesn't start with guesses at parts, you've got to find the problem. Nearly dying and suddenly recovering (in this kind of application), that just screams fuel. Specifically fuel supply.

You said that this will idle for a minute, almost die, then take off again- And you said it's undrivable. Does it drive for a bit and die, then recover, or does it just not have enough to drive at all? I'm assuming you could probably get it rolling in between the "almost dies", but under any load it just shuts off?

I'd want to know how much fuel was being supplied to the carburetor. Take the fuel line loose at the carburetor, and into a bucket, open the petcock, and see how fast it runs out. The pint in a minute mentioned in another post sounds very reasonable. Option B is to set a gas can on top of the hood (carefully.... You said it's restored.....). Put a clean rubber hose into said gas can, start a siphon from it, attach it to the carburetor, and while steadying the can, start the tractor? Does that help?

Ignition is another thing that can do intermittent things, but those are either random (not cyclic) having to do with loose connections, or they're related to heat, which means good running and then dead once they've heat soaked. And good again once it's cooled off.

 

[Deleted member 69715]

What's been said is all good advice. I'll add my 2 cents.
Chinese parts. Parts you can't buy new. Buy off ebay and find out majority of "re-pop" parts aren't worth the box they came in.
If this problem started with the hot weather, could you be experiencing interminent (spl?) vapor lock? An old trick is to put a couple of spring type wooden clothespins on your metal fuel line. Acts as a heat sink. It works.
Your ignition capacitor. Probably not the problem, but if it's been replaced look there. Anymore they're all chinese made. Like the carburetors from china they're junk too.

 

[Karl_T]

Sorry to not get back to my own thread. I grow'n'sell apples for a living at a roadside market. What was I thinking posting this on a fall saturday morning?

General agreement that its got to be fuel. I thought I had beat this horse into the ground but must have missed something.

At this point the old carb is back on the tractor - chinese one looked like a POS to me. I am going to yank a one gallon gas tank off an old gravelly and try a complete separate fuel supply. My test for fuel flow had been just let it run disconnected at the carb, looked good to me.. I like the measure to a jar idea at the bottom of the carb.

I am pretty sure that there is plenty of fuel flow but these actions should double check it. I will try to get this done in a couple a days or less and report back.

 

[Barncat]

As previously mentioned the ballast resistor is good to check, otherwise it seems unlikely anything else in the ignition circuit would get heat saturated so quickly to cause your issues, since it sounds as if they crop up quickly after starting. I would still take the plug out of the carb bottom and check for a pint in less than a minute. That will rule out most fuel delivery issues, including a stuck needle, using the reserve of the fuel tank, tank vent, (was new tank vented) or mis-adjusted floats.

 

[Ulma Doctor]

one thing i have not seen mentioned is the springs for the flyweights inside the distributor for the timing advance.
just a thought

 

[Karl_T]

OK, did a quickie measurement this AM. I get .8 lb./min out fuel line with screen. see pic. my conclusion is good flow.

I get .15 lb./min out of bottom of carb. That means carb is bad?? I am NOT good enough to go inside a carb. A man should know his limits. Try to find a carb repair guy? The Chinese one I bought is worse than this 80 year old unit.