I don't know if it's too late, since you asked the question back in February. The thing is, I have one of those. It's a '77 Coupe DeVille with 90,000 miles on it. I bought it last October07.
If the starter, batteries and battery cables are good, the starter should crank the engine a bunch of times, before it runs down the battery.
That other person who answered your question was right, in that more information is needed.
When did the problem start? Was it running before, or did it not run when you bought it? (The one I bought ran on the test drive, but seemed like maybe it wasn't running on all 8, btw.)
Anyway, your car quite possibly has a same problem as mine. However, since you did not elaborate on the details, one could only guess what exactly is going on (or what else is going on, along with the problem described below) with your car.
My car has/had choke adjustment problem(s), and the 4 bbl Quadrajet carb (on the 7.0L /425 cu. In. V8 ) might be leaking fuel into the engine whenever it sits for a while. A local mechanic said that there are lead plugs in that carburetor that deteriorate in time. With that being a '77, these things have deteriorated by now -- if the mechanic is right. So gas seeps down into the intake through the cracks where the lead plugs have given out, whenever the car is sitting with the engine off.
The car just wouldn't start when it was cold, a couple months ago, until you cranked it a whole lot of times, then had to jump it, because the starter would run down the battery from all that cranking.
I have no information except a Haynes manual on the car, and it's missing a lot of specific details on the '77 because the manual covers a wide range of Caddies from '70 through '93 (but is only about 3/4 inch thick). Particularly, the carburetor details are not in that manual, and I wonder about wiring diagrams and a lot of things, since it covers so many different vehicles.
Anyway, I get mine started, now, by just pushing down on the gas pedal, slowly, only about an inch or so, then let up on it, before turning the key. You do this slowly so that the accelerator pump -- in the carburetor -- hardly spurts any extra gas into the already-flooded carburetor.
You need to push down on the gas pedal just far enough to get the choke to close. That is all. The choke is open (fully or to some degree) from the last time you warmed up and drove your car. When you press the gas pedal enough (not a whole lot), the choke coil spring action will close the choke and latch the accelerator linkage onto the fast idle cam step.
So before you first crank the engine when it is cold:
1. The choke needs to be closed all the way.
2. There should be enough gas in the carburetor float bowl to get it to turn over.
3. Assuming your old carburetor is leaking fuel into the engine while it sits, the engine is flooded when you first go to start it, after it has been sitting. So, you won't have to pump the gas pedal any. That would just make it harder to start.
Btw, evidence of this, with my car, is the longer the car sits (like 4hrs, overnight, or 2 days) the more cranking it takes to get it to turn over.
4. So all I do, when the car is cold, is push down on the gas pedal about an inch or so, let up, then turn the key. I only crank it about 15 seconds at a time, then let it sit about 15-30 seconds. (That's so the starter "don't" burn out. I don't have an owner's manual for this car/just going by experience with some other GM cars I have owned).
5. You may be tempted, but after the one small push on the gas pedal, keep your foot completely off the gas. Under these conditions, after a few more 15 second cranks, mine starts, before cranking it so much that the starter runs down the battery. However, I don't time this exactly, and when it acts like it's trying to kick over, I keep the starter engaged until it starts running (well not for as long as a minute or so).
6. I don't give it any more gas until it just starts running. Then you have to rev it up some, because the whole idea is to clear the flood out of the engine.
If that doesn't work, there are a bunch of other things that could be wrong. Possibly your car has the problem described plus one or more other problems. Some of the most obvious things are broken/cracked/burnt spark plug wires, worn distributor cap and rotor, fuel pump, or other things.
Note that carburetors are supposed to be reliablle, and don't wear out as quickly as the other things, like spark plugs, etc. Things can get screwed up more by trying to adjust the carb, when it's fine and the problem is something else.
I need some help on where some vacuum hoses are supposed to be hooked up on my '77 DeVille. So maybe we can keep in touch? I don't know if the hose that goes straight back, at the back of the carburetor is supposed to go to the EGR valve, the rear choke pull-out or the air cleaner.
My car's rear choke pull-out doesn't work (supposed to open the choke all the way when the car is warmed up, but the choke coil opens mine all the way, without the secondary pull-out working-- depends on choke coil adjustment).
P.S. Not to go on and on, but there is also, a "choke unloader" mechanism that is supposed to clear out a flooded engine. See your owner's manual on that, but the manual probably doesn't cover special procedures for starting the car with an old carburetor in it. :Mrgreen:
Monday, March 17th, 2008 AT 12:34 PM