Engine dies when I step on the gas

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rivertaff

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I'm thinking my accelerator pump has gone bad in my 67' dart. Few days ago I was driving it home, I barely pressed the gas and it stumbled and died. I've been driving the car pretty much everyday since then with no observable issues. The carb is a 1920 that the previous owner replaced fairly recently now (1-2 years old) The car still idles fine but as soon as I press the pedal the slightest in park, drive, or neutral that's when it gives up. Any thoughts?
 
I'm thinking my accelerator pump has gone bad in my 67' dart. Few days ago I was driving it home, I barely pressed the gas and it stumbled and died. I've been driving the car pretty much everyday since then with no observable issues. The carb is a 1920 that the previous owner replaced fairly recently now (1-2 years old) The car still idles fine but as soon as I press the pedal the slightest in park, drive, or neutral that's when it gives up. Any thoughts?
Could be the accelerator pump, but could also be a clogged fuel filter. When the engine is off, look into the throat of the carb and move the throttle open. Do you see a strong shot of fuel? If not, the carb should probably be rebuilt. How long has it been since the fuel filter has been replaced?
 
Could be the accelerator pump, but could also be a clogged fuel filter. When the engine is off, look into the throat of the carb and move the throttle open. Do you see a strong shot of fuel? If not, the carb should probably be rebuilt. How long has it been since the fuel filter has been replaced?

I tried this yesterday, It appears to give a good shot of fuel. I had replaced the fuel filter when I got it with one of those cleanable aluminum edelbrock filters, but I'm gonna take it apart today and take a look when I get home. Hopefully it's something as basic as the filter.
 
If its just the accelerator pump, you would still be able to rev the engine up and maintain speed, as long as you open the throttle slowly. If it falls off no matter what, then you have a clog or lack of fuel pressure somewhere along the line, whether it be at the tank end, fuel pump, or filter, or maybe needle and seat stuck.
 
If it dies when you step on the gas, don't step on the gas....
 
The pump in those is kinda weird. It may have a weep hole that will piss fuel onto the exhaust manifold if the seal goes bad when the pump is relaxed. Easy to replace. Whats your timing set at?
 
I was having this exact same problem this week. I started the Dart ('70 Swinger w/ 225/auto) Saturday morning for the first time in ~ 2 weeks and it started/ idled as usual for about 3-4 minutes, then I gave it some gas and it stumbled and died. It did that about 5-6 times over the next 5 minutes while I was trying to drive, then it stopped dying after that ( I drove it for another 15 minutes without a problem). I started it this morning after it sat for 3 days, I let it warm up about 5 minutes, and it stalled once about 50 feet from my driveway, then no more while I drove it 20 minutes to work.

For what its worth, it was ~ 40*F out both mornings here. Any ideas or advice? Im not sure its the fuel filter since it stops stalling after ~5-10 minutes. And it never did it before this week, but I've only had the car since September-put a whopping 60 miles on it since then!
 
This happened to me as well, shortly after I got my '71 Valiant last summer. Turns out the Holley 1920 had a small crack near the accelerator pump. When you stepped on it, it would leak gas out the carb onto the intake manifold! With the gas not going into the engine, it obviously leaned out and wanted to die. So I got a Carter BBS and rebuilt it with good quality parts. Runs great now!
 
Here are some possibilities; start at the top, and work down

1) closed bowl-vent
2) stale gas; all the VOCs have evaporated, and the thick-chit won't light off. On a hot day, or after the engine is up to temp and shut off; the gas in the vented bowl will be stale in just hours.
3) low fuel level in the bowl
4) varnished slow-jet or passages
5) throttle is too far closed and the Transfers cannot respond fast enough
6) Cold intake manifold
7) loss of timing with loss of vacuum, or failure of the advance system
8) lazy accelerator pump.
9) bad coil.

Notice I put the A-pump near the bottom. This is because from idle to off-idle, as you described it, that pump is NOT the main player. The main players on a clean carb,are;
1) the freshness of the fuel
2) the fuel level, and
3) the transfer slots willingness to respond.
4) the entire fuel/air charge ALL making it into the cylinder, not puddling in the plenum or sticking to the cold runners.

Notice I didn't mention the power-valve/ metering rods either. They don't come on line until much later.

Happy Hot-Rodding

BTW, if the fuel is fresh, and the fuel level is correct, then it will run for a very long time; perhaps more than a minute, at idle; edit; with the fuel line disconnected or pinched. I forgot that part,lol.
 
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Thanks all, the car isnt at my house so I cant check it right away, but I will. This is my first carburated auto so Im by no means an expert at diagnosing carb issues. Like I said, it seems to idle fine but when it died it was the instant I tapped the accelerator (and only while in "Drive"). It is old fuel and fuel filter which will be changed shortly ( the gas in the tank is at least from September when I bought the car)

FWIW, I think its probably running a little too rich, I noticed black soot on the floor by the tailpipe where I left it to idle for ~5 minutes. Not sure if that narrows it down (at all).

Thanks everyone!
 
Buddy with a boat twin engines had the exact problem . Water condensation inside distributor cap, once it warmed up to full temp it as ok.
 
If the stalling occurs once the engine is warm, most likely the choke is still closed or [ partially closed ]. At operating temp, choke blade should be vertical & not able to flop around.

If this happens with cold engine, then choke may not be closing fully.
 
