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Unread 11-21-2009, 11:51 PM   #1
jjdtaylor
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Carter BBD problems--accelerator pump?

Still trying to figure this out. 258 idles great, when I mash the gas, it bogs down, misses, stops running. Gradual acceleration has no problems. Greater minds than mine had suggested the accelerator pump is the issue. Checked it according to rebuild kit specs and it appears to be fine (1/2"). Also, when I work the throttle by hand, I get a shot of gas the first time and then nothing. Please help, I've forgotten what it's like to drive my jeep!

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Unread 11-22-2009, 01:18 AM   #2
thantos858
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Have you rebuilt the carb recently? Could be you got some gunk in the carb and its getting sucked into a spot to stop fuel flow.
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Unread 11-22-2009, 07:05 AM   #3
Mike Romain
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As mentioned in the 'other' thread, a dirty gas filter will cause those symptoms. So could missing or wrong check valve ball bearings. Did you get them in the right place, they are not the same size.

You know having several threads going on about the same thing isn't a good idea. I for one don't want to have to go read a whole other thread just to remember what was suggested and already done.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
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Unread 11-22-2009, 08:25 AM   #4
jjdtaylor
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Good point, Mike. Didn't think about that; just frustrated that I can't get the POS running properly. I think the fuel filter is relatively new--which means I'll be picking up a new one today. As for the bearings, the big one went in the big hole, and the little one went in the little hole. If the new filter doesn't work, I think I shall have to back-burner the beast for a while--getting too pissed-off...Thanks for everyone's help.
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Unread 11-22-2009, 08:49 AM   #5
JeepHammer
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Also, just because you have full travel of the arm doesn't mean there isn't a valve leaking internally in the accelerator pump, or there isn't problems with slack in the linkage before it starts to 'Shoot' fuel.

*IF*...
When you hit the throttle, it 'Tries' to take off, then bogs,
You have a problem with valving, air in the system, ect.
Or just not enough pump shot getting into the throttle bore.

*IF*...
It IMMEDIATELY boggs down when you hit the throttle,
Then you probably have an issue with slop in linkage and the pump shot isn't happening fast enough to be timed with the extra air.
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Unread 11-22-2009, 03:06 PM   #6
swatson454
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My BBD pulled a sneaky little trick on me where the the plunger would travel down the pump well, as it should, and then separate from the shaft and stay wedged at the bottom of the well. It too was good for one shot and then nothing.

Just a thought...

Weber Carburetors
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Unread 11-22-2009, 11:23 PM   #7
jjdtaylor
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JH, can you clarify what you mean in your second "if" in regards to the pump shot? As far as I can tell, the linkage fine...
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Unread 11-23-2009, 07:30 AM   #8
Mike Romain
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Quote:
Originally Posted by jjdtaylor View Post
JH, can you clarify what you mean in your second "if" in regards to the pump shot? As far as I can tell, the linkage fine...
This was mentioned in your 'other' thread. make sure the linkage on the outside is in the correct hole. There are two holes out there, one for the spring, one for the pump rod linkage. The outer one is for the springs, the inner one is for the rod linkage. If you look at the carb from the top, the linkage goes straight down, it doesn't angle outward.

I would also want to watch what the pump and the vacuum piston do when giving it gas. I have seen many that go over center causing a bog because that adjustment is real picky.

That is if you have changed the gas filter yet and it still bogs?
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 11-23-2009, 03:55 PM   #9
jjdtaylor
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Ok, the new filter is on, still doing the same thing. The linkage has never been changed (from when it used to work fine). I looked at the accelerator pump and vacuum piston while revving it up, and they appeared to be moving as they should. Nothing was moving out of line or binding up. I did notice that when I revved it way up (to where it would bog down and try to die) that the shot of gas was "interrupted"--that is, not constant. It would shoot a spurt of gas for the first half of the throttle travel, then nothing. Would that be an effect of the accelerator pump/diaphragm? Autozone doesn't have the pump, just the diaphragm, for $4. I'm not at familiar w/ the workings of a carb, so tearing into it will be my last resort, but I think I'm just about there...Any other thoughts before I try this? Thanks for all your guidance.
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Unread 11-24-2009, 08:59 AM   #10
Mike Romain
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Ahh, so it hasn't been rebuilt then? When you used that word rebuild spec, well...

The accelerator pumps just plain wear out. A new pump comes in the $20.00 rebuild kit along with a new float needle and seat.

But but but, in your 'other' thread you say the carb was just rebuilt??????????

That aside the pump can go in wrong, The ball bearings can be wrong.

The accelerator pump or the vacuum piston can go overcenter causing a bad bog. These need to be looked at with the engine OFF and the throttle worked slowly to wide open.

The base plate under the carb can be upside down, it has two notches in the bores, they must be at the top.

Other than that, I am out of ideas, good luck.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 11-24-2009, 04:58 PM   #11
jjdtaylor
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Yes, it was just rebuilt, but the rebuild kit only had o-rings, gaskets, and the like--no accelerator pump. Pretty sure that the pump and piston are not over-centering. I will check the base plate tomorrow--not sure about that one. Sorry for the confusion w/ the two threads, but I appreciate everyone's help. If the base plate doesn't fix it, I guess I'll be putting in a new accelerator pump (if I can one--Autozone is clueless) and if that doesn't work....I'll probably be back on here next week. Happy Thanksgiving everyone!
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Unread 12-02-2009, 10:24 AM   #12
jjdtaylor
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Problem solved! Pulled the carb apart to check on accelerator pump and checked measurements--float level was off by about half. Put it back together and, lo and behold, it works! Thanks for everyone's help, I'm sure I'll need it again soon.
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Unread 12-07-2009, 03:44 PM   #13
theguy427
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Hey guys I've been having the exact same problem with my 79 cj7 258, I know nothing of carbs so I didn't want to mess around I just bought a whole new carb but it did not solve the problem. I have replaced the sending