Engine lags and stalls when initially pressing gas-Solution Found?!

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Stihl011

Stihl011

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I recently replaced the carb with a more correct carter 2 barrel (the one that was on there was not original, the one I bought looks right but didn't come with a tag) and am having some issues where the engine will lose power if I quickly press the gas. The faster I press the gas, the more power it loses for a few seconds, up to the point of stalling the engine. A few seconds later, the engine revs up to what you would normally expect. It does not do this when not in gear, and the slower you are going, the bigger the problem is.

My first guess was air/fuel too lean, the extra vacuum leans out the mixture and the engine stalls I don't have a air fuel mixture meter and want to avoid buying one. I saw on you tube that you can adjust that by looking at the vacuum (I do have a vacuum gauge) but the screws don't seem to have any affect on the vacuum, or how the engine runs at idle for that matter. That seems not right to me, but I thought I read somewhere that on some models of BBD carbs, those adjustments don't do anything?

I have also confirmed that the carb does squirt fuel into the barrels when the gas is pressed, so maybe its just not squirting enough? Too much? which brings me to...

In the service manual, in the accelerator pump and bowl vent adjustment section there are references to a bowl vent clip. My carb did not come with one as far as I know, so I think this could be the issue, but I'm not really sure what its supposed to look like. Right now the bowl vent is just sorta sitting on top of the bowl, no clip, and I'm not sure this is what I need.

Carter BBD Bowl Vent Clip

I don't see anything in the figure from the service manual that looks like that.
upload_2019-4-5_14-28-3.png




Any info is appreciated.

68 barracuda, 318
 
Sounds like the accelerator pump is faulty. Probably needs a kit.
 
I have even seen remanufactured BBSs with the heavy zinc electroplating and polishing have problems with the accelerator pumps sealing. A lot of them had leather accelerator pump cups and they are pretty hard on the carb body as far as wear goes.
 
My 67 273 2bbl, did the same thing. Turns out someone had plugged the vacuum line right before the vacuum advance canister. I removed the plug and all is good.

Get a vacuum pump and hook it directly to the vacuum advance can (short hose).

First as you increase vacuum the engine rpm should raise.

Second it should hold vacuum.

Also be sure you have the vacuum hooked up to the correct port on the carb.

Also if you have a green canister device between the advance can and the carb. Temporally bypass it and see if there is any change.

My CAP engine calls for initial advance to be 5 after TDC try 5 before TDC and see how things go.

Lastly with the vacuum advance disconnected does the timing advance as you you increase engine RPM.


All of this assumes the carb is in good shape. You can check you factory service manual for stock jets and rods.
 
You mentioning no change when adjusting idle screws. Carb needs a proper cleaning. I have seen them so bad you could take the screws right out.
 
The bowl vent has to remain open in order for atmosphere to push the fuel thru the low speed circuits.
If yours is clear, then I agree the pump is lazy, and the carb is not transitioning well from the transfers to the mains; it may be that the step-up piston is stuck.
Or you have a large vacuum leak somewhere;does yours have a PCV port and if yes is it hooked up?
This is a pretty basic carb and shouldn't take much to sweeten up. Unscrew the cluster and make sure the right gasket is in there; I think there are about three that come in the kit, and they are not all the same. Same with the intermediate gasket; two of those, and two or possibly three base gaskets. It's easy to mess up for a newbe. If/when you take that cluster out don't turn that main body upside down! or you'll lose the pump check-ball.
 
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Stihl011 said:
I recently replaced the carb with a more correct carter 2 barrel (the one that was on there was not original, the one I bought looks right but didn't come with a tag) and am having some issues where the engine will lose power if I quickly press the gas. The faster I press the gas, the more power it loses for a few seconds, up to the point of stalling the engine. A few seconds later, the engine revs up to what you would normally expect. It does not do this when not in gear, and the slower you are going, the bigger the problem is.

My first guess was air/fuel too lean, the extra vacuum leans out the mixture and the engine stalls I don't have a air fuel mixture meter and want to avoid buying one. I saw on you tube that you can adjust that by looking at the vacuum (I do have a vacuum gauge) but the screws don't seem to have any affect on the vacuum, or how the engine runs at idle for that matter. That seems not right to me, but I thought I read somewhere that on some models of BBD carbs, those adjustments don't do anything?

