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RPM drop Problem

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dennisvh

Joined: 21 Aug 2006
Posts: 3

Posted: Mon Aug 21, 2006 6:35 pm Post subject: RPM drop Problem

I have a 1946 Ercoupe with a 85 HP (started out as a 75HP) Continental engine with a 200 RPM drop on the right mag at run-up.  Mechanics have 100% eliminated as the problem both mags, all plugs, P-leads, and switch system.  Also, the engine ran perfectly for the last 25 hours after a new wiring harness was installed.  The harness was checked out and all wires were fine.  We do not know what to check next.  I would appreciate any advice anyone can give us.  Thanks.  Dennis Hatfield

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Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Aug 21, 2006 7:19 pm Post subject: RPM drop Problem

Well, you don't mention the timing being checked.



dennisvh wrote:

 	  Quote: 	
		   

 

 I have a 1946 Ercoupe with a 85 HP (started out as a 75HP) Continental engine with a 200 RPM drop on the right mag at run-up.  Mechanics have 100% eliminated as the problem both mags, all plugs, P-leads, and switch system.  Also, the engine ran perfectly for the last 25 hours after a new wiring harness was installed.  The harness was checked out and all wires were fine.  We do not know what to check next.  I would appreciate any advice anyone can give us.  Thanks.  Dennis Hatfield [Question]

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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

altoq(at)cebridge.net
Guest

Posted: Mon Aug 21, 2006 7:23 pm Post subject: RPM drop Problem

Dennis,



The only thing left is timing. If the Mags have not been moved, the timing 

might be off because the impulse coupling does not return to the stop or 

because the point gaps are wrong. Point gaps change because of metal 

transfer at the contacts indicating a condenser problem or the fiber block 

that follows the point cam is worn away by a rusty cam.



Good Luck

John D.



DO NOT ARCHIVE



 We do not know what to check next.  I would appreciate any advice anyone 

can give us.

Thanks.

Dennis Hatfield

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jindoguy(at)gmail.com
Guest

Posted: Mon Aug 21, 2006 7:31 pm Post subject: RPM drop Problem

You say that mechanics have 100% eliminated. What did they do to eliminate those items? It'll save a lot of guessing games if you tell us that.



On 8/21/06,  Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:[quote] --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>



Well, you don't mention the timing being checked.



dennisvh wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: "dennisvh" < dennisvh(at)adelphia.net (dennisvh(at)adelphia.net)>



 I have a 1946 Ercoupe with a 85 HP (started out as a 75HP) Continental engine with a 200 RPM drop on the right mag at run-up.  Mechanics have 100% eliminated as the problem both mags, all plugs, P-leads, and switch system.  Also, the engine ran perfectly for the last 25 hours after a new wiring harness was installed.  The harness was checked out and all wires were fine.  We do not know what to check next.  I would appreciate any advice anyone can give us.  Thanks.  Dennis Hatfield [Question] 

-- 
	


Rick Girard

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

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FLYaDIVE(at)aol.com
Guest

Posted: Tue Aug 22, 2006 2:42 am Post subject: RPM drop Problem

Dennis:



Here are a few things I would check:

~ Timing 

~ Fuel - Have you been using AvGas? If so you may have some coking around the 

exhaust valve(s).

~ Spark Plug - Bad plug, carbon or lead fouling, cracked porcelain (swap left 

and right plugs.  If the problem follows the plugs, then just search down the 

bad plug.)

~ Harness - Check the length of the coil springs.  Give them a slight pull to 

stretch the length.  Also check down into the plugs looking for carbon or 

arcing. (I'm assuming you are using massive plugs?)

Plugs - While looking down, make sure the screw down there is tight.

Mags - You said you eliminated them as being the problem, but why and how?  

Have you looked inside?  What is the e-gap and condition of the coil?  Does the 

problem get worse with time and heat?



OK, that is all I can think about before I have my coffee.  Let us know how 

you make out.



Barry (McCoy)

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

=============================================

I have a 1946 Ercoupe with a 85 HP (started out as a 75HP) Continental engine 

with a 200 RPM drop on the right mag at run-up.  Mechanics have 100% 

eliminated as the problem both mags, all plugs, P-leads, and switch system.  Also, the 

engine ran perfectly for the last 25 hours after a new wiring harness was 

installed.  The harness was checked out and all wires were fine.  We do not know 

what to check next.  I would appreciate any advice anyone can give us.  

Thanks.  Dennis Hatfield

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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