Packard Forum Index » V-8 (1955-56)

I have a 52 Mayfair ultramatic that always hesitates and nearly dies when accelerating from a stop, I have replaced the accelerator pump. I was told one time I could bend the rod on the side of the carb (to the accelerator pump I think) to cure this but I am not sure just how to do this...any advice?

33

Get a Motor's manual that covers your year of car. It will have complete rebuild and adjustment instructions with pictures for the carb on your car. You wo';t have to guess

They can be found at flea markets for $10 to $20. Maybe one of your friends has one you can borrow

Regards

John Harley

Do a really simple test: with the engine stopped, but the carb full of fuel, take off the air cleaner and filter. Then with engine NOT running, look down the carb throat and blip the throttle by hand. If gas squirts into the venturii throats then the accel pump is OK. If not, then NOT.

There are lots of reasons why the accel pump does not work properly even with a carb rebuild kit installed. If it is beyond your ken as to why, then take the carb off and take it to someone who knows carbs. It should not be too hard to figure out once narrowed down to that.

Craig

G'day all, Sorry to come in late on this one but my 56 Patrician did the same thing for the past few years, since I got the car in fact. You would pull up at a set of lights and the engine would idle smoothly but "stumble' then pick up when you went to take off. It used to stall occassionally but it was always at the most inappropriate time. I fixed the problem about a month ago and have had no problems since.
On manual cars i have always adjusted the idle mixture screw in on each carbi barrel until the engine started to die, then screwed it out again until the engine ran smoothly. This is then repeated for the other carbi barrel, making sure that the engine did not stumble when the throttle was blipped.
When the Patrician continued to stumble during driving off at lights, I decided to set the mixture with the engine under idle load at about 450 RPM. I set the "working" handbrake, put the Twin-Ultra into H with my trusted and loving wife behind the wheel with her foot firmly on the brake. I then readjusted each of the mixture screws in turn, firstly inwards until the engine started to falter, then outwards until the engine ran smoothly.
I am pleased to report that it cured the engine stumble completely. It worked for me and it may be worth trying on your 52. best regards Peter Toet

Peter - I'm glad that method solved your problem. I don't know if that method of adjusting idle mixtures is right or wrong, or if the way I was taught in high school auto shop is right or wrong, or if it even makes a difference. But the method we were taught was to use a vacuum gauge whenever possible, and to screw the idle mixture screws (one at a time) OUTWARD (richer) until you either saw the manifold vacuum drop or felt the idle stumble, and then screw back in (leaner) only the very slightest amount until the idle smoothness returns and/or the vacuum is again maximum.

Thus you'd be on the rich end of the acceptable adjustment range as opposed to Peter Packard's method which puts you on the lean end.

Anyone have any authoritative references as to the various techniques?

G.day all, Thanks Owen, I believe that your method of adjusting the idle mixture would be better than making it leaner. As it happened, the non stumble setting was on the richer side of my original adjustment. I'm not certain why I have always adjusted them leaner rather than richer, I may have read it somewhere, and it always appeared to work OK, except for my 56 Patrician. best regards Peter Toet

Does your Mayfair have the WCFB 4bbl? If so, there should be an internal one way check-valve and ball that allows the accelerator pump chamber to fill. I had the same symptoms on a '54 4bbl and that was the problem...crud was intermittently holding the check-valve closed and the chamber was not filling properly.

Good luck