50 Dodge Wayfarer engine surges on off idle condition

[Bill Stephens]

Stock engine.  Car idles OK but surges badly when going off idle, good accelerator pump action.  OK when hard accelerating. New fuel pump, checked float level, good ignition spark and advance action, checked for vacuum leaks ??? 

[Don Coatney]

Describe your good accelerator pump action?

[Bill Stephens]

A little more info.  The car had run fine for several years. Then progressively got harder to start (more cranking time) when cold.  At street speed I noticed what appeared to be intermittent loss of power which then progressed to surging.  I changed out the fuel pump which seemed to fix the hard starting but the surging started getting worse.  I checked for vacuum leaks and blocked off the windshield wiper feed. I then check the carburetor float level which was close but made fine adjustment using cranking to fill the bowl to full.  The surging got worse.  Have a strong spark and using a timing light I verified timing was correct and advanced when engine was revved. Loosened gas cap to eliminate venting problem.  ???

 

The pump provides a strong spray right off the idle strop.

 

Thanks for your help.  Bill

[Don Coatney]

Have you done a compression check?

[greg g]

have you done a fuel pump flow quantity check?  There have been several instances lately of power jet stiction.  The vacuum piston inside the carb gets gunked up causing the valve to be inoperative, either getting stuck open causing rich mix and poor gas mileage, or stuck closed causing stumble and bogging under load.  The valve should move freely against the pressure of the spring.  If not disassemble, clean and assure free movement of the piston and tha the needle is free in the jet. 

 

Also assure you have no air leaks on the suction side of the fuel pump.

Edited August 29, 2015 by greg g

[Dodgeb4ya]

You might check for bad primary wires in the distributor too.

[Bill Stephens]

Installed carb overhaul kit and runs fine.  Fuel pressure 7lbs.  Inspected it carefully during disassemble.  Found nothing amiss, which worries me.  Will see how things hold up. The NAPA rebuild kit (#2-5106 made by Echlin --$36.25) did not include a new dash pot plunger which I rebuilt with scavenged parts.  Check valve gaskets also missing.  Instructions were pretty good.

 

Thanks everyone for you help.

[TodFitch]

Isn't 7 psi a bit high for a carburetor? Thought is was supposed to be something like 3 to 5 psi. That might be a cause of the problem.

[greg g]

what do your sparkplugs look like?

[Bill Stephens]

7 psi does seem high but no flooding problem.  The test gauge is really old and may not be accurate but the pressure was steady.  I replace the plugs when the problems started.  The old plugs were a light brown colored.  I have not driver the car more than a few miles since the repair so the jury is still out on the fix.  Thanks all. Bill