troubleshooting 73 dart slant six...

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bigjohnson88

bigjohnson88

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little back round info:1973 dart, slant six auto-new gas tank, fuel lines, pump and filter-new plugs, cap, rotor, plugs and wires-new intake/exhaust gasket-all emissions components removed (egr, tac, charcoal canister, ect.) tank vent line has a little filter on it and egr is blocked.-one ported vacuum line for advance (new hose), all others plugged-small open filter on carb-original 1920 carb, recently cleaned and looks good except the bowl vent tube is missing and the hole for it is chewed up pretty good, but it is open. Ok, the car will crank right up cold and idle great when the choke kicks off, and idle fine forever. if I drive the car a little cold it will drive fine for a while, till it heats up to normal temp, then it wants to cut out in 3rd, if I pull over and let it chill it will usually fire right up and drive good up in till it shifts into 3rd the starts sputtering and dies. The car shifts good, but it does kinda feel like the rear I geared pretty steep (55-60mph cruising speed) but I don't know if this is normal or part of the problem. Any Ideas or tips? Thanks in advance.
 
Herare some basic first thoughts: If it sputters each times it dies or wants to die, then likely you still have a problem in the fuel system; as you drive faster and faster, you are normally going to increase the rate of flow, and it sounds like something is finally sucked into the fuel line somewhere. Was there a new fuel pickup put in with the new fuel tank? If not, the fuel sock could be blocking up. Pull out the fuel filter, empty it, and blow through it in the direction of fuel flow; it ought to blow-through freely. Put in another new filter; they are cheap. Also, check all the line connections and make sure the clamps are tight; a loose clamp on a hose before the pump can allow air to get sucked in.

Also check that tank vent line filter to make sure it actually allows air into the tank; if not, then the tank can be drawing a vacuum as you pull fuel from it and causing low fuel flow; easy enough to check by driving with the gas cap loose for a test drive; just don't let anyone rear end you with the cap loose!

BTW, are your igntion coil and ballast the originals? Coils can open up like you describe... when hot.
 
If you can, run it with a fuel pressure gauge. Also check the fuel volume. Airtex pumps have a bad reputation for being bad out of the box. They seem normal when bench tested but the travel is out of range for the cam sometimes.
 
nm9stheham said:
Herare some basic first thoughts: If it sputters each times it dies or wants to die, then likely you still have a problem in the fuel system; as you drive faster and faster, you are normally going to increase the rate of flow, and it sounds like something is finally sucked into the fuel line somewhere. Was there a new fuel pickup put in with the new fuel tank? If not, the fuel sock could be blocking up. Pull out the fuel filter, empty it, and blow through it in the direction of fuel flow; it ought to blow-through freely. Put in another new filter; they are cheap. Also, check all the line connections and make sure the clamps are tight; a loose clamp on a hose before the pump can allow air to get sucked in. Also check that tank vent line filter to make sure it actually allows air into the tank; if not, then the tank can be drawing a vacuum as you pull fuel from it and causing low fuel flow; easy enough to check by driving with the gas cap loose for a test drive; just don't let anyone rear end you with the cap loose! BTW, are your igntion coil and ballast the originals? Coils can open up like you describe... when hot.
Click to expand...

new pickup, I tried the gas cap trick, no change. so I guess I'm leaning towards the fuel pump. should there be any kind of tape on the inlet fitting on the pump? as of now there just snugged in.
 
Usually work fine without it....

As for the fuel pump tests, that is a darned good idea. But an open outlet fuel volume test is not always sufficient by itself; the pump can flow well with no back pressure but this will not reveal a bad outlet valve. The test with a pressure guage is needed too.
 
ok, new info.

-broke down and got a rebuilt carb (and tuned it to factory specs)
-good fuel pressure while driving and even when it sputters out
-just rechecked and set timing (is #1 tdc at idle normal for a stock six with no emissions components/auto?)
-done the rubber fuel line trick with new filter
-new batt, starter and alt.

it runs a lot smoother now, but still wants to die out. It cranks up with no hesitation, the vac advance hose is plugged into the port on the left side of the carb (the small one right in the middle) I tuned the carb and set timing with it unplugged then reinstalled it. I have no idea with this thing. could it be the actual distributer/advance (looks original)? Maybe valve adjustment? Are these Holley 1920s fidgety? I've tuned plenty Holley 2&4 bbls with no problem, this one seemed pretty straight forward. Maybe worn timing set? Thanks guys.
 
bigjohnson88 said:
Are these Holley 1920s fidgety?
Click to expand...
Yessir, but more that they can be plugged internally in the sealed metering block and no way to see it, and a typical rebuild will not fix it. Some people have said they fixed it by blowing air thru some of the lower ports of the metering block. My 69 Dart slant idled like cr@p for 20 yrs, despite wasting money on many mechanics, valve jobs, intakes, 3 auto parts carbs, ... It sputtered at idle and liked to die coming off idle once warmed up. A 4th Holley 1920 made it purr like a kitten. I wish I had known it was the carb(s) all along. I was smart enough to suspect it was a lean idle condition, smarter than the gomer mechanics who supposedly had diagnostic tools. Today, that wouldn't bite me since I know much more about cars, plus put O2 sensors in all my classics.
 
