Help, car is still stalling in D :(

[Nico383]

Hi gents,

It's been 3 months now since I'm looking for the reason why my 383 Duster is stalling when I brake in "Drive".
Most of the time it happens when I make a big acceleration and then stop on the side of the road, braking until I fully stop.
I feel like the difference in RPMs between idle and idle in "Drive" changes getting bigger when the car gets hot.
I set a total timing advance of 39°, with 19° of initial timing.
Mastervac is unplugged. (intake manifold is plugged)
Carb is new (QF 650 SS) (float level is good),idle mixture is hard to set as behaviour is unstable.
Coil is new
Dizzy is almost new (MSD ready-to-run)

When the car stalls, the few minutes after it's pretty hard to start it again.
I just set up a gap of 0.055 to my spark plugs, idle sounds more regular but the car is still ending with stalling. When I unscrewed my spark plugs, #3, 4, 5, 6 were wet.

I wonder if all the power needed goes to the spark plugs.

When I changed my distributor to the msd one, I linked the constant +12v to the ignition switched one to jump the ballast resistor. Is it right?

I'm getting lost, and the thing is that there are not a lot of skilled guys over here in France in local shops regarding american oldtimers.. Thank you for your help guys.

Nico

 

[pishta]

sounds like you have a vacuum leak. Can you run a vacuum gauge into the cab so you can monitor it? Also may want to check your fuel level/pressure when you stop and it stalls. cant miss with those huge sight glasses.

 

[67Dart273]

Might be either way too lean or way too rich, or changing vastly between somewhat warm and "hot." Some of the older OEM carbs had what was known as an "idle compensator." This was basically a bleed hole that opened with a small thermostat to lean up the idle a bit when hot and add a bit of idle speed.

"Sometimes" you might need to go to a throttle dashpot. Ford used to use them a LOT back in the day. This is simply a spring loaded can with a bleed hole. When the throttle closes, the can delays allowing the throttle to "settle down" to idle

 

[Nico383]

sounds like you have a vacuum leak. Can you run a vacuum gauge into the cab so you can monitor it? Also may want to check your fuel level/pressure when you stop and it stalls. cant miss with those huge sight glasses.

Hi Pishta, thanks for these leads. I'm going to buy a vacuum gauge to monitor it, good idea. When it stalls, the fuel level is good. However I don't have any fuel pressure gauge. Do you think I could stall by the lack of fuel pressure? I could try to run a float level a bit higher to see if their is a change.
I have to say I had the same problem before changing my carb for a brand new one...

 

[pishta]

If your car idles faster warm then cold and then its hard to start after you stop it, it may be an intake leak. Metal expands when warm and it could be causing more leak when hot. Id also look at mixture but you say it was happening before carb change...I had a 340 that was a bear to start when hot, turned out it was running pretty lean from the start..and the distributor was gummed up and wasnt returning to a baseline.

 

[Nico383]

If your car idles faster warm then cold and then its hard to start after you stop it, it may be an intake leak. Metal expands when warm and it could be causing more leak when hot. Id also look at mixture but you say it was happening before carb change...I had a 340 that was a bear to start when hot, turned out it was running pretty lean from the start..and the distributor was gummed up and wasnt returning to a baseline.

I think one of the intake manifold nut is not screwing well into the passenger side cylinder head.
Do you think I should screw it a bit more when warm to compensate mechanical slack due to temperature?
Do you have a solution to avoid cylinder head disassembly?
Thanks!

 

[TrailBeast]

An intake leak won't cause wet plugs.

I'd like to see what the plugs look like when pulled right after a drive.
All four center of engine plugs wet means something, but I'm not sure what/where.

Vac leaks at both ends of the intake?
WAY over fueling?
Both?

Maybe.

 

[GeorgeH]

Are you doing your initial timing and carb adjustments in gear? sounds like intake is not sealing. .055 seems large even with msd? Wrong power valve? If it is flooding don't continue running it like that, you'll fuel wash the rings.

 

[Nico383]

An intake leak won't cause wet plugs.

I'd like to see what the plugs look like when pulled right after a drive.
All four center of engine plugs wet means something, but I'm not sure what/where.

Vac leaks at both ends of the intake?
WAY over fueling?
Both?

Maybe.

Hi,

wet plug may be due to the too rich set up I decided to have to be able to come back home when I stalled few kilometers from here. I decided to go richer with a pretty high idle to avoid stalling. But yes, the different look of the spark plugs is weird...

Are you doing your initial timing and carb adjustments in gear? sounds like intake is not sealing. .055 seems large even with msd? Wrong power valve? If it is flooding don't continue running it like that, you'll fuel wash the rings.

Timing had not been done in gear but at 3000RPM with a stroboscopic light.
I'm waiting for the AFR gauge I order to make a proper carb adjustment (for the moment it's pretty much in "stock configuration" except for the idle mixture screws).

My bad, spark plug gab is .050 and not .055 but I guess it is still too much? (I have to say I don't have the 6AL box, only the ready to run by itself).

