| fordmerc | -- 09-02-2010 @ 1:29 PM |
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Rebuilt engine stalls at stops, runs a little roughly at idle and requires higher idle speed than other engines I've heard. It starts easily, seems to run OK (?) on the street. I need help troubleshooting. Suggestions appreciated.
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| alanwoodieman | -- 09-02-2010 @ 3:27 PM |
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did you rebuild the carb? sounds like a high float level in the carb, when it loads up can you clear it up by gunning the accelerator?
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| fordmerc | -- 09-02-2010 @ 3:33 PM |
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Carb rebuilt professionally. If I can "catch it" before it stalls a gentle touch of the accelerator will keep the engine going; hand throttle also works.
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| supereal | -- 09-02-2010 @ 3:45 PM |
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The quickest way to diagnose that problem is to use a vacuum gauge. When you have that kind of problem, it is important to find the cause before you start to change things, which usually add another problem or two before you find the actual cause.
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| 37RAGTOPMAN | -- 09-02-2010 @ 4:27 PM |
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On rough idle, maybe the plugs got fouled,this happens sometime with new engine, find out why a rough idle,I think this is most of your problems, bad ignition wires, spark plugs, dirty, or fouled, like super says, stick a vacuunm gauge on it and see what reading , 37RAGTOPMAN and KEEP on FORDIN
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| fordmerc | -- 09-02-2010 @ 5:11 PM |
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Spark plugs pulled; =OK. Ignition wires new (repro). I'll check with vacuum gauge tomorrow. Thanks for the chart.
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| 37RAGTOPMAN | -- 09-03-2010 @ 6:12 AM |
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check the ignition wires ,by when running and in a dark area, spray the wire with water, [ Windex sprayer will do ] and see if you get arcing, do this to rule these out. if it ran good before. What did you do that is different and making it run different,??? my 3 cents worth,37RAGTOPMAN, an KEEP on FORDIN,,!!!
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| fordmerc | -- 09-03-2010 @ 12:54 PM |
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No arc with water spray. Vacuum readings don't conform to the algorithm from Supereal.: At idle, needle wavers irregularly at 17-18. Quick throttle push/release, drops to 0-1 then back to previous. Sustained throttle (5 sec) then release, drops to 0-1, stays in the 17-18 range with waver, returns to 12-13 with very irregular fluctuation and rough engine ready to stall up[on release of throttle). After running up and down the street, I have 23 miles on rebuilt engine; I can't say it ever ran perfectly smoothly. I'm reluctant to take it on a long drive because I had a hard time starting it when it stalled at a stop on the last trip, which is what sent me to the forum. Before that I would have been willing to accept "it'll break in later" as an answer. (It did and continues to start easily except for that one episode) Maybe "break-in is still the answer??
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| supereal | -- 09-03-2010 @ 1:59 PM |
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Which vacuum readings don't conform to those on the chart? All of the conditions cited are basic, and a large deviation in any one indicates a problem with the area in question. In my opinion, nothing spoils the ownership of an old car more than being unsure that it is dependable. Compared to today's vehicles, our old Fords are very simple machines, and were designed so they could be repaired by those with limited skills, making them ideal for a hobbyist.
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| fordmerc | -- 09-03-2010 @ 3:03 PM |
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I may have used words incorrectly: my vacuum readings are on the "edge" of each step: -at idle: wavering @17 = really not good, but within range -open/close throttle quickly: drops to 0-2, rebounds to 22 =not good enough but shouldn't be worn rings --not much else fits, especially on a newly rebuilt engine and carburetor (the engine rebuilder has done consistent good work on other engines) I agree that fear of undependability takes the fun out of it.
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| deluxe40 | -- 09-03-2010 @ 4:04 PM |
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My '46 ran as you describe (rough idle, idle set high to keep it running, hard to start after it ran for a while). After switching carburetors and adjusting everything in sight with no change, I pulled a plug wire and observed a puny 1/8" blue/orange spark (when held near a head stud). Changed the coil and everything cleared up just fine. I could then set the idle down and adjust the mixture screws on the carburetor to fine tune.
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| Pauls39 | -- 09-03-2010 @ 5:25 PM |
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What year flathead do you have? My best guess is that you have one or more cylinders not working or working intermittantly. I would suspect some ignition related problem and it would help to know which distributor you have. That said things to look for would be incorrect timming (timming set wrong, points adjusted incorrectly, vacuum advance not working on a 8BA). Recheck your plug wires to be sure the firing order is correct, on an early engine besure the distributor caps are registered correctly. Pull the plug wires one at a time and listen for a drop in RPM. Dead cylindars won't affect RPM. The spark should jump a 1/4 gap and be bright blue. Your engine should run better as the rings and valves get seated better and your vacuum should improve.
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| 37RAGTOPMAN | -- 09-03-2010 @ 6:20 PM |
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fordmerc let us know,what year and what engine, did you try a little richer mixture at idle on the carb. and also jump the ignition resister, with aligator clips and a jumper wire, just jump it for a few seconds,and see if it runs better, you might have a weak coil, if it runs better I would suspect the coil,or condensor. like said before.,see if you are getting a blue spark, if not a GOOD hot spark, it will never run right, also I had problems with a weak spark,and running very bad with no power, I put a ICE PACK on the coil,, YES a ice pack and it ran much better, changed the coil and NOW runs Great. 37RAGTOPMAN an KEEP on FORDIN,,,!!!!!!!!!
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| fordmerc | -- 09-04-2010 @ 5:29 AM |
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car is '39 Mercury, engine is rebuilt original, carb and distributor are the original ones, rebuilt. I have adjusted the fuel mix and a very rich mix does seem to run a little better.I will pursue the various checks on the spark, coil etc. I know that all the rebuilt stuff and "new"coil are potential problems, but I have been giving them the benefit of doubt; I'll try to check each.
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| supereal | -- 09-04-2010 @ 9:32 AM |
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From what you have described, I suspect that the valve clearances were improperly set by the rebuilder. The clearance closes up somewhat when the engine rises to, or above, operating temperature, and a too close original setting prevents valves from seating fully. This is particularly true if new valve springs were not installed. The exhaust clearance is .014 to .016, and the intakes should be set at .010 to .012. We like to set them on the higher side To allow for some change as the valves settle into their seats, even though it risks some valve noise. There may also be a problem with a mismatch between the angle of the seats and the valve faces. Usually, this type of problem doesn't ease as time passes, and likely will get worse.
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