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| Won't idle cold https://slantsix.org/forum/viewtopic.php?t=21946 |
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| Author: | stuggin [ Tue Feb 20, 2007 5:06 pm ] |
| Post subject: | Won't idle cold |
Okay everyone, I have a question for you. So I converted to a super six intake and dutra dual exhaust, installed as per the "manifold installation" article. Now the problem is, it will run cold, but only if I keep my foot on the gas. It won't idle cold, but it will idle if it warms up. So the question is, what do you guys think is wrong? If it's a vacuum leak i think I'm gonna cry cause I just re-did the manifold installation with a composition gasket (i installed it with a stamped steel gasket before and it wouldn't run). It seems to be getting fuel and spark. The timing is probably a little off but it ran fine before the super six. I also did the fuel line mod and an electronic choke conversion, both of which seem to be working fine. Please help me out here guys! Thanks, Allen |
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| Author: | slantedview [ Tue Feb 20, 2007 5:15 pm ] |
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Sounds like it is time to break out the propane torch. Don't need to light it, just crack it open enough to get some gas flow. Run the unlit torch over likely vacuum leak areas and see if the engine picks up and runs better. I'm betting you need to bush the throttle shaft. Hope this helps. 
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| Author: | Doc [ Tue Feb 20, 2007 5:20 pm ] |
| Post subject: | |
It sounds like it needs a richer choke setting. If you choke it more by hand, will it stay running? Try giving it less choke "pull-off" when it first starts. DD |
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| Author: | dakight [ Tue Feb 20, 2007 6:01 pm ] |
| Post subject: | |
Also be sure the fast idle cam is at the proper flat and the fast idle screw adjusted correctly. |
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| Author: | stuggin [ Tue Feb 20, 2007 6:19 pm ] |
| Post subject: | |
Alright so there is definitely a vacuum leak at the throttle shaft, which i haven't come across before (no idea why, I thought i checked up and down this thing like four times for those), but I thought that vacuum leaks were present at idle regardless of the temperature of the engine? Do you think that this is my only problem? Thanks, Allen |
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| Author: | SlantSixDan [ Tue Feb 20, 2007 6:53 pm ] |
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No, I think that's contributing, but I don't think your choke system is set up correctly. What exactly did you use for a carburetor? Was it a BBD off a 225, a BBD from a V8, something else? What kind of choke thermostat and modulator are you using? |
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| Author: | dakight [ Tue Feb 20, 2007 7:00 pm ] |
| Post subject: | |
A vacuum leak causes a lean condition but when the engine is cold it needs to be richer. You can compensate to some degree when the engine is warmed up and idling normally but the requirements are radically different for a cold engine with the choke closed. |
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| Author: | stuggin [ Tue Feb 20, 2007 7:06 pm ] |
| Post subject: | |
Dan - Well I don't exactly know where the carb came from as i got it second-hand, but there's no holes in the throttle blades, so i believe that it's a BBD from a 225. As for a choke thermostat and modulator, i actually don't know what that is. I just hooked the electric choke up as per the directions that were sent along with it (the electric choke conversion kit you always recommend). The sensor is mounted on one of the bosses on the manifold side of the head, right by the choke. If you mean the actual thermostat, then it's a 180* one, as per the FSM. David - That makes sense, thanks. Thanks, Allen |
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| Author: | SlantSixDan [ Tue Feb 20, 2007 7:40 pm ] |
| Post subject: | |
Do keep in mind that out of the box, those electric choke kits don't come pre-adjusted. Usually they're slacked all the way off and you have to dial-in some tension before they'll work. When the engine's cold (sitting overnight) and you open the throttle before trying to start the engine, does the choke plate snap shut with a fair amount of tension? Not all of the V8 BBDs had holes in the throttle plates. The reason why it matters is that the V8 choke lever is differently orientated. You can usually get the slant-6 choke thermostat to hook up to it, but the geometry's out of whack and it won't work reliably without choke lever mods. How 'bout a good clear couple of pictures of your carb, have you got a digital camera? |
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| Author: | stuggin [ Tue Feb 20, 2007 7:52 pm ] |
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Quote: When the engine's cold (sitting overnight) and you open the throttle before trying to start the engine, does the choke plate snap shut with a fair amount of tension?
No, it doesn't, but my dad adjusted the choke the other way so that it would be a little bit (about 1/4") open as to allow a little bit of air into the carb at startup. I take it this was a mistake?Pictures of Carb are here, here, and here. Thanks, Allen |
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| Author: | SlantSixDan [ Tue Feb 20, 2007 8:55 pm ] |
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Yep, there's your problem. The choke needs to be adjusted so that when the car's been sitting overnight (or in the cold for a couple hours) and you open the throttle without starting the engine, the choke plate closes all the way closed. The choke plate is mounted offset on the shaft so that the force of air flowing downward will act more on one side of the plate than on the other, tending to swing it open, and the choke pull-off's whole entire job is to pull the choke partially open when the engine fires. Before the engine starts, it really needs to close all the way. A good "quick 'n' dirty" gauge for choke tension is that in cold temperatures after the engine's been sitting all night, once the choke plate is closed (with the throttle held open, without the engine running) you should be able to push it open by pointing your index finger and pushing on the choke plate. It shouldn't fly open at a feather-light touch, but neither should it require much of any muscle to push it open. Get it adjusted to that loose spec and then you can twiddle it a little this way or that for final adjustment. That is a slant-6 carb, so that's good  Looks like it's been through a sandblaster a few times, though. 
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| Author: | stuggin [ Tue Feb 20, 2007 9:03 pm ] |
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Alright sounds good, will get the choke thing sorted out shortly. I'll also get the carb re-bushed (assuming it's worth re-bushing, the casting's pretty straight and it looks ok. I'll get the guy at the carb shop to tell me i guess). Thanks a bunch everyone, Allen |
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| Author: | stuggin [ Thu Feb 22, 2007 10:10 pm ] |
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Alright one more question: Just got my carb back today from getting re-bushed. Now, the car won't even start, no matter what i do for it (i adjusted the choke the way you told me to, Dan). So, my question is, what do you guys think the problem is? It would seem that it's a carb-related problem, but there's gas shooting out of it, so i don't know if it is. The timing is the same as when it did work, and it's getting spark. If you fella's think it needs a rebuild, could someone recommend a kit (a NAPA part # would be helpful)? Thanks a ton, Allen |
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