WC carburetor problems
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=133611
Printed Date: 14 Jun 2025 at 9:39am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: WC carburetor problems
Posted By: 7060
Subject: WC carburetor problems
Date Posted: 10 Jan 2017 at 10:05am
| My 1935 WC is causing problems again. A year ago I put a rebuilt carburetor (7078) on it and it would only run on full choke. I called the place I got it and they send me another one and that fixed it. I ran it on a water pump all summer irrigating sweet corn. Left it set for a few months and wouldn't start. Turned out the tip of the spark plugs were rusty and wasn't getting fire. But now it's back to running only full choke. I bought a carb kit and have had it apart twice now cleaning it but nothing looked to be in the jets. I can screw the bottom screw all the way in and it will start to die but. O matter how far out I screw it it won't run with the shutter open. I've checked for manifold leaks with starting fluid and never found anything. It's almost as though it just doesn't have enough suck to pull the gas out. I've never messed with the timing and don't think that could be it, but any ideas? |
Replies:
Posted By: Gerald J.
Date Posted: 10 Jan 2017 at 10:20am
|
Fuel starvation can come from several causes, sometimes more than one at a time. Varnish in the fuel line. Varnish or dirt in the screen sometimes part of the inlet elbow at the carburetor. Sticking float, sticking float needle. Wrong gas tank cap, not venting. Junk in the gas tank sticking to the screen at the inlet of the sediment bowl. Sediment bowl screen plugged with varnish or dirt. Wrong inline filter. Those easy to find have a significant pressure drop, way more than the available pressure in the WC gravity fuel flow system. The standard test for fuel supply starvation is to remove the drain plug from the float bowl and watch for a steady stream at least the size of a pencil for much longer than it takes just to drain the float bowl. By replacing the drain plug with a hose barb fitting and a piece of clear hose bent to stick up above the carburetor you can determine the fuel level in the float bowl. If it takes full choke to run the gas level in the float bowl is most likely very low. Gerald J. |
Posted By: 7060
Date Posted: 10 Jan 2017 at 1:29pm
| I pulled the plug out last night and it had a steady stream coming out. Then I pulled the adjustment needle out of the bottom and had a steady stream of gas there. I tweaked the float to where it shuts off higher and no change. I will try the clear hose thing and see how high it's getting. I can't imagine why it would have ran fine and now all of a sudden it's not. Almost like it would be dirt in it, but i can't find anything. |
Posted By: LeonR2013
Date Posted: 10 Jan 2017 at 6:59pm
| Have you checked the quality of your gas? There is a product called START that I get at Orschlen's that you put in the gas and if it is varnish or the like it will take it out in an hour or so. I use it on lawn mowers and it works great. Might save a carb. tear down. |
Posted By: oldways
Date Posted: 10 Jan 2017 at 11:16pm
|
Man I hope you can figure it out. I had the same deal with my 37 WC. The tractor ran great on the zenith and when I restored the tractor I rebuilt the carb. Never could get the thing to run without hold my hand over it and almost shutting the air completely off. I dipped the carb and cleaned and cleaned and rebuilt and got Dad to try it had an old caerb guy look at it. Never could get it right. Wound up taking a Marvel off a junk tractor that had sat outside for years off rebuilding and using it. ------------- 1 Corinthians 1:18 1969-190xt-III. 1966 190xt gas. 1966 190xt Cab. 1948-G. 1937-WC unstyled. 1950-B. 1951-CA. 1966-D17-IV |
Posted By: KenBWisc
Date Posted: 11 Jan 2017 at 9:16am
|
I had the same issue with my "rebuilt" 7078 but it would also overflow fuel! Took it to a Model A Ford carb man who pointed out the two (as I recall) interior air tubes that are an integral part of the carb casting. We used carb cleaner to confirm these passages were open. I was then fortunate to find a NOS main needle valve which seemed to be the cure. I hear there is an outside chance the seat for the main value may need replacement or smoothing. ------------- '34 WC #629, '49 G, '49 B, '49 WD, '62 D-19, '38 All Crop 60 and still hunting! |
Posted By: 7060
Date Posted: 11 Jan 2017 at 10:01am
| Now that you mention that my carb did drip occasionally before. Maybe the only reason it ran before was the float was sticking. I disassembled the whole carb and sprayed ether and air through all the passages. Cleaned all the brass parts using a strand of copper wire and blew through them. I'm going to try raising the float again and see what happens. I read somewhere about adding a new Venturi with more suck? I did drain all of the old gas out and put a gallon of new in. Thought about dumping some carb cleaner in the tank and running it on choke until maybe it straightened out. |
Posted By: tadams(OH)
Date Posted: 11 Jan 2017 at 2:18pm
| Put some fuel additive in it, I have had fuel additive clear out a carb that wouldn't start and leave it set over night with additive in the fuel and it started the next day. This cheap gas they are selling now draws water when it sets. I don't use gas in any of my tractors without additive. |
Posted By: Ted J
Date Posted: 12 Jan 2017 at 11:31am
------------- "Allis-Express" 19?? WC / 1941 C / 1952 CA / 1956 WD45 / 1957 WD45 / 1958 D-17 |
tadams(OH) wrote:Posted By: LeonR2013
Date Posted: 12 Jan 2017 at 3:24pm
| I suspect the venturi. If they're loose or cracked they can cause a problem. |