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View Full Version : Stihl Blower.. spark and compression but will not fire at all. I am getting P****!


summej
02-12-2011, 01:14 PM
Have a Stihl BG 55 handheld. Has plenty of compression good spark with plug out. I CAN NOT GET IT TO FIRE FOR ANYTHING with plug in!!

Anyone know how to properly set the gap on the flywheel and ignition coil?

Also I am thinking that maybe the flywheel key spun?


I am trying to start with starting fluid... sprayed a lil in plug hole-nothing
sprayed a little in carb throat....Nothing. No Fire either time


Cleaned carb.

I am going to dump the gas and ad fresh 93 50:1.
running out of ideas...
Any suggestions

How do I check/set the flywheel timing?

It appears to me that Stihl USA locks down the PDF repair manuals tighter than the The National Security Admin. /NSA.
They want us all to go to the dealer/steelerships
Maybe I will call Wikileaks.

jkilov
02-12-2011, 03:47 PM
First of all this is not a proper spark test. Under compression air is about 9x denser, a better insulator and may prevent the voltage from sparking.

It does sound like an ignition issue, check the key, flywheel gap, and measure the resistance of both primary and secondary circuits on the ignition. If unsure have a dealer do a spark test. Some stihls have a programmed timing ignition module, these sometimes get stuck in advanced mode making them impossible to start. I'm pretty sure the bg55 does not have this type.

A good redneck spark tester: leave the original plug in, connect the lead to a second, preferably non-resistor plug with minimum electrode gap and ground on original plug. If the coil manages to spark both plugs it's definitively good.

ricky86
02-12-2011, 04:31 PM
"Since there is no mechanical wear
in these systems, ignition timing
cannot get out of adjustment.
However, an internal fault in the
circuit can alter the switching point
in such a way that a spark test will
still show the system to be in order
although timing is outside the
permissible tolerance. This will
impair engine starting and running
behaviour."
This above quote is out of a BG55 dealer service manual. Translation is, you might have to try a new module to rule out an ignition problem (if, in fact, it is an ignition problem). Spark testers can't help if it's a timing issue. You can, if you're capable, hook up a timing light to it. If It fires ATDC (after checking flywheel key), you found your problem. One word of caution: that crankcase is most likely filled with fuel and starting fluid Watch out pulling the rope. If it ignites, and you face is in the way...........

onlythebest
02-12-2011, 04:53 PM
to set the gap i believe they have 2 or three screws holding the ignition coil loosen maybe 1/2 turn and set the gap to 0.014 across both sides of the coil then tighten screws and check again... had to change all three of my sh56 blower vacs

summej
02-12-2011, 04:55 PM
I removed the flywheel and the key does appear to be worn. Stihl does not have the traditional type of flywheel key that slides out-it looks to be formed onto the actual flywheel... looks like a crush key. I think the flywheel may have spun a little on the shaft.

I am still able to tighten and adjust the position of the flywheel in relation to TDC.

Question: what position should the magnetic pickup be on the flywheel when piston is top dead center? In other words.. the plug needs to fire at TDC. The coil needs to be firing then too correct? there are two obvious pickup/ firing points on the coil-one in the center of the coil and one 1" below it. I need to know where my firing point is on the coil in relations to the flywheel.

ricky86
02-12-2011, 05:23 PM
Do you know anyone who has a BG55/65/85 ? If so, swap coils. Your engine fires BTDC (about 5 to 25 degree's depending on RPM). There are no hard spec for what your looking for because it's considered fixed, meaning non- adjustable.. With a light on it, if it's firing 90 degree's after TDC, then you have a problem. Those modules had a 5 year warranty on them. Is your's older? I'm telling you again, if everything else checks out, you will have to replace the module to rule out a ignition problem. The list price is about 30.00 (29.50} to be exact

jabirt1
02-14-2011, 10:10 AM
Maybe it's not ignition?

Check the spark arrester, muffler and exhaust ports. If they're carboned up--especially the spark arrester screen--it will not fire.

BigFish
02-14-2011, 01:52 PM
I removed the flywheel and the key does appear to be worn. Stihl does not have the traditional type of flywheel key that slides out-it looks to be formed onto the actual flywheel... looks like a crush key. I think the flywheel may have spun a little on the shaft.

I am still able to tighten and adjust the position of the flywheel in relation to TDC.

Question: what position should the magnetic pickup be on the flywheel when piston is top dead center? In other words.. the plug needs to fire at TDC. The coil needs to be firing then too correct? there are two obvious pickup/ firing points on the coil-one in the center of the coil and one 1" below it. I need to know where my firing point is on the coil in relations to the flywheel.


If you can move/rotate the flywheel on the crank,even a little bit, then your screwed!!
You either need to replace the flywheel or the crank.
Pay attention to WTF people are telling ya!!

StihlMechanic
02-14-2011, 08:27 PM
Have you removed the exhaust to inspect the pistion? If its scored/scratched its junk. Also, you mention it has comp, how much psi? You need at leat 120.

dboyd351
02-17-2011, 08:04 PM
I'm no expert mechanic, but if it won't fire at all when you shoot starting fluid in the intake, or the cylinder, I don't see how you can have spark.

dutch1
02-17-2011, 08:57 PM
If it is convenient, isolate the kill lead at the coil then check for spark. It's been a while since I've seen a 55 and it's configuratiion and it may be simpler to pull both leads from the ignition switch to accomplish the same thing. Just another thing you may want to check if you've checked all that others have suggested. Could be as simple as the coil and ground pinched together, causing a continual "off" condition, particularly if it has been torn down previously. Don't ask how I know this can happen.

Mac B.
02-21-2011, 08:47 PM
My BG85 did the same thing. It ran fine one day and would not start the next. I took the starter cover off and disconnected the kill switch wires and then cranked it. It fired up and I had to choke it to cut off. The problem is in your rocker kill switch.

Mac

kawasaki guy
09-02-2012, 08:30 PM
my bg55 ran a day ago. today, it does not fire! what is the problem?

BigFish
09-03-2012, 10:25 AM
After resurrecting/ reading this old post, you ain't learned nothing???
Get real.