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Starting issue

cubdrvr

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YKN(mother city of the dakotas)
O-320-E2D.........1700 since new in 75......flown very little in last 12 years but this is a new issue.
Slick mags just serviced. Checked timing twice. Carb just back from overhaul. No intake or primer leaks.
No fuel restrictions. Plugs and harness good. Leads spark at TDC at impulse click pulling the prop through.
Compressions good.

Engine will not start with normal procedures(not even a pop). Will eventually start if 1) primer is
used continuously while cranking 2) Throttle is pumped continuously with cranking
Once started there are no issues. Shut down and restart is the same as cold start.

Could it be starting on the right mag? Could the starter switch ground the left mag?
Never had an issue like this before :banghead::banghead::banghead::banghead:
 
I have had these exact same symptoms twice with same engine. In each case it was slick mag related. Sent mags to mag shop next door and it fixed the problem. But you have done that. I assume you are confident in the mag service performed?

Jerry
 
Physically trace out the p-leads. It's an easy check. Make sure you have the shorting bar on the correct tabs on the switch (I'm assuming a key switch).

Web
 
Did you check the internal mag timing not just engine timing. Slicks are notorious for issues after human 10 or 15 hours.
DENNY
 
Don't bother throwing money/time at a slick mag. Just check the internal timing, if the problem continues get Bendix mags and be done with it.
DENNY
 
Pull the grounding wires off both mags and see if it starts before tearing too much apart..
 
He thinks he has a switch grounding out the wrong mag or at least his impulse... unhook them both and see if it fires like it should.
 
Leads spark at TDC at impulse click pulling the prop through.
What does the spark look like?
A fat blue spark?
Or a thin weak yellow spark?

Should be fat bluish.

The fix if not, can be the points are not set properly in relation to E-gap. OR the magnet is weak.

Sometimes the proper setting of the points can be very fussy. Also not unusual to find that proper setting is slightly different than the magneto manual says it should be.
 
Most likely bad impulse mag. Swap it out and test. Had the same identical issue until finally it did not start. Surefly might be a way to go. I like mine. I have the same engine in my X18.
 
Update: Stopped at Roger's hangar to help out today.
Left mag was removed, inspected, points adjusted. Carb is good.
So now, 1-2 shots prime ( only one primer line) engine will start after a dozen revolutions or so.
Or, if starter is energized and throttle is pumped twice engine will start.
Almost like its not drafting well.......and takes a good number of prop rotations to start.
But using the accelerator pump gets an immediate start.
Additional starting attempts are the same.
Most 320's normally start right up with no input after they are warm.
Could some of this be internal with cam/followers worn?
 
Might need to clean primer nozzle. Sounds like primer is not actually getting sufficient fuel into the cylinder.
 
+1 for what Troy said. Primer should deliver fuel to the backside of the intake valve so it's drawn immediately into the cylinder. If that's not working and pumping the throttle works, it's telling you that fuel is not getting into the cylinder with the primer.
Easy check. Remove the primer from the cylinder. Re attach it to the primer line and pump the primer. Should be an even, fine, spray pattern.

Web
 
Did that Troy...........not much we didn't try :banghead:

What bothers me is that a warm start is just the same. Should need no primer or throttle jockying.
 
OK......here is the best I could come up with.
Since one cam lobe controls 2 intake valves, and if that lobe is bad, I'm assuming that could be the issue in that
it won't draft enough fuel/air mixture. Engine starts fine with one/two pumps of the throttle.....or a dozen or so prop revolutions
until fuel is drawn into the cylinder. Same with restarts.
1700+ hrs. since new in 1974 and maybe only 10 hrs. in the past dozen years. Gotta be the cam......gotta be.
 
I would agree with Steve you should have been making metal if the cam or lifters are going bad.
DENNY
 
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