Acceleration hits a dead wall

[72smallairparticler]

Can’t figure this one out. Slant 6 when under acceleration only accelerates as fast as it would if you were feathering it. If you push harder it just makes a hissing loud sound like air rushing through the carb but no power. Previously the carb was a holly 1920 which I ditched for the Carter bbs.

I’ll try to take a video of the issue

 

[RustyRatRod]

Running out of fuel.

 

[340sFastback]

Make sure pickup filter in gas tank is not plugged up

 

[dirty white boy]

make sure your inline gas filter is good, just went threw that with mine and it was hissing bad!

 

[volaredon]

Exhaust plugged?

 

[72smallairparticler]

Filter is good
Exhaust not plugged
I checked tank filter 2 months ago and it was good.

Here’s a quick video. Second half shows the in car sound which is faint

 

[Ricks70Duster340]

Can’t figure this one out. Slant 6 when under acceleration only accelerates as fast as it would if you were feathering it. If you push harder it just makes a hissing loud sound like air rushing through the carb but no power. Previously the carb was a holly 1920 which I ditched for the Carter bbs.

I’ll try to take a video of the issue

Did the engine run properly with the 1920? Did you change anything else (fuel pump, etc.) when you swapped carbs? If not, sure sounds like you are running out of fuel in the carb. You might want to check the float level to ensure it is set properly.

 

[RustyRatRod]

Have you checked fuel pressure at idle and on the road? Have you inspected ALL rubber hoses in the fuel system to assure none are cracked and sucking air? Remember, "NEW" and "GOOD" don't have the same definitions.

 

[72smallairparticler]

I rebuilt the 1920 but never got it to idle quite right. Then put in a new Fuel pump and got stuck for a while doing a full ignition upgrade to the HEI mod with electronic distributor etc. The AutoLine remanufacturer is a canadian based company and seemed like a good quality rebuild, although lots of great folks here have said you can't really trust any remanufacturer these days...

Rusty, I don't quite have a way to check fuel pressure I guess without installing some gauge, mid-fuel line, but I trust all the input im hearing about it sounding like it's running out of fuel so i'm gonna go on that. What's the ideal pressure I should be looking for?

 

[72smallairparticler]

You might want to check the float level to ensure it is set properly.

For sure doing this today, thanks Rick

 

[72smallairparticler]

From the AutoLine Tech in response to my inquiry.
Hello,
I ordered a remanufactured Carter BBS carburetor from you through RockAuto.
After installation my slant 6 started right up. It's a stock 225 motor in a 72 Duster.
The idle was great and Ignition was easy enough after a couple pedal pumps.
The issue im having is that upon accelerating the vehicle acts like it is not getting any gas. As I depress the accelerator pedal in drive there is virtually no power. I can slowly get it up to speed but the power does not move in proportion to the amount of throttle I give the vehicle. It makes a hissing sound like it's waiting for more gas but is not getting any.
I have done the following:
- new mechanical fuel pump (stock)
- all new fuel hose
- new fuel filter
- new vacuum line to distributor
- new crankcase to carb line
- stable vacuum around 15lbs at idle
It's like the accelerator pump is not working. Is this a defect of the rebuild or is there some sort of adjustment that is missing from the installation guide?
Appreciate your help.

" I would agree that it sounds like a accelerator pump is not working. You could open it up to see if the accelerator pump has rolled over on it self."

Anyone know what the hell that means? Also I aint opening the thing up if it's gonna void my 90-day warranty so I asked that as a response before I end up opening the thing and lose my $230 investment.

 

[TT5.9mag]

If it was just an an accelerator pump problem, as you applied throttle quickly the engine would cough, then recover and accelerate normally. This is not what you’re describing. It seems like you have a fuel delivery problem. As in volume.

 

[TT5.9mag]

You should see 4-7 psi of fuel pressure before the carb and after the pump. Disconnect the rubber line to the carb and stick it in a bucket. Crank the engine a while and see how much the fuel pump pumps in to the bucket. Should be a significant pump every engine revolution.

 

[RustyRatRod]

I rebuilt the 1920 but never got it to idle quite right. Then put in a new Fuel pump and got stuck for a while doing a full ignition upgrade to the HEI mod with electronic distributor etc. The AutoLine remanufacturer is a canadian based company and seemed like a good quality rebuild, although lots of great folks here have said you can't really trust any remanufacturer these days...

