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| Hesitation from a standing stop https://slantsix.org/forum/viewtopic.php?t=2980 |
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| Author: | Chris [ Mon Dec 10, 2001 6:17 pm ] |
| Post subject: | Hesitation from a standing stop |
Help! I have a 1972 Demon with a 225, automatic tranny, and a Holly 1920 1 barrel carb. The car has developed a hesitation from a standing stop. It idles great and accelerates great when it is moving. The real problem is just pulling away from stop signs. If the gas is applied gently, it will stumble and ocassionally stall. If the gas is pushed harder, it will hesitate slightly, but not nearly as bad as a gentle application. This happens at all temperatures. Setting the idle speed up to 850 to 875 rpm does minimize the hesitation, but does not eluminate it. I checked the vacuum advance in the distributor. It holds 25 psi and when a vacuum is pulled on it while the engine is running it does advance the timing. The mechanical advance is also working. I checked the fuel level in the carb bowl and found it just a little lower than spec. I adjusted it and it is now just a hair over spec. This made no difference. This is the original carb that I rebuilt about 5 or 6 years ago. I checked all of the hoses and they are all good. I am willing to believe that something has gone south in the carb but I am open to any other troubleshooting tips before I pull it off. Thanks winslow120@cs.com |
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| Author: | Eric W [ Mon Dec 10, 2001 8:01 pm ] |
| Post subject: | Re: Hesitation from a standing stop |
Quote:
: Help! : : I have a 1972 Demon with a 225, automatic : tranny, and a Holly 1920 1 barrel carb. The : car has developed a hesitation from a : standing stop. It idles great and : accelerates great when it is moving. The : real problem is just pulling away from stop : signs. If the gas is applied gently, it will : stumble and ocassionally stall. If the gas : is pushed harder, it will hesitate slightly, : but not nearly as bad as a gentle : application. This happens at all : temperatures. Setting the idle speed up to : 850 to 875 rpm does minimize the hesitation, : but does not eluminate it. : : I checked the vacuum advance in the : distributor. It holds 25 psi and when a : vacuum is pulled on it while the engine is : running it does advance the timing. The : mechanical advance is also working. : : I checked the fuel level in the carb bowl and : found it just a little lower than spec. I : adjusted it and it is now just a hair over : spec. This made no difference. This is the : original carb that I rebuilt about 5 or 6 : years ago. : : I checked all of the hoses and they are all : good. : : I am willing to believe that something has gone : south in the carb but I am open to any other : troubleshooting tips before I pull it off. : : Thanks Kinda sounds like your accelerator pump is on its way out. Throw a rebuilt kit at it and see if that helps out. Eric W My Big B |
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| Author: | Doctor Dodge (Doug Dutra) [ Mon Dec 10, 2001 9:12 pm ] |
| Post subject: | Re: Hesitation from a standing stop |
Quote:
: I have a 1972 Demon with a 225, automatic : tranny, and a Holly 1920 1 barrel carb. The : car has developed a hesitation from a : standing stop. It idles great and : accelerates great when it is moving. The : real problem is just pulling away from stop : signs. If the gas is applied gently, it will : stumble and ocassionally stall. If the gas : is pushed harder, it will hesitate slightly, : but not nearly as bad as a gentle : application. This happens at all : temperatures. Setting the idle speed up to : 850 to 875 rpm does minimize the hesitation, : but does not eluminate it. : : I checked the vacuum advance in the : distributor. It holds 25 psi and when a : vacuum is pulled on it while the engine is : running it does advance the timing. The : mechanical advance is also working. : : I checked the fuel level in the carb bowl and : found it just a little lower than spec. I : adjusted it and it is now just a hair over : spec. This made no difference. This is the : original carb that I rebuilt about 5 or 6 : years ago. : : I checked all of the hoses and they are all : good. : : I am willing to believe that something has gone : south in the carb but I am open to any other : troubleshooting tips before I pull it off. Check you initial timing, try 8 to 10º and see if that helps with-out pings. Also check to see if the "economiser valve" is blown or if the 3 screws holding down the cover are loose. DD |
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| Author: | Chris [ Tue Dec 11, 2001 4:34 am ] |
| Post subject: | Re: Hesitation from a standing stop |
Quote:
: Check you initial timing, try 8 to 10º and see : if that helps with-out pings. : : Also check to see if the "economiser : valve" is blown or if the 3 screws : holding down the cover are loose. : DD I have the timing set currently at 2.5 degrees ATDC which is where I have had it for years to aviod knock. The sticker on the fender says to set it between 0 and 5 degrees ATDC so it is within factory specs. I will give it a shot, though, and let you know the results. On the economizer valve, I did have it out last night to check the float level. It is fairly new because I rebuilt the carb a few years back and I only put about 5 to 8 thousand miles a year on the car. The thing is still shiney and showed no signs of deterioration. I will say, though, that gas here has changed over to the 10% ethenol pretty much everywhere and I have heard that that can cause problems for seals not designed for it. It may be worthwhile to pop for a rebuild kit for the carb and get all new seals and a new econimizer valve. Thanks, Chris Winslow120@cs.com |
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