I have also confirmed that the carb does squirt fuel into the barrels when the gas is pressed, so maybe its just not squirting enough? Too much? which brings me to...

In the service manual, in the accelerator pump and bowl vent adjustment section there are references to a bowl vent clip. My carb did not come with one as far as I know, so I think this could be the issue, but I'm not really sure what its supposed to look like. Right now the bowl vent is just sorta sitting on top of the bowl, no clip, and I'm not sure this is what I need.

Carter BBD Bowl Vent Clip

I don't see anything in the figure from the service manual that looks like that.
View attachment 1715315353



Any info is appreciated.

68 barracuda, 318
Click to expand...
 
Check the gap in Choke plate, too much can cause the wee carb a problem of choking on too much air, also agree with checking the Accelerator pump.. the clip looks like a bent paper clip, and yes it will come in a rebuild kit. I own Three of these BBD carbs, used in pieces one Brand New that did this and One on my 318 now that I rebuilt out of 1st used one and 2nd..
 
Also check the Floats.. could be flooding.. I've had so many problems with my BBD that I've tried, also everything I think lol, too much gas coming in, or too much air.. that fact that you stated it was losing power, makes me think it's one of the two.. people do have some real hatred for this Carb but I drive mine everyday hope that's helpful, I've found tech films from the era that will show you all about it..
 
Check to make sure the accelerator pump is squirting... Pull up on the pump shaft and let it go and it should squirt gas...

If you are getting squirt from the accelerator pump and it's stumbling, move the linkage for the accelerator pump to another hole on the arm for more or less squirt to see if that helps or not...


If no squirt, the accelerator pump is worn... They wear out easily on the bbd with the leather of the accelerator pump riding on the metal casting... Get a rebuild kit and go through the carb while replacing the accelerator pump... When installing the new accelerator pump, lube the leather first before installing it to help it "wear in" and not tear when installing it...
 
The small arm is only to be used in two of it's 3 or sometimes only 2 holes.. winter and summer.. if you can find them the tech films will teach you a lot about the settings.. learning what the techs had to watch to service our cars from back in the day is valued information.. if I find it I'll post the link. My Mopar channel on YT.
 
I think I have it figured out.

That bowl vent clip was sorta key. There isn't one in my carb, but probably supposed to be there. The accelerator pump was working (knew that before because saw gas being squirted in), but I think was probably adjusted so that it was flooding the engine.

If there were the bowl vent would have been wide open and it would be obvious that it was adjusted way off, based on the instructions in the service manual, the bowl vent is supposed to be 1/16" open with throttle completely closed. But with the clip missing, you keep thinking "what F**ing clip? My bowl vent doesn't lift at all"

Those little notches in the accelerator pump are for a clip that will hold open the bowl vent slightly, like 1/16" when completely close, and I assume, when accelerator pressed, closes completely.
upload_2019-4-6_12-44-57.png


Now look at where those clip notches are when my throttle completely closed. Like way too high.
upload_2019-4-6_12-47-37.png


Moving the accelerator pump rod to the outside hole of the accelerator pump rocker arm moved that 2nd clip notch (which is where the clip should be when the accelerator pump rod is in the middle hole of the throttle lever much closer to where it would be lifting the vent 1/16" when completely closed.

upload_2019-4-6_12-50-20.png


I took it out for a spin after this adjustment and it performs WAY better. It still stalls a little if I really step on it when stopped, but I also think I have more like 1/8" between the bowl vent and that second notch, so I need to do some bending of the accelerator pump rod. Also, pretty sure I need that clip. I had a rebuild kit with instructions that show what that clip is supposed to look like, and its definitely not on my carb, but at least I know what its supposed to look like now. I'm not too sure what that clip does though, other than to make it easier to adjust the accelerator pump.

upload_2019-4-6_12-55-53.png



Thanks all for the help.
 
Stihl011 said:
I think I have it figured out.