 

[zac_F71]

A 650 should not run rich on a 383.. what gaskets did you use to put the intake on? Any silicone on them?

Part number for the carb?

What's the main jetting?

How many turns on the idle mixture screws?

Lower the plug gap to .040" - .045" - wet plugs usually mean not firing or weak spark

Set total timing at 2,000rpm not 3,000rpm

Test the distributor for good spark at the plug.. MSD's quality is hit or miss, a good OEM dist will make the same power an MSD unit does...

 

[AJ/FormS]

Hi gents,

It's been 3 months now since I'm looking for the reason why my 383 Duster is stalling when I brake in "Drive".
Most of the time it happens when I make a big acceleration and then stop on the side of the road, braking until I fully stop.
I feel like the difference in RPMs between idle and idle in "Drive" changes getting bigger when the car gets hot.
I set a total timing advance of 39°, with 19° of initial timing.
Mastervac is unplugged. (intake manifold is plugged)
Carb is new (QF 650 SS) (float level is good),idle mixture is hard to set as behaviour is unstable.
Coil is new
Dizzy is almost new (MSD ready-to-run)

When the car stalls, the few minutes after it's pretty hard to start it again.
I just set up a gap of 0.055 to my spark plugs, idle sounds more regular but the car is still ending with stalling. When I unscrewed my spark plugs, #3, 4, 5, 6 were wet.

I wonder if all the power needed goes to the spark plugs.

When I changed my distributor to the msd one, I linked the constant +12v to the ignition switched one to jump the ballast resistor. Is it right?

I'm getting lost, and the thing is that there are not a lot of skilled guys over here in France in local shops regarding american oldtimers.. Thank you for your help guys.

Nico

So to recap; the problem ONLY occurs or mostly occurs with a hard braking after a hard acceleration, and ONLY in Drive?

It takes a heck of a coil to reliably fire .050 plugs. And unless you bought special wide-gap plugs,you need a special tool to regap .035 plugs to .050. Otherwise,the gap can be crossed up, and the coil will not fire the tip, but will fire the electrode somewhere else where the gap may be easier for it to bridge.

Its obviously running rich. Rich at WOT;rich at idle;rich after you slam the butterflys shut. Whether it's jets, or a momentary high fuel level, or fuel slosh, or misadjusted butterflys, or an overly rich low-speed circuit; I cannot say.
What I would do is verify the T-port sync,defeat the vacuum advance system,back up the power timing to 36*,disconnect the secondaries and lock them closed.With the T-port now synced I would reset the Mixture screws.which should now be working.If not,find out why, and fix it. It could be a vacuum leak,but I doubt it. I would suspect a high or unstable float level, or a faulty power-valve circuit, first. If you have to, get eyes on the boosters and look for fuel dribbling in there at idle.Make sure the power valve circuit is not active at idle, and not active at low throttle settings.
But again, first get the T-port synced.
Then I would retest.
And then I would retest with smaller primary jets, and repeat as may be necessary to dry up the plugs.Using an A/F gauge will speed up this process immensely.
After the primary side is working correctly, then I would tackle the secondary side.And
after that I would fine-tune the timing systems.
That's what I would do.

 

[Nico383]

A 650 should not run rich on a 383.. what gaskets did you use to put the intake on? Any silicone on them?

Part number for the carb?

What's the main jetting?

How many turns on the idle mixture screws?

Lower the plug gap to .040" - .045" - wet plugs usually mean not firing or weak spark

Set total timing at 2,000rpm not 3,000rpm

Test the distributor for good spark at the plug.. MSD's quality is hit or miss, a good OEM dist will make the same power an MSD unit does...

Carb is a Quick Fuel 650 Street Series.
Idle mixture screws were set to 3/4 turn each.
Plugs were wet before setting them at 0.05 (is it still too much??)

So to recap; the problem ONLY occurs or mostly occurs with a hard braking after a hard acceleration, and ONLY in Drive?

It takes a heck of a coil to reliably fire .050 plugs. And unless you bought special wide-gap plugs,you need a special tool to regap .035 plugs to .050. Otherwise,the gap can be crossed up, and the coil will not fire the tip, but will fire the electrode somewhere else where the gap may be easier for it to bridge.

Its obviously running rich. Rich at WOT;rich at idle;rich after you slam the butterflys shut. Whether it's jets, or a momentary high fuel level, or fuel slosh, or misadjusted butterflys, or an overly rich low-speed circuit; I cannot say.
What I would do is verify the T-port sync,defeat the vacuum advance system,back up the power timing to 36*,disconnect the secondaries and lock them closed.With the T-port now synced I would reset the Mixture screws.which should now be working.If not,find out why, and fix it. It could be a vacuum leak,but I doubt it. I would suspect a high or unstable float level, or a faulty power-valve circuit, first. If you have to, get eyes on the boosters and look for fuel dribbling in there at idle.Make sure the power valve circuit is not active at idle, and not active at low throttle settings.
But again, first get the T-port synced.
Then I would retest.
And then I would retest with smaller primary jets, and repeat as may be necessary to dry up the plugs.Using an A/F gauge will speed up this process immensely.
After the primary side is working correctly, then I would tackle the secondary side.And
after that I would fine-tune the timing systems.
That's what I would do.