A little update- was finally able to take it for a cruise on Saturday. Checked the carb choke before I started the car- it was fully closed. Checked it again after letting it idle about 5 minutes, the choke was fully open. Seems to be working as it should, and the car didn't stall once during the 20 minute drive. Guess I'll let it warm up a little bit before I drive and keep an eye on it for now.
 
Hey all, I wanted to update this thread since I've been driving the Dart all summer and fall and still having the same problem. Fresh 93-octane refilled 3-4 times, new fuel filter, oil change, etc. Choke operates like it should. The car drives fine once its fully warmed up to operating temperature (good thing the temp gauge still works...) but if its cold it keeps stalling in EXACTLY the same way...

If the engine isn't warmed up, the car will idle fine in "Park". It has never stalled in Park. It will idle fine down the street in "Drive" if I go slowly, but it will stall like clockwork the instant I push the gas pedal enough to require the transmission to downshift.

Case in point: The Dart will go down my driveway and into my short street. The first turn I have is a left which goes up a long hill. When I push hard on the accelerator to go up the hill, the engine cuts out the instant when the car should downshift into first. (does that make sense?). It will start up again fine and idle fine, when I rev the engine it revs fine, but put it in "Drive" again and try to accelerate up that hill, it cuts out again the instant the transmission feels like its about to downshift. Once the engine is warmed up to operating temps, it feels like it stumbles a tiny bit the first time I press the gas hard (but doesnt stall), but then it goes fine like nothing ever happened.

This happens every time I don't let the car warm up fully first. With these additional facts does any of you fine folks have any insights? I'm not sure if its a carb issue, or a linkage issue, or a transmission issue? She drives like a champ once shes warm but its annoying having to idle 5-10 minutes waiting to leave. Thanks in advance

I do love the damn car :D
 
When I push hard on the accelerator to go up the hill, the engine cuts out the instant when the car should downshift into first.

Are you at the bottom of the hill ?
Or part way up all ready.
You said long hill. You did not say steep hill?

Ima thinking accelerator pump circuit; but
just for kicks, leave it in first to climb that hill, and keep the throttle open enough to climb at a steady pace, neither gaining nor losing speed.
Then report back.
 
Are you at the bottom of the hill ?
Or part way up all ready.
You said long hill. You did not say steep hill?

Ima thinking accelerator pump circuit; but
just for kicks, leave it in first to climb that hill, and keep the throttle open enough to climb at a steady pace, neither gaining nor losing speed.
Then report back.

Sorry, Im at the bottom of a moderately steep and longish hill. Not crazy steep, but enough to require the car to downshift to start up it.
I will try leaving it in first gear instead of "Drive" tomorrow when i start out- see what happens! :thumbsup:
 
Sounds to me like you're simply rushing it. If it runs fine as you say when it's warmed up, then warm it up before you drive it. These things don't run like EFI cars.

One thing you might look at though, is the exhaust flap in the exhaust manifold. If it has frozen up, that could have an effect on how the engine runs, especially if it is frozen in the position that does not allow heat to the bottom of the intake manifold.
 
I'm thinking my accelerator pump has gone bad in my 67' dart. Few days ago I was driving it home, I barely pressed the gas and it stumbled and died. I've been driving the car pretty much everyday since then with no observable issues. The carb is a 1920 that the previous owner replaced fairly recently now (1-2 years old) The car still idles fine but as soon as I press the pedal the slightest in park, drive, or neutral that's when it gives up. Any thoughts?
Believe it or not, I was having the same problem on mine. I ended up replacing the fuel pump (because it was the least expensive thing to change out), then I purchased a rebuild kit for my carb. I went through and replaced the gaskets and adjusted the bowls and the thing cranks like a champ. Not only that, but I adjusted the choke and linkage while I was there and I have seen an improvement in its run/idle. This video helped me a lot (of course, it won't be much help if you're not running a Holley 1940 or 45).


Best of luck!
 
Sounds to me like you're simply rushing it. If it runs fine as you say when it's warmed up, then warm it up before you drive it. These things don't run like EFI cars.

One thing you might look at though, is the exhaust flap in the exhaust manifold. If it has frozen up, that could have an effect on how the engine runs, especially if it is frozen in the position that does not allow heat to the bottom of the intake manifold.

I know what you're saying, and normally I don't mind letting it warm up (I let all my cars idle for a minute or two before driving off), but sometimes its a little embarrassing waiting in the car for 10 minutes idling at the cars and coffee. I feel shame being the local Slant-6 ambassador and having an unaddressed issue.:)
 
I'm thinking my accelerator pump has gone bad in my 67' dart. Few days ago I was driving it home, I barely pressed the gas and it stumbled and died. I've been driving the car pretty much everyday since then with no observable issues. The carb is a 1920 that the previous owner replaced fairly recently now (1-2 years old) The car still idles fine but as soon as I press the pedal the slightest in park, drive, or neutral that's when it gives up. Any thoughts?


Don't step on the gas....
 
Ima thinking accelerator pump circuit; but
just for kicks, leave it in first to climb that hill, and keep the throttle open enough to climb at a steady pace, neither gaining nor losing speed.
Then report back.

This morning, I didn't let it warm up completely (only 2-3 minutes) and left the garage in 1st gear and not "Drive". When I made the turn to go up the hill and stepped on the gas- BOOM- the engine cut right off and stalled, same as id she were in "Drive". So I'm guessing its not a transmission or shifting issue at least. It was an insightful and good idea- thanks
 
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