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Old 10-28-2016, 07:21 AM
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What could be causing flooding in 61 Cadillac w/390?

A little backstory on this: About two years ago a (not very mechanical) friend inherited a 61 Cadillac Deville, it had some drivability problems so I helped him go through it and we ended up putting an edelbrock 600 on it because the Carter AFB had a crack in the base. At the same time I also installed a reman fuel pump as the factory pumps spring was broken. He's probably put several thousand miles on it and drove it to his new home about 8 hours away with the car performing flawlessly..until a few weeks ago. He called and said that the car was having a hard time starting and that it smoked black when it finally started, but once going it ran fine. Then it got to where it was having trouble idling and would stall. Not being in front of the car I took a stab at it and thought maybe it was the carb, since I've heard of others having issues with Edelbrocks leaking when the car is shut off. I sent him a brand new holley 600 I'd had on the shelf and a carb adapter, he put it all on himself but said that the car still won't idle and will load up and die. I've asked for him to get a cheap fuel pressure gauge so he can see what kind of fuel pressure the pump is putting out, but would a mechanical fuel pump suddenly start pushing too much pressure? Or could there be another problem in the fuel system like a clogged fuel tank vent (do these cars even have a vented fuel tank?). I'd really like to help him out as he's one of my closest friends, but it's kind of hard without me being there. Just trying to figure anything out that he should be checking for. Thanks!

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Old 10-28-2016, 08:17 AM
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Have him start at the tank and look for any kind of fuel filter that might be in the line from the tank to the carb.
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Old 10-28-2016, 11:09 AM
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I'd go back further than tech!!
Check the gas cap. It should be a vented type. Could be stuck.
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Old 10-28-2016, 03:53 PM
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I'll tell him to check all of that, though I believe the gas cap hasn't been changed since all of the work has been completed. Would a clogged fuel filter cause too much fuel pressure?
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Old 10-28-2016, 04:57 PM
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flooding is usually caused by sediment in the fuel system..

a 10 micron fuel filter directly before the fuel pump... so the pump ONLY gets filtered fuel.. i use 1990 ranger fuel filters as they are available everywhere but they are big and ugly. so other options are available but you have to verify 10 micron.. most of the clear filters are 70 micron.. let the dirt right thru..

once installed... disconnect the ignition system so NO sparks can be created.. disconnect the fuel line at the carb.. extend it into a clean clear soda bottle... have somebody crank the engine for 15 seconds while you look at the pulses.

do the 15 second trick 3 times.. this allows filtered fuel to surge thru the pump at full speed so most of the crud is cleared out.

hook the fuel line back up to the carb.. reconnect the ignition.. get the engine started... with a pair of long nose pliers.. pinch the hose between the filter and the pump inlet closed.. with your other hand take the engine up to around 1500 to 2000 RPMs... when it starts to run out of fuel and stumbles.. release the pliers.. this lets a surge of clean fuel thru the wide open needle and seats ... do this at least twice..

i have been doing this since 1983... using 10 micron filters before the pump... this is the best cure..

super magnets in the fuel tank is another good idea... try to get them in away from the sending unit arm.. i have stuck them to the bottom before..

you can stick a big speaker magnet to the bottom of the fuel tank and that will help also. .the magnetic field will pull the Red dUST close to it and keep it out of the fuel lines, fuel pump and carb..

if the engine is still idling bad.. take out the idle mixture screws.. blast some carb spray into them. followed instantly by some compressed air. this blows crud out of the idle feed restriction and idle air bleeds and allows the carb to work again..

sometimes the sediment is just too much in the carb and it has to be taken apart..

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