Fuel System: Surging when hot

[Cissell]

I have a 57 Commander. It is currently 90 degrees here, and it seems to be affecting my car. Whenever the car gets to normal operating temp, it starts surging as if it is running out of gas, or the gas is sporatically getting there. I have the fuel line wrapped in aluminum foil as a heat shield, and the fuel filter is fine.
Any help is appreciated! Thanks!

[Bud]

There is a good possibility that you are developing vapor lock when the engine gets hot. Don't overlook things like a faulty ignition condenser or ignition coil that can cause problems when they get hot. If you can, check for a weak or missing spark when the engine is hot. You can also look down the throat of the carburetor with the engine shut down. Actuate the throttle linkage a couple of times to see if you see 2 fine streams of gasoline squirting out of the accelerator pump jets. That should indicate a vapor lock if you don't see any gas. It's also possible that the fuel pump is reaching the end of its life too. Bud

[Mike Van Veghten]

Everyone jumps on "vapor lock"...???
I've driven my 259 Stude in 104 degree F days here in So. Cal. with no more problems than a rise in coolant temp.

Yes...surging is normally caused by the lack of fuel. Vapor lock is a "plug" of air in the system. Just like getting air in your blood stream...It (vapor is just that, more air thAn liquid fuel) stops the flow of fuel (blood !).....


Cissell - How do you know the filter is "good" ?
1. Have you checked the fuel pump for correct pressure ?
2. Float level incorrect ?
3. A kink or partial blockage in the fuel line (from the carb. to the inlet inside the tank).
4. Someone rebuild the carburetor reciently and install the wrong jets ? (the "expert" shops do it all the time !)

As far as "vapor lock" goes...just make sure the closest part of the fuel line is at least 12" from any heat source...like any part of the exhaust system.

Good luch finding the problem.

Mike

[ROADRACELARK]

One item people overlook is the mixture of coolant in the cooling system. If you are in Alabama, there is no need for you to run a 50/50 mix of antifreeze, that translates to -34 degrees! Coverage to 0 degrees should be more than enough. Too much antifreeze will restrict the transfer of heat, causing the engine to run higher than necessary. Straight water will give maximum cooling ability, but the addition of some antifreeze will offer the corrosion protection needed. The cooler you can run the engine, the less likely you'll have "vapor lock" issues show up. If you haven't already, check your thermostat....is it the correct temperature rating...160, 170, 180 etc. for your location? Is it operating properly. When is the last time you had the radiator boiled out and the engine block flushed? Just some suggestions from personal experience. Hope this helps. For more information on this topic, you might try the "Advanced Search" feature at the top right side of the first page.

Dan Miller
Auburn, GA

[Cissell]

Thanks for all the responses. I am now leaning toward the fuel pump being the problem. I got it home after it was stalled out at a gas station. It seemed to require me to press more on the gas when shifting gears, however it ran fine otherwise. The next day when attempting to start it in the morning at around 67 degrees, i encountered the same lack of gas flow when simply idling. Does this seem to lend itself to a fuel pump. I would like to have another vote of confidence before expending $80 on another.

Thanks!

[52 Ragtop]

How old is the fuel pump? and if you don't have a spare, good idea to get one. About the only things you will not find at a parts store are: fuel pumps, and water pumps. I usually carry a fuel pump, water pump and a rebuilt distributor! If it needs anything more than that, it'll come home on a trailer!

Jim

[brian6373]

You might try this: To test the fuel pump volume, ground the wire from the coil to the distributor, then disconect the fuel line at the carb. Crank the engine about 6 or 7 revolutions with the fuel discharging into a glass jar. This will tell you if the pump is delivering enogh fuel to the carb. An added bonue is you can see if any crud is in the fuel. If you let the fuel in the jar sit for awhile you can also tell if there is water mixed in the fuel, as it will seperate.
I hope this helps, Good Luck!
Brian

[SN-60]

To: cissell,----- If You end up replacing the fuel pump, avoid buying an Airtex 4227.....they're oil leakers!

[Cissell]

I disconnected the fuel line from the fuel filter to the carb and epmtied the fuel that was in the glass jar. I tried to crank it and the jar filled back up with full volume. Does this eliminate the problem being with the pump? I took out the carb and i am in the process of cleaning it now, however did not appear all that grimey. I will put it back in tommorow and have updates on the status. All of the fuel lines seemed unblocked.

[brian6373]

It appears that the fuel pump is getting enough fuel to the carb. Another thing you could checkis the heat riser. If that's stuck closed it could cause the fuel to boil in the carb. As others have stated, don't overlook a heat sensitive coil or condencer.
Brian