That bowl vent clip was sorta key. There isn't one in my carb, but probably supposed to be there. The accelerator pump was working (knew that before because saw gas being squirted in), but I think was probably adjusted so that it was flooding the engine.

If there were the bowl vent would have been wide open and it would be obvious that it was adjusted way off, based on the instructions in the service manual, the bowl vent is supposed to be 1/16" open with throttle completely closed. But with the clip missing, you keep thinking "what F**ing clip? My bowl vent doesn't lift at all"

Those little notches in the accelerator pump are for a clip that will hold open the bowl vent slightly, like 1/16" when completely close, and I assume, when accelerator pressed, closes completely.
View attachment 1715315781

Now look at where those clip notches are when my throttle completely closed. Like way too high.
View attachment 1715315782

Moving the accelerator pump rod to the outside hole of the accelerator pump rocker arm moved that 2nd clip notch (which is where the clip should be when the accelerator pump rod is in the middle hole of the throttle lever much closer to where it would be lifting the vent 1/16" when completely closed.

View attachment 1715315783

I took it out for a spin after this adjustment and it performs WAY better. It still stalls a little if I really step on it when stopped, but I also think I have more like 1/8" between the bowl vent and that second notch, so I need to do some bending of the accelerator pump rod. Also, pretty sure I need that clip. I had a rebuild kit with instructions that show what that clip is supposed to look like, and its definitely not on my carb, but at least I know what its supposed to look like now. I'm not too sure what that clip does though, other than to make it easier to adjust the accelerator pump.

View attachment 1715315784


Thanks all for the help.
Click to expand...
 
krazykuda said:
If no squirt, the accelerator pump is worn... They wear out easily on the bbd with the leather of the accelerator pump riding on the metal casting... Get a rebuild kit and go through the carb while replacing the accelerator pump... When installing the new accelerator pump, lube the leather first before installing it to help it "wear in" and not tear when installing it...
Click to expand...

I am reviving this thread , hope that is ok....?

My son had his accelerator pump on his 2 BBL BBD carb "fold over" on itself about a year ago.....so he replaced it with one from a kit.....its red with a green cup.....

Well, it has once again "folded" on itself so he bought a new kit and replaced it.......worked great at first.....but then while TESTING, the damn cup folded again....this cup is BLACK.

You mention lubing....he didnt...its not torn, but like I said, partially folded/warped back on itself. what kind of lube would you use for that? Seems like the gas would instantly wash out any kind of oil or grease....????

He is in the driveway now, 90 degrees, and frustrated.
HELP!
 
I would check the bore for catch points.

Back in the day the seal was leather and you were supposed to soak it in fuel before putting it in.
 
IDK if that clip for the bowl vent does anything of running value 'cept hold the vent cap open a hair at idle. And a lack of that would not prevent the bowl from venting as the slot for the pump is not sealed. If it were a holley that had a vent that was actually sealed (opens with the throttle linkage) it may have an effect but I cant figure out why (from afar) that lack of a clip would alter anything. As for the seal lip folding over, take a look at the bore and maybe there is a ridge in there. possible a brake cylinder hone could smooth it out if a piece of sandpaper doesnt.
 
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If it is folding over, my guess is that it is rising up too high in the bore. You have to bend the link-rod to the arm, to prevent that.
You can check this by spacing up the pump,to it's normally parked position and then dropping the cover back on. Measure from the top of the pump to the cover. Then remove whatever you used for a spacer, and put it back together. Then adjust the linkrod to achieve less than or equal to, that predetermined maximum height. If your engine is set up right as to timing and fueling, then you won't need all of that stroke, so no sense in pushing the limit.
As for lube, I use silicon O-ring lube.
If you have a treadmill in your house, mine came with that silicon lube to put between the track and the support works, where your feet land; samechit.
But silicon lube washes out over time.
I agree on the idea of polishing the bore. But I also think that after you set the plunger-height, your problems should be over.
 
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shadango said:
He is in the driveway now, 90 degrees, and frustrated.
HELP
Click to expand...
Well, when I was young; 90s was not too hot to change; engines, transmissions or rearends; try not to show too much compassion,lol. Heck, I rebuilt my first engine in Mums chicken-coop, and I swear the thing was an oven.
 
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