Signs carbs are clogging up?

[Pleadingbark]

What are the signs the carbs are clogging up? Last night I was driving the car and it seemed like it lost almost all power and was running on 3 cylinders. The car had no power, could hardly rev and was constantly back firing. Pulled the plugs and the front 3 are half brown/half black and the back 3 are brown but were soaking wet. Would that indicate that the rear carb was stuck open? If you shut the car off it would be fine until you got on it while driving then it would suddenly run like total crap again. Any thoughts? Its got a pertronix on it now with a new coil, but it was running like a top all day then just suddenly started running like crap. Does it sound like the back carb's clogging up? Its done this before when it gets low on gas and the fuel filter gets clogged up, but I stuffed a new one on. Did have to drive w/o one for about 2 miles though as the car pooped its pants on the side of the road.

[Bruce Palmer]

What year car? What kind of carbs?

[Pleadingbark]

71/ non emission ones.

[Bruce Palmer]

Remove the aircleaner, start the engine let it idle. Pull the over flow tubes to the aircleaner off the float bowl lid nipples, keep a fire extinguisher handy and report back....

[dltalfa]

OK,...here is how to check the fuel flow to the carbs.

Disconnect the fuel line to the front carb, (where it connects to the float bowl). Now, have someone hold a cup or bottle with the open end of the fuel line inside, and turn the engine over a couple of times. You should get a steady flow of fuel.

If you have ample fuel flow to the front carb,..replace the hose and try the same procedure on the rear carb.

If you have ample fuel flow to BOTH carbs,..it's a sign your needle valve is sticking.

Edited November 1, 2011 by dltalfa

[Pleadingbark]

Remove the aircleaner, start the engine let it idle. Pull the over flow tubes to the aircleaner off the float bowl lid nipples, keep a fire extinguisher handy and report back....

It doesnt come out, pulled the air cleaner last night thinking maybe it was clogged, nothing. Both carbs are also sucking in equal amounts of air it felt.

OK,...here is how to check the fuel flow to the carbs.

Disconnect the fuel line to the front carb, (where it connects to the float bowl). Now, have someone hold a cup or bottle with the open end of the fuel line inside, and turn the engine over a couple of times. You should get a steady flow of fuel.

If you have ample fuel flow to the front carb,..replace the hose and try the same procedure on the rear carb.

If you have ample fuel flow to BOTH carbs,..it's a sign your needle valve is sticking.

Ok will try that, was also advised there are little filters in the carbs where the metal fuel line feeds to the bowl, so I will clean those also. The car revs completly fine when the cars freshly turned off and on, its only after a load is applied that it starts falling on its face, I guess debris in the line would cause this?

[dltalfa]

Ok will try that, was also advised there are little filters in the carbs where the metal fuel line feeds to the bowl, so I will clean those also. The car revs completly fine when the cars freshly turned off and on, its only after a load is applied that it starts falling on its face, I guess debris in the line would cause this?

This is either

1)- Weak fuel pump.

2)- Clogged fuel filter(s).

3)- Stuck needle valves, (ususally due to trash).

[Reverend]

Check out the carburator section, there is plenty of info about cases like this.

[Travel'n Man]

Do you have any in-line fuel filter other then the ones inside the carbs? If your carbs filters have filled full of debris in the past do you actually have a larger problem in your tank?

[Bruce Palmer]

Having real trouble understanding your plug readings. Fronts are half brown half black (No idea what that means) and rears are all brown but soaking wet.....

Do you have a choke cable set too tight of a choke nozzle stuck on? I'm done....

[Pleadingbark]

This is either

1)- Weak fuel pump.

2)- Clogged fuel filter(s).

3)- Stuck needle valves, (ususally due to trash).

Whats a needle valve?

Do you have any in-line fuel filter other then the ones inside the carbs? If your carbs filters have filled full of debris in the past do you actually have a larger problem in your tank?

I had the stock one for the car' date=' but I thought it was clogging up so i temp. bypassed it and ran w/o a filter. Im thinking the carb's filters caught it all, more specifically the rear carb.

Having real trouble understanding your plug readings. Fronts are half brown half black (No idea what that means) and rears are all brown but soaking wet.....

Do you have a choke cable set too tight of a choke nozzle stuck on? I'm done....

Ill try to take a pic tonight to show you of the spark plug. I dont think so on the choke stuff, like I said it only does this when its fuel filter is clogging up.

[dltalfa]

Whats a needle valve?

QUOTE]

OK,...your carb set up has a fuel line that is split, delivering fuel to each carb. The fuel lines connect to a float chamber attached to the side of each carb. It looks a small canister. Inside, there is a "needle valve" that rides on the end of the float lever. The needle vale rides up and down with the fuel evel in the chamber. It has a pointed end that moves up and seals off the flow of fuel into the chamber from the fuel line. The float rises up and down based on the amount of fuel in the float chamber, thus allowing the fuel to cut on and off a needed. Without this needle valve, the fuel would continue to run all the time and float the carbs.

Here is a link to a vendor and shows the needle valves that come in a carb rebuild kit.

http://www.thezstore.com/page/TZS/PROD/11-3150