The Stovebolt Site Forums The Shop Area General Truck Talk Stuck float?

OK bolters need help. Trying to start this old Pontiac. I know, I know its not a bolt but thought maybe could get some advice from some kindly knowing bolters. Tried all the usual things. New battery,new plugs, points are opening and closing but show a weak yellow spark, fresh gas. By the way IRWIPI but has been setting for 2 years. When changing plugs I noticed a strong smell of gas from the open spark plug holes. Could a stuck float cause gas to run through the manifold into the cylinders? I'm thinking maybe this thing is boucoup flooded. Any advice? Forgive the Pontiac. Didn't GMC trucks use Pontiac engines in some trucks? Maybe its relevant after all. Weeds

Hey Weeds...Pull the top off the carb, and see if your float has a hole in it and filling up with gas..It's not a GTO is it?

Shoop, its a 72 Grandeville convertible. Got it sold if we can make it run. Weeds

Might be worth your while to pull the carb off, and do a cheap rebuild..Or maybe just a good clean up and adjustments..I know you are very knowledgeable, but I know that a messed up carb will dump gas into the cylinders..Just a Sunday morning thought, but how about pulling all the plugs and cranking it for awhile to clean out the cylinders..Clean and gap the plugs, and give it another try..Good Luck, Steve

If it's a 72, I'm almost sure it's got a Quadrajet, right? They're nototious for the float getting soaked with fuel (it's plastic), and sinking. The Q-jet is no picnic to work on, and even a simple float replacement is a hassle. There's a real danger of bending the primary metering rods when you try to reinstall the top.

A rebuild by a professional carb tech should run somewhere in the $100.00 range for a correct job. There are 22 consecutive adjustments during a rebuild, so unless you've got a lot of experience, "don't try this at home" applies. You might investigate the purchsae of a rebuilt carb, but be sure it's a direct swap. There are approximately 250 different Q-jet part numbers, and they've been installed on everything from a 230 cubic inch Pontiac OHC 6 to a 500 CI Cadillac.
Jerry

Great advice..worked on them myself on the kitchen table, and never did get them to work well..An aftermarket rebuild is a good idea..Steve

Crank it a bit & look into the carb. If the float is bad gas will be running into the engine. This weak yellow spark if it is comeing from the points that is normal. Remove the coil wire going to the center of the dist. While cranking the engine or opening & closing the points with a screwdriver you should get a fat blue spark from the coil wire to ground. Check these things & post back to us.

Shoop, Bender and HR Lincoln. I knew you guys would come thru. Thanks. Coil wire to ground while cranking shows a weak yellow spark. Bad coil? Might pull the top off the carb to check the float. If gas logged can I buy just a float and put it back together? If not I will probably buy a rebuilt carb if only about $100. This is a rusty old car but have a couple of lookers who are interested in the 455 but want to hear it run. Weeds

Yes, you can get a float separately from a kit. In fact, when I build a Q-jet, I always replace the float. What's not available by itself is the air horn gasket. Be VERY careful removing the top of the carb, as all the fuel metering flows through the gasket between the air horn and the float chamber. If you can get a needle valve and seat assembly, change it while you're in there. Some better-quality parts stores will have the needle & seat available separate from a repair kit, especially if they happen to be an AC-Delco parts distributor. Be sure to set the float level to the correct specification.
Jerry

Jerry Thanks for the advice. I will procede slowly and carefully and let you know what happens. Weeds

I believe you may have a Carter Thermoquad carb. These carbs were put on all SD455 Pontiacs. They were used on a lot of the large cars(Gran Ville and Bonneville) and they are a bear to rebuild. If you think a Q-Jet is tough, open up one of these jewels. However, they are very good carbs if rebuilt properly. Here's a good site-http://www.offroadexchange.com/projects/CrtRbld.htm. Get a new set of points and a condenser. Coils will usually fire okay until they get hot from running for a while.