My buddy has a 65 Caddy with a '76 500 engine. The car was starting and driving great until it say for almost 2 years. We got it to start up with some Starter fluid, and once it was going it fired up easily. But after it sat overnight it wont start again. I haven't been back to his house with the starting fluid, but Im assuming that will make it fire again. I should mention that we had to put a new mechanical fuel pump on after it sat for so long. The old one developed a bad diaphragm when it was sitting. Whats the best way to go about figuring out the issue with it not starting when its cold? Here is the only pic I have...
Is the choke working? Fuel bowl leaking? I have an OT car with a slant 6 where the choke had stopped working & the fuel bowl would slowly lose fuel overnight. It would then take quite a while both to fire in the first place & then for it to get enough fuel to stay running on its own but if you started it on ether and nursed it a bit it went faster.
TO be honest, im not even sure the choke is hooked up. If its not, it hasn't been for a LONG time, and the car has always started after 1 pump of the pedal. How do we know if the bowls are leaking? There are no signs of wet fuel outside the carb.
On my Dart, every time I lifted the hood to try and figure out the problem when it was doing it, the car had been sitting overnight so the fuel had evaporated already. It wasn't until I happened to pop the hood to look at something else after a long drive that I noticed the wetness around the bowl and it suddenly made sense. So I'd say get it running and let it run for a bit, then look. My knowledge is limited but I would think there's not a lot else it could be given that it fires easily with ether, then works after that, and the fuel pump works. That says it isn't a spark problem and not an issue with the pump or lines. But I could be mistaken... I'm still a rookie.
If it’s pumping fuel, make sure the carb is squirting. Sitting up is bad on those. A q-jet can leak out underneath. A plug on the bottom of the fuel bowl into the intake. Corn fuel evaporates bad enough on its own. But, a possible leak is secondary. If the spark is good, then check the carb.
Compression? If yes, check spark, spark? If yes go to fuel. If no, get some spark. Ignition module went to the toilet. Oh, and if the valves all stuck or bent, causing no compression, drink beer. Search for replacement Cadillac 500.
Thanks for the replies everyone! Spark is good, and compression is good. Its a strong running motor once it starts, its getting it started cold thats the trick. maybe the 2 years if sitting caused some carb issues. Maybe its time for a rebuild...
I'm guessing the dreaded Q-jet bottom bowl plugs are leaking. Next time, before doing anything, carefully pour a little gas down a bowl vent to fill the float chamber. (Not into a venturi) Then try starting. If it fires right up, then the gas is probably leaking out the bottom of the bowl through those plugs. If so, pull the carb off, find a good fuel resistant epoxy and seal those plugs up. If it won't start, it has to be getting out some other way. And yes, modern gasoline in a carburetor can evaporate in a couple days.
It looks to me like you have an electric choke with no power going to it,( no visible power wire) so it's not going to work. That is the first thing I would correct.
If it's been sitting for any length of time, the carb is probably going to need to be disassembled and cleaned (plus checked for other leaks). Do you have another Good carb to try in the mean time?
I don't even piss around with Q-Jets, my rebuilding is more miss than hit. I have a good carb shop that does them at a decent price, or Holley makes a nice replacement. Definitely look for something with an electric choke. Less moving parts, less problems.
I think the poster referring to the choke not functioning solved the issue. Starting with no choke (before) implies the carburetor is rich. Even a rich carburetor is going to either not start at all, or be extremely difficult when the weather is cooler without a functioning choke. The comments about fuel evaporation are spot on, but probably not the issue at this time. The comments about the fuel bowl plugs leaking refer to all 1965~1967 and a few EARLY 1968 Q-Jets. Rochester corrected the problem in 1968. The newer carbs do not have this issue. Suggestion: get the choke working. Second suggestion: once the engine is running again, unless your friend owns stock in Shell Oil, consider rebuilding the carb; reiterating, starting without the choke is a symptom of a VERY rich condition, and is certainly wasting fuel. Jon.
Obviously its not getting enough fuel and the starting fluid gets it going. It should be easy to move the choke a little more closed by pushing on it with your finger or a screwdriver while cranking. Be careful not to get any body parts above the carb incase it backfires. If you get it running, I'd drive it and get the old gas out of it. Might want to replace the fuel filter first though as it could be holding fuel back some. After that I'd follow Carb Kings advice. I always wonder why people let perfectly good engines sit for years without starting them ocassionally.
WOW.....reading some of the comments on this post makes it plainly clear that not everyone takes the time to read the entire post. Since the engine RUNS after spraying starting fluid it's apparent spark is present, and has compression. There's no need to start looking for a replacement engine or start rebuilding the valvetrain. Carbking, whom I would assume knows his way around a carb, has stated the likely culprit. Get the choke working, make necessary carb adjustments and let us know how it worked out.
If this carb uses the paper fuel filter their are 2 styles available. One has a flap or check valve that prevents fuel from draining from the bowls . The other is just a gasket with a hole in it,this one can cause hard overnight,am starts. A spring should be behind the filter also.
CarbKing is pointing you in the right direction. If it is the correct O.E. carb, have it rebuilt if at all possible. Much easier to replace O.E. carb than an aftermarket piece, less "adapting" required, fittings and linkages are all in the right places. Get the choke t-stat working and the choke adjusted properly. A cheaper, easier approach to "maybe" fixing "some" of your problems . . ? Get the choke working like it should. Fill carb with fresh gas with a squirt bottle thru the vent tubes and check for a good strong accelerator pump stream. If necessary, try replacing the accelerator pump plunger and seal.
I think it’s the choke too. The pic below probably doesn’t apply to you being from So-Cal but up here in the NE……..it’s the norm.
Carburetion 101, lesson 2: There are 3 major ways to improve fuel atomization: (1) increase the air velocity (choke) (2) increase the heat (hot engine) (3) throw more fuel at it (carb needs rebuilding) Guessing that the combination of a rich carburetor and fresh fuel (when it would start before it sat for years) and location (southern CA) would allow starting, although maybe not on the first revolution as it should. Two year old fuel is going to be difficult to fire with a cold engine even with the choke functional. Once the engine is hot, the old fuel will fire, albeit not as well as if it were fresh. How much trouble is it to drain the tank, and dispose of the old fuel? Jon.
WOW. Thanks for all the replies! Draining the tank would be tough, but not impossible. Thats being said, there were only a few gallons in it while it was parked, and we added about 10 gallons too it. So its not ALL old gas. I really think the choke is the first attack, and then see how it is from there.
My 500 caddy just started running bad. Sit for a couple months, drove to the gas station and hit the interstate. Started feeling underpowered. Then running rough under a load but idled fine. Fuel filter needed cleaning. Yep never felt the urge to rebuild it
So we hooked up the electric choke, and would you believe it, the car starts and drives great! Thanks for all the help!!
This is most likely the issue. I've had this exact issue on mine including the one on my ot 1 ton with a 454. It worked great if you drove it every day but let it sit for a few days and it was a fight to get it started and that truck never leaves the driveway unless it has a job to do as it drinks gas faster than a barfly sucks down happy hour beer. It isn't a hard fix but you do have to take the carb off and do some drilling and tapping to do it right. one of the Q jet gurus who rebuilds carbs and sells great kits sells a plug kit with instructions that is a lot better than the rubber plug in the kits.
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