Jerking hunting sputtering along

Bcontheroad

Bcontheroad

Junior Member
It seems recently my beloved '31 seems to be running on 3 cylinders or something. It really runs rough from the time I pull out of the garage. No matter what gear I'm in or RPM it hesitates every revolution jerking and hunting down the road. Can't get up steep hills easily. I've replaced the rotor/distributor cap combination twice, oiled the distributor shaft, new coil, checked for good spark going to each plug. What should I check or replace next? Is it points, condenser, ethanol vapor lock, clogged jet, GAV setting...?
 
You're going to get about ten hundred diagnosis.
Here's the first. I think you have a vacuum leak. Take a piece of tubing of some sort (I use a length of vacuum cleaner tubing) to move the actual air intake of the carburettor well away from the carby. Then, with engine idling, spray starting fluid or similar (even fly spray will do) around the inlet manifold where it meets the block and around the carburettor connection to the manifold while listening for a change in the engine's idle.
Without moving the air intake from the area of the manifold, you will get false results.
 
X2 on Syncro's comments.

Examine the points. Open them and look with a magnifier. Are they burnt, dirty, oily, or pitted? Run folded white paper through the points until no dirt is seen on the paper. If they are pitted or have a spike, high spot on one side, the condenser is likely faulty. Replace the points.

Otherwise check their gap. Should be .018 -.022. If the rub block is worn excessively, the gap closes up and the timing has become retarded. The points arm will get very close to the distributor cam and can short across from mid arm to the cam. It can start intermittently and get worse.
 
I would try changing the condenser next. They can go bad on a regular basis and it is easy to swap out. All A owners should have a spare or two for this reason.
 
Thanks for the ideas all.
Checked the condenser with multimeter - .220 uF =acceptable.
Inspected and ran paper through points - flat, clean, a little oily
Distributor shaft and cam no wobble, but new rotors sure don't fit snug. I have a full set.
OEM points were 018 so I opened them up 1/4 turn.
Timing is spot on using a NuRex wrench.
Champion 3X plugs were inspected a year ago when I did compression checks
Started the car - still hunting.
I remembered that 'tune ups' always included new spark plug wire sets working on modern cars in the old days; so ...
The coil to distributor wire looked old. I took it off and found discolored brass on one end. Cleaned it with sandpaper. Runs 50% better. Ordered a new wire from Snyder's.
Looking for a 1 3/4 inch hose to try the test to find any carb leaks next while the ignition wire ships.
 
You must log in or register to reply here.
Back
Top