you really need to give alittle more info to go on, ie carb/EFI size bla bla bla,
i'm no expert but off idle hesitations are mostly: 1) low fuel bowl levels, 2) wrong size or out of adjustment accelerator pumps, 3) idle screw mixture adjustment, 4) maybe fuel regulator pressure.
I work with this guy...he wont have access to this board till monday. But let me try to answer the questions that were asked...the carb is a stock motorcraft 2150 2bbl on the amc 360 motor. I am sure the electrical connections are good. The timing is set at 8 BTDC and yes it does put out a little black smoke at hesitation, but not much. When you punch the gas it seems like it floods out, sputters and then gets going. We just rebuilt the carb, which fixed some other problems, but still has the hesitation problem. When you push the gas slowly it will go...hit a spot where it hesittates and sputters a little...then takes off! any ideas?
verify teh accelerator pump diapraghm is good, stroke the throttle with teh air cleaner removed/engine off, look down into the car while strokeing it, it should spray a fine mist into both sides
remove the distributer cap
remove the vac hose from the vac advance nipple
rotate the advance plate by hand, then use your thumb to plug the nipple, it should hold the plate advanced until you break the suction by removing your thumb, if it doesnt the vac advance diapraghm is bad..
of course you could just pump on teh nipple with a mighty vac pump and see if it holds pressure
also, keep advancing the timing until it just starts to ping under load, then retard only enough to get rid of the ping under load.
well go from there
77 CJ5, in a bunch of sanded and primered pieces
well, we checked the vac advance as you said and it worked as advertised. I thought it was a little stiff, but when compared to mine, seemed about the same. We connected the vac advance to the manifold vac and plugged the port off the carb and believe it or not, that fixed the hesitation problem...why? could it be the vac advance is not working right and the greater suction from the manifold was enough to make it work?
It was on the outside hole, we moved it to the inside hole when we rebuilt the carb. We also moved the opposite end from the hole end of the rod to the third hole from the bottom...all this according to the rebuild kit. Dont know size of jets...assume stock, whatever that is.
You said the ported vacuum was not pulling the advance plate around like it should? This is on a rebuilt 2150,,, did you check the base for a warp? what kind of gasket are you using,,, thin,,, or thick,, has this gasket got the cut out for the ported vacuum port? some times the base is just warped enough to leak by vacuum when using the single thin gasket, sometimes this can be fixed by using the thicker base gasket. some kits come with 2 thin gaskets. One is used on the manifold under a spacer and the other is used under the carb on top of the base, these 2 gaskets are different. These carbs were used on several manufactures and models of vehicles and the applications and variations of the kits are 100's make sure all parts and gaskets are identicle to your application.
well, i really dont think your running enough advanced if your at 8 deg BTDC
most of us with a properly tuned 360 can get to 10 before the pinging starts, so more htan likely now that its advanced all the time ( vac from manifold) its probably running like 10-12 degrees base timing..
you could try advanceing the timing, then moving the vac advance back..
im not a big fan of numbers, or books, or stickers..
move those things around until the desired effect is felt..
just DONT LET IT PING
77 CJ5, in a bunch of sanded and primered pieces
Between the float bowl and the accelerator pump, there is a small (usually orange on a motorcraft 21-- carb) piece of rubber. It goes in a hole between the two sides (float and pump). If it is properly seated, the flat rubber part of it should be inside the spring on the pump side, and a little rubber tip should stick out just a pinch into the float side. If this isn't seated perfectly, and snugly in place, stepping on the gas (and activating the accelerator pump) simply pushes fuel out of the pump and back into the bowl. Check it out. I had the same problem, and this fixed it.
Evolution of tools: stone, hammer, wrench, socket, impact, really big hammer, blue wrench.
I had this problem REAL bad last night! almost no power at all. I blasted out the Jets and everythings works A-OK.... If things were working fine and then all of a sudden you had this problem, that could be the culprit.
I had the exact same problem. After alot of help and alot more cussing I got the timing right and went out with my buddy only to find severe hesitation problems. Got it back home and haven't touched it. I suspect that advancing the timing will work as ozark said. Without a very smart man on this post I'd still be adjusting my timing with earplugs /wwwthreads_images/icons/smile.gif. Thanks Dave. Oh yeah whebn I got home it dieseled and backfired slightly throught the exhaust. What was that all about?
Can you fix it?
I got a welder and a grinder. Heck yeah I can fix it./wwwthreads_images/icons/cool.gif
I have to agree with GPn. I had this problem when I bought my Jeep. The previous owner put the wrong gasket(came with three different) on the carb and created a carbon-rich mixture. After awhile the jeep just bogged down and had no power because too much carbon built up on the plugs. After I replaced the plugs it ran pretty good, but still carbon. Gettin to carb, I rebuilt it being sure I would use the same gaskets, but it ended up he put the wrong gasket on. It was the gasket. Just make sure the holes on the gasket are in line with the holes on the carb. Thats all,
OK...wow, lots of posts. I really need to get a computer so I can do this at home. We advaced the timing out to 10 degrees BTDC (eng sped up and smoothed out a little) and put the vac adv back on the carb port, but haven't had a chance to drive it yet. Before I drive it I will verify the gaskets on the carb and then let everyone know what happened.
Well, the hesitation is gone now. Advanced the timing to 10 BTDC and that seems to have fixed it. I still need to pull off the carb and just verify that the gasket is on right, but the vac adv is plugged into the carb now and seems to work as advertised...thanks!
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