I have a 350 Chevy engine in my car with 3 Rochester 2 G carburetors. If I drive it every day, it starts fine. If I let it set for 5 days it has no gas in the carb and I have to turn it over with the starter for far too long before any gas gets to the engine. Any ideas?
I just pour a splash of gas into the primary carb before trying to start it. It will fire up right up. It might stall out again, but that short amount of run time is usually enough to get the gas flowing, and another short crank will get it running again.
Should not happen. Two-three weeks maybe do to ethanol in the gasoline today. Do you have insulate plates under the carbs, I use 1/4“ phenolic I bought off E-Bay. I don’t know your manifold but if it has an exhaust carb heat crossover mine uses gaskets with very small holes which helped a lot.( metal around the opening) If you garage your car try opening the hood when you park it inside let it breathe out and not confine the heat; maybe a small fan blowing air by the engine for an hour or two (use a timer so t you won’t forget to turn it off) If this fixes it you know it’s a heat sink problem and do the above.
Maybe it depends where you live, but around here, gas evaporates out of most carburetors pretty quickly, and that seems to be the cause of your problem. Modern fuel seems to be more volatile than older fuel was, since now they make it to work with fuel injection, not carbs. The electric fuel primer pump, and the manual priming method, both would work. They're both a pain. Driving the car every day or two also works, but I can understand how that doesn't happen....I've been only driving a few times a week lately, and with a bunch of cars to keep in action, they seem to be sitting longer than they should.
The gas these days does seem to evaporate much faster than just 10 years ago, especially here in hot central California. I have the same problem with my ‘56 Chevy. It’s very evident in my riding mower with it’s see-through gas tank. An inch of gas left in the tank is gone in a day or so it seems. That half cup in the carburetor bowl doesn’t stand a chance. I think a small auxiliary electric fuel pump is a good idea for cars that sit for a week at a time or more. Sent from my iPhone using The H.A.M.B. mobile app
I'm thinking that has become a universal problem with rigs with carbs that tend to sit more than a day or so between getting driven. My 77 dualie is a pain to start after it sits and that gas hog doesn't leave the yard unless it has work to do. I've run a somewhat inexpensive inline pump on my other truck that I left on it after I replaced the mechanical pump as a flow though auxiliary pump. It doesn't seem to cause a noticeable restriction on that truck. I may be doing it wrong as this guy dealing with flathead Cads suggests running a parallel fuel line and having it tie in on the outlet side of the mechanical pump. http://rmrclc.com/WaltsWorkBench/6-2000 Auxiliary fuel pumps.html
Plus 100 for adding a electric pump. The Q-jet on my landlords car would dry up in 4 or 5 days. Added one of those airtex in-lines with a push button switch, and it kicks right away. I thought the pump being inline would be a restriction, but it has been fine. That darn Q-jet is so dialed it might as well be FI.
Plastic ketchup bottle w/fuel mix. Squirt it in the fuel bowel vent ‘till it runs over. Starts right up. ‘67 Corvette BB. I hate electric pumps.
The gas in my Coupes Q-jet will evaporate in 2 days here in Florida, and no, it's not leaking out. I just crank the engine until I get 60#'s of oil pressure and by then I just pump the throttle and Vrooom !!! It's the junk gas they sell us today, it's a wonder our old engines run at all. Just gotta live with it.
It's not the carbs but the fuel pump. The check valves are leaking ,allowing the fuel to siphon back. Our 57 does that because it is seldom driven [We are running AvGas] An electric pump will remedy this, but it is not a good practice to pressurize the inlet of an already worn out pump. You can use an electric "flow-thru" type pump to prime it. [eg: Airtex E8090] The mechanical pump will still draw gas through it [when switched off]. Run dual core wiring back to the pump, with the pos+ hooked up to the Ign / fuse box. The ground - wire is T'eed into to the oil light sender. When you switch the Ign on , the pump primes the fuel. When you start the engine and the oil light goes out, the pump also switches off.
It's now a very common complaint across many makes and models, with the modern gasoline blends. The carburetor bowl won't likely be completely dry. But the "light ends" will definitely boil off very quickly, because unlike EFI, a carburetor is more or less open to the atmosphere. What's left in the carb bowl won't ignite readily, even though you can see plenty of fuel squirting into the intake from the accelerator pump. This explains why pouring a couple tablespoons of fresh fuel down the carb instantly remedies the issue, or pumping fresh fuel electronically into the bowl does the same.
The needle and seat becomes a break in the line much like a anti syphon valve. This means carb can not be emptied by any sort of back flow.
I have a small 1 gallon container of gas mixed with 2 stroke oil for my weed eater & chain saw, I use that. It's handy, it has a pour spout, and I figure having a little top end lubrication in that splash of gasoline doesn't hurt.
Probably [I'm not disputing that] If the fuel in the bowl evaporates slightly, the float lowers and the needle and seat is open, allowing air to leak in the vents and out past the needle and seat [gravity allows the fuel to siphon back to the tank] The fuel in the bowl cant siphon [or leak] below the level of the jets anyway [ but it can evaporate] What I have observed is the glass fuel filter is empty after sitting for a while. So there is no fuel in the system to fill the float bowl. I don't have a vapor lock issues with AvGas. [it is leaking past the fuel pump check valves] What happens is the engine will just"fire" but wont catch and run until the is fuel pumped up. So don't touch the gas pedal at all while starting as it will lean out.
How about one of these boat squeeze bulb pumps in the line or many diesels have a manual pump to bleed the filters.
Very common issue! So common, I added a paragraph addressing this in my "troubleshooting" section about 10 years ago: http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstartcold As to siphoning: the Rochester 2G carbs have the fuel valves ABOVE the fuel. There is no path for siphoning to occur. Siphoning would only be possible if the vehicle were parked upside down or you live where there is a gravity anomaly. Jon.
first I have a mechanical fuel pump in my roadster but I also put a electric pump in the line. It is wired with an On/Off/Momentary switch. If the car sits for a while I run the electric pump to fill the bowl using the momentary switch. Starts up and runs off the mechanical. Also if the mechanical ever quits out on the road I can switch the electric pump to on to get home.
I read the article linked in @Mr48chev post #7 and found it very interesting, particularly about the parallel routing of the auxiliary pump line, rather than through the mechanical pump. Worth your time to read it. I did find one aspect of that discussion that is especially interesting....if the aux pump is in series with mech pump, and the diaphragm fails, the aux pump can fill the crankcase with fuel via the failed part. However, if the aux pump is routed parallel, the aux pump is teed in on the output side of the mech pump. That means the mech pump output check valve prevents the aux pump from pushing fuel into the crankcase. Result, engine runs on the aux pump and there is no diversion of fuel to where it shouldn’t be. Not an insignificant consideration. Ray
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