8n not running right. intermittent issue

[LD1]

Got one that has us stumped. This is dads 8n. IT was rebuilt completely 2 or 3 years ago, and has ran perfect since. About 150 hours.

Now we are having what I believe is a fuel issue, but cannot put a finger on it.

The tractor starts up and runs just perfect. But after a few minutes, it will start running really rough, like it is starving for fuel. No power, cough, choke, etc. That will last anywhere from 5 seconds to 30 seconds. Then clear up and run perfect again for anywhere from 1 minute to 5 minutes and the issue happens again.

The timing isnt consistant. Sometimes it will go along time and not have an issue. Others, it seems it no more than clears up and it does it again. Also, sometimes it does it and comes out of it instantly, othertimes it will linger for a good 30 seconds and sometimes even die as a result.

Messing with the load screw on the carb anywhere from 1 turn out to 3 turns out and anywhere inbetween does nothing to help. Even pulling on the choke does nothing to help while it is acting up.

Coil and ignition parts are all new. Plugs are new. Getting good fuel flow to carb. and screen in the elbow is clean. Carb has been apart 3 or 4 times now and cleaned and all passages cleared with air. Last time we put in a comprehensive rebuild kit that included new jets, seats, seals, and whatnot.

Still doing it. Cant figure it out. He is bout to throw down ~$160 and just buy a complete carb to see if the issue goes away. But worried about spending that kind of money to not fix the issue if it is something else.

Anyone got any ideas?

 

[ideburger]

I had similar symptoms last summer on my 861. Turned out to be a loose wire on the resistor going to the coil (was a 6 volt coil being used on a 12 volt conversion). It almost always started easily when cold and then it sounded like it was starving for fuel and sometimes died. I messed with the fuel lines and carb for days before finding the loose wire. Every time I would check the spark it was strong and blue. It was frustrating.

 

[LD1]

Thanks. Definataly worth a looking at all the ignition connections. Pretty sure there is no resistor though. Cause its still 6v and a 6v coil. Connections at the distributor and coil all look good, and coil is new. But certainly worth a look at the ignition switch, and I think there is a terminal block too. Havent checked those yet as we have been suspecting fuel being the issue.

 

[rsallen]

This happens at idle speed?

 

[PapaPerk]

Sounds like fuel starvation. Have you cleaned all fuel lines and sediment bowl? This includes removing the sediment bowl and checking little screen. I have issues with this area collecting particles and causing similar issues.

 

[LD1]

Yes, happes at idle, wot, under load, no load. None of that matters. It does it regardless and is random.

 

[rsallen]

If memory serves 8n has two different types of distributors.
Yours is?

Can you check the dwell easily enough to watch that along with the timing?
You changed the ignitions parts as a result of this problem or before it started giving problems?
I'd double check that ignition system before thinking about fuel starvation or a fuel dump.

 

[LD1]

Changed ignition parts as a result of the problem. And its a side mount 1951

 

[eddie48]

Because you have rebuilt the carb and because it cures itself quickly, I agree that it sounds more like an ignition problem than fuel. The two thing often act similarly. Perhaps a primary wire shorting out? Even a plug wire could be rubbing intermittantly and shorting.

 

[8N Ren]

To quote someone from another forum and Soundguy will know this, "Check yer weak-sister ignition switch!"
Those things are all garbage once the weather is on them for awhile.
While it's running wiggle some wires around, on the entire tractor, could be something simple like a loose wire maybe?
Are all the wire connections tight and rust free? Clean, Bright and tight as the saying goes.
For your fuel delivery, pull the sediment bulb, check and clean. Did someone along the way add in a secondary inline fuel filter?
If so yank that thing out and don't put it back, it will definitely screw with the gas flow.
Try pulling off the gas line at the carb and turn your bulb to on and let it flow into a jar for a good min or 2, you should have lots of gas there if there's no blockage from the tank down.
I've seen all of this happen and had the same problems you describe.
All your plugs gapped properly? .025
Plug wires snapped on tight?
That new coil hooked up correctly?
Points screwed down nice and snug with a .015 gap as well as clean and lubed?
Water in the gas tank?

I'm trying to think of anything and everything to check that won't cost you anything but sometime.
Post back with results.

 

[LD1]

I am thinking it is ignition related as most of you are advising. I have instructed dad to check out the switch and terminal block connections. Everything at the coil and beyond is good. Plug gap good. Points and gap good, etc.

No one added a inline filter. We can remove the inlet line off the carb and has great flow. There is no doubt there is some stuff floating around in the tank given its age. But I dont suspect that as we have good flow. AND, it dont matter if it is under load or at idle, it will act up. And even when acting up at idle, bad enough to kill the tractor, we can wait 5 minutes (more than enough time to get enough fuel to bowl even if partially blocked screen), and upon restart it act up just like when it died. and eventually it will smooth out and be fine for another 5 minutes or whatever.

 

[rsallen]

Fuel flow for carbs in my experience is rarely a problem unless a pump is required to get it from point a to point b.
Is that the case?

You've had the timing light on it while running poorly, was the light flash obviously breaking down at the same time the engine was? Or was it steady while the engine went to garbage?
Have you checked the (or does the dis. have) the advance weights on the dis. shaft?
The lobes on the dis. cam?
The play of the bearing sleeves for the dis. shaft?
Dwell would help with those questions.

 

[LD1]

Not sure I have a meter that checks dwell.

And no I havent had a timing light on it when it goes to crap. But I may try that.

And no pump either. Strictly a gravity feed system. Not sure on the advance weights, but I think they are in the distributor itself. We can check them out too and make sure they arent hanging up

 

[Soundguy]

deffinately check spark first. it's easy.

you can bypass and hot wire directly to coil and run and see if that prevents the issue.

 

[Soundguy]

Fuel flow for carbs in my experience is rarely a problem unless a pump is required to get it from point a to point b.
Is that the case?

.

no fuel pump on 8n

 

[LD1]

you can bypass and hot wire directly to coil and run and see if that prevents the issue.

That is what I told him to do. Would rule out the switch and terminal block.

Not sure if he has had a chance to try that or check out the connections yet or not.

 

[Soundguy]

when you find out some info, post back.

 

[rsallen]

Glad you're here Soundguy.
I'm learning more about 8n's then I thought I'd ever need to know. LOL

 

[LD1]

Glad you're here Soundguy.
I'm learning more about 8n's then I thought I'd ever need to know. LOL

Usually they aint difficult to work on.

 

[rsallen]

I don't doubt that.
I've just never had the dubious pleasure of putting hands on one.

I've just made a living working on 4 and 2 cycle engines for most of my life.
Another dubious pleasure.