Well, it occurs after a big acceleration but not after a hard braking. It can be in drive or after changing down to 1st gear.
Ok I'll give it a go next saturday... Thanks!

 

[Dubob]

I'm dealing with an extremely rich idle issue on my quick fuel 780, tried to tweak everything out idle transition slots etc etc. Only able to turn idle mixtures out 1/2 to 3/4 turn each. Using vacuum gauge. Called quick fuel this morning and they recommended changing the idle feed restricters from the .031 to .028. The issue on mine is that the idle mixtures are too far in which is causing stalling issues for me. Just some info to keep in the back of your mind. Ideally the mixture screw should be a turn to a turn and a half. For me the only way to get there is to restrict the fuel into the idle circuit. The ifr's and idle air bleeds control the idle "mixture" and the mixture screws control this "mixture" into the engine.

 

[Nico383]

I'm dealing with an extremely rich idle issue on my quick fuel 780, tried to tweak everything out idle transition slots etc etc. Only able to turn idle mixtures out 1/2 to 3/4 turn each. Using vacuum gauge. Called quick fuel this morning and they recommended changing the idle feed restricters from the .031 to .028. The issue on mine is that the idle mixtures are too far in which is causing stalling issues for me. Just some info to keep in the back of your mind. Ideally the mixture screw should be a turn to a turn and a half. For me the only way to get there is to restrict the fuel into the idle circuit. The ifr's and idle air bleeds control the idle "mixture" and the mixture screws control this "mixture" into the engine.

For each of the four screws??

 

[Dubob]

Yes 1/2 to 3/4 on the screws. If you're asking about the idle feed restricters, they are located in the idle feed passages on the the metering blocks.

This shows the location of the "ifr's".


[ame]http://www.quickfueltechnology.com/Instruction_Sheets/99-34-6.pdf[/ame]

 

[Dubob]

Here is the best description I have found on how the idle circuit operates. I installed new spark plugs in mine and within a couple of minutes my plugs were black. Your fuel pressure should be 6.5 psi according to QFT. Anyway I found it educating and maybe it will help you.

"This is how the idle and transition circuits work -- maybe understanding this will help you realize why I am pushing you the direction I am.

The idle air bleed and idle feed restrictor work together to control the amount and the ratio of air and fuel that get premixed for two circuits in the idle well. The idle feed restrictor controls the amount of fuel and the idle air bleed controls the amount of air. The idle circuit and the transition circuit both get their fuel from this source.

When the car is idling this premixed fuel is controlled by the idle mixture screws. The more the screws are open the more pre-mixed fuel is pulled from the idle well and allowed to pass the mixture screws. After passing the mixture screws the fuel is pulled into the engine through the idle port, a small hole below the throttle blades.

As the throttle is opened very slightly, the transition circuit kicks in. The idle transfer slot (a slot about .020" wide and .200" long) is exposed as the throttle is cracked open. As more of this slot is exposed it begins to draw a suction on a passage connecting to the back of the slot that tees into the the idle well. There is no adjustment or screw to control the amount of premixed fuel that is pulled through the transfer slot so the amount is only controlled by the IFR and IAB.

So if your IFR is too big you can control the AF ratio the idle circuit provides by closing the idle mixture screws, but the transition circuit has no adjustment screws so the low RPM cruise will be too rich. You can lean the transition circuit by making the IFR smaller or the idle bleed bigger. The down side of making the idle bleed bigger is that it makes the transition circuit react slower and often causes a lean tip in. "



"What QFT do you have? Most are built on a Proform body with screw-in air bleeds and down-leg boosters. They also come with billet metering blocks that have screw-in idle feed restrictors. I assumed you had set the idle screws and couldn't get rid of the rich idle without the engine dying in gear. The idle mixture screw should normally be around 1 to 1.5 turns out and the t-slot maybe .020" exposed up to .040", depends. If the IFR is too large and/or the idle air bleed to small then you have to restrict the idle mixture screw to get it correct at idle in neutral. When you put it into gear the revs drop a little and then the vac drops and then the flow restriction of the idle mixture screw has too much influence and it leans out and the engine dies. The idle screw restriction needs to be so that it doesn't restrict it too hard and early as the revs slightly. The t-slot comes on very slowly at first and the idle has to make up the difference so that the mixture is consistent. If the mixture is set correct without using as much idle screw restriction the mixture from neutral to in gear will be more consistent, See when you use the idle screw you introduce a second restriction area; when there is only one as in the jet it works more consistently. The Idle mixture screw needs to viewed as a fine trim adjustment not a dominant adjustment. You can then get a better balance from idle to t-slot. It takes a combination of idle air bleed and idle feed restrictor. Finding that combination is painstaking. "