The Stovebolt Site Forums The Shop Area Engine Shop A Problem, I Think its the Carb

After I fixed the last problems with my truck (76 Chevy with a 454 and auto trans)it ran well. About 2 weeks later while I was driving home from work it stalled. But before it stalled it sputtered a few times. I would try to start it and same thing. After spraying some gumout in it, it ran fine the rest of the way home. I checked it this morning and drove it around and it was fine. But again on my way home from work it did the same thing. I didn't get it home tonight. My questions are, Is this from the carb or something else? Those this happen because its alittle damper and cooler at night(Southern California)? What can I do to fixs this problem

If it's a condensation problem, a can of "dry gas" added to the tank will clear it up ... when it gets cold and damp out, my truck can run horribly -- the dry gas clears it right up.

Assuming you have the original Rochester carb:

Q-Jets as a general rule have no personality. They either work or they don't. Also, the engine should run BETTER, not worse, under damp cooler conditions (more oxygen).

Possibilities:

Partially clogged fuel filter
Partially clogged fuel sock in tank
Ignition
Icing (rare with a large 8, but it does occur, particularly if headers and/or aftermarket aircleaner)

If the "dry gas" (alcohol) is helping, I would try a tank of gasoline from a different source. Here is Missouri the humidity often exceeds the temperature, and I have not ever needed (in fact avoid) the alcohol in over 40 years of driving.

Jon.

well I went today and tryied it again. Its warmer out and same thing. It took me awhile to get it started and when it started I let it idle for 10 mins, when I started to drive off, after about maybe 100 yards same thing. I then had it running and when I took off the air fliter to put some GumOut in it, it sounded like alot of air was coming out and it sputtered again and thats when I stopped. The Igintion is good, but it seams like its not getting gas. I have both tanks on full. What are some ideas I can try? Where would I get the Dry Gas at and is it called dry gas or another name?

u done the fuel filter? I think you should start with that - its relatively easy. And if you don't know/remember when it was done, then it probably needs doing. Engine will idle with fuel filter partially clogged, but once it has a demand, the bowl will empty, not get replenished, and then stall.

Well, I changed the fuel fliter and it ran for about a day and the same problems. The sputter and it dies. I can start it every once and awhile, but then will die after like 3 mins of driving. I have no Idea what it could be, do you ?

When it dies, can you spray some starting fluid in the carb (or pour some gas in) and get it to start again? If so, it's a fuel feed problem and could be the fuel pump.

Another thing to check. Is the choke opening fully when it's warmed up? Could be that it's running too rich.

Some stuff to check.

Check the crankcase oil level to see if it is above full and smells like gas. If it is your fuel pump is leaking. This will cause an engine to stop while running and will also keep it from starting.

If no gas is in the oil try to start it as usual. If it won't start spray some carb carb cleaner from a spray can into the carb with the choke held open. If the choke is closed this won't work. Don't pour gas into the carb it could backfire and start a huge fire.

If it starts with the carb cleaner and runs check that the choke plate opens after a few minutes as Asylum says above. However, if only the automatic choke were your problem it would start easily when cold.

If the choke plate opens ok and the engine stops after running a short time take off the air cleaner and move the throttle quickly a couple of times to see if it sprays gas into the venturi. If not you have a fuel supply problem.

My first guess would be a bad condenser because I have had all these problems with condensers, but I think a '76 has HEI so that theory is no good if it has HEI. If you have a condenser, change it.

Be sure to let us know what you find out if you solve the problem.

one more thing to check is a leak at the carb base or at a gasket cauing a vacuum leak. you mention that the truck runs better shortly after spraying stuff down the carb, the spray may seal a vacuum leak for a short time.

I changed the carb, now I just need to fine tune a few things and it will run great.

Hey, Salinaz

The "dry gas" I use comes in a red bottle and is called STP Gas Treatment. If it rains heavy in cold weather, I get condensation in my fuel lines, but if I add a bottle of the STP Gas Treatment it won't happen. I'm in New Jersey and when winter comes around, I buy a half dozen bottles handy ... I only used 3 bottles this winter.

What kind of carb did you put in? My 54 had a Rochester in it when I bought it ... I don't like Rochesters, so I put an Edelbrock in and never have to adjust it - my favorite carb.

ita a rochester, I dont like it much, but it works and thats all I care about now. I am stalling alot some times, what can I do to stop it? I adjusted the idle, but I think I need to do it again maybe.

If you have changed carbs and are still stalling I think it is time to forget the carb and look at something else!!

Have you checked that you are getting plenty of fuel to the carb?

My money is still on something in the ignition system, either the coil or condenser if it has one. Sometimes it is nothing more than a loose connection in the primary ignition circuit. Happened to me on my dump truck, the wire into the ballast resistor was just loose enough to kill the engine once in a while.

Last but not least, if you don't have a repair manual for this truck you should get one. There were some important changes to GM engine tuning specs in the mid '70s not the least of which was spark plug gaps, timing advance. GM was trying to comply with emission standards and get the engines to run well, didn't do very well at either.

If you are stalling at idle, it's possible that you are running the carb too lean ... if you give it a little more gas and it clears up then you know you aren't getting any gas in the idle position - too lean.

Have you checked to see if you have good fuel flow through the fuel pump?
Sisnce you changed carbs,,, did you use a new carb or a used one?
If it was a new or rebuilt carb, I would check out the fuel tank the fuel lines and the fuel pump.
Now it is possible that you have a poor connection to the ignition feed from the battery. Look the connections over real well and with the truck running at idle, wiggle the wires and connections to see if you get anything to cause the engine to stall or die.
Be careful you don`t get zapped by the spark-plug wires
One more thing, check the wiring and connections close to the heat of the exhaust first so you do not get burned

I checked fuel lines, fuel pumps, distbutor, rotor, ignition coil and everything is fine. I adjusted the idle again and it was better today. No stalling. Now its a leak in the power sterling hose. But at least its not that hard to fix.