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11-24-2019, 08:05 PM | #81 |
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Re: Sudden rough running, out of ideas
Wanted to circle back to this since I finally had time to make some changes:
After all that I think I was able to get the idle down a little bit. Not to where it was when I got this car 2 years ago, though. Also I discovered that the rebuilt Bert's carb had been sent with a filter screen that had stripped threads. First time I opened the gas cut-off, a steady stream of gas came out the front of the carb where the screen inserts. I rigged up a temporary plug by putting a nut halfway up a 1/2x20 bolt, threading the bolt a few turns into the carb, and then tightening down the nut to seal it. Still leaks a bit but it'll work until the new part arrives. Haven't had time to drive it yet to see if it still stalls on stop. If it does then I'll really be out of ideas. |
11-25-2019, 10:39 AM | #82 |
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Re: Sudden rough running, out of ideas
Not sure at this point what you know, or what has been troubleshot after all of your efforts above. Seems at this point we are unsure if it is a carb/fuel mixture issue, or if an ignition issue. You may want to run ignition and plug reads again. Do not mean to insult you, just reviewing what I think I know, others can chime in and correct me where needed.
Here is a site with lots of Carb info that is supported by Berts. More info than you probably want, but perhaps it will give you additional ideas. https://www.modela.org/ Not sure where you stand at this point since so much has been attempted. Do another plug read to base line the carb. Perhaps resort to a timing light to see were your advance at idle is at, and if it is stable or varying. You could also try an ignition tester to see the quality of your spark at each plug, there are a few different types, this is my preference. https://www.mikes-afordable.com/product/T12117.html On an A plug reads are done from running at med/high speeds and should be tan on the center porcelain. Black but not sooty is ok on the rest of the plug. Clean up plugs, run at higher speeds (country driving for awhile), turn off ignition and chop the throttle, coast to side of road or parking area, read plugs. At idle /lower speeds it is not uncommon for the porcelain to be black, but not sooty. My understanding of Carbs. At idle rpms (650 rpm and less) the carb idle mixture screw controls mixture, GAV does not affect the mixture. At fast idle (above 650 rpms) to med speeds (revs) the GAV affects mixture and the idle mixture screw mostly does not affect the mixture. The higher the motor speed (revs) the GAV has less affect on the mixture as the Jets take over most control of the mixture. The GAV still has some effect, will run very lean if GAV is completely closed. If running closed you may have poor running at lower speeds , and perhaps a slight pop/backfire when shifting or letting your foot completely off the gas, and will not fast idle. Typically adjustment of GAV a little richer solves this. If plugs are sooty at higher speeds could try a hotter plug, or the issue is with the jets or a vacuum leak. |
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11-25-2019, 10:55 AM | #83 |
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Re: Sudden rough running, out of ideas
If unresolved you may be at a point where you need want to remove the valve access cover and check to see if the valves are seating properly on cylinder 2. You still have weak compression of 50lbs compared to 60-65lbs on the others. Maybe you will get lucky and have a sticky valve, or a piece of carbon under one of the valves and it can be resolved without removing the head.
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11-25-2019, 11:09 AM | #84 |
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Re: Sudden rough running, out of ideas
Have you put a vacuum gauge on it? That is, if you have a port on the intake manifold.
That low idle might come back if you push the throttle closed at the carb. My throttle plate was ever so slightly out of alignment and wouldn't close completely resulting in a high idle. Adjusting the throttle plate dropped my idle considerably. Most common fix for stalling on a fast stop is to adjust the float level. |
11-25-2019, 11:29 AM | #85 | ||||
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Re: Sudden rough running, out of ideas
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Thanks everyone for the continued feedback, I still hope to get this resolved. |
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11-25-2019, 11:33 AM | #86 |
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Re: Sudden rough running, out of ideas
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http://www.fordgarage.com/pages/vacuumtune.htm Here is the string it is in. https://www.fordbarn.com/forum/showt...t=vacuum+guage More info https://www.fordbarn.com/forum/showt...t=vacuum+guage |
11-25-2019, 11:41 AM | #87 | |
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Re: Sudden rough running, out of ideas
Quote:
Edit: Just bought one off eBay, will have a report in a week or so. Last edited by alexiskai; 11-25-2019 at 11:52 AM. |
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11-25-2019, 11:51 AM | #88 |
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Re: Sudden rough running, out of ideas
Some good links there. If you don't have a vac gauge, horrible freight sells one for ~$15 and it works decently well. It might not be the best way to diagnose a problem but it should give you some good info to work with.
