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Discussion Topic:
39 Mercury running rough
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supereal |
01-16-2013 @ 10:58 AM
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Senior
Posts: 6819
Joined: Oct 2009
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Be aware that many of the carb kits being sold are not "fuel proof" for the new gas. Many also have weak accelerator shaft springs and other inferior parts. The best advice is to not fool with your carb unless you are having problems. If you do need to rebuild it, get parts from a vendor that sells lots of them, or have a pro do it so the throttle shaft can be properly bushed, and the power valve fitted to the boss on the carb bowl. Many replacement valves will not seal properly because the gasket flange doesn't match the valve face, causing fuel leakage and loss of vacuum to the valve.
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TomO |
01-16-2013 @ 7:30 AM
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Senior
Posts: 7250
Joined: Oct 2009
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Roger, Welcome to the Forum.
Tom
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RogerMitchell |
01-15-2013 @ 12:49 PM
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Member
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Joined: Jan 2013
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I have a 1940 Mercury town sedan that I just finished restoring. I rebuilt the carburetor and after that it wouldn't idle worth a darn and ran rich. Turned out that the new power valve had a bad diaphram and was leaking fuel from the carburetor fuel bowl directly into the intake manifold. I got a new one at NAPA and it has run fine since.
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Mercury8 |
11-08-2012 @ 8:27 AM
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Member
Posts: 16
Joined: Dec 2011
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Greetings: I have a 40 Mercury coupe, currently doing a body off restoration. When I first bought the car, I was having some of the same running and shutting down problems you are having. From the electrical standpoint, my problem traced down to the most overlooked, yet very crucial, resistor. A bad resistor can work fine, and the reduced voltage will show correct. As soon as you turn your back, the voltage will drop and shut you down. Wait a few minutes for the resistor to cool, and the problem goes away. In the meantime, you change the coil, wires, condensor, points and what else, then the problem surfaces again. The resistor is so often overlooked. From a fuel problem, my car turned out to have a 37 intake manifold, that was burning up the power valve in the carb with hot exhaust gas. The burned power valve would allow un-metered fuel to drip into the intake, causing a rich condition, and rough running. Just a thought. Good luck, leave me an email and we can chat further.
Alan
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39mercury |
06-05-2012 @ 8:38 AM
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Member
Posts: 47
Joined: Mar 2011
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Attached are some images of the before and after for the 39 Mercury 99A Town Sedan.
This message was edited by 39mercury on 6-5-12 @ 8:40 AM
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TomO |
06-05-2012 @ 6:30 AM
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Senior
Posts: 7250
Joined: Oct 2009
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Glad that you fixed it. Now you can enjoy driving it this summer.
Tom
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39mercury |
06-04-2012 @ 8:43 AM
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Member
Posts: 47
Joined: Mar 2011
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First thanks for all the comments and technical help. Here is the update. Checked the spark by grounding a plug wire to the block while cranking the engine. No spark. Removed the distributor and found that the points were burned. So we cleaned off the contacts and put the distributor on the block with a jumper from the battery and spun the rotor. Sparks inside!! Put the distributor and coil back on the engine. Hit the starter and it fired right off and runs great.
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supereal |
05-30-2012 @ 11:16 AM
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Senior
Posts: 6819
Joined: Oct 2009
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You didn't mention whether the distributor points have been checked or replaced. One set of points "makes" the circuit, the other "breaks" it. If either set is making poor contact, rough running, if running at all, is likely. This is not rare when a car hasn't been run for a long time. Fuel will enter the bowl while cranking if the fuel level is low enough to open the input needle. If an obstruction is holding the needle off the seat, the carb will flood. This can result in rough running and very hard starting, and sooty plugs.
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39mercury |
05-29-2012 @ 8:39 AM
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Member
Posts: 47
Joined: Mar 2011
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Thanks Tom. I will check this out per your instructions starting with the presence of any spark. I will let you know what I find. Steve
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TomO |
05-29-2012 @ 8:05 AM
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Senior
Posts: 7250
Joined: Oct 2009
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You should not see fuel entering the bowl when cranking the engine, unless you are operating the accelerator. Your float is probably set too high. If you have the steel tipped needle set your float to specs. If you have the rubber tipped needle set the float 1/32" to 1/16" lower. If you have the gross jet (the one with the little ball in the window) set the float 1/16" to 3/32" lower. Before you mess with the carburetor, it is best to solve the reason that the car will not start. Check your spark by holding one of the plug wires near a head nut (use a small screwdriver with an insulated handle. Insert the blade in the plug wire end). If you have no spark, check the input to the coil. The voltage should go from battery voltage to around 3.5-4.0 volts when the points are closed. If you have a weak spark, change the coil.
Tom
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