Ford 8n Running Poorly

'49 8N · Oct 29, 2016

I ahve a '49 8N I have been bringing back from the dead. The prior owner did it no favors. I changed fluids, points, cap, rotor, plug wires, spark plugs, rebuilt the carb, new fuel line, new sediment bowl, cleaned the tank, among other things. First issue was that the distributor grounded out, and It wouldn't start. Fixed that and it started, but only wanted to run with the choke out a little. If I held the choke in the sweet spot, I could throttle up fine and it ran fine.

I drained the tank, took apart the carb, and checked filters after checking fuel flow. Flow seemed okay at first but then a little more of a trickle. Put everything back together again and it started right up and idled fine without the choke pulled, but when I try to throttle it up, it runs rough and will die. It now only likes idle and slightly above.

Nothing else has been changed between the two rounds.

I will check spark tomorrow, but what else? Why such a difference in the way it runs when nothing else changed?

Thanks

Bruce (VA) · Oct 29, 2016

" Flow seemed okay at first but then a little more of a trickle. "

Well, that's your problem.

Only open the gas valve 2 turns. Remove the bolt at the bottom of the carb & check for flow. The flow should fill a pint jar in under 2 minutes.

Post back w/ results.
75 Tips

'49 8N · Oct 29, 2016

(quoted from post at 15:50:03 10/29/16) " Flow seemed okay at first but then a little more of a trickle. "

Well, that's your problem.

The poor flow was the first round when it only ran with the choke out.

Only open the gas valve 2 turns. Remove the bolt at the bottom of the carb & check for flow. The flow should fill a pint jar in under 2 minutes.

Post back w/ results.
75 Tips

Den N Ms · Oct 29, 2016

49 8N,After checking the fuel flow,you may want to recheck the point gap as they could have slipped.Star washers placed under point screws will prevent them from slipping.

Royse · Oct 29, 2016

"Flow seemed okay at first but then a little more of a trickle."

Leave your gas cap loose and try testing flow again.
Or try running it with the cap loose/off.

Skip Burney · Oct 29, 2016

Check to see if you have a piece of trash in the high speed jet in the carb

Phil N · Oct 30, 2016

Fuel flow to carb is important but usually shows up when under a load. Check the attached photo. All those little passages
must be clean. With these cast iron carbs, lots of times some of those fine passages rust up and get restricted or blocked.
Completely disassemble the carb and be sure all passages are clear with a fine wire, spray carb cleaner, and compressed air
if you have it available.

Phil N · Oct 30, 2016

Check this diagram at following site
https://www.google.com/search?
q=marvel+schebler+carburetor+diagram&rlz=1C1NHXL_enUS707US707&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiU6-
WXtYLQAhWB7CYKHW04DsEQsAQIQQ&biw=1164&bih=537#imgrc=Zo1jS4AqrukqBM%3A

Skip Burney · Oct 30, 2016

Go to a welding supply house and ask for a torch tip cleaning set costs about 6 bucks and it has all of the really small cleaning wires that people use to clean cutting torches with and find the wire that will run through the small passages and jets. Just remember not to use to big of a cleaning wire you don't want to enlarge the passage just make sure it is open. I have a set that has done everything from antique airplane carbs to Corvettes.

'49 8N · Oct 30, 2016

(quoted from post at 04:30:37 10/30/16) Check this diagram at following site
https://www.google.com/search?
q=marvel+schebler+carburetor+diagram&rlz=1C1NHXL_enUS707US707&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiU6-
WXtYLQAhWB7CYKHW04DsEQsAQIQQ&biw=1164&bih=537#imgrc=Zo1jS4AqrukqBM%3A

Not sure what you were trying to show, I couldn't get the link to work. I did see the carb rebuild tips on Bruce's site and a number of diagrams. I will try round three on the carb. I will also check the points and spark just to rule them out.

Royse · Oct 30, 2016

(quoted from post at 20:11:39 10/30/16)

(quoted from post at 04:30:37 10/30/16) Check this diagram at following site
https://www.google.com/search?
q=marvel+schebler+carburetor+diagram&rlz=1C1NHXL_enUS707US707&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiU6-
WXtYLQAhWB7CYKHW04DsEQsAQIQQ&biw=1164&bih=537#imgrc=Zo1jS4AqrukqBM%3A

Click to expand...

Not sure what you were trying to show, I couldn't get the link to work. I did see the carb rebuild tips on Bruce's site and a number of diagrams. I will try round three on the carb. I will also check the points and spark just to rule them out.

Let's tackle one problem at a time.
You said you had insufficient fuel flow. Where are you checking that?

