Hard Starting Techumseh

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  #1  
Old 02-14-08, 09:22 AM
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Hard Starting Techumseh

I was having trouble starting a mid-80's vintage Ariens snowblower with a Techumseh engine (HM100-159119N), so I decided to replace the carb entirely as I've had bad luck with rebuilding in the past. Thanks to aj-allen for finding the part number for me.

With the old carb, I would have to hold the electric start on for about 10 seconds to get the engine cold started, then baby the choke for about another 20 seconds in order to get the engine to stay running. The choke would have to remain partially on thereafter, otherwise the engine would quit. Under load, the engine would periodically sputter and bog down. I messed with the adjustment screws, but the condition never improved.

With the new carb, the engine cold starts right away (with both electric start and recoil), but it spews alot of grey/black smoke initially, and is EXTREMELY sensistive to the choke setting for about the first 10 seconds. I usually have to re-start it 3 or 4 times before it finally stays running. Thereafter, the choke can be turned fully off and the engine runs smoothly and does NOT sputter or bog down under load - it feels like it is brand new.

I have tried different setting on the adjustment screws, but nothing seems to affect the starting problem. Is there anything else I should try?
 
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  #2  
Old 02-14-08, 09:47 AM
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if its a diaphragm type replace the diaphragm and see if that helps. sometimes they sit in a warehouse for a while and the rubber drys up.
 
  #3  
Old 02-14-08, 11:55 AM
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The replacement carb is not a diaphram and most likely has nothing to do with the problem. Set the bottom main screw at 1 1/2 turns out after seating and the idle mixture on the side at 1 turn out after seating. What is most likely causing the black smoke is excessive carbon build up inside the head and valves due to running the old carb for so long with the choke on. You may try running a few tanks of gasoline through with some Seafoam additive, it may clear it up some, other wise remove head and clean it up. Also if you have not changed your spark plug after running it with choke you should do so know.
 
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Old 02-18-08, 11:03 AM
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Thanks! I looked up the spark plug needed, which was a J17LM. However, I couldn't find that particular one and was told that J19LM would work. The old spark plug turned out to be a J8C, which was somewhat longer than the J19LM. The J8C is used on other Techumseh engines but not on the "HM" series. Could this discrepency have possibly caused any problems?

The engine now starts right away with no smoke. However, once it is running, it bogs down intermittently with no load. I reset the main and idle mixture screws as suggested, but that didn't seem to help. There is a second screw on the bottom of the bowl, which is spring loaded and drips copious amounts of gasoline if pushed in. I'm pretty sure I changed the setting of this screw by mistake when trying to adjust the main mixture screw. What should its original position be?
 
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Old 02-18-08, 11:48 AM
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The second thingy on the bottom of the carb is a bowl drain device. Gas should drain when pushed, but no gas should come out when not pushed.
RJ17LM is Tecumseh recommended plug, most places selling plugs will have it.
hope this helps,
thanks,
 
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Old 02-18-08, 12:01 PM
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Oh Ok, it had a slotted screw so I thought it could be adjusted. Thanks for the quick reply. I'm not sure what else to try, unless the head and valves are sooty. But wouldn't there still be a lot of smoke?
 
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Old 02-18-08, 01:06 PM
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Describe what you mean as "bogging down" not under load. Does this mean if you start it and have it on full throttle in neutral the engine bogs? If you have a new carb, you now have correct plug and all is adjusted I would ask that if we are dealing with fresh gasoline i:e from the pump not from a can that has been around a while. I just like to have a clear starting point moving forward in trying to resolve your problem.
 
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Old 02-18-08, 01:26 PM
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do you have good spark and compression.
 
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Old 02-18-08, 02:26 PM
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The gas is about 4 months old and is 10% ethanol mix.

Here is step by step what happens:

Set choke to full, turn key to "on", prime 3 times.
Pull recoil once, engine starts, choke set to 1/4.
Engine struggles a little, choke set to "off", engine runs fine for about 20 seconds.
Engine begins to falter, like it was being turned off, then picks back up to full speed for another 5-10 seconds. Then falters again, then picks up. Repeat for 5 minutes until I turn it off.

When I apply load, the faltering cycles continue, and seems like the engine might quit if I was actually blowing snow. Adjusting main mixture screw does not improve situation.

This faltering did not occur with the old, dirty spark plug.

Thanks again for the help and suggestions!
 
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Old 02-18-08, 08:13 PM
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If your carb has a slotted screw at the center of the underside of the carb bowl, then back that screw out 1/4 turn or so and see if it improves. This isn't the same as the spring loaded bowl drain that will pour fuel if you push it up.
 
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Old 03-22-08, 03:20 PM
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Here's a followup to my situation: I got a can of Seafoam and put 3 or 4 oz in the gas tank, and ran the engine for about 15 minutes at a time every few days, to burn off the soot. The first time I ran it, the engine came close to quitting a number times while idling. However, each successive time the engine sounded better than the previous time. I did this a total of 7 times over the course of the last month, as we didn't have any snow during that time. Yesterday we got 12" of heavy, wet snow and the engine performed flawlessly; not a single hiccup. It hasn't run this well in years. Yipee!
 
  #12  
Old 03-22-08, 05:26 PM
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Glad to hear it, sounds like the head is cleaned up.
 
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