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Engine starts after priming, then dies in 2-3 seconds

#1

S

Schef

I have a Craftsman with the 3.5hp Tecumseh engine.
The last time I used it was October 2017.
I broke it out this spring and the primer bulb was rotted out, so I replaced it.
After I fixed the bulb, it sputtered to life. I let it run for a couple minutes until the smoke cleared, and then shut it off.
The next time I started it, the mower ran for 2-3 seconds and then abruptly died. Time and again that happened.
I progressed through various repairs, including replacing the fuel line, then the carburetor and all the gas in the tank (and added a stabilizer), then the gas cap and spark plug.
It started noticeably easier after I replaced the gas cap, but it still abruptly dies in 2-3 seconds.
If I depress the primer bulb after it starts, the injections of gas keep it running, but it promptly dies if I stop depressing the primer bulb.
Any suggestions?


#2

cpurvis

cpurvis

Why did you replace the carburetor and what did you replace it with?

It sounds like you replaced a defective carburetor with another defective carburetor.


#3

R

Rivets

Give us the model and spec numbers for the engine. Also, did you purchase an OEM carb or just one off the Internet which they say will work for your engine? What was the part number for the new carb?


#4

S

Schef

cpurvis said:
Why did you replace the carburetor and what did you replace it with?

It sounds like you replaced a defective carburetor with another defective carburetor.
Click to expand...

Thanks for the reply, CPurvis. Frankly, the first place I went for a possible fix was YouTube, where the majority of clips diagnose problems like this as one as either a problem with a plugged or faulty carb, plugged gas cap, leaky or blocked gas line, or spark plug problem. Given that a new carb from Sears was only $26 and it was a relatively easy job, as well as the fact that replacing the carb seemed like the next logical step in trying to address the problem, I opted to go that route. I also elected to replace the whole carb, given the price, instead of it part-by-part to try to diagnose the problem.

Yeah, it's possible I replaced a defective carb with another defective one, though I obtained the replacement carburetor directly from Sears (the manufacturer of Craftsman).

Incidentally, during the process I learned they no longer make the carb for my mower. I looked up the carb they said was the replacement and it is for a snow blower...but given they manufactured it, I figured they should know which part was the correct replacement.


#5

S

Schef

Rivets said:
Give us the model and spec numbers for the engine. Also, did you purchase an OEM carb or just one off the Internet which they say will work for your engine? What was the part number for the new carb?]

Thanks, Rivets. The model number for the mower is 917.383280. Here are some of the specs:

HP: 3.5
Spark plug: .030 inch gap; Champion RJ19LM/Sears 33312/STD 361458 or 360950
Valve clearance: Intake .008 inch; Exhaust .008 inch
Solid state ignition air gap: .0125 inch
Engine: Craftsman model 143.424012
20" rear discharge

As I told CPurvis, I obtained the replacement carb from Sears. The part number for the carb is 632795A, which they said replaces the original carb (part number 632046A). I believe the replacement carb is OEM, but I have no way of knowing. I'm only taking Sears' word for it, but I can tell you that 632795A definitely wasn't designed specifically for that mower; only 1 of the 3 seals for the new carb they sent even aligned properly, though they appeared to create a solid seal...

All that being said, I don't necessarily believe that the new carb is not functioning properly, as the mower is still doing exactly what it did (start, then die) before I replaced the carburetor...
Click to expand...


#6

R

Rivets

With the engine model you gave us, you have a Tecumseh model TVS90-43504H. This is a 2-cycle engine, which changes a few things, as we were figuring a 4-cycle engine. That’s why I asked for numbers in post 3. If you did get a carb, with part number 632795A, it should be an adjustable carb. This means you have to adjust that carb according to the manual attached. Should have one high speed mixture adjustment, button of carb, one idle mixture adjustment, side of carb and one idle speed control, top of carb. Does this sound right?
https://www.mymowerparts.com/pdf/Tecumseh-Service-and-Repair-Manuals/TECUMSEH-SERVICE--REPAIR-MANUAL-2-CYCLE-TVS-TVXL-HXL-HSK-840-850-694988.pdf


#7

Cusser

Cusser

Schef said:
I obtained the replacement carburetor directly from Sears (the manufacturer of Craftsman).
Click to expand...

Actually, Sears did not manufacture ANY of these, they contracted out and put the Craftsman name on them.


#8

S

Schef

[Sears did not manufacture ANY of these, they contracted out and put the Craftsman name on them.

They don't even go so far as to have the CRAFTSMAN name on them.


#9

S

Schef

That’s why I asked for numbers in post 3. If you did get a carb, with part number 632795A, it should be an adjustable carb. This means you have to adjust that carb according to the manual attached. Should have one high speed mixture adjustment, button of carb, one idle mixture adjustment, side of carb and one idle speed control, top of carb. Does this sound right?

That makes sense. It didn't come with a manual, though your description does sound about right. I found the adjustment on the bottom of the bowl when I installed it, and adjusted that one.

I'll get the manual off the internet and take a look for the other adjustments...


#10

R

Rivets

Because we now know that it is a 2-cycle engine, not 4-cycle, it may not be the carb at all. 2 and 4 cycle engine needed to be troubleshooted in a totally different way. Things like PTO and magneto seals could be leaking. Muffler and muffler ports may be plugged. Compression ratios are different, requiring different sealing requirements. If we had know this earlier, we probably would have had you look in another direction first. Good luck.


#11

B

bertsmobile1

For starters take the needle right out of the bottom of the bowl to check you are getting a good fuel flow.
Once that has been established screw it back in till it seats lightly then back it off the number of turns specified in the manual.
Usually that is slightly rich.
However if the engine will not run, back it out a little further , around 1/6th of a turn at a time till it is 2 turns out past what the manual says.
If that is not good enough then strt at the same place and go the other way.

A lot of new parts for old EPA non compliant engines are now compliant so things like needles are longer with a finer thread so the number of turns off lightly seated can be nearly double what the manual said.

My rough as guts method of diagnosis is to spray carb cleaner down the carb throat.
If I can keep the engine running for a minute or so then the carb is elevated to prime suspect.

If not then the exhaust becomes number one as a blocked off exhaust will allow the engine to run a short while till it chokes the engine preventing fresh fuel getting in cause the burned cant get out.
Then there is a gummed up reed valve ( where fitted ) that will allow enough very rich fuel in to maintain running but not enough lean mix to support combustion.


#12

S

Schef

Rivets,

Upon closer inspection, the carb appears to have just one adjustment, which is on the bottom of the bowl. Then, there are adjustment screws for throttle control for both the high- and low-speed settings. That appears to be it; according to the Tecumseh manual, it appears as if this carb is their Series 9 carburetor, which has an idle discharge port/fixed idle system.

First, I got the adjustment on the bottom of the bowl in the ballpark. Then, I adjusted both of the throttle screws, so it ran consistently at both speeds. Then, I went back to the nut on the bottom of the bowl and fine-tuned that. Now it purrs like a kitten at both speed settings.

Thank you so much for your help and input. I'm new to small engine repair and am really glad it wasn't something more complex. Take care~


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