 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / September 2006weak ignition? (small engine)
I have an old tiller with a Kohler single-cylinder 4-stroke engine. It lost all power (over about 30 secs), and now won't start. Since then, - Replaced spark plug. (Which does spark, when grounded to the head.) - Points look OK. - Compression looks OK (75 psi). - Cylinder is getting fuel (plug gets wet, and exhaust smells.) - Carb float valve works, and float seems OK. - Coil resistances look OK. - I cranked it in the dark, and didn't see or hear anything bad around the coil. I wonder if I have a weak spark when the plug is installed. But, a new coil costs $75, which is a kind of expensive experiment. To test the coil, I made a 10:1 voltage divider (with a HV 10M resistor), and looked at the spark plug voltage with a scope. With the plug not grounded, I see a 4-6KV pulse. When the plug is grounded, this drops to about 1KV. I get the same 1KV when the plug is in the cylinder (no fuel). Questions: - Is above consistent with a 'weak' coil? - Is there another way to test that? And, any other thoughts would be appreciated. G George Wrote: > I have an old tiller with a Kohler single-cylinder 4-stroke engine. It > lost all power (over about 30 secs), and now won't start. Since then, [quoted text clipped - 31 lines] > > G 75 psi compression doesn't sound like enough for a gas engine to run....usually around twice that...  Signaturejeffcoslacker http://www.automotiveforums.com jeffcoslacker Wrote: > 75 psi compression doesn't sound like enough for a gas engine to > run....usually around twice that... I seached on a lawn equipment site I post on sometimes...the consensus seemed to be a small engine won't run very strong below 120 psi, and probably wouldn't start below 90 psi...new compression spec on that motor is probably around 160 psi. Signaturejeffcoslacker http://www.automotiveforums.com >George Wrote: >> I have an old tiller with a Kohler single-cylinder 4-stroke engine. It [quoted text clipped - 35 lines] >75 psi compression doesn't sound like enough for a gas engine to >run....usually around twice that... This is a 7 hp pull start, and it has some sort of compression relief to reduce the starting effort. It works off the crankshaft speed. I figured it out once, but I don't remember the details. G George Wrote: > >George Wrote: > >> I have an old tiller with a Kohler single-cylinder 4-stroke engine. [quoted text clipped - 48 lines] > > G See if it will start with a dry plug and the air cleaner removed. Let me know. I did see Kohler has a compression release, I was wondering if you figured that into the compression reading... Your spark, fat and blue or thin and yellow/white? Signaturejeffcoslacker http://www.automotiveforums.com >George Wrote: >> >> >George Wrote: >> >> I have an old tiller with a Kohler single-cylinder 4-stroke engine. >> >> It lost all power (over about 30 secs), and now won't start. Since >> >> then, ... >> >> Questions: >> >> - Is above consistent with a 'weak' coil? [quoted text clipped - 15 lines] > >See if it will start with a dry plug and the air cleaner removed. No. Tried that, early on. >I did see Kohler has a compression release, I was wondering if you >figured that into the compression reading... No - that was just a raw reading while I pulled it. >Your spark, fat and blue or thin and yellow/white? I'd call it violet and thin (watching it in the dark). It's not inspiring, but it is there. (That's spinning the crank with a drill.) G George Wrote: > >George Wrote: > >> [quoted text clipped - 39 lines] > > G I think I'd put a new points and condensor in just for laughs and see where that gets you... Signaturejeffcoslacker http://www.automotiveforums.com >>>>This is a 7 hp pull start, and it has some sort of compression >> [quoted text clipped - 3 lines] >>>>reduce the starting effort. It works off the crankshaft speed. I >>>>figured it out once, but I don't remember the details. The mechansim is actually on the camshaft, not the crank. When the cam is below a certain speed, a tab moves onto the back of the exhaust valve lobe so that the exhaust valve lifts partway through the compression stroke and reduces compression dramatically. Once the engine starts, the tab moves out of the way and the exhaust valve stays closed on the compression stroke. Here's a manual for the K161 (7-horse) and k181 (8-horse) engine families: http://www.kohlerengines.com/common/resources/ens_593_f_all.pdf > I have an old tiller with a Kohler single-cylinder 4-stroke engine. > It lost all power (over about 30 secs), and now won't start. Since [quoted text clipped - 32 lines] > > G First of all, read this carefully: http://www.gotfusion.com/tutsTD/ask.cfm Then, learn the difference between multi-posting and cross-posting and DO IT RIGHT! Jeez, |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.