2 things come to mind since apparently you have replaced the carb . Does it wet the spark plug ? if not then fuel filter or line is restricted . Next check for spark as soon as it dies , it may have a bad coil . Last but not least , sometimes just the gas cap if vented may be restricted give it a check or simply remove when it begins to die and see if there is any difference .

When I get it started and keep pressing the primer bulb, it stays running so it's a problem with not getting enough gas. The confusing thing is, I've replaced everything I can think of.

There is no fuel filter. It's a direct line from the gas tank to the carb. Gas cap isn't the problem either because I've removed it before starting it and it still dies.

As for the coil, if it were bad, then it wouldn't start to begin with, so I don't think that's it either.

If you manually pressing the primer and the engine continues to run then fuel starvation "IS" your problem . Even though you have apparently replaced the carb fouling with ethanol fuel for any extended period over 2- 3 weeks can cause a problem . Concentrated fuel clean 2 ounces within fresh fuel may help . As for the coil , often they fail when the engine is up to temp . Once cold the engine will start but falter within a few minutes . I think you have gum or residue within you fuel circuits since you have pretty well ruled every thing else out . Let us know how you make out .

Thanks guys. I will take your suggestions and follow them through. Saxman1, there is no bolt on this carb in the way you are referring to. Do an Ebay search for 640020 and you will see my carb.

Thanks guys. I will take your suggestions and follow them through. Saxman1, there is no bolt on this carb in the way you are referring to. Do an Ebay search for 640020 and you will see my carb.

i have the 640020 carb and cannot start. i have put in a new spark plug, air filter, fuel line and plastic bowl and have fresh gas. i have cleaned fuel tank and replaced the gas cap. i have not removed the extruded metal part of the carb but have shot carb cleaner and air into it i can get it to start but immediately quits i am looking for advice.it is a 1999 sears craftsman 6.75 lawn mower

I've never seen a carb like the 640020 you have.
Lokking at pictures from Ebay listings it looks very cheaply made.

Did you buy the new replacement carb on Ebay and install it yourself? Even new carbs are sometimes defective.

The bowl is secured by a clip rather than the conventional bolt. I suspect your problem may possibly be the float being out of adjustment, or sticking, and not permitting enough fiel to enter.

http://www.ebay.com/itm/Tecumseh-Carburetor-Part-640020B-New-/150469862906?pt=LH_DefaultDomain_0amp;hash=item2308b3e5fa#ht_331wt_677

I would remove the carb intact from the mower and check the float settings. Removing the bowl with the mower in the upright position will cause the float to fall out. You will need to find the specs for the carb model to learn what the correct float setting is.

Follow Up:
Sorry for the two typo's on my previous post, lokking instead of LOOKING, and fiel instead of FUEL. Another brain fart on my part.

The Ebay link also doesn't work. Below are links that shows the carb, hopefully they will work.

New Carb (640020B)
http://www.ebay.com/itm/Tecumseh-Carburetor-Part-640020B-New-/150469862906?pt=LH_DefaultDomain_0amp;hash=item2308b3e5fa#ht_331wt_677

Used Carb (640020B)
http://www.ebay.com/itm/TECUMSEH-VLV60-CARBURETOR-640020B-/160604814350?pt=LH_DefaultDomain_0amp;hash=item2564cafc0e#ht_834wt_915

I was wrong, the float needle CANNOT be adjusted on this carb. Below is a link for some helpful information on rebuilding the carb.

http://outdoorpowerinfo.com/repairs/tecumseh_vector_carb.asp

Thank the environmentalists.

I just had the same issue. It resulted in buying a new carburetor. Replaced everything in the mower before doing so. As soon as the new carburetor was installed, the mower ran perfectly. For one use. I didn't run the tank dry.

Two weeks later when I attempted to use it again, it was back to 5 seconds and dead. Put some seafoam in the tank--still 5 seconds and dead. Removed, and cleaned the (brand new, used only once) carburetor, which had "gunk" from its ONE use. Thanks ethanol.

From now on, will put only enough gas in the tank to mow once, and will make sure to run the engine dry each time. Yuck.

