craftsman 4 stroke weedeater, 31679191 hard to start

M

Mark H_NO

Well-Known Member
I think that's the model #. The 7 is almost gone.

It takes me a bunch of pulls to get this started. The label says full choke, prime, pull with throttle open. I get better results no throttle, 1/2 choke, but it still takes a bunch of pulls to start. Once started, and with a minute to warm up, it runs fine and works well.

Too much prime? It never seems to fire up on first pull after prime. It's 4 stroke, so some pulls don't hiit compression/ignition, adding extra pulls.

Clean the carb? I did a quick clean when I got it, removed carb, blew carb cleaner through passages, but didn't probe anything. I did replace the pickup/filter and fuel lines.
 
is it gravity fed into a carb bowl, or does the carb have a passage for forcing fuel transfer? If it does not have a carb bowl then it has some sort of fuel pumping mechanism built in. If that is the case, then that has likely failed. The gaskets warp and flaps cease to seal each pulse. Once you get it going it pulls fuel well enough to run, but not well enough to start as designed.
 
sgkent said:
is it gravity fed into a carb bowl, or does the carb have a passage for forcing fuel transfer? If it does not have a carb bowl then it has some sort of fuel pumping mechanism built in. If that is the case, then that has likely failed. The gaskets warp and flaps cease to seal each pulse. Once you get it going it pulls fuel well enough to run, but not well enough to start as designed.
Click to expand...
Does this look like it has a fuel bowl?
1776906834582.png
 
Here’s an excerpt from the owners manual. The machine is not designed to start on the first pull. I left out the figures. Choke position 1 is full choke, 2 is half choke and 3 is no choke.

WARNING:
Operate this unit only in a well-ventilated
outdoor area. Carbon monoxide exhaust fumes can be
lethal in a confined area.
WARNING:
Avoid accidental starting. Make sure you
are in the starting position when pulling the starter rope
(Fig. 8). To avoid serious injury, the operator and unit must
be in a stable position while starting.
STARTING INSTRUCTIONS
1. Check the oil level in the crankcase. Refer to
Checking the Oil Level.
2. Fill the fuel tank with fresh, clean unleaded gasoline.
Refer to Fueling the Unit.
NOTE: There is no need to turn the unit on. The On/Off
Stop Control is in the ON ( I ) position at all
times.
3. Fully press and release the primer bulb 10 times,
slowly. Some amount of fuel should be visible in
the primer bulb and fuel lines (Fig. 7). If you can't
see fuel in the bulb, press and release the bulb as
many times as it takes before you can see fuel in it.
COLD UNIT START
4. Place the choke lever in Position 1 (Fig. 7).
5. Crouch in the starting position (Fig. 8). While
squeezing the throttle control, pull the starter rope
out with a slow and steady motion 5 times.
6. Place the choke lever in Position 2 (Fig. 7).
7. While squeezing the throttle control, pull the starter
rope out with a slow and steady motion 1 to 4 times
to start the engine.
8. Keep the throttle squeezed and allow the engine to
warm up for 15 to 30 seconds.
9. Place the choke lever in Position 3 (Fig. 7). The unit
is ready for use
 
I'll look at it tomorrow. I don't think it's gravity fed, as the tank is under the engine, which is the norm for weed eaters, as far as I know.
 
Thanks, that is essentially how I've been starting it, but without squeezing throttle. If I give it throttle, it does not start. When it starts, if I add throttle, it dies. After a little warmup, I put choke in position 3 and I can give it throttle, and it runs fine.
 
the carb in the image posted by Star Tech has a flap that opens to let fuel in and closes as the piston cycles so the fuel can'trun back to the tank. It acts as a fuel pump. That flap loses its abilty to seal as it ages. The flap curls. If it is that carb, it will run really crappy until it is warm and at full speed. Acceleration will lag and have a terrible flat spot. Cold idle will be almost non-existant and it will be really finicky. I used to keep a couple carb kits around for it, and also a spare carb I could just swap out if a couple minutes. After 2 - 3 years it would happen again. Avoiding fuels with ethanol, and running it dry between uses would extend it's life considerably. Nothing else to add really. Someone either believes me or not. I've had that carb in maybe four or five motors and they all did it. There are Zama and Walbro variants, probably more. Good luck.
 
316.791910 [41BD546G799]

Clean the carb? I did a quick clean when I got it
Click to expand...
Okay the first thing you mention is that this an used 4 cycle trimmer which is strike one. These AC3 and AC4 versions are known to have cylinder problems due the way they oil themselves. You are lucky if these last more than 2 years. If it is cylinder problem basically you just go and buy another hunk of junk as no internal parts are available.

The only 4 cycle handheld that worth the money is a Stihl 4 mix version. Now Matika does make a decent 4 cycle too.

Also the valves has to be adjusted every so often to .003-.006".

As for the carb it is a Ruixing Zama clone diaphragm carburetor. These are at least two gasket and diaphragm kits and I have see these gaskets and diaphragms to know which kit it uses.

As for priming you only have to prime until the primer bulb starts to fill and not all 10 X most times.

Basically I would not spend a lot of time trying to repair it.

Attached is the service manual for the AC4 version. Now it will show a rotary carburetor so that section is useless.
 

Attachments

StarTech said:
316.791910 [41BD546G799]


Okay the first thing you mention is that this an used 4 cycle trimmer which is strike one. These AC3 and AC4 versions are known to have cylinder problems due the way they oil themselves. You are lucky if these last more than 2 years. If it is cylinder problem basically you just go and buy another hunk of junk as no internal parts are available.

The only 4 cycle handheld that worth the money is a Stihl 4 mix version. Now Matika does make a decent 4 cycle too.

Also the valves has to be adjusted every so often to .003-.006".

As for the carb it is a Ruixing Zama clone diaphragm carburetor. These are at least two gasket and diaphragm kits and I have see these gaskets and diaphragms to know which kit it uses.

As for priming you only have to prime until the primer bulb starts to fill and not all 10 X most times.

Basically I would not spend a lot of time trying to repair it.

Attached is the service manual for the AC4 version. Now it will show a rotary carburetor so that section is useless.
Click to expand...
Yep. Any 4-stroke trimmer such as Craftsman, Ryobi, Troy Bilt, etc. is basically junk from the start. A relatively short life span, difficult to start at times, unreliable, and not worth fixing most times.
Go buy a Stihl, Husqvarna, Echo, or Redmax and you will be happy and productive for many years to come.
 
My suggestion is to dispose of that thing and buy you a new 2 stoke trimmer by Echo, Stihl, or Husqvarna.
 
You must log in or register to reply here.
Back
Top