carb problem

General help and support for your Lindeman through 2010 John Deere crawler
mnfordtech
40C crawler
40C crawler
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Location: Northern Minnesota

carb problem

Post by mnfordtech » Sun Oct 21, 2018 2:48 pm

Hoping someone can shed some light on my problem. Recently bought an older 440 crawler and the guy I bought it from said it has had a carb problem for years - namely it will only run with any kind of power if you keep it on at least 1/2 choke. Since I'm a retired auto mechanic with a lot of carb experience I thought this would be an easy fix. After all, how hard can it be to set up a simple carb as this. Well, it has me stumped. I've taken this thing apart and cleaned/inspected it at least a half dozen times. Tried to back out the power needle until it is just about ready to fall out but I can't seem to get enough fuel under load. It will idle just fine with no choke, but if you advance the throttle much past 1/4 throttle it will die unless you give it some choke. I'm to the point of ordering a rebuilt carb but I thought that if anyone here with more experience with these carbs can shed some light on why this thing is acting this way, maybe I could still fix the one I have.

fundytides
440 crawler
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Re: carb problem

Post by fundytides » Sun Oct 21, 2018 4:49 pm

Certainly sounds like a fuel flow problem. You have probably covered this but the first thing I would check is the flow through the fuel line. Your problem is a typical symptom of a plugged filter or partially obstructed fuel line. I'm not familiar with the 440 but if it has gravity feed make sure it doesn't have an aftermarket in-line filter. These filters will play havoc with a gravity flow system as there is not enough pressure to provide enough volume of fuel. Good luck!
have 40c 4 roller crawler, 1927 Ford T Touring car, 1931 Ford A Roadster, 1951 Standard Vanguard Saloon. Never a dull moment!

mnfordtech
40C crawler
40C crawler
Posts: 21
Joined: Sun Oct 21, 2018 9:57 am
Location: Northern Minnesota

Re: carb problem

Post by mnfordtech » Sun Oct 21, 2018 5:08 pm

Thanks, but I've checked that. Even pulled the fuel inlet elbow off of the carb to check the strainer - clean as a whistle. No additional filter in line. It's definetly something in the carb ( I think ). Open to other suggestions. :)

B Town
1010 crawler
1010 crawler
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Location: Western Iowa

Re: carb problem

Post by B Town » Sun Oct 21, 2018 5:43 pm

I risk be over-simple, but is the air cleaner clear of obstructions? I know you said it was running, but it was unclear to me if the air cleaner was "hooked up". Is the governor functioning properly?

I have much more experience with Waterloo two-cylinder carbs. We actually use small drill bits about 4-5" long to hand drill out fuel-air passages. Are there super small passages that could be blocked?

Best regards, Bruce

mnfordtech
40C crawler
40C crawler
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Joined: Sun Oct 21, 2018 9:57 am
Location: Northern Minnesota

Re: carb problem

Post by mnfordtech » Sun Oct 21, 2018 8:56 pm

Air cleaner is hooked up, clean and functioning properly. I've taken apart the carb several times and blew out every passage in it. Thanks for the replies but so far everything mentioned has been checked or done.

mnfordtech
40C crawler
40C crawler
Posts: 21
Joined: Sun Oct 21, 2018 9:57 am
Location: Northern Minnesota

Re: carb problem

Post by mnfordtech » Sun Oct 21, 2018 8:57 pm

And the governor is working as it should.

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gregjo1948
350 crawler
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Re: carb problem

Post by gregjo1948 » Mon Oct 22, 2018 4:04 am

A plugged air filter would do the same thing as chocking it. Have you checked the compression? Low compression is also low vacuum. You need vacuum to draw the air/fuel mixture up through the carb and manifold to get into the cylinders. Perhaps, if it has low vacuum, by chocking, it's forcing inflowing air to be pulled with more force and drawing the air/fuel mixture into the cylinders. Basing this idea on an air hose or water hose being reduced down in diameter and seeing the pressure results. Vacuum works the same except instead of pushing it's pulling.
JD 350B diesel w/rops & 6way blade, Case 580B Loader/backhoe, Farmall 504 highcrop, International 404 utility, International 284 diesel w/belly mower, 1972 Ford F600 dump truck, Galion 3-5 roller

mnfordtech
40C crawler
40C crawler
Posts: 21
Joined: Sun Oct 21, 2018 9:57 am
Location: Northern Minnesota

Re: carb problem

Post by mnfordtech » Mon Oct 22, 2018 5:20 am

Have not checked compression. I don't think that is the problem because it idles so well. If the compression was low I would think the idle would not be as good as it is. I will check it just to be sure.

B Town
1010 crawler
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Location: Western Iowa

Re: carb problem

Post by B Town » Mon Oct 22, 2018 5:41 am

If the fuel and carb system are up to spec as you have discussed, I would start to troubleshoot the ignition. It has been my experience that many a problem blamed on the carb were actually ignition system problems, condenser, points, etc..

I think the compression test is a great idea, also.

I agree with the air cleaner blockage causing a fuel rich situation. But when focused on a problem that doesn't seem to be getting better with your intervention it is time to step back and take a wider POV.

Best regards, Bruce

mnfordtech
40C crawler
40C crawler
Posts: 21
Joined: Sun Oct 21, 2018 9:57 am
Location: Northern Minnesota

Re: carb problem

Post by mnfordtech » Mon Oct 22, 2018 6:50 am

I was wondering about an ignition problem. I have cleaned and set the points, but do you think a coil going south could cause these symptoms? It has new plugs.

B Town
1010 crawler
1010 crawler
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Location: Western Iowa

Re: carb problem

Post by B Town » Mon Oct 22, 2018 7:12 am

I have had condensers do weird stuff as well. My JD 630 had a lean issue with throttle, lots of troubleshooting later, I changed the condenser with an NOS (USA made) one. No more issues. Maybe it can store a charge at slow idle but no faster ??

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Lavoy
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Re: carb problem

Post by Lavoy » Mon Oct 22, 2018 8:23 am

Have you completely disassembled the carb? Removed main nozzle, all the jets, etc? Something is plugged it seems like.
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mnfordtech
40C crawler
40C crawler
Posts: 21
Joined: Sun Oct 21, 2018 9:57 am
Location: Northern Minnesota

Re: carb problem

Post by mnfordtech » Mon Oct 22, 2018 8:55 am

Yes, I have completely disassembled it several times. That is what I'm thinking, something is plugged somewhere but I just can't see it or find it.

B Town
1010 crawler
1010 crawler
Posts: 314
Joined: Fri Dec 11, 2015 7:04 pm
Location: Western Iowa

Re: carb problem

Post by B Town » Mon Oct 22, 2018 8:58 am

? To Lavoy. Do the Dubuque carbs have passages that can be stubborn and need cleaned with a drill bit(by hand) like the Waterloo carbs can be known. Bruce

original possum
440 crawler
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Re: carb problem

Post by original possum » Mon Oct 22, 2018 9:07 am

Run it up to where it runs poorly (while reasonably cool) and hose down the entire intake with WD40 (everything above carburetor), looking for an intake leak bigger than you would have with throttle shaft wear alone.
Early 40C w/Yakima toolbar and homebuilt ripper: 350 w/6-way

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