Carburetor adjustment

[tree grower]

I just entered several searches, and came up with nothing, so will post. I have a 1956 Ford 800 (850) with a Marvel Schebler TSX 692 carb. This tractor has been running like a top for the 7 or 8 years I have had it About 2 months ago it wouldn't start, and discovered some distributor parts were broken. Replaced them, timed it, and it started right up. Problem is, it wouldn't stay running unless I kept the choke pulled halfway out. Tore the carb down, cleaned everything, put it back together, same problem. Tore the carb down, put in a full rebuild kit--everything except the float- same problem. No evidence of flaws in the float. In the rebuild process I set the float using a 4" long 1/4" bolt--easier than using a ruler. Main difficulty is that I cannot hold the choke and make adjustments to the carb at the same time. Tried shutting down, making adjustments, and restarting, but same problem.

Prior to this problem, the tractor would start by choking it for about two revolutions, let the choke in, it would fire, and was ready to work--no warm-up needed.

Any ideas out there in Ford land?

 

[JC-jetro]

Although I'm not familiar with your model, but can you see a possibility of vacuum leak ? if choke is compensating might indicate some leakage.

JC,

 

[jimmysisson]

I'm not familiar with that model, but your description goes like this: tractor doesn't start; repaired broken distributor; tractor starts then quits; tore down/rebuilt carb twice with no improvement. Are you sure of everything you did in the distributor? Since what you're doing to the carb isn't changing anything, and the distributor is what was the original problem. Am I missing something?
Jim

 

[Hooked_on_HP]

I agree with Jim as to the problem being in the distributor. When it is running with the choke out does it run normaly.
Bill

 

[tree grower]

You guys may be on to something. With the choke halfway out it seems to run OK, but can't really test it at various RPMs, and under load because I have to keep ahold of the choke. Maybe what I need to do is bring it in the shop, re-examine the distributor, and try again

 

[JC-jetro]

I think we're talking about two separate things here. Distributor, coil and spark plugs as part of ignition and the fuel and combustion air as part of carburettion.

manipulating of choke lever causes various amount of air to pass thru and venturi action pulls less or more fuel in. Running of the engine with choke half full can be a good clue that ignition is fine. The issue might be not getting adequate fuel in. If the carb gasket is leaking where is mounted to intake manifold then it might not allow enough suction to get the fuel in. half closed choke is helping there with the fuel. The jets might be okay with a rebuilt but I think there is still chance of partial blockage of fuel internally in the carburetor itself.

JC,

 

[mostly_gas]

I would go back to the distributor and check the free play at rotor. I never have had rotor and/or cap break without a good reason, and if something did not bump up against it, then something along the lines too much slop if upper dist. bearings may be affecting the spark getting to the plugs. Check point gap (0.025 ?) . And if that does not help, check for plugged exhaust by bypassing muffler. If carb were the main culprit you should see some improvement by now.

 

[tree grower]

The distributor problem was the rotor and dust cap. There is a clip which slips over the dist. shaft and snaps into place before the rotor goes on. I replaced that clip and the rotor. The dust cap has a notch molded into the edge to accept a corresponding boss from the dist cap. Somewhere in history the dust cap had been damaged so that notch was not crisp enough to hold the dist. cap. I replaced both the dust cap and dist. cap. Gapped the points, but did not replace them. Followed the service manual instructions for timing. I was able to get the motor to idle to set the timing correctly (5 deg. BTDC), but in gear it would bog down and stall quickly unless choked. That's when I started the saga of carb attacks.

 

[Soundguy]

Initial settings on the carb should be about 1.5 turns out on idle air screw, and main jet. main jet is in to lean, and idle jet is in to enrich.

needing choke to run could be:

clogged fuel system, more choke = more vacume

vacume leak, sea above.. .. leaks lean out the mix.. choke re-enriches it.

more rarely.. weak sparks.. rich mixes fire easier if you have weak sparks.



Having just been thru this on my ford 660.. I'd say keep looking at the carb.. mine was coroded on the inside with green crystals from this darn paint thinner and cologne the government is passing off as gas these days... I rebuilt my carb 2 times and never got it to run good without needing choke.. and that ain't the first time I've rebuilt a ford carb.. it was simply so pitted up ont he inside that notheing was sealing good. answer was a 280$ replacement MS style carb from CNH.. fired on the first rev as soon as I got it installed.

check al the free stuff.. then move on.. for sure won't hurt to check for weak sparks.. or a vac leak ( wd40 or a propane torch can help.. )

good luck.

soundguy

 

[Jerry/MT]

I just entered several searches, and came up with nothing, so will post. I have a 1956 Ford 800 (850) with a Marvel Schebler TSX 692 carb. This tractor has been running like a top for the 7 or 8 years I have had it About 2 months ago it wouldn't start, and discovered some distributor parts were broken. Replaced them, timed it, and it started right up. Problem is, it wouldn't stay running unless I kept the choke pulled halfway out. Tore the carb down, cleaned everything, put it back together, same problem. Tore the carb down, put in a full rebuild kit--everything except the float- same problem. No evidence of flaws in the float. In the rebuild process I set the float using a 4" long 1/4" bolt--easier than using a ruler. Main difficulty is that I cannot hold the choke and make adjustments to the carb at the same time. Tried shutting down, making adjustments, and restarting, but same problem.

Prior to this problem, the tractor would start by choking it for about two revolutions, let the choke in, it would fire, and was ready to work--no warm-up needed.

Any ideas out there in Ford land?

From your description of the problem, your mixture is too lean. But the problem can also be due to a weak spark. So check the spark by pulling the center wire out of the distributor cap, hold it near a good ground and try a start. You should have a FAT, BLUISH-WHITE SPARK, the color of lightning. If it redish or yelowish,or apindly blue that's not good. If that's the case, check the points and all the connections 'cuz there's probably something wrong in the primary ignition circuit.

If you have the requsite FAT, BLUISH-WHITE SPARK, then increase the mixture setting by an eighth of turn at a time an see if you can get it to run with out choking.

If you can't, then most likely you have an air leak around the metering section of the carb. Look for a loose connection or bad gasket at he carb to intake manifold connection, cracks or rust holes in the intake manifold, or a leaky intake manifold to cylinder head gasket. The throttle shaft can be worn and also cause this problem. A way to check for this is to CAREFULLY use an unlit propane torch around the aforementioned location while the engine is running.When you hit the spot where the leak is, the engine will speed up.