| dggohl | -- 06-12-2016 @ 7:47 PM |
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Hi, I just put a 53 mercury 255 into my 52 Mainline. At idle the car runs great. But when I accelerate just before the shift the car bogs down with that jerky motion, hesitation. I thought it might be the accelerator pump, replaced it, i little better but problem still persists. I also turned out the jets about a half turn. No change.
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| 40 Coupe | -- 06-13-2016 @ 4:42 AM |
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Make sure the distributor advance is working properly. Can do this with a timing light. Put a vacuum gauge on the engine and look for results. This message was edited by 40 Coupe on 6-13-16 @ 4:44 AM
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| dggohl | -- 06-20-2016 @ 6:44 AM |
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Hi, the timing is right on. I checked the vacuum and it shows on constant 18 on the gauge at idle. Could this be something with the fuel pump?
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| TomO | -- 06-20-2016 @ 7:10 AM |
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I believe that 40Coupe meant for you to watch the timing marks when operating the accelerator. You should see the timing advance. Turning the idle mixture screws (what you called jets) will only affect the idle. Do you have the Mercury carburetor and distributor or the Ford ones? Tom
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| dggohl | -- 06-20-2016 @ 8:17 AM |
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I have the Merc carburetor on it.
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| dggohl | -- 06-20-2016 @ 8:18 AM |
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And, the Merc distributor is on with the Ford distributor cap.
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| TomO | -- 06-21-2016 @ 8:16 AM |
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Run the car until the engine is at normal operating temperatures. Shut off the engine, remove the air cleaner and operate the accelerator linkage while observing the carburetor. You should see 2 streams of gas. If you do not see them, your carburetor needs to be rebuilt. If you see them, the problem is probably in the distributor. Set the idle speed to 450 RPM. Disconnect the vacuum hose going to the distributor and check the timing. Adjust it if it is not 2degrees BTDC. Connect the vacuum hose and recheck timing. Accelerate the engine while watching the timing. It should advance. If you have a vacuum pump, try applying 7 inches of vacuum to the vacuum advance. It should hold the 7 inches. If not the diaphragm is bad. Tom
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| juergen | -- 06-23-2016 @ 7:21 AM |
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Tom, are you sure that the timing should advance on acceleration? I thought in normal cruise (high vacuum) the fuel ratio is lean and takes a longer time to complete combustion, hence maximum advance. On acceleration, the vacuum goes down, the fuel mixture is richer and less time is needed for combustion. So like disconnecting the vacuum, the timing is retarded.
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| TomO | -- 06-23-2016 @ 7:54 AM |
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Juergen, you are correct during acceleration, the timing will not advance, but once the engine is at a steady speed you will see advance from the vacuum advance. There are no mechanical advance weights in this distributor, the timing is controlled by the springs inside the distributor and the vacuum advance. This is just a rough test. The better test is to have the distributor set up on a distributor machine by a qualified operator. Again, I am sorry that I did not make myself clear. Tom
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| dggohl | -- 06-23-2016 @ 9:07 AM |
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Tom, I have gas coming out of both jets in the carburetor. If it is the distributor, what would be at fault to cause the hesitation? Thanks in advance for your feed back.
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| dggohl | -- 06-23-2016 @ 9:17 AM |
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Tom, OK, i get it. I see where if the diaphragm is bad why it would cause the hesitation. I'll replace and let you know. Thanks again. David
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| TomO | -- 06-25-2016 @ 7:33 AM |
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I strongly suggest that you have your distributor set up on a distributor machine before you replace the vacuum advance. The Ford distributor is unique in that it does not have mechanical advance weights to set up the mechanical advance, it uses springs to accomplish this. If it is not set properly, the gas mileage and performance will suffer. If the diaphragm is bad on the vacuum advance, it will show up on the tests done on the distributor machine. I don't have any personal experience with shops that do this, but if you post your location, someone else may be able to give a recommendation. Tom
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| dggohl | -- 06-25-2016 @ 8:31 AM |
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Tom, I did replace the vacuum advance. This is a Merc distributor. Seem to help a bit, but still have hesitation. I re-timed, and now experiencing a little back fire. Now, there is a screw on the side of the distributor, haven't turned not knowing what its for. Doing research now to determine. Plenty of vacuum from the carb upon acceleration. 18 inches of vacuum on test. Still stumped.