Rusty, I don't quite have a way to check fuel pressure I guess without installing some gauge, mid-fuel line, but I trust all the input im hearing about it sounding like it's running out of fuel so i'm gonna go on that. What's the ideal pressure I should be looking for?

Meh, probably somewhere tween 5 and 7.

 

[RustyRatRod]

From the AutoLine Tech in response to my inquiry.
Hello,
I ordered a remanufactured Carter BBS carburetor from you through RockAuto.
After installation my slant 6 started right up. It's a stock 225 motor in a 72 Duster.
The idle was great and Ignition was easy enough after a couple pedal pumps.
The issue im having is that upon accelerating the vehicle acts like it is not getting any gas. As I depress the accelerator pedal in drive there is virtually no power. I can slowly get it up to speed but the power does not move in proportion to the amount of throttle I give the vehicle. It makes a hissing sound like it's waiting for more gas but is not getting any.
I have done the following:
- new mechanical fuel pump (stock)
- all new fuel hose
- new fuel filter
- new vacuum line to distributor
- new crankcase to carb line
- stable vacuum around 15lbs at idle
It's like the accelerator pump is not working. Is this a defect of the rebuild or is there some sort of adjustment that is missing from the installation guide?
Appreciate your help.

" I would agree that it sounds like a accelerator pump is not working. You could open it up to see if the accelerator pump has rolled over on it self."

Anyone know what the hell that means? Also I aint opening the thing up if it's gonna void my 90-day warranty so I asked that as a response before I end up opening the thing and lose my $230 investment.

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View attachment 1716113009

It means exactly what it says. The accelerator pump is only a little cup made from either leather or some kind of rubber, with the open end of the cup facing down. Sometimes, if you're not real careful assembling, the open end of the cup can roll up backwards and then it would lose the seal making the accelerator pump completely ineffective. It's funny they would mention that, as that would mean it was their fault when they rebuilt it. LOOK into the carburetor throat and operate the throttle lever wile the engine is off. You should get a strong stream of gas shooting into the carburetor throat. If not, that is likely the issue.

 

[RustyRatRod]

If it was just an an accelerator pump problem, as you applied throttle quickly the engine would cough, then recover and accelerate normally. This is not what you’re describing. It seems like you have a fuel delivery problem. As in volume.

That's what I was thinking from his description as well.

 

[72smallairparticler]

Thanks all, beyond helpful as always. I'll do both the fuel pressure test first and validate PSI - easiest to do.

If its within a good range then i'll pull the pump out to see if it was flipped. Tech contact said they'd approve a continued warranty if I pull it apart (which they should if it's their faulty work that's causing it)

 

[72smallairparticler]

fuel pump hose pressure before carb. I just pulled it off, pointed at the cup and turned the engine over:



Forgive the use of an old paint bin to catch the fuel lol

 

[TT5.9mag]

I’d say that’s not enough

 

[MOPAROFFICIAL]

We need a line of sight on the fuel shooting out of the hose to compare shots / revolutions . It seemed like it was missing shots per rev.. but again, hard to tell from your vid...and tic tack vid never played

 

[72smallairparticler]

Getting my fuel pressure gauge in the mail today to put in line before the carb and after the filter. We'll see how much pressure its getting and then if low i'll pull the top off the Carter BBS and check the accelerator pump

 

[Dartswinger70]

I have a Carter BBD on my bench for a rebuild right now...

 

[TT5.9mag]

Getting my fuel pressure gauge in the mail today to put in line before the carb and after the filter. We'll see how much pressure its getting and then if low i'll pull the top off the Carter BBS and check the accelerator pump

You can check the acc pump by just looking down the carb bore and activating the throttle by hand. Working or not the accelerator pump isn’t your issue.

 

[72smallairparticler]

You can check the acc pump by just looking down the carb bore and activating the throttle by hand. Working or not the accelerator pump isn’t your issue.

Curious what would be your suggestion if the pressure is low, considering the manual Carter fuel pump about 3 weeks old. Would you recommend an in-line electric fuel pump as an alternative route?

 

[TT5.9mag]

Curious what would be your suggestion if the pressure is low, considering the manual Carter fuel pump about 3 weeks old. Would you recommend an in-line electric fuel pump as an alternative route?

No, in your situation I see no need for anything more than a stock replacement fuel pump if the eccentric is in good shape and not loose. Someone like @slantsixdan or @RustyRatRod will have a suggestion for a part number that will be better advice than I could give you.