| 39mercury | -- 09-18-2011 @ 7:02 PM |
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Looking for some help. This weekend I was out for a cruise in my 39 Mercury sedan. I have not driven it much this summer, and only short distances. After about 40 minutes on rual Indiana roads it acted like it was running on 6 cylinder when under load, and was idling kind of rough. When I got to my destination, I checked all the spark plug connections but did not find anything loose. I let the engine cool off although it was not running hot, then started it again. It started up immediately and seemed to run smooth again. Any thoughts on where to start trouble shooting? Gas, Carb, ignition or all of them. The points and wires are new as are the water pumps. I have not rebuilt the carb. Thanks. Steve Middleton
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| supereal | -- 09-18-2011 @ 8:35 PM |
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Two things come to mind. If you are running an old coil, it is more than likely it is failing as the under hood temperature rises. This accounts for the reason it runs fine after a cooling period. You didn't mention whether you have replaced your spark plugs when the points and wires were renewed. It is also possible your condenser is weak. We are finding many new condensers and point sets are not of good quality. The trouble you have is not likely fuel related. That is why "vapor lock" is often blamed, but usually turns out to be ignition related.
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| 39mercury | -- 09-19-2011 @ 11:54 AM |
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Thanks for the information. I did not replace the coil so I am ordering a new one from Mac's. I will also replace the condensor. The spark plugs were replaced and have very few miles on them. I will check them however to look for any fouling evidence. It makes sense that the coil and or condensor would work well cold but intermittant as the temp rises under the hood. Steve
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| supereal | -- 09-19-2011 @ 12:00 PM |
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You may wish to send your old coil to Skip Haney for a rebuild, too. Then you will have a spare, always a good idea with old Fords, and if the new coil fails, as is not rare, you can be ready. Be sure that you have the ignition resistor on your car, and that it is properly connected. Without the resistor, the coil will overheat from too much voltage. The resistor drops the voltage to the coil to about 3 1/2 volts, and steadies it by increasing resistance as the system voltage goes up with engine speed. Many resistors were removed or bypassed in the mistaken notion that it would increase the spark.
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| ford38v8 | -- 09-19-2011 @ 1:27 PM |
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Steve, I just looked on the Mac's website for the coil you ordered. I never buy from Mac's, so I wasn't familiar with their current offerings. I was surtprised that in addition to the new junk chinese coils they sell, they also offer rebuilt coils. They do not, however, say who rebuilt them or any warranty info, so I would suggest you stick with a known quantity: Skip Haney in Florida. Skip may have some cores, but you do need to send him your old coil. In any case, consider dumping your contact info with Mac's. I've never heard a good word about them. Not one. Skip Haney www.fordcollector.com Remanufactured coils and high volume modified water pumps for flatheads Alan
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| 39mercury | -- 09-19-2011 @ 1:40 PM |
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All, Thanks for the updated advice. I have not ordered it yet. I just looked at Skip Haney's webpage, and I am going to take my old coil off the car and send it to him. Also thanks for the heads up about Mac's. There is alot of Chinese knock offs out there. And Mac's wants over $90 bucks for theirs. Skip's appears to have modifications which will prevent it from overheating (ie. a resistor). I am doing some rust prevention on the ol Merc right now anyway so it is not being driven much. Now is the time to fix the Ignition problems. Thanks again.
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| TomO | -- 09-20-2011 @ 7:16 AM |
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Skip's rebuilt 6 volt coils use the original resistor. If you bypass yours, the coil will overheat. If your car starts reliably and idles nicely, leave your carburetor alone. Don't fix something that is not broke. I would check the spark when your engine is at normal operating temperatures to see if that is your problem. It should be about 1/2" long and blue in color when you hold a wire near a head nut and the engine is idling. If it is OK, check your plugs for a combustion problem. Here is a link to a good chart for diagnosis http://www.spark-plugs.co.uk/pages/technical/diagnosis.htm Tom
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