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Posted By Discussion Topic: 39 Merc Engine trouble     40fordconvert 07-21-2011 @ 7:38 AM reply profile send p.m. Member Posts: 3 Joined: Apr 2011 My dad's 39 Merc is running rough over 1500 rpms. It's the original flathead V-8 (95hp). The gas mileage is about 9 miles to the gallon and he has noticed gas on the floor of his shop (from the tail pipes after taking it for a drive). Can't seem to get the idle adjustments on the carb to facilitate any noticeable change in rpms. Also, when he switches plug wires around, in some cases the engine idles about the same. He has been through the carb, distributor, adjusted the timing numerous times, all to no avail. The engine was rebuilt about a year ago. He even pulled the radiator and check to make sure the timing marks were lined up. Nothing seems to work and it's driving him nuts. Help or suggestions? Mike alanwoodieman 07-21-2011 @ 9:15 AM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 look at the plugs, are they covered in black soot? One of my guess's is the carb power valve is leaking, throwing way too much gas into the engine. ford38v8 07-21-2011 @ 9:46 AM reply profile send p.m. Senior Posts: 2793 Joined: Oct 2009 Mike, Your problems may seem unsurmountable, but they are all addressable, as the flathead is pretty simple when compared to a modern engine! Rather than to write a book in answer to your questions, I'd suggest that you obtain a book that has all the answers you seek. There is one I'd be certain to have, available from most antique Ford dealers: "Ford V8 Service Bulletins 1938 - 1940". Here is one listing for that book from C&G Early Ford Parts: https://secure435.hostgator.com/~dlvry40/ufolder/ShowProducts.php?c=1&s=1&g=2&t=5 If your father has attempted to make adjustments on the distributor without success, he would do well now to remove it from the engine and send it out to be serviced, as a distributor machine produces better results than can be done manually. Here is the website of Skip Haney, who comes highly recommended for this service: http://www.fordcollector.com/ When you receive the distributor back from Skip, it will be timed perfectly, and will need only to be installed correctly to function properly. I know I haven't answered any of your questions, but the book does that so much better! Alan deluxe40 07-21-2011 @ 9:51 AM reply profile send p.m. Member Posts: 413 Joined: Oct 2009 The last two times I had similar problems ('41 & '46 Fords) it turned out to be weak coils. The idle mixture screws not having any effect is because gas is getting through some other channel. In my case it was because I had to set the idle up too high to keep the engine running with the weak spark. Pull a plug wire and hold it next to a head stud. You should see a steady blue spark about 3/8" long. Orange spark or a spark of less than 1/4" indicates ignition trouble. Other problems could be a leaky or improperly set float in the carburetor, a leaking power valve (as already mentioned), a bad capacitor or a faulty distributor. I have experienced several of these problems causing the same symptoms. The most bizarre, however, was a leaking water pump that was throwing water into the distributor. We made it to our next stop but the guys behind us had runny eyes from the fuel I was losing out of the tailpipe. 37RAGTOPMAN 07-21-2011 @ 6:11 PM reply profile send p.m. Senior Posts: 1971 Joined: Oct 2009 take a compression test, I do not care if the engine was rebuilt. so you know for sure it will hit on all 8 cylinders, it may have some valves that sticking . check the float and float level in the carb and the needle and seat for any dirt that may have come from some place, alowing gas to leak down the thoat of the venturi, not shutting the fuel off and causing a high float level, while it is running, using a mirror and a flash light look down the venturi, if any gas running down the thoat.??? black smoke out the back ???? eyes watering while running,???/ let us know how you made out,give us more info, my 3 cents 37RAGTOPMAN TomO 07-22-2011 @ 8:18 AM reply profile send p.m. Senior Posts: 7272 Joined: Oct 2009 All of the above advise is good, but don't do a wholesale parts replacement. Start with checking the spark. It should be blue in color and be about 1/2" in length when a plug wire is held near a head nut, while the engine is idling. Weak spark can be caused by a weak coil, a bad condenser, and incorrect point dwell. Dwell can be checked by setting the points on a distributor machine. If your spark is OK, let the car sit for a day and check for fuel in the carb bowl, by either taking the top of the carb off or operating the accelerator 3 time and while looking down the throat of the carb and seeing 2 streams of fuel with each operation. If the carb fails this test, the power valve or its gasket is failing. If it passes this test, start the car and let it idle until it is at operating temperature. Shut it off and look for signs of fuel leaking into the throat of the carb. This would happen if the float is set too high. You could also remove the top of the carburetor and observe the fuel level, it should be no higher than 11/16" from the top surface of the bowl to the fuel. Tom supereal 07-23-2011 @ 10:12 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 I'm not sure why he pulled the radiator to "check the timing marks". If it is not the later style (post '49) engine, there are no timing marks. The distributor drive tang is offset to align the distributor with the camshaft, and the adjuster on the side of the unit will have little or no effect on the problem. I suspect either the carb float valve is not closing, or the carb float has sprung a leak and is not shutting off flow when the bowl is full, causing the carb to be swamped. That may cause enough overflow to allow gas to come out the tailpipes, but only if a vast amount is being pumped into the intake manifold, a very unusual event. Don't drive it until it is fixed. 40fordconvert 07-26-2011 @ 8:42 PM reply profile send p.m. Member Posts: 3 Joined: Apr 2011 Thanks so much for all the suggestions. I'll pass them on to my dad. Very much appreciated. Is anyone out there close to Owatonna Minnesota? My dad lives in Steele County. 40fordconvert 07-29-2011 @ 8:41 PM reply profile send p.m. Member Posts: 3 Joined: Apr 2011 Alan, I just wanted to thank you for your input as well as the recommendation to purchase the 38-40 service bulletin. It's the best book I have. After considerable reading, I'm going to suggest dad start with the fuel pump and check the outlet pressure. I suspect the diaphram might be too tight after years of sitting and causing too much pressure. After that I think we'll check for vacuum leaks and then carburetor, etc. Again, thank you so much for taking the time. mike mikehill@rsvpre.com

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