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1956 Cadillac de Ville Sedan
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7 Posts
Discussion Starter #1
Good afternoon ladies and gentlemen,

I've had a series of setbacks on the road ever since leaving the cabin light switch on overnight and running down the battery. The car lost power on a hill later that day after jumping the battery. After rolling it back downhill I was able to get the car running again with another jump and some gas down the carb. It ran home fine that night some 10 miles back. I figured the battery was sore so I hooked it up to the 1.5 amp trickle charge and let her be for a few days. Displayed no symptoms of the problems when out for a ride, so figured all was back to normal. On a ride a few days on, all of a sudden some unresponsiveness on the throttle, and alternating bursts of fuel. This was on flat ground this time. Let her be for a few hours on the side of the road, came back later that night, repeated the same start method and it fired and the engine caught. Once again, seemed to be the battery, but now the fuel system was beginning to be suspect. At this time, I checked all three systems. We have good spark at the coil, spark plugs are new, so its not the spark. Battery is showing perfect on ignition and is turning over the engine. Got the car home that night, and got the trickle charger back on. Replaced the fuel filter, checked connector hose running between pump and carb and clean. I removed the connector hose and brought in a reservoir to test the volume of gas moved by the pump. The car fired up instantly upon turn, was running normally, smooth and quiet, for the brief moment the gas burned in the carb. The test yielded a small amount of gas brought up over a few moments of turning over. The hobo mechanic method, gas down the carb & jump, no longer gets the engine to catch, though it will rev - but the revs themselves are sometimes choppy and the sparks are audible in the cylinder. Seemed that the battery stressed out the fuel pump on some of the hills, resulting in it to lose power on hills and under load. Now I think the pump diaphragm might be toast, but I haven't checked the fuel line or the voltage showing from the pump. I would very much appreciate any help, suggestions and advice in the coming days getting the classic Caddy back on the road!

Best,
Sam

Kelowna BC
 

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2003 Deville base, 69 Eldorado, 68 Impala, If I tell you the rest......well....
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492 Posts
You say gas down the carb doesn't catch (fire?) but revs? Maybe time for a carb rebuilt. Look in the carb do you see 2 streams of fuel when you pull the throttle open? Also check fuel pump pressure and voltage if you have an electric pump. The pump on the side of motor is mechanical.

When you say battery is perfect what are the volts before you crank and while you crank? 12.5 is battery volt, If it drops battery needs replacing. Check ground, power wires to be safe. But you said car died after gas in carb ran out, I agree with fuel then.
 

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1956 Cadillac de Ville Sedan
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7 Posts
Discussion Starter #3
This morning's update:

Gas down the carb fires, constant revving keeps it alive but does not catch and sustain, even after trying to settle into fast-idle. Fuel not reaching carb, yet the mechanical fuel pump is relatively new (3-4yrs). The gas isn't getting from the tank up to the carburetor, the fuel pump is still a suspect. Focus now has gone to finding a big vacuum leak, a detached or broken vacuum line off the manifold. Will also try checking ground and power wires. Anything I'm missing?
 
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