1968 Eldorado Runs for a Few Seconds & Dies

[Cadillac Nut]

I'm trying to get a '68 Eldorado running that has been sitting for a while.  Car will run briefly (a few seconds) with gas down the carb. It quits after that and won't start, unless gas is again put down the carb. It will not run longer than a few seconds   Fuel pump and filter inside carb was replaced (filter was completely blocked).  I assume the carb has some kind of internal blockage/ dirt and should be rebuilt just wondered if anyone had any other thoughts or opinions

[V63]

The fuel in the tank is probably 'stale' (has distinctive Odor, yellow or brown color) ) and not volatile enough. It's bad to run that thru the engine because it can seize the valves in the guides ...requiring the heads to be removed.

The needle valve in the carburetor could be seized in its bore

Typically the fuel pump diaphragm is damaged as well

Or all of the above.

[Daryl Chesterman]

Try disconnecting the fuel line from the carburetor and put a hose on the end of it and direct it into a container.  Have a helper crank the engine for you while you watch to see if there is fuel coming out of the line.  If there is fuel coming out in short bursts commensurate with the strokes of the fuel pump, then you know that there is fuel up to the carburetor.  I don't know how many times you have put fuel directly down the throat of the carburetor, but it takes a fair bit of cranking to get enough fuel in the float bowl to start the car.  Have you propped the choke butterfly open and operated the throttle linkage to see if there is fuel squirting into the primary venturi?  If it is squirting fuel and still not starting, V63 would be correct in that the fuel is stale and not volatile enough.

Daryl Chesterman

[TJ Hopland]

I too say run the test with the line disconnected from the carb to make sure you are actually pumping gas and see what it looks like.    That filter being plugged up isn't a good sign.  Even if you get rid of all the bad gas in the tank there is likely a lot of crap too.  I don't know if they were using sock filters in the tanks in 68 if so that could be a problem too because they tend to work for a while after things settle out but fairly quickly suck up all the crap again and clog.

If you can get the tank drained and flushed best as possible you maybe can get away with installing a clear inline filter between the tank and pump and keep an eye on that for how much crap ends up in it.  If its not too bad maybe you can cycle through several of those and get it mostly worked out.   If those plug up quick tank will have to come out and get cleaned.

Also note that that round tube that sticks up just in front of the choke on top of the carb is the bowl vent.  This tube leads directly into the float bowl which is where the gas supply for the carb.  If you pour some fuel in there you can fill up the bowl and as long as the jets are not clogged it should run a little longer.  Not long enough to drive but thats the best way to make the engine run to get the rest of the fuel system primed assuming its otherwise working.  It doesn't take much but its better than just pouring it down the throat.

[Highwayman68]

1968 does have a sock filter on the pickup in the tank and replacements are available.

[James Landi]

All of the above are important steps to follow.  Pouring raw fuel down the carburetor is dangerous... do you have a fire extinguisher handy? Are you standing away when you crank? TJ's advice, "having a small enough orifice, such as a mustard plastic squeeze bottle, to inject fuel into the carburetor air vents will provide some specific diagnostics regarding the health of the carb, and get your engine to run for about a minute.  But please, you need to be clear thinking about this--- as stated above, there's likely a pile of crap in the fuel tank, fuel lines, and fuel pump, and no amount of cranking is going to fix that problem. Old fuel, especially ethanol, creates a fine sandy gunk as well as water... this is the by product of old gas, and NO engine will run on this. You might wish to start another topic focusing on techniques to clean tanks and fuel delivery systems of old gas by products.  Having owned an Eldorado of that generation, they are terrific cars and really fun to drive. James

[J. Skelly]

IF you decide to pour fuel down the carb, let it sit overnight before attempting to start it. All of the above advice is excellent.

[Dave Shepherd]

Don't forget the the filter inside the carb inlet fitting if it is a Quadrajet, often overlooked.

[TJ Hopland]

He did mention that it ran when gas was poured down the carb in the original post.  This statement was why I and I'm sure others were comfortable talking about doing that again without a ton of warnings and cautions.

Don't forget the the filter inside the carb inlet fitting if it is a Quadrajet, often overlooked.

He did mention that that was plugged and replaced in the original post.

[Dave Shepherd]

That's what happens when I get lazy and don't read through everything.  Lol, but that filter can be put in backwards, restricting fuel flow.

[jwwseville60]

Also,
If the gas is bad it will smell like horrible spoiled milk and vinegar, not gasoline at the pump.
Add fresh gas and Marvels oil, which will help and sticking valves or rings.
We did that when I took delivery of my 61 CDV with a tank of two year old gas that we drained out. It ran fine after pouring Marvels down the cap drop by drop slowly.

[Cadillac Nut]

I am not pulling old gas from the tank I am using a gas can with fresh gas, the fuel pump and hoses have been replaced and I have pulled off the line going to the carb and verified that fuel is coming out (plenty of it too). I cannot see any gas getting into the carb though so that's why I assume something in the carb is gummed up or seized. 

[V63]

It's probably the fuel intake needle stuck (glued) with varnish gas as a typical scenario.