Early Ford V-8 Club Forum

EFV-8 Club Forum / General Ford Discussion / Malfunctioning coil resistor ???

Reply to Discussion | New Discussion << previous || next >>

Posted By Discussion Topic: Malfunctioning coil resistor ???     Grant 07-20-2015 @ 7:59 PM reply profile send p.m. Senior Posts: 537 Joined: Oct 2009 Thanks for the ongoing advice. I'll be at it again next weekend. TomO 07-20-2015 @ 1:46 PM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 I would get the engine to operating temperature and then pull one wire at a time and hold it near a head nut while the engine is idling. You should see a spark that will jump about 1/2". you can use a fuse puller that looks like a pair of plastic pliers to prevent shock. If your spark does not look blue in color and jump a 1/2" gap, on some plugs and looks OK on others, your coil and condenser are OK. If all are weak, check the condenser grounding and the condenser to coil connection. Also check the voltage into the coil, it should be above 3.5 volts at idle. If some plugs have a weak spark, check the wire connections at the inner caps, check the rotor to cap clearance. If all wires give a strong spark, check the plugs for fouling. Tom cliftford 07-20-2015 @ 6:02 AM reply profile send p.m. Senior Posts: 845 Joined: Jan 2014 Two things come to mind. Have you checked the condition of the spark plug wires, and the big wire from coil to distributor? From my experience, with a manifold leak you get a low fairly constant vacuum reading at idle. Have you taken the dist. out and checked it out, including the cap? Pull each wire out one at a time and check for corosion. As for the spark, it can be weak and still bite you pretty good. Good luck Grant 07-20-2015 @ 5:28 AM reply profile send p.m. Senior Posts: 537 Joined: Oct 2009 Thank you, gentlemen, for your responses. This weekend there was time to work on the '36. Shorting out the coil resistor made no difference. The car starts easily and the engine runs fine when it's cold, but not for long. Putting a vacuum gauge on the intake manifold showed the same intermittent reading as has been occurring off and on for about a year now ......... needle deflecting back and forth between 12 and 15 with the engine warmed up. According to the 1935-1950 Motors Manual this may be due to a vacuum leak. There is an intake manifold gasket in stock here which likely should be installed. Also, Ken Isidor has sent us a freshly rebuilt fuel pump which perhaps will help. With respect to ignition, the car has had four different coils and five condensers since August 2014. The problem has repeatedly come back. Tom O ........ Shorting out the plugs to the cylinder head one at a time a couple of weeks ago, I got a pretty good shock from the screwdriver (wood handle with full length steel shaft). On that basis it seemed that spark was fairly strong. What would the proper test be to determine if a weak spark could be involved? trjford8 07-16-2015 @ 7:30 AM reply profile send p.m. Senior Posts: 4222 Joined: Oct 2009 I have had coil resistors act like yours, but also condensers and coils that gave the same symptoms. The advice to bypass the resistor temporarily is good. It will eliminate or confirm the resistor as the culprit. TomO 07-16-2015 @ 7:12 AM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 Grant In my experience when the ignition resister fails, the car will not run until the resister is bypassed. Have you determined that you have a weak spark when the engine warms up? Tom 4dFordSC 07-16-2015 @ 6:27 AM reply profile send p.m. Member Posts: 266 Joined: Oct 2009 x 2. I'd try a new condenser first. If the problem persists, bypass the resistor with a jumper wire, and run the car until it warms up. If it runs better, you probably have a weak/failing coil. It won't hurt anything to run the car without the resistor temporarily. IMHO, resistors are rarely the problem, although soldered connections have been known to crack. This message was edited by 4dFordSC on 7-16-15 @ 6:29 AM cliftford 07-16-2015 @ 6:05 AM reply profile send p.m. Senior Posts: 845 Joined: Jan 2014 I would suspect the coil , condenser or other ignition problem as more likely. Grant 07-16-2015 @ 5:39 AM reply profile send p.m. Senior Posts: 537 Joined: Oct 2009 Our '36 has a 1939-style charging system with a regulator and a coil resistor. If the coil resistor was malfunctioning, would the car start and run fine when it's cold, but lose power and run poorly as soon as it warms up?

<< previous || next >>

NOTE: YOU MUST BE A REGISTERED USER AND BE LOGGED IN TO POST (and reply to) messages in this forum. If you are a first time user, please click the CREATE A NEW ACCOUNT in the masthead above to register and Log In. After that, all you do is LOG IN to enjoy using this site.

DISCLAIMER: The V-8 Club does no independent testing of any of the opinions, thoughts or suggestions presented in the website on the Forum, in the Tech Tips section, or any section. A reader should consider the website to be a forum wherein differing solutions to a particular set of circumstances may be discussed. Ultimately, the selection of an item for an individual's vehicle must be based upon the independent study of the vehicle owner in consultation with people in the hobby and restoration experts.

EFV-8 Club Forum Home | Back to Home Page | Contact the Webmaster

Copyright © 2009 - EFV-8.org
Powered by < CF FORUM > v.2.1