62 surging when RPMs go over 3000

[Greg S.]

I think my problem is the fuel pump but wanted to get second opinion. Age and condition of the pump is unknown. Engine is 340 horse. All electronic components are new, plugs, plug wires, coil, condenser, points, battery. Carb (4721 AFB) has fresh rebuild. Problem existed before and after rebuild by professional carb shop. Fuel filter is new. Fuel tank was removed, cleaned and sealed. No sediment in the glass filter bowl. Timing at 12 degrees, dwell for dual point distributor is at 34 degrees and vacuum at 800 RPM idle is steady 15.

After engine warms up and is driven for ten to fifteen minutes it will surge and stumble when you go into third gear under moderate acceleration over 3000 RPM. Then will stumble under load as I gently drive (limp) back home. Feels like it is running on four cylinders but will idle OK.

Last time I drove the car I checked the fuel filter glass bowl after shut off and it was only half full.

Is my fuel pump trying to tell me it needs help before a total collapse? Is this symptom typical for fuel pump problems? Should I replace it? I don't know what else to do. Lastly, where is the best place to get a correct 4656 fuel pump. Current pump does not have AC logo.

[Mike McKown]

Could be a fuel pump.

The way I read your post, it sounds like you have a fuel filter in addition to your sediment bowl type. If you do, take it out of the system and try to blow through it. Air should pass freely. If it doesn't, replace it.

You could have the tank strainer stopped up but I won't go there yet. You could have a rubber hose on the suction side that is hard and cracked and sucking air instead of gasoline. Check this.

If your sediment bowl filter has a ceramic filter in it, make sure you can pass air through it freely.

If you want to keep the original type pump, you can purchase a generic replacement for a few bucks and try it. That is assuming you have no way to check pressure when your engine starts to fade away.

Half full bowl on the filter is normal.

[Roy B.]

Re: 62 surging when RPMs go over 3000

You have a "HEAT" related problem.
1 hair line crack in rotor = look
2 hair line crack in Dist cap = look
3 gas boiling in Carb = check
4 fuel pump weak = test
5 rubber fuel line collapsing = check
6 Dist vacuum advance going = disconnect and drive
7 condenser at ( points) weak = change
8 ballast wrong = change
9 battery weak or poor ground some where? = clean
These are some of the things I would look at , easy and cheep .Good luck

[Edward Boyd]

Re: 62 surging when RPMs go over 3000

Agree that this is a heat related problem - do not forget the coil; even new items are sometimes less than perfect.

[chris burbage]

Re: 62 surging when RPMs go over 3000

Just curious. If the surging took place at a lower rpm, say 2000 rpm, would the diagnosis be the same?

[Greg S.]

Re: 62 surging when RPMs go over 3000

How can the ballast be checked? It is not new and may be original. Could it give a different voltage output when warmed up? Could it be causing the surging? All the other components you mentioned are new except fuel pump and the rubber fuel line from steel line to pump.

[Clem Z.]

Re: 62 surging when RPMs go over 3000

just bypass the resistor for a quick check we did this all the time when drag racing BUT change it back after the test so not to burn up the points

[Roy B.]

Re: 62 surging when RPMs go over 3000

When the ballast gets HOT one of the coils could be corroded or what ever. Just jump it! run a wire from one side to the other and drive her, it wont hurt any thing for a short drive. You just get 12V instead of 8V.
If the gas systems is OK , it has to be some where in the electrical system braking down or losing contact.
It could also be in the key switch!( braking down) run a wire from the posit side of the battery to the coil- and drive it. That will by pass the key switch, and drive her.
If it's an electrical problem then it's a matter of BY-PASSING systems till you locate it