Bruce recommended that you check that flow through the drain
on the bottom of the carb with the sediment bowl valve open
two full turns. I suggested the same but with the gas cap loose.
Have you checked those things?

You will need at least two gallons of gas in the tank as two
turns opens the main valve but not the reserve that tends to
suck up dirt and rust off the bottom of the tank.

Checking spark is free and easy. I see no reason not to check it.

Tearing your carb apart for a third time when the first two
didn't do it doesn't make much sense to me.
Passages do plug up inside and they need to be thoroughly cleaned.
But those passages do not affect the fuel flow to the carb or through
it and out of the drain plug. Once you have good fuel flow
through it, if it doesn't work right, then worry about the inside.

Kenockee 8N · Oct 31, 2016

Also if you have rebuilt the carb, have you adjusted it properly?

I just recently rebuilt my carb and if I wouldn't have adjusted the carb according to the procedure that a couple of people have on here, I would have a tractor that ran like crap.
Now that it is adjusted properly, starting cold only takes half choke and 3 seconds of cranking. Hot starting is a blip of the starter and before I can pull my finger off the button, she's running.

'49 8N · Oct 31, 2016

Fuel flow to the carb is fine.

Fuel flow from the carb turns to a steady trickle, but definitely same flow.

I am going to thoroughly go through the carb and check everything out.

Royse · Oct 31, 2016

"Fuel flow to the carb is fine.

Fuel flow from the carb turns to a steady trickle, but definitely same flow."

I'm confused. If fuel flow to the carb is fine but fuel flow
from the carb turns to a trickle, how are they the same?
Do you get a pint in 2 minutes or close from the plug?
Does that flow change with the gas cap loose or off?

'49 8N · Oct 31, 2016

(quoted from post at 19:17:33 10/31/16) "Fuel flow to the carb is fine.

Fuel flow from the carb turns to a steady trickle, but definitely same flow."

I'm confused. If fuel flow to the carb is fine but fuel flow
from the carb turns to a trickle, how are they the same?
Do you get a pint in 2 minutes or close from the plug?
Does that flow change with the gas cap loose or off?

Sorry, fat fingered. Definitely not the same flow. I got at least double the fuel from the tank as opposed from the carb.

Cap or no cap, it's the same.

Bruce (VA) · Nov 1, 2016

Have you replaced the brass elbow screen? (see tip # 68)
75 Tips

Kenockee 8N · Nov 1, 2016

Maybe I'm looking at this wrong, but if the tractor will not idle without the choke pulled out some, that is more of a mixture issue than a volume issue. It does not require more than a trickle to idle or bring RPM's up without a load.

If pulling the choke out some makes it run smoother, how is this a fuel flow problem?

HFJ · Nov 1, 2016

kenockee, i had a similar issue this spring, had to manually play with the choke to keep it running. in my case, it absolutely turned out to be a fuel flow problem, my brand new sediment bowl's reserve pickup was already plugged to the point of only letting a trickle thru. poured in more gas to reach the main pickup, and the problem went away immediately and has not returned.

Kenockee 8N · Nov 1, 2016

HFJ

Thanks for the personal experience. I would have never guessed that.

'49 8N · Nov 2, 2016

(quoted from post at 05:50:41 11/01/16) Have you replaced the brass elbow screen? (see tip # 68)
75 Tips

The elbow and screen are new and clean.

Bruce (VA) · Nov 2, 2016

Good.

So where are we now?

After reading all of this again, it appears that you have a good steady strem of gas out of the bottom of the carb that will fill a pint jar under 2 minutes. Is that correcT?

You checked spark how? With a spark checker opened to 1/4"? In other words, do you have a spark that will jump 1/4"?

If not, then take care of that before you spend any more time on the carb.

If you need to pull the carb down again, follow the guidance from GB & JMOR: http://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=nboard&th=731405
75 Tips

'49 8N · Nov 2, 2016

(quoted from post at 15:30:44 11/02/16) Good.

So where are we now?

After reading all of this again, it appears that you have a good steady strem of gas out of the bottom of the carb that will fill a pint jar under 2 minutes. Is that correcT?

You checked spark how? With a spark checker opened to 1/4"? In other words, do you have a spark that will jump 1/4"?

If not, then take care of that before you spend any more time on the carb.

If you need to pull the carb down again, follow the guidance from GB & JMOR: http://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=nboard&th=731405
75 Tips

Bruce,

The gas flow from the tank was probably twice as much as from the base of the carb. I pulled the carb and I am going through everything again. I have not finished yet as life has gotten in the way. Hopefully tomorrow. I will update.

Ford 8n Running Poorly

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