Need carb help as usual

[Mercury Kid]

But I've got video to help you guys get an idea of whats wrong! I put about 150 miles on the car today, and about the same in the past couple days as well. It's run fine until this afternoon when it stalled pulling up to a stop light. The carb was just rebuilt and run through an ultrasonic so it was squeaky clean when it went on. It still runs flawlessly under acceleration and while cruising at any speed above 40. It lurches on decceleration and at low speed, and idles just like in the video. It likes to stall pretty often as well. Here's the video of it idling. It's a manual transmission for those that will likely ask. Thanks for any help.

 

[JackFish]

Maybe a failing fuel pump?

 

[Mercury Kid]

I thought that as well, but I have no way to know. Also thought maybe a plugged up filter, which will get changed either way.

 

[ludwig]

Get one of those big clear bubble filters and mount it ahead of the built in carb filter. That way you can at least see what is flowing through the lines. Although this a a bit of a poser because it doesn't work at LOW speeds and filter fouling should happen at HIGH speeds as debris gets sucked up.

Do you have your idle F/A mix set up properly? Is the choke butterfly drifting closed at idle perhaps? Or not pulling off all the way?

 

[Mercury Kid]

I've checked the timing, the A/F screw, the idle screw, everything. I did set the idle a bit higher and adjusted the timing by ear to get it to idle slightly better, but that was before I made the video. I don't think I actually changed the timing any, just moved the dist. back and forth to see if it made any difference, it didn't. I added fresh gas before the clip as well, but there was no change. I even tried some WOT acceleration to try and blow out any debris but to no avail. It's driveable, but I have to drop it into neutral instead of letting the engine slow the car, and keep an eye on the generator light incase of a stall, so I'll keep driving it and hope for a definate problem to arise.

 

[ArtemisI6]

Do you by any chance have a Pertonix module installed? I have the exact same problem, and the idling issue only popped up when I installed the module. Before, when it was points, it idled great.

 

[Mercury Kid]

Nope, it's still got points, and they look brand new. The condenser, cap, and rotor are new as well.

I tried a bottle of carb and injector cleaner in the tank but haven't had a chance to drive it enough to notice any difference. I guess I'll just keep trying various snake oils until something definate happens.

I've also got a used fuel pump in my stash that I might try as well.

 

[Frankenstang]

It's run fine until this afternoon when it stalled pulling up to a stop light.

Hey Mercury Kid, I'm guessing you got your accelerator pump (or bogging) issue resolved, and if I understand your statement here, it was running fine until the stall? No bogging issues etc?

It's very possible (especially the 1100), that there is crud in the fuel system. It could also be timing related vacuum etc, but the fact that it went from running fine to not, could be due to crud entering your rebuilt carb from the tank. What kind of condition is your gas tank in?

The inline filter on the 1100, the metal one that threads into the fuel bowl on the carb, has pretty poor filtering element...it will let alot of junk through that can dirty your needle valve&seat. The a/f mixture screw you mention only affects a/f mixture at idle. Once out of the idle circuit, the a/f ratio is a relatively fixed ratio controlled by the size of the main jet relative to venturi cfm. Point is that if the car runs fine at higher rpms and bad at idle, and the problem at idle just started occuring, I would think you've introduced some crud from the tank into the fuel bowl, which will keep the needle&seat from sealing properly and causing a rich/stumbling idle. Best way to confirm this is to check the condition of your plugs (would likely be black in color...maybe even wet...from the rich idle).

If this is your problem, I'd take the carb back apart, clean the needle/seat, and fuel bowl, flush the passages with some carb cleaner, and install an additional inline clear type fuel filter as Ludwig suggests (IIRC Fram G2 is one type) ahead of the stock one. This will keep crud from getting back into the carb/fuel bowl, but you may still need to flush/clean your tank and lines depending on their condtion.

 

[Harte3]

Go back to the timing and get something a bit more definitive than checking by ear. A good starting place is to use a vacuum gauge, obtain the highest steady reading and back off 1-2 hg and then go to the carb adjustments.

 

[Mercury Kid]

Thanks guys, I'm thinking the same thing. Dirt in the fuel. No idea on the condition of the tank. Looks really clean out the outside but obviously not on the inside. It's got new fuel lines from the tank to the pump as well. Somebody put some work/money into this car. I'll take the carb apart tomorrow and clean it out again. Might even try two inline filters it there's enough rubber in the line, I'm tired of this crap.

I've gotten pretty good at predicting the stall and keeping it running, just a little choke here and there lol. And luckily it starts up pretty regular as well.

Here's a pic of the car.

 

[Mercury Kid]

Took the carb apart, sprayed it out with carb cleaner and then an air hose, still runs the same. Added an inline fuel filter, looks clean and clear so far. I'm just going to bite the bullet and take a spare carb to be professionally rebuilt. I'm tired of fooling with it, I'm just cursed when it comes to carbs.

 

['68falconohio]

Mercury Kid,
If you get in a pinch and need an 1100 I have the one off of my 200 and I'm in cbus. This carb had been on my 200 since I bought the falcon 4 yrs ago and worked fine. I just pulled the old 200 engine and dropped in rebuilt engine with modified log so I won't be needing it anymore. If you're interested, let me know.

Stephen

 

[Frankenstang]

I've gotten pretty good at predicting the stall and keeping it running, just a little choke here and there lol.

Just caught this. Giving it a little choke to prevent the stall would actually indicate the mixture is leaning out prior to stall not too rich...I shoulda checked back before

Are you sure the float is adjusted correctly, although it seems unlikely that would suddenly go out of adjustment, and a leaky one would cause a rich condition.

Harte3 suggestion of setting timing by vacuum is a good idea as well for a couple reasons. One, set the most efficient timing at where the engine develops the most vacuum. Two, can help indicate a vacum leak as well...IIRC you should be pulling a minimum of 18hg.

Checking plug condition can also be helpful in diagnosing running condition.

I'd still be inclilned to think you have an obstruction in the carb somewhere, especially if it came about all of a sudden after running fine. For example, IIRC the idle mix screw is a vacuum feed, so an obstruction there or elsewhere in the vacuum feed for the idle circuit would mean you're not drawing enough fuel at idle. A vacuum leak elswere could also effect this.Do you get any difference in idle when you adjust the idle mix screw? What's the idle rpm set at? Just a friendly fyi, it's always helpful to include some specs in your forum profile re: engine size, carb model, tranny, etc. Let us know how it's going.

 

[BetsyBabe64]

Hey, i haven't read any other posts aside from the first one, but basically my engine sounds just like that as well. Before i started rebuilding my car, it didn't sound like that. For the last year i haven't started the car, what i have done is install a new fuel pump, new dist. cap, wires, spark plugs, air filter, and coil. I got my carb rebuilt, installed a new gas tank. I had to cut my muffler off because the new gas tank. I started the car up for the first time the other day, and it started right up, however after a little bit it starts to go up and down like your does. I'll push the choke in, or pull it out depending on what sound it makes, and then let it sit some more. a little bit of black smoke comes out the tail, and for the most part it revs up and down. I myself is trying to figure this out. BASICALLY what i'm getting at, is with a tune up, my car is doing this.

 

[Mercury Kid]

I don't know if it's going lean or not, but the idle is very irregular and pulling out the choke a small amount raises the idle enough that it is less likely to actually stall. It is still erratic but high enough that it never drops and stalls. Lately it hasn't needed as choke, but it still idles the came.

On a side note, the car has been a riot to drive everyday. I've put close to 600 miles on it since I first posted about the accelerator pump bog. That issue actually worked itself out, probably caused by the same dirt that is messing with my idle.