Engine missing at highway speeds

S

SteveR.

Member
My 1930 Tudor runs fine at low-load and low speed. At highway speed, the engine misses amd surges noticeably. My guess is that it is not getting enough fuel...the finger strainer in the tank is fine. Where else should I check the fuel lines and carb for blockages?
 
Check your GAV, your setting might have to change under speed or load.

Old gas?

I think it’s your GAV setting. Enjoy.
 
I would zero in on the ignition secondary circuit. Cracks in the plastic upper section of the distributor. The contacts inside may be burned or not the correct distant. The rotor tip burned away. Do you have the correct high tension wire (solid wire)? Check to see if the ends are burned away. The little end caps with the small spike, could be burned away. It is a good idea to cut the spikes off, strip the wire back, pull it through the hole and solder it to the end caps. The coil itself could be the problem, the secondary winding shorting due to expansion with heat. A faulty coil is difficult to determine. Best to have a known good spare.


Tom Endy
 
I had the same problem. Opened the GAV valve a quarter of a turn and the problem went away.
 
Fiddle with the GAV! Model A carbs were set up on the slightly lean side and the GAV is set to compensate altitude as well as gas delivery at running speed. I would try that first while driving and if that does not help, then there is a fuel flow problem someplace. Some folks put in an inline filter and if you have done that, be aware, when they get a little bit used with no fuel pump to push the fuel thru them, they can tend to limit fuel flow. Just FYI
 
Your fuel line might be going in too far into the carb. The end hits the screen in there and just lets a little fuel flow. It should be cut off right after the ferrule.
 
Mine twice now has had a loss of power from the alternator. Both times the exact symptom with backfiring and loss of power, but intermittent. Make sure you are getting the proper voltage to your system.
 
How do you know the engine is missing, do you have photographic proof that someone took it? Was it ever there? Is it still gone? Did you look behind the car, maybe it just fell out on the ground? A missing engine is a serious offence, I'd call the fuzz.

Oh wait, I'm sorry, I bet you meant it was miss-firing. My bad!

I predict the problem is within 2 feet of the distributor, but I suppose it will be a loose electrical connection. Or, the condenser. Or, the points adjustment, or floating, or distributor shaft bearings. Or, a bad coil. Or, if not ignition, a restricted fuel flow. Or, a plugged carb passage. Or, water in the gas. Or. . . Just gotta work through the possibilities.

But, if the engine is actually missing, as in ' gone', well that's a whole different matter.
 
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Thanks for all the help everyone, I finally found the problem. As Davey said, it was electrical rather than fuel related. The wire that connects to the condenser in the bottom of the distributor had frayed insulation, I taped it up (and changed the condenser), but I believe the frayed wire was the problem. I'll swap the old condenser out sometime to verify.
 
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