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| trjford8 | -- 06-25-2016 @ 3:43 PM |
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Did you change the condenser? The backfiring can be a sign of a bad condenser.
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| shogun1940 | -- 06-25-2016 @ 6:42 PM |
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What happens if you wind it up in first to 3500 rpm does it run out of gas,, just curious ?
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| dggohl | -- 06-26-2016 @ 5:41 AM |
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I didn't. After re-adjusting the timing to the 2 degrees advance timing, the backfire ceased.
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| dggohl | -- 06-26-2016 @ 5:44 AM |
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I'm not sure what you mean by running out of gas. In first gear I can rev it high, (i don't have an rpm gauge) and all i get is mild hesitation. I did the same in 2nd gear, high rev and more hesitation persisted.
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| len47merc | -- 06-26-2016 @ 7:41 AM |
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I don't want to put words in shogun1940's mouth so will leave it to him to respond to your question but think I know what he means and will describe a flathead experience and solution that sounds somewhat similar to yours. When accelerating up to 3,000-3,500 rpm and shifting, and when running steady on the highway at 55 mph on a flat then starting up a long grade/slope, the car would 'dive' on me, meaning the motor simply quit as if it had lost spark or, as found out to be the case later, was starving for fuel. When not accelerating so aggressively or slowing back down to 40-45 mph, respectively, the engine would not do this when shifting and would re-fire when slowing down to 40-45 on the highway and continue on. Using input from this Forum it was quickly diagnosed as the glass bowl seal on the fuel pump was leaking air and the pump was not supplying enough fuel to the carb under both these conditions. After removing the bowl and seal, cleaning all and then reinserting the seal (flipped over) and firmly tightening the bowl the problem was effectively eliminated. The seal would leak air during operation but never leaked fuel either during operation or when off. The bowl was always full as well so it was not intuitively obvious what was going on - under higher rpms or extended runs any further demand for fuel could not be met by the fuel pump sucking air. Any air leak in your fuel delivery system can create this fuel starvation condition. If this sounds similar to your situation, have you thoroughly examined this from fuel tank to the carb? Again, leaks of this nature will allow air into the system but may very likely not leak or show fuel. Fwiw. Steve
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| TomO | -- 06-26-2016 @ 9:59 AM |
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The Ford and Mercury distributors share the same design in 53. The springs may not have the correct tension to create the correct advance curve. This can only be correctly determined on a distributor machine. Tom
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| len47merc | -- 06-26-2016 @ 5:23 PM |
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dogghl - I re-read this entire thread and may have gotten side tracked a bit with my earlier post but you may have multiple problems going on now so keep my fuel system air leak discussion in your back pocket. Up until you started talking 'back fire' and timing changes your symtoms sounded quite familiar to my fuel pump bowl seal air leak. Given your comments about your work on the distributor I agree completely with Tom that you should have it set-up properly on the proper equipment as a first order of business. Take Tom's recommendations as more than just suggestions - he's one of (if not The) best on this Forum when it comes to these types of issues. As simple as these distributors look they are not intuitively obvious (kind of like the air leak on the fuel pump bowl) to work on. Get your distributor right and eliminate it as a root cause of your problem. Btw - my leak on the gas bowl seal spontaneously started several thousand miles after installing a new fuel pump and was not tied to any work done on the car. Again, you may ultimately find you had or may now have more than one issue going on, particularly given your changes to your distributor. It may be helpful for you to work one aspect at a time to be sure you know what truly is the root cause and it will also better help these seasoned experts like Tom and others get you running again more quickly. Steve This message was edited by len47merc on 6-26-16 @ 5:24 PM
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| dggohl | -- 06-26-2016 @ 5:49 PM |
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Thanks all for the suggestions. As i was driving home from my farm today, i too thought about the fuel pump, bowl etc. I'll look into that. If not the answer, I'll take your suggestions. When I purchased the motor from a "seasoned flathead veteran" he said the motor sat out of the car for about 7 year. When pulled, it was a smooth running unit. Thanks.
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