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Starter hangs on 1st compression on O-320 160 hp

kiwicubber

kiwicubber

PATRON
Te Kowhai, New Zealand
Hi, first start the engine hangs on the first compression on a cold start. Have checked all wiring connections for bad earths etc but no fault found. I have heard this is common on the high compression engines. Does anyone know of a fix?
 
What starter do you have? An original direct drive or a reduction gear starter? Electric motors work better when they are spinning, rather than if they have to start rotating under a load. Your issue is not uncommon with the direct drive starter. If there is any rust or wear on the starter gear teeth and/or the ring gear teeth, the rust will create enough extra friction to make rotation difficult.
 
skywagon8a said:
What starter do you have? An original direct drive or a reduction gear starter? Electric motors work better when they are spinning, rather than if they have to start rotating under a load. Your issue is not uncommon with the direct drive starter. If there is any rust or wear on the starter gear teeth and/or the ring gear teeth, the rust will create enough extra friction to make rotation difficult.
Click to expand...


yeah sorry Skywagon, forgot to mention. It is the Prestolite direct drive, overhauled with the engine 18 months ago and has done 100 hours in he last year. I’ll have a look at the ring gear tomorrow 😀
once the starter gets over the first compression it rotates at normal speed.

cheers Bill
 
Be certain the starter shaft at the end of the housing has enough lubrication. This is a bushing which when dry has a lot of friction particularly when under the high loads of trying to turn an engine through compression. It helps to oil this shaft when it is turning to work the oil into the bushing. To do this: engage the starter, then release the start button. This will engage the starter gear with the ring gear. Then while squirting oil between the starter gear and the bushing, manually rotate the propeller backwards. This will turn the starter working the oil into the bushing.
Of course this is done with the mag switches OFF.
This bushing when combined with a little amount of rust on the gears on top of the cylinder compression produces high friction which provides more resistance than the starter can overpower.
 
Use silicone spray, it doesn't attract dirt. I would also check the voltage at the starter when starting just to make sure.
 
Hi Stewart, yup thanks, tried that. Have an Odyssy dry cell battery as part of the underseat battery STC. Certainly affects it if the battery is low but even fully charged can’t quite make the first compression straight away. ��
 
Yep. Make sure you have a good ground strap from the crankcase to the airframe (not the engine mount). Also check the start relay for voltage drop. With the amount of current flowing, even a small amount of resistance will produce a large voltage drop. And a cold startup compounds this as this is the time when the engine is hardest to turn over.

Web
 
I had the same issue with my old C150/150,
and replaced the recently-gone-through prestolite starter with a Skytec "flyweight" starter.
Huge improvement in cranking power.
 
Make sure the timing is correct, do you have impulse couplings on both mags??? If you only have an impulse coupling on one mag, start with that mag only.
 
Try starting on just the left mag, or whatever mag has the impulse coupler. I can’t start mine with both mags hot when it’s cold.
 
stid2677 said:
Make sure the timing is correct, do you have impulse couplings on both mags??? If you only have an impulse coupling on one mag, start with that mag only.
Click to expand...

md11freighter said:
Try starting on just the left mag, or whatever mag has the impulse coupler. I can’t start mine with both mags hot when it’s cold.
Click to expand...
This wasn't ignition timing, he couldn't get it to top dead center on compression. The magneto fires after that.
 
Test your battery. Make sure it's taking/holding a good charge. Are you using an appropriate charger for it?

MTV
 
Thanks stid and md11. Yup it’s not a mag problem, only a problem with cranking. Once the engine gets over the first compression it starts on the 2nd or 3rd blade �� Subsequent starts during the day are no problem. ��

cheers Bill
 
sjohnson said:
No opinion on this, just trying to understand. Wouldn't the non-impulse mag fire 25 deg. BTDC?
Click to expand...
IF, the non impulse magneto was very good and could fire with a very slow rotation, then yes it could retard the rotation or possibly create a kickback. Magnetos are very poor at sparking at extremely low rpms. They work best at high rpms due to their rotating magnet being able to create a stronger magnetic field.

This issue of kiwicubber's doesn't appear to be ignition as he has not suggested any indication of kickback, only an inability to turn through the first compression stroke.
Once he gets over the first compression stroke, even a weak spark igniting the fuel will give the engine the inertia needed to turn through the second compression stroke.

Barring the solving of the rust or worn gear situation, the best solution is to install an original geared starter which was used on the O-360s and bigger or one of the newer light weight high rpm starters.

I do not blame the battery. Years ago prior to the newer lightweight geared high rpm starters becoming available, kiwi's issue was common.
 
For anyone with an aging battery this situation is common, too. My 180 is doing the same thing. I know it's the battery. That Odyssey is 12 years old so no surprise. Kiwi says he's ruled that out.
 
stewartb said:
For anyone with an aging battery this situation is common, too. My 180 is doing the same thing. I know it's the battery. That Odyssey is 12 years old so no surprise. Kiwi says he's ruled that out.
Click to expand...

If on installation, the stud on the starter turned at all, it could have cracked the field winding solder joint inside the starter. That puts up a high resistant point internally that shows up on initial start when it needs the most juice. Take the brush cover off and see if the stud is loose of its windings.

Steve
 
Hmmm. Sounds like a hydraulic lock. Theres no possibility of fuel leaking into a cylinder (primer)??


Sent from my iPhone using SuperCub.Org
 
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