BillGrissom said:
Yessir, but more that they can be plugged internally in the sealed metering block and no way to see it, and a typical rebuild will not fix it. Some people have said they fixed it by blowing air thru some of the lower ports of the metering block. My 69 Dart slant idled like cr@p for 20 yrs, despite wasting money on many mechanics, valve jobs, intakes, 3 auto parts carbs, ... It sputtered at idle and liked to die coming off idle once warmed up. A 4th Holley 1920 made it purr like a kitten. I wish I had known it was the carb(s) all along. I was smart enough to suspect it was a lean idle condition, smarter than the gomer mechanics who supposedly had diagnostic tools. Today, that wouldn't bite me since I know much more about cars, plus put O2 sensors in all my classics.
Click to expand...


I bought a new rebuilt carb from advance, took it apart and checked it over. any experience with these? it looked nice, and was clean inside. it defiantly made a difference in performance.... until it sputters and dies, lol. I took my day off today and adjusted the valves (way loose) went back thru adjusting the carb while it was warm, and everything I do seems to help out but it still has the dying out issue.
 
It looks like you're not too far away from me. If I knew more, I'd offer to help, but the best I could probably do is sit with you while it dies.

Back when my 73 Duster was a slant six, I never had much luck with rebuilt carbs, but you can get lucky once in a while. Since it happens with both carbs, could it be something with 3rd gear in the transmission? Have you tried keeping it in 2nd after it heats up and seeing if it dies out?

You can also try running it with the vacuum advance plugged to see if that is contributing to the problem.
 
Let's back up with the symptoms.

- Can you drive it around in 2nd gear all day with no issues?
- When you drive around cold is that in 3rd and does it run OK in 3rd when cold?
- When it dies, dos it act like it is running out of gas? Or does it suddenly cout out, or cut in anout completely several times and then quit?
- Have you blown out the main fuel line?
 
nm9stheham said:
Let's back up with the symptoms.

- Can you drive it around in 2nd gear all day with no issues?
- When you drive around cold is that in 3rd and does it run OK in 3rd when cold?
- When it dies, dos it act like it is running out of gas? Or does it suddenly cout out, or cut in anout completely several times and then quit?
- Have you blown out the main fuel line?
Click to expand...

-it will still die in 2nd, I say 3rd, but I basically mean cruising speed.
-it takes a little longer to die out when it's cold, but it still dies.
-it feels like its running outta gas, it starts sputtering, and if I don't feather the gas it will shut off, when I do feather the gas it sounds like its pulling in a lot of air and dies, but if I pop it in neutral I can sometimes get it to idle again but most times it runs rough until I shut it off and let it cool down, then its fine until I drive it again.
-yes.

thanks for the help.
 
Well, dang, sure acts like it has to be running out of gas somehow. Have you looked at your fuel line in the engine compartment to see if it is in a place to get hot? The car losing fuel due to fuel percolation while running seems like a long shot but.....

I think you said in an earlier post that you had good fuel pressure while running. So for sure it was gdodo when it died? Were you actually able to observe the pressure the instant it died.

Has the fuel pump been changed?

The one other area might be a coil getting hot and internally breaking down. I hate to send you off on any wild goose chases though. Let me ask, when it dies, does it take while before it will start up again? Or does it start up right away once you stop?

BTW, a worn timing chain would just make it sluggish at low/mid RPM's.
 
Next time you have the front exhaust tube off, have an O2 bung welded on. You can get rich/lean indicators cheap, and wideband O2 systems are now affordable used on ebay as tuners move to the latest/greatest. Without that, you are "flying blind". Some people look at their spark plugs to judge rich/lean, but that is tedious and haphazard.

I recently put two O2 bungs on my 1964 slant's exhaust pipe. One will be a wideband O2 sensor and the other a simple on/off sensor to in-place calibrate the wideband. Even if you don't have the sensor kit yet, put in a bung & plug when convenient since costs ~$7 (ebay). All sensors have the same threads.
 
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