Only idles will not rev. Step on gas it dies. Has a duraspark I with electronic dizzy. Carb rebuilt new coil. Was working great then next day start but only a crudy idle. Touch the gas and it dies. Manual car. I check spark looks good. Pour gas in carb still no Rev. Weird?

 

Can you tell us more about your car? Don't want to start waxing about accelerator pumps just to find you have fuel injection.

 

He mentions a carb rebuild and putting fuel down the carb so we can assume he does not have fuel injection

@OP when did the problem start? All of a sudden or did you start to have gradual problems? Dumping fuel down a carb will only flood the motor which will make the problem worse. Starter Fluid is the preferred material for trouble shooting since it has a higher vapor pressure than fuel, that means it evaporates faster and is less likely to pool in the cylinders (flood your engine).

 

With the engine off, when you roll the throttle linkage open while looking down the carburetor's venturis, do you see a squirt of raw gas in both sides? - and it should start squirting immediately as you move the throttle linkage. I'm still curious about the Duraspark 1 in a classic mustang.

 

It gets gas. Changed the coil. Still same. Has duraspark. Pulled a plug spark looks good to me. When I use carb cleaner still doesnt rev just dies when i slightly use the accelerator. Battery is good., This happened all of a sudden for reasons that I cant find.

 

You don’t happen to have a clogged exhaust pipe do you?

 

no...no rats in exhaust or carb. It was running just fine and then on the next start up it starts but idles like a boat and will not rev up at all. SO since carb cleaner does not help it rev, and I saw spark from the plug and it gets gas (has a pressure gauge) I was thinking duraspark is messed up somehow?

 

When idling, is there any change in engine speed when you remove the vacuum line from the distributor?

 

No change removing vac line. Im going to take out the duraspark and see if autozone still tests them. Or NAPA....or just buy a new one and eliminate that as a problem. Usually dont throw money at issues but its old anyway.

 

I can't say I've seen an engine not rev at all due to no ignition advance, so I wouldn't say that's the smoking gun. That being said, I don't know how the Duraspark uses the vacuum, whether it is mechanically actuated or electronically used to create the ignition advance. Regardless, there is either no vacuum coming through that line, or the advance mechanism in the distributor is not functioning (I'm assuming the vacuum line is connected to manifold vacuum since it worked before).