And now, a McCulloch question

[Rocosil]

While I'm waiting for the carburetor kit Curt Bailey is sending me for the 028 WB, I decided to take another crack at the Mac 3200 I gave up on a couple of years ago. BTW, the 028 I'm having starting problems with, besides 155 lbs compression, turns out to have a beautiful fat, consistent spark, all the rubber fuel system parts are sound, and it seems to hold 15 Hg of vacuum indefinitely. So, at this point, I'm putting all my hopes on the carb kit.

About the Mac: It starts, idles, and runs fine, but once it is warmed up and I shut it down, there is no way I can get it to start up again - with or without pumping the primer, with or without choke, half choke; no way. If I let it sit for a couple of hours till it is stone cold, it starts right up again. Anyone have any suggestions as to what I should be looking for? Yes, I know, "a better saw", but I did that already. :greenchainsaw:

Thanks,

Bob

 

[lawnmowertech37]

While I'm waiting for the carburetor kit Curt Bailey is sending me for the 028 WB, I decided to take another crack at the Mac 3200 I gave up on a couple of years ago. BTW, the 028 I'm having starting problems with, besides 155 lbs compression, turns out to have a beautiful fat, consistent spark, all the rubber fuel system parts are sound, and it seems to hold 15 Hg of vacuum indefinitely. So, at this point, I'm putting all my hopes on the carb kit.

About the Mac: It starts, idles, and runs fine, but once it is warmed up and I shut it down, there is no way I can get it to start up again - with or without pumping the primer, with or without choke, half choke; no way. If I let it sit for a couple of hours till it is stone cold, it starts right up again. Anyone have any suggestions as to what I should be looking for? Yes, I know, "a better saw", but I did that already. :greenchainsaw:

Thanks,

Bob

About the Mac: It starts, idles, and runs fine, but once it is warmed up and I shut it down, there is no way I can get it to start up again - with or without pumping the primer, with or without choke, half choke; no way. If I let it sit for a couple of hours till it is stone cold, it starts right up again. Anyone have any suggestions as to what I should be looking for? Yes, I know, "a better saw", but I did that already.

i hate to break the news to you bob but i already diagnosed your problem by the symptoms you gave me the true give away is when it starts fine cold and warms up then you shut it down you notice it wont start till it gets cold again the first thing that comes to my mind is


how much compression do you have when it is hot ?? and not running is there a way you can do a compression test on the saw when it is warmed up ?


if that checks out to 110 or higher when hot then we have no cylinder ring problem the next step is we check foir spark when it gets hot




when it gets to that poiint of hotness does it even start acting up like running under serge or anything ?


the step you take then is check the fire on the spark plug when it gets warm to the point where you normally shut it down at take the plug out and check the fire on the plug tell me what color of spark you get on this plug when the engine is hot


from there we can determine the exact problem we have with this saw


i will wait till you get this checked out


thanks
calvin

 

[Rocosil]

Thanks, Calvin, for giving me a logical diagnostic sequence. Will do. I doubt that it is a compression problem because the saw has less than eight hours of total running time on it, but I'll check that out anyway.

I'm not quite sure what you mean by "running under serge", but once it is running, it behaves like a good little chainsaw should - normal trigger response and a nice steady run under load, or without.

Is the hot plug test to determine the condition of the plug, or of the other ignition components? I'll try both, with the hot plug and with my special (home-made) spark tester plug.

I'll be back to report results tomorrow after I've fixed another problem. The saw won't shut down when I push the "stop" switch down - must have messed up something the last time I was trying to chase down the hot start problem. At the moment I have to pull the plug wire to shut down the saw.

Thanks again,

Bob

 

[ericjeeper]

My guess on the Mac

The fuel tank is warming up pressurizing the carb and flooding it out. Inlet needle, and tank vent would be where I would start

 

[sugarbush]

The fuel tank is warming up pressurizing the carb and flooding it out. Inlet needle, and tank vent would be where I would start

+ 1--- try loosening the gas cap when you shut it off, relieves the pressure, if it starts back up where it wouldn't before, then its a carb problem or vent.

 

[romeo]

My Mac 3200 works great! It keeps my youngest son from messing with the important saws:greenchainsaw:

 

[Rocosil]

My Mac 3200 works great! It keeps my youngest son from messing with the important saws:greenchainsaw:

Great kid! Nice funky saw!
All saws are important while you are using them. :monkey:

Bob

 

[lawnmowertech37]

a future technician there in that photo

 

[Rocosil]

Tried to start the saw today to follow up on lawnmowertech's recommendations re hot spark and hot compression, and to then check out what effect loosening the gas cap would have on a hot non-start. Well, no dice: wouldn't start at all. I farted around some more, finding the following: cold compression, 135 lbs; spark, nice and blue and strong, both on the tester and on the plug being used; the primer pump moves fuel to the carb as it should, however, while pumping I hear a sucking sound at the carb (Is that normal?)
Furthermore, when I pulled the plug, it was wet. I squirted some mix down the carb throat, but got no action that way either. What's got me baffled is that yesterday it started right up, at least, when cold, and today, zip. The only difference between today and yesterday was that I reconnected the kill wire that had come loose, and it snowed last night and this morning. Maybe I should wait for a nice, sunny day before I try again.
BTW, how does the fuel tank vent on these things? The cap is solid, and I don't see a little plastic tube like I have on my Stihls.

Bob

 

[Rocosil]

how much compression do you have when it is hot ?? and not running is there a way you can do a compression test on the saw when it is warmed up ?

if that checks out to 110 or higher when hot then we have no cylinder ring problem the next step is we check foir spark when it gets hot

O.K., Calvin, do your stuff. The sun came out to day, and I got the thing started. Hot compression is 130 lbs and the spark appears to be very weak. So small that I can't really tell the color, however, when I check it on my tester plug (a lawn mower plug with the ground electrode cut off) it looks like a pretty decent, blue spark - maybe not quite as solid as when cold. I tried restarting it hot again, and, of course, no go.

BTW, I find no impulse tube on this saw, so I'm assuming the carb diaphragm gets moved by a direct carburetor/crankcase passage.
Right? I also can't find a gas tank vent. Does that mean that the gas tank somehow vents through the primer pump?

Any light you can throw on this situation will be much appreciated.

Bob