I have the same problem with mine. Craftsman mower w/tecumseh 6.75 hp Vector engine.Did the same as the others on here. New sparkplug, air filter, bottom half of the carb, new primer bulb. Started right up and seemed fine. Ran it for about a minute. Went back out about an hour later. Back to the same problem. Starts for a few seconds then dies. Did anyone find the answer to this problem?
Thanks

Well, I think i have the answer! Find a deep pond, or lake, and toss the whole mess into it! Then go buy a new mower!

Thoe carbs can (maybe,sometimes, infrequently,) can be rebuilt, by buying the whole new bottom part. I bought one. My success was very limited, as i tossed the whole machine on the scrap pile, and gave up!
I don't know how much the factory paid the goon who designed that carburetor, but they should have hung him by his heels, for that fiasco! Evidently, the factory thought they had a winner, in that new carb.

ya I have a new husqvarna AWD on order. It should be here next friday. But my father-in law needs a mower and I was hoping to give him this one. It wasn't used much and I changed the oil and air filter frequently. It should be good for a long time. I noticed the inside of the fuel line looks like it is deteriorating. I wonder if bits of rubber are getting into the seat or jet. I am going to flush the carb and install a new fuel line. I hope that does it. I asked at a shop that repairs small engines. They have at least 20 lawn mowers lined up to work on at any given time. He said that if people would put seafoam in all the fuel used in there mowers he would be out of a job. He said One ounce per gallon in all the fuel used. He pulls carbs apart all the time with goo in all the small parts. I will definitely do this in the new husqvarna. Not sure if this would have helped the tecumseh. But there was goo in the old bowl.

it may seem obvious.....but.....the carburetor intake flap must be opened for air....oxygen....to flow.....i virtually banged my head doing the same thing......third time is always a charm...i noticed the positioning....or lack of....adjusted...and....Voila!....started right up.

it may seem obvious.....but.....the carburetor intake flap must be opened for air....oxygen....to flow.....i virtually banged my head doing the same thing......third time is always a charm...i noticed the positioning....or lack of....adjusted...and....Voila!....started right up.

I wished that Tecumseh still made the LEV120 engine. I have one on a 2004 Lawnboy that it still running great. I love how they have an oil pump.

Your problem sounds as if the fuel filter screen in the fuel tank may be clogged and not allowing enough fuel to reach the carb.

Otherwise sounds like water in the float bowl or one of the carbs jets. But you stated that you installed a new carb.

If you lawnmower just stops, I bet the little jet is clogged. Easy and fast to fix.

http://youtu.be/NbdY05yhTEc

Here is a link that might be useful: Link to Show How to Clean

OK, I found and fixed my lawn mower. It's the carburetor. The solenoid that opens to let gas into the carburetor is the problem. The little rubber "seat" came off the solenoid plunger and gets stuck at the gas intake of the carburetor. This allowed a little gas in to the carb but when I throttl up doesn't allow enough gas into carb.

Simple fix. I cleaned surfaces an crazy clued the rubber tip to the end of the plunger of the carburetor.

IT RUNS LIKE A CHAMP.

I joined only to say thanks to 1saxman over 5 years later. Your suggestion was my fix. Thank you, wherever you are today.

To preface: I have an old Toro with a Tecumseh engine which has never really given me any grief. I pulled it out for the first time this spring and brushed out the air filter (pbly shd have replaced it) and checked the oil. The latter seemed a little low and I had a quart with a bit left in it. So I dumped it in, checking a few times. At the end it looked barely high.

I mowed for a while (15 min) with success and it suddenly died. I could restart the motor but it would die after ~10 seconds.

Googling suggested the carburetor, but I did some more research (especially on youtube) and came across a video (it was like the sixth one I watched) that laid the blame for this failure mode on too much oil.

So I checked my oil again and it was way too high. I probably hadn't let it settle down the tube when I was checking originally. I dumped all the old oil out and refilled with new. Fresh oil is kinda hard to see on the dipstick so take your time.

Then I finished mowing my yard.

After reading all comments and getting nowhere I finally took a closer look at the carburetor. Well if you are mower is anything like mine there's a brass bolt that holds to float Bowl on. Now if you take that brass bolt off and look at it very carefully you'll see an orifice on the side and one of the top that was the problem with my lawn mower.