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By 58rancho - 8 Years Ago
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Still fighting this problem, Revs drop to zero if car not held at 1500 rpm. I have plenty of volts, have tried my spare carb, looked at the distributor wiring.
No difference. 292 w/points, alternator conversion (happened before and after conversion. As an aside, I bought the alternator conversion off ebay. It is a good installation, but the directions could be more specific (or perhaps I could be smarter...). A well spent $189. Any ideas would be appreciated.
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By Steve - 8 Years Ago
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Sounds like a big vacuum leak. I take it this problem happened after some change to carb or ignition.
Are you running with PCV?
Not likely an alternator problem as the ignition would operate on the battery.
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By charliemccraney - 8 Years Ago
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"Still fighting" implies an ongoing problem. What have you done so far?
Which carbs?
Which distributor?
Is the timing advancing properly?
How old is the crankshaft damper?
Do you have vacuum leaks?
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By 58rancho - 8 Years Ago
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No vacuum leaks. Holley 2bbls, replacement was fresh rebuild, Ford distributor, don't know about the age of the damper. No PCV, has a road draft tube.
I have a spare rebuilt distributor, I guess that will be next. My mechanic skills are not getting better with age and the distributor is difficult to get to on my Ranchero.
This problem came on suddenly, car was running great one minute and not the next. Thanks for the input!
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By DANIEL TINDER - 8 Years Ago
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Failure of distributor diaphragm integrity can result in a sudden vacuum leak, but not sure how that might relate to your problem.
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By paul2748 - 8 Years Ago
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Have you checked to see if all the plugs are firing. Maybe pull the valve covers to check all push rods and rockers. Check valve lash. Have you tried to spray stuff around the intake and carb to see if a vacuum leak. Check the vacuum lines - sometimes there is a small crack you can't see if the lines are in place.
Had a bad idle that drove me nuts. All the lines looked good. One day I happened to hit one line and it fell off. Found it cracked, replaced it and everything was good
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By MoonShadow - 8 Years Ago
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Did it run before with the new carb? If not there could be something in there.
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By 58rancho - 8 Years Ago
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Thanks for the replies! It did run before the carb swap. I have a hard line from carb to distributor for advance, no other vacuum leaks.
It is a violent stall below 1500. It's difficult to describe, but it's like the engine loses all power. Above 1500 it runs pretty smooth.
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By 57RancheroJim - 8 Years Ago
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If it ran before the carb change thats tells you something. I saw a similar situation on a friends car not long ago. Who ever rebuilt the carb used a wrong gasket between the metering block and body and the thing was flooding the engine at lower rpms, also heavy black smoke until it would die. Could be a bad power valve also.
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By NoShortcuts - 8 Years Ago
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Numerous good items to check have been mentioned. What hasn't been mentioned is the ignition coil... Rare, but when they malfunction it's like throwing a kill switch in my experience.
Hope this helps! 
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By charliemccraney - 8 Years Ago
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In your original post, you said you "have tried my spare carb... no difference." Now you're saying it ran before the swap. Which is it?
If it was fine before the swap, then the problem is with your carb - most likely, the idle circuit is not working.
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By Pete 55Tbird - 8 Years Ago
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I`m curious. If the engine will not run below 1500 RPM how can you be so sure that you have no vacuum leak (s)? Pete
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By 58rancho - 8 Years Ago
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I apologize to Mr McCraney for my imprecise language, the change in carb made no difference, it ran the same as before. I neglected to mention that I had changed out the coil, thanks for that thought. As to Petes' comment, it doesn't stall out like a vacuum leak, it loses power like it doesn't have enough electrical juice to keep it running,. It almost diesels at low rpm. Thanks for everyones' patience and responses.
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By MoonShadow - 8 Years Ago
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Will it rev higher? Could be a fuel delivery problem. It's so hard to trouble shoot a problem over the internet but you will solve it I'm sure. Endeavor to persevere!
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By Sandbird - 8 Years Ago
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The pigtail lead that connects the coil to the points in the distributor has been known to have broken wires from year of flexing from the continuous motion of the breaker plate from the vacuum advance. You can't tell by just looking at it because the insulation is still intact. The broken wires can sometimes still make contact when the vacuum advance is in various positions which results from certain rpms.
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By paul2748 - 8 Years Ago
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What distributor are you running? If it's a 57 or later, try it without the vacuum advance hooked up. Be sure to plug the vacuum line.
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By 58rancho - 8 Years Ago
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Problem solved! This is a first for me, the points were physically broken. The contact spring mount where the primary and condenser wires attach was broken at
the bottom. The points could be set, but this whole assembly would move due to the breakage. Sorry for the lack of general knowledge, but I really appreciate all the input.
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By charliemccraney - 8 Years Ago
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I'm surprised it ran well at any rpm with that kind of problem. Never would have guessed that.
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By paul2748 - 8 Years Ago
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Glad you got it sorted out and told us about it
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By MoonShadow - 8 Years Ago
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That's one of those mystery problems that can take months or minutes to find all depending on luck. Glad you found it. Enjoy the cruzing.
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