Also, note that last sentence on the fordgarage link. If you see a reading like that, I would definitely be looking at the throttle plate alignment. Definitely hold of on adjusting the float until you know how the car performs. No need to pull the carb back apart unless you know you have to. |
11-25-2019, 11:53 AM | #89 | |
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Re: Sudden rough running, out of ideas
Quote:
Right, that was another question. Do you use anything in your gas? MMO or 2-stroke oil? That low compression could be a sluggish valve. Not sure if someone said that yet or not. |
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11-25-2019, 12:02 PM | #90 |
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Re: Sudden rough running, out of ideas
I do not use MMO in the gas, but I have some on hand and, based on that other MMO thread, seems like it's worth a try.
Just bought this guy for $18, looking forward to taking some readings and reporting back. |
11-25-2019, 12:06 PM | #91 | |
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Re: Sudden rough running, out of ideas
Quote:
Last edited by 30 Closed Cab PU; 11-25-2019 at 12:25 PM. Reason: I had a brain fart |
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11-25-2019, 12:16 PM | #92 | |
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Re: Sudden rough running, out of ideas
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Almost missed this, pretty funny, you made my day Ryan |
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11-25-2019, 12:26 PM | #93 |
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Re: Sudden rough running, out of ideas
Edited my post #91 - had a brain fart.
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11-25-2019, 01:40 PM | #94 |
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Re: Sudden rough running, out of ideas
OK, thanks, so my to-do list is:
Gonna hold off on removing the valve cover for the moment because it's a pain and I'll probably need to replace the gasket. If it is valves (based on vacuum reading), I'll see if I can free them up with MMO or penetrating oil. |
11-25-2019, 02:02 PM | #95 |
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Re: Sudden rough running, out of ideas
Sounds like a good plan.
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11-25-2019, 08:53 PM | #96 |
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Re: Sudden rough running, out of ideas
Five pages of information and no one has suggested that an easy way to find ignition system short circuits is to run the engine at night in total darkness. No guaranty of course but sometimes the problem is quickly solved if ignition related.
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11-26-2019, 12:08 AM | #97 |
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Re: Sudden rough running, out of ideas
Is there reason to think that the current stage of the problem (fast idle) may be related to a short circuit?
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11-26-2019, 10:07 AM | #98 |
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Re: Sudden rough running, out of ideas
Is the motor running rough, not even firing at idle?
Sometimes sneak paths are resistive, causing marginal/poor spark instead of a direct short. An example is a bad distributor body where the internal electrical path from the dist. internal contact to where the spark plug wire is connected has opened, or the body has developed a resistive path to ground. This is why it is best to clean off the distributor parts to prevent dirt/lube/etc from creating a sneak path to ground. . Running at night sometimes allows you to see a sneak path . I've seen mechanics in the past use a water misting bottle while the motor is running to trouble shoot this, and to trouble shoot bad (too high resistance) plug wires in modern cars. |
11-26-2019, 11:39 AM | #99 |
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Re: Sudden rough running, out of ideas
Although the title of the thread is "rough running," somewhere along the five pages of posts I got that fixed. However the fast idle remains.
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11-26-2019, 01:09 PM | #100 | |
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Re: Sudden rough running, out of ideas
Quote:
Thanks for clarifying. So is a case it is stalling, or a case of not being adjustable enough at the carb and or steering column lever, or running erratically when running at low rpms and then stalling? |
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