| 39mercury | -- 06-04-2023 @ 7:44 PM |
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Yesterday I drove my 39 Mercury door the first time in a couple months time. The temperature outside was in the mid 80’s and I drove it to my destination and it ran great in all gears. After a couple hours I began my drive home of 8+ miles it began to run rough and lose power in all gears. This has happened before and I have replaced so far these items only to have it return : Coil and ignition distributor from Skip Haney, fuel pump, Carburetor, plugs, wires, and vented gas cap. What am I missing! I’ve owned the Mercury 14 years and have restored it to driver quality but I cannot trust it to not leave me stranded??
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| carcrazy | -- 06-04-2023 @ 8:45 PM |
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There may be some rust or other crud in your fuel tank which has shaken loose and is plugging your fuel line, fuel pump or carburetor. There may be a marginally loose connection somewhere in the primary ignition circuit that is momentarily causing an open circuit. One or more of the wires somewhere in your wiring harness may have compromised insulation that is causing a short circuit. There may be a blockage in your exhaust system that is causing too much backpressure. Your air cleaner may have a blockage due to rodents, wasps or birds depositing items there.
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| TomO | -- 06-05-2023 @ 5:17 PM |
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Did it start running rough right away or after you had driven a few miles? Did it improve after you replaced the parts and then return after a couple of years or has it been lurking in the background and occasionally acting up? Some things that you can do to help diagnose the problem are: Do a fuel delivery check ( see vapor lock topic for instructions) When you have the problem, pull the choke out in small increments to see if performance improves. Check your spark when the engine is at operating temperature. Tom
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| 39mercury | -- 06-05-2023 @ 5:51 PM |
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Thanks I appreciate the feedback. I’m going to check the possible causes you mentioned. I do have a noticeable tick when accelerating and I know there’s very small pinhole in the right bank exhaust manifold weld when dual exhaust was installed several years ago. Could this be enough to cause back pressures after the engine is warm. I also agree about the possibility of particulates in the tank and fuel lines. I can drop the gas tank and have it cleaned as well. Maybe check the gas line from the tank to the fuel pump and carb. Steve
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| 39mercury | -- 06-05-2023 @ 6:30 PM |
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Hi Tom good to hear from you. A. It only began running rough on the way home an after sitting idle for 3+ hours. I did not exceed 45 mph. B. The performance improved with each item replaced, however the vented gas cap ended the car suddenly dying and not restarting easily. It would begin running rough then die. After the gas cap replacement I was beginning to trust driving it to events without issue. I was disappointed this weekend when the problem returned. I will try the items you mentioned and will let you know. Thanks much
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