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The last few times I have driven my 47 Packard-when I come to a stop the engine dies. I jacked up the idle and it partially is successful. I believe my problem is in the carb but not totally convinced. It accelerates and drives ok at normal speeds. I have attempted adjustment of the idle screws at the base of the carb. The first attempt-they seemed to be operating normally(screw in engine starts to die-then back off). I do notice some carbon out the tailpipe which I assumes means too rich

Any help appreciated.

David

One place to start - measure the manifold vacuum. If it's normal, use the vacuum gauge to set the idle mixtures. If it's abnormally low, start looking for the leak.

OK-I went out yesterday and purchased a Mityvac-hand vacuum pump. I measured 14-11 in on the intake manifold. If I remove the air filter it will slowly die. I also checked out the vacuum advance and was never able to get a reading/nor any action on the breaker plate. I capped off the vacuum advance and took it for a ride-it did not die but it was barely running. I hooked the line back to the vacuum advance and took it for another ride-did not die.
I also put a new coil on it which seems to help-not too sure why.
If I start it in the driveway-it will idle all day. It only happens after driving and coming to a stop.

The carb and fuel pump were rebuilt in 2006 by local Packard wizard-Mark Lambert.

thoughts appreciated

David

For one thing the Mityvac is a vacuum pump not a vacuum gauge which is what Dave was referring to. The instument you have is handy for checking the vacuum advance and bleeding brakes however. When hooked up to the intake manifold via the small plug on the intake the vacuum gauge will measure the amount of vacuum the engine is creating and it should be around 18-22" (unless you live at high altitude) if all is normal. With the gauge installed and engine running the idle screws can be adjusted to achieve maximum vacuum for that which should be where they are set although I like to turn them out just a tad more to give a slightly richer mixture. The gauge will also give you information on valve condition, late timing and a number of other useful information. It is a must have instrument.
There are any number of websites which will explain how to use and interpret a vacuum gauge but here is a good one.
http://autospeed.com/cms/title_Using-a-Vacuum-Gauge-for-Engine-Diagnostics/A_2393/article.html

Check the points gap also as that will affect idle and timing as well.

Thks for the reply-I have known this engine probably is not in the greatest shape-I have some blow by-however it started dieing after driving when I came to a stop in the past few weeks. It appears that the vacuum advance is shot-would this be enough of a leak to cause this?

I will check the point-gap.

thks

David

A vacuum leak usually results in increase in engine speed but a the vacuum advance is important for driveability. Have you checked the ignition timing and the condition of points etc? Would adjusting the throttle adjustment screw to give a slight increase in idle speed help. A little blowby on these engines is pretty normal.

To put a closure-I have cleaned fuel filter/new coil/adjusted points/found vac adv open/adjust idle circuit. Each item up to the vac adv improved things some. Yesterday-I disconnected the tube to vac adv and plugged the tube-I then took a test drive and engine did not stop on me. Repeated again today same result. Now I have to figure out how to get the vac adv out of the car-suggestions

thks

David

David, are you asking how to remove the vacuum advance unit?

Disconnect the vacuum line. Remove the two external screws that attach it to the outside of the distributor housing. Then remove the distributor cap and remove the arm from it's pin which is attached to the moveable breaker plate. It may have some sort of retaining clip or possibly a machine screw. You can do all this w/o removing the distributor from the engine though it will be a bit of a reach.

Photo is from a 56 Delco unit but typical of most others. This uses a screw to retain the arm and a ground lead.

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Thks-will try tomorrow. It looks like a clip that is on top of the arm. I drove it again today with the vac adv line plugged and did not stop on me.


Maybe-maybe this is the problem

While you're in there look carefully at the wire going from the points to the outside terminal -- (yours may be in a different spot from picture or even under the plate). The fabric insulation is old, sometimes rotten and then a hole wears or a chunk falls off. If it has, wire could be shorting out when the vacuum advance moves the top plate. That will kill the engine.