ok.. so ive got my carb that i just rebuilt on.. and im STILL experiencing problems... last week it took the air horn off and a chunk of the float fell off and somehow was flooding the carb.. now im having a hesitation right as i ease on the gas coming from a stop and also noticeable when im coasting and then step on it slightly. i checked the accelerator pump.. squirt looked ok... but i replaced it anyway and still the same problem.. im thinking its a timing problem which is something i dont know much about. the vac advance canister is hooked to the front of the carb bowl(ported i guess), and i think its working because idle increased when i hooked it to manifold vacuum. My question is... what could be causing this?... the only thing that isnt stock is the inline filter from the pump to carb with a 3/8 inch fuel line. any imput would be great. hate to bother with dumb stuff.. but i hope you guys can help. thanks o No: Vic 78 Buick estate Wag(403 olds/350, rebuilt qjet)
If you don't have a timing light you need to borrow or buy one. Without checking your timing properly any other work you do to try and tune it us is useless. I'm sure the great people here can help you out. Goodluck.
well.. im gonna have to wait till monday to have the timing checked around here.. but im stil curious about what other things might be causing this besides timing. is it possible that the acc pump could be squirting too much fuel or is this sort of hesitation always a lean situation? what about other parts of the carb? float... power piston?... thanks for the help. Vic
anytime I've had a hesitation problem and the ignition system was right, it was the accelerator pump. You can do a quick test to see if it's a lean miss. If it will hesitate from idle in neutral you can choke the carb a little with a rag and nail the gas with the other hand. If the problem goes away you need to fix whatever is wrong the the accel pump. If it gets worse you need to get the ignition right. I never saw an accel pump pump too much. It's hard to imagine a guy that can rebuild a carb that doesn't own a timing light. o No:
And we presume that the float was replaced when it started shedding bits of itself into the float bowl. We further presume the new one was adjusted to the proper height. Do you have an EGR valve? That'd be my second guess right after the accelerator pump that's already been mentioned.
idle setting? one of the things that causes an off idle hesitation is if the idle speed is set to high, basically the throttle blades (?) are to far open exposing to much of the transition slot. It's late and Im not making much sense put if you turn the carb over and look to see if the transistion slot is almost completley exposed this will cuase the hesitation. you may need to reduce the idle speed, retime the car and adjust the idle mixture screws to compensate for the extra gas needed at idle without opening the throttle plate to far. Joe
well.. i DO own a timing lite technically but its broke.. i bought it from a freind who skipped town.. the damn thing bliked 3 times and no more... i did replace the float and just replaced the acc pump. i do have an EGR and it is hooked up. i dont know if the float setting could be a culprit but if it could be would it be a sign of being to high or low?.. the hesitation wont happen(or isnt noticeable) when hit the pedal hard. i will try to adjust the idle setting as Schurkey said... if close the throttle blades a bit, i would have to enrichen the mixture right?(turn screws out a bit) thanks for all the help Vic
richen the mixture if needed yes turn the mixture screws out. you can also adjust the idle setting with a vacuum guage adust the setting to get the highest vacuum reading.
First, disconnect the hose from the EGR valve. If the hesitation disappears, you should install a delay valve in the EGR vacuum supply hose. By all means, adjust the idle mixture screws for best vacuum, but then TURN THEM EACH ABOUT 1/8-1/4 turn LEAN from best idle. You'll hardly notice a reduction in idle quality, but you'll cut the pollution at idle dramatically.
alright.. i guess ill find myself a vacuum gauge and adjust it, earlier i was messing with the screws at work, i remember i had them out to the point that they were jiggling as i was turning them because they were so far out. the idle was preety smooth but the hesitation is still there. ill keep you all informed. thanks
try this link http://www.moparchat.com/forums/showthread.php?s=&threadid=56571 Try this link it has some very good information on tuning carbs. I have used this process successfully a few times. if it does not work try seraching the board for edelbrock tuning Joe I copied and pasted form the site above, to cut threw all of the extra reading. if that's not appropriate the moderator can take it out, and I'll know not to do it in the future. Ok so here we go, get out your note pads and there will be homework err ahh trackwork for ya'll this weekend. You'll need a vacuum gauge, not a good one, I got mine at Baxter's here in town for $9.95. Plug the gauge on the lower port on the front of the carb, this should NOT have your vacuum advance unit hooked to it.....right? Ok Now lets get the idle down as low as it'll go without stalling, now start turning one of the idle screws in until it starts to loose vacuum or the engine starts to sputter, .....now count the turns as you turn the screw out until the same thing happens. lets say your number is 2 so now go in 1/2 of that or 1 right....OK now same with the other side. Remember to keep bring that idle down to compensate for your tuning, you want it as low as possible so you can get a true reading on the idle mixture. Now start all over again..Idle, in, out, count and set. By now you should have a pretty good smooth idle easy huh.... Now lets watch the vacuum gauge 1/2 turn in 1/2 turn out slowly turn the screw back and forth no more than a 1/2 turn in either direction until you get the highest reading on your gauge, thats it your done.....runs good now doesn't it.....set the idle up to your desired RPM for most of you using a Edelbrock your probably running a pretty mild engine so 750-950 is probably about right. Now crack the throttle off idle...sounds pretty good huh ) OK now check your timing and set it where you want it. Start over and do the whole process again...Idle down..the old in and out...vacuum gauge and now your done.
Thanks... ill go ahead and follow those procedures tomarrow morning.. but where can i buy a vacuum gauge for 10 bucks?.. i only see some really expensive ones
ok fellas, so i got up this morning, went to get a vacuum gauge(28 bux from the auto parts), and started playing with the adjustment screws. i cant back the air valve screw any more because the blades are as far closed as they will go. pulled the screws as far as they would come out without falling out and got 17 inches with the idle a bit high, if i push the throttle blades back to close them, it will die. does this sound right to you guys? by the way i still havnt had the timing checked which i will do tomarrow so bear with me.
Should be no need to have the idle mix screws that far out. I'm wondering if you have a plugged--or partially plugged--passage in the carb that is driving the idle mix overly lean. A vacuum leak could also account for that. A vacuum leak would also allow the engine to continue running with the throttle blades shut tight, too.
besides an open port on teh carb and the base gasket, where else can a vacuum leak come from?... i have sprayed the outside of the carb with carb cleaner and i cant find anything? even when i ran the car before, the mixture screws were way out, so it must be a problem that has always been there. again, could it be timing? thanks
Defective vacuum advance, defective brake booster, vacuum hoses rotted out, wrong PCV valve, wrong carb gaskets, defective vacuum-operated HVAC servos, the list of possible vacuum leaks is nearly endless. You may wind up just pinching closed every vacuum hose connected to the carb/manifold to see if the engine responds to shutting off the false air supply.
ok well ill definately take a look at those. ive replaced most the vacuum hoses recently but ill check that brake booster line. if i remove it and plug the fitting in the rear of the carb, it should react somehow if thats the line that is corrupt right? thanks guys i appreciate all the help
Sure sounds like a vacuum leak to me. However, I am confused by these two statements: So, is the throttle closed all the way or not? With the motor running and warmed up, off fast idle, slowly close the choke blade. If the motor speeds up at any point you have a vacuum leak. It should stay the same speed unitl it slows down and dies as the choke blade closes all the way.
yea, if i close the choke it dies. the thing about the throttle blades is that, they are closed as far as the spring will pull them, but i can close them more if i push on them a bit, i guess the spring isnt strong enough or something??? i duno, but im having the timing done today, ill have the car back by tomarrow because the guy was real busy or whatever, so ill keep yall posted, thanks
