Okay 72 have a 72 Electra 455/q-jet and it seems as though when I get up to highway speed and I keep my foot in it it seems to be starving for fuel! Has this happened to any one else? I have put a new pump on, new filter but it still does it, it seems as though the new pump is not supplying the demand of the motor...any thoughts!!??
When is the last time the carb was rebuilt? Sometimes a simple cleainig and rebuild takes care of alot of problems. Also some brand new pumps are no good from sitting on the shelf for so many years. Another common problem often overlooked is a badly clogged mesh filter on the fuel pick-up inside the tank. I have an old time GM mechanic friend who always told me about several similair problems that were solved by cutting off this mesh and just changing carb filter more often. If tank and sender are original it will be full of crud!
Try blockin the fuel pump return line mine was bypassing too much fuel and starving, i checked it by crimping it with a small pair of vice grips just for one test run. i then cut a stainless bolt and blocked the line, solved the problem!
Have you checked the float level? That's very important on Q-jets and most of these are set very low on the smog motors, I find that 11/32" will work well and even helps the cold weather operation. I hate to beat this to death on all these carb threads but it seems to be ignored and is a critical adjustment on these carbs. :TU:
Another board member had a similar problem and ended up blowing compressed air through the lines to clear the lines up a bit.
Granted, you say it "feels like" it's starving for fuel, but do you have anything to go by to indicate that it IS a fuel problem, and not ignition. I would look at your timing, vacuum advance and total advance. See the "Power timing your Buick" sticky thread in the Buick FAQ section.
I to thouhgt it may be ignition but it has the HEI conversion on it and I have also double checked the timing and installed new plugs and wires as a routine thing I do for every vechicle I buy so I don't think it has anything to do with that one. I don't know when the last time the carb was rebuilt but I am tackling that one tonight any advice before I dive in?????? I installed an edlebrock 750 and carb adapter to see if my diagnosis were right and it ran like a bat out of hell to say the least it ran alot stronger (which indicates I may have q-jet issues so the rebuild is in order) I still noticed a "slight" hesitation in the upper RPM range I let off the gas and it goes away so I attribute this to once again a fuel delivery problem (I think the pinching off the return line may help this, it is worth a try) I really appreciate all the replies you have expressed this board is defintely one of the most informative and helpful boards I frequent! THANK YOU!
Guys I disassembled the carb and found that a portion has been epoxied can some one tell me what the purpose of this is? I have attached a pic the smaller circled ones had the epoxy half way worn off and it seem to be "leaking" what are these for? Also how do I adjust the tensioner on the secondary air valves (top) they don't seem to be opening and before I removed them they seemto not have been opening up! Thanks a bunch
It is common to use epoxy on those spots when doing a rebuild. The plugs that originally blocked off those passageways start to leak. The epoxy just keeps the fuel from draining out of the bowl of the cab into the manifold. When they start leaking it is hard to start after it sits for a few days because you have to crank the engine untill the fuel pump fills the bowl back up. You should re epoxy the ones that are worn off. Make sure you use an epoxy that is gas resistant and clean the area very well before you apply the epoxy. To adjust the secondarys you need to adjust a screw on the passenger side of the carb near the secondary flap (red arrow), but before you can adjust it you need to loosen the allen head screw (blue arrow) below it that locks it into place. You can loosen the spring so that it just holds the flap closed. Then while driving the car if it has a bog at wide open throttle you need to tighten the spring untill the bog goes away. Also make sure that the choke is fully disengaged, if not it can keep the secondaries from opening.
To add to Kelly's comments, a good starting point for the airvalve adjustment is to rotate the screw counterclockwise until the valve is open, then rotate clockwise until the valve just touches closed and rotate 1/2 turn more. Then snug the lock screw. In a high mileage carburetor both the airvalve tension spring and the airvalve secondary cam should always be replaced. The airvalve spring will fatigue, and the plastic cam wears. Jon.
