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My name is Joe and I am from Alaska. I own a 1985 Jeep CJ7. I use it for hunting and fishing up here in Alaska. I have one problem. I have to inject fuel into the carborator when ever I have to start it for the first time that day. I get it running and then it runs fine until I stop for a long period of time like 4 hours. Then I will have to put more fuel into the carborator. When I am just using it for the time its running I can shut it off and start it 5,10, or 20 minutes after I just ran it. I have a Rochester Carb on it and have an inline 6 cylinder AMC engine. What causes it not to run after long periods of time? Why do I have to keep putting fuel into the carb after it hasn’t ran in a while? Thanks for any help provided!

The gas is returning to the tank.

You may have a faulty fuel pump with a bad check valve or possibly a defective fuel pressure regulator not holding the fuel pressure up.

Is the choke plate closed when you go to pour the fuel in?

I would put a electric fuel pump in and then if you turn key to 2nd click 2-4 times for 5 seconds. After you try it a few times you will know how many times and how long to leave key on to get gas back to carb.

Shouldn’t there still be some gas in the bowl?

Carburetors have an “accelerator pump” that squirts a little extra fuel into the engine when you pump the gas pedal. Check and see that yours is working. (Look down the carb throat and open and close the throttle several times. you should see the fuel squirting in). Also, on a cold start, the choke must be closed…

Carburetors have a “float bowl” full of gasoline. This is what the engine runs on. It is possible for this gasoline to leak out (or boil out) of the float bowl so after some time has past, the carb is empty when you attempt to start the engine. The fuel pump must refill the carb before the engine will start.

All of these problems can be cured by rebuilding the carburetor. 1985 means you have a feedback carburetor (computer controlled) But since you live in Alaska, I suspect the emissions controls have been removed a long time ago…This leaves the carb’s overall condition a big question mark. Good Luck.

Carburetor … it’s been a while, but as I recall, this sort of problem is often caused by the fuel leaking out of the carburetor bowl. As long as there is fuel in the bowl, the engine can suck it out when it turns over, generate a vapor that the car will run on. And when the car starts the fuel pump will refill the bowl. But if the bowl is empty, the vehicle won’t start unless you crank it long enough to pump some gas into the bowl – or you introduce some gas or starter fluid into the engine to make it start.

The good news. This may not be a complicated repair … if you can find anyone willing to work on a carburetor. Maybe you can do it yourself if you are meticulous about noting which hoses and linkages go where. Probably, most of the zillion tiny mysterious parts that give carburetor repair a reputation for black magic will not have to be disturbed.

I did successfully do a couple of carb repairs about 20-30 years ago. I’d do my homework on how carburetors work and how to repair them before I took tools to one. It is very easy to screw things up and much less easy to set things right if you do things wrong.

Check the carburetor to see if the choke is actually free to operate. It seems that the AMC/Jeep engines used Carter 2 bbls in 1985 and a Rochester might be a patch up repair. The original Carter 2 bbl was a problematic model at that time and was usually replaced with earlier versions without the mixture control system.

Roadrunner may be right.

If the check valve is faulty the gas returning down the fuel line can draw the fuel out of the bowl. Think of it as a small bowl of gas with a line running to a lower level tank. Gas will run downhill, and it can pull the bowl supply with it.

Try two tests after the Jeep has been sitting for a while.
First, prop the choke open, look down the carb’s throat with a flashlight, and activate the accelerator linkage by hand. You should see a spray of fuel. If not that means either the accelerator pump is failed or the bowl is empty. Generally a vehicle will stumble and accelerate extremely poorly if the accelerator pump is bad, and you didn;t mention that as a symptom, so I doubt if that’s the problem.

Second, try turning the key to “on” a few times for 4 seconds each before hitting the gas and turning it to “start”. You have an electric fuel pump, and if the gas truely is flowing back into the tank the pump will refill the float bowl and the engine will start fine with the usual rocedure of pumping the gas once to set the high idle cam and prime the carb.

If the second “test” works, you can just build that into your normal starting protocol and you’ll be fine.

Post back with the results.