C-150 starting problem

[crazynut52]

I have a Cessna 150 with the 0-200. Lately it hasnt been starting well. It will kinda studder for a while, but won't "catch" and take off. Once in a while it will start right up with no problem. My mechanic can't seem to think of what the problem is. Maybe someone can give us an idea....

we took all the plugs out, cleaned them and checked their spark. We rotated the prop by hand to make sure they were are getting spark. We checked the timing, it is set at 28 degrees which is because of the superior cylinders. It has a brand new carb, and fuel does not seem to be the problem. He thinks possibly it could be the impulse coupling, but wasnt sure, because it sparks when turning it over by hand.

Any ideas, please let me know
I appreciate the help.

 

[Gofish]

I am assuming you give it a shot or two of primer?...That always worked for mine. Either that or firewall the throttle a couple of times to get some fuel into the cylinders.

Hope that helps.

 

[NW_Pilot]

What's the temp out side? I lean mine about an inch when starting on hot days and she pops off every time.

 

[erj-145mech]

The impulse coupling should be snapping around TDC. With the switch to both, the bottom leads off, the top leads on the removed top plugs, and the plugs on the cyklinder fins, and a prop degree wheel on the prop/spinner, as he pulls the prop thru by hand, with a thumb on the top spark plug hole to check for piston position. But he should already know that, basic recip knowledge.

 

[crazynut52]

Hey guys, we're sure its not my starting procedures. I have started this plane and thousands of times. The problem actually started when the mechanic had the mag off when working on the plane. I think he had one mag off when changing the generator. He said the previous mechanic had it timed to 32 degrees, and said it had to be turned back to 28. I do not know if this caused the problem, but it was around this time it began to start hard. He went throught he procedure of checking the plugs and spark etc... and all checked out fine. As far as we can tell, both mags have impluse couplings, which makes me wonder how they could both go bad... and if they were both bad, then we wouldnt have a spark when turning the engine over by hand, right?? I sure hope it's not a cam... the engine has 350 hours on it.

 

[bocefus]

Like erj said, check to make sure the impulse coupling is catching, winding and snapping. A lot of times when a mag is removed and re-timed, the angle gets changed. This can cause the impulse coupling pawls to miss the striker pin and cause it do not wind up.

 

[GravityHater]

impluse couplings, which makes me wonder how they could both go bad... and if they were both bad, then we wouldnt have a spark when turning the engine over by hand, right??

this is wrong, not right. A mag will still spark even though the IC is weak. Ive had this problem in a Lyc., where the IC spring is weak and will not make the spark hot enough.
It may also appear that they both went bad when in fact one has been bad for a long long time and you were starting on only the other one....which recently went bad.

BTW, in your posts I did not see where the compression (do it cold if the problem is when starting only) was checked* or the points visually examined.

 

[crazynut52]

The mechanic said he visually did check the points, and it seems to do it whether cold or warm.... but he did check the compressions and all were high 70's

 

[Gryphon]

Hey guys, we're sure its not my starting procedures. I have started this plane and thousands of times. The problem actually started when the mechanic had the mag off when working on the plane. I think he had one mag off when changing the generator. He said the previous mechanic had it timed to 32 degrees, and said it had to be turned back to 28. I do not know if this caused the problem, but it was around this time it began to start hard. He went throught he procedure of checking the plugs and spark etc... and all checked out fine. As far as we can tell, both mags have impluse couplings, which makes me wonder how they could both go bad... and if they were both bad, then we wouldnt have a spark when turning the engine over by hand, right?? I sure hope it's not a cam... the engine has 350 hours on it.

Basic common sense... he took the mag out, put it back, and changed the timing and now you have a hard start problem.. what about putting the timing back to where it was and see if that changes anything? Obviously thats where the problem started, go back to the beginning and start over. There may have been a reason it was set at 32 and not 28.. good luck.

 

[TrafficInSight]

Basic common sense... he took the mag out, put it back, and changed the timing and now you have a hard start problem.. what about putting the timing back to where it was and see if that changes anything? Obviously thats where the problem started, go back to the beginning and start over. There may have been a reason it was set at 32 and not 28.. good luck.

I can't imagine any good reason for the timing to be wrong.