so recently i purchsed my first 3rd gen and went to tinkering like i usually do. i removed the AIR equip put pipe plugs in manifolds and capped the vaccum on the carb., removed EGR equip and capped vaccum on the carb, replaced intake w/ weiand 8004 non-egr a coolant neck w/ NO sensors, removed charcoal canister and left pressure valve vented to the fender w/ vacuum on the valve open and return line on the carb. capped., also capped the vacuum to the air cleaner and charcoal canister control valve. so the only lines running to carb are the brake booster, the vacuum sensor, the pcv, and the fuel line. im some how getting a syphoning effect and fuel is filling up combustion chambers and getting into oil. does it have something to do w/ the line routing from removing the charcoal canister? the line that fed to the canister is there w/ check valve then routed to the fender. is there some kind of vacuum prob. having 4 ports capped(egr,aircleaner,canister control valve vacuum and feed)? also i noticed w/ i replaced the fuel filter the spring that is supposed to be behind it inside the carb was NOT there. im baffled at the moment. could it be a bad diaphram in the fuel pump? sorry guys im kind of just spitballing. any help would be greatly apprieciated. thanks Mark

 

If you removed the Carbs ability to vent you force raw gas into the intake. You can remove the canister you cannot plug the hose that vents the fuel bowl. Now after saying that I would be a little concerned you may have something else going on. Normally when this happens the result is the car floods and will not start until you have cranked it with the gas pedal on the floor for about 10 minutes or you clean the plugs. Gas in the oil without flooding normally points to a cracked fuel pump diaphragm and would require a new fuel pump. Either way get that gas out of your oil ASAP. Last thing you want to do is blow your valve covers off.

 

also if your not venting the gas tank it can build up pressure and overwelm the carb

 

The 85 Z28 came both carbureted and TPI, which was yours? If it was TPI, what was done with the in tank fuel pump. If it was hot wired to still run (without a regulator), it'll be putting out too much pressure for the carb to handle, causing it to flood. If it was originally carbureted, the carb is either running way too rich, it's flooding, or you have a vent issue.
Since you mentioned a filter, I'm figuring you have the Quadrajunk carb? Does it/did it have an electrical plug going to it? If so, the carb has a fuel mixture solenoid, and solenoid operated metering rods, which are controlled by the computer. If the plug has been disconnected, your carb operation will be all messed up.

 

thanks for all the input guys. the previous owner said he just replaced the fuel pump but i think im going to put another one on being that they are so cheap. i also noticed when i replaced the fuel filter that the spring that is supposed to go in the carb b4 the filter is NOT there. im thinking that the spring may be the problem. im assuming that when the fuel pump is not running that the spring pushes the filter against the fuel inlet and seals the fuel off from coming in the carb. maybe the suction of the pump from running is continuing syphoning the fuel after the car is turned off??????im going to rebuild the carb and replace the fuel pump and see what happens. im pretty sure the charcoal canister line routing is correct. ive got the pressure relief valve still on the end of the line so it should allow pressure in the tank to be purged. any more advice or insight is def. welcome. again thanks guys for replying and all the advice. thanks Mark

 

No, the filter does not act as a check valve. The spring is there to push the filter forward against the fitting so that it stays sealed. Otherwise, gas would go around the filter instead of through it. Spring there, or spring not there, that's not your flooding problem.

 

thanks camaro 69 for the info. i guess the spring idea is out. ill go ahead and rebuild the carb tomorrow and put on a new fuel pump. if that doesnt take care of the problem would you mind if i pm'd about it. you seem to be knowledgeable and willing to help. thank you for that. also i have all the electrical connections to the carb plugged in, i know you mentioned that previously. quick question, what acts as the fuel stop? my thinking is that the fuel pump almost acts as a syphon to the fuel tank and there is some mechanical??? device that acts as the check valve so fuel is at or in the carb for the next start. i guess im needing a tutorial in how the fuel gets from the tank to the combustion chamber. could anyone direct me to a website or article explaning this. again thanks to all that took the time to reply. Mark

 

Like the back of a toilet there is certain amount fuel in the fuel bowl once that bowl is level reach a certain level the flow is cut off. As air passes the venturi it draws fuel out of the bowl into the motor. Your metering rods and jets are all ways they carb controls how much gas goes into the motor as the air pass thru. Since the motor draws fuel in you really should not see fuel going into a motor once it shuts off if everything is working. If the fuel bowl gets over run with fuel it will find its way into the motor.

Since the fuel bowl is full of gas all the time it need to be able to vent fumes or it will build pressure as temperatures change. This can force gas into the engine.

If the fuel tank is not vented it can cause a lot of pressure in the fuel line with could cause fuel to push past the float and overfill the bowl.

If the float no longer floats in the gas it would not seal off the float bowl to over flow (this would cause the car to run like crap if it ran at all)

The needle and seat that the float pushes against can get dirty and cause the fuel bowl to over flow (this would cause the car to run like crap if it ran at all)

A crack in the fuel bowl itself can cause the motor to fill up once if cools down (very rare and most of the time the car runs like crap)

I am sure Camaro 69 will post a nice link explaining it better. He is the link master.

 

thanks for the explination GORN. im only familiar with fuel injection and learning the ins and outs of the carb. actually ive taken apart the carb this morning and soaked it in a gallon of carb cleaner. ill be putting it back together after the kids go to sleep so i can focus on the task at hand. ill get the carb rebuilt this evening and put it and a new fuel pump on tomorrow. ill def. post up results. thanks for the help Mark

 

just posting up results for anyone who may read this thread w/ the same problem. i purchased a rebuild kit from O'reilleys and also a new float. problem SOLVED. must have been something hanging up in the carb or a bad float not sure exactlly what the prob. was but its fixxed now..wooohooo. thanks to all that chimed in with advice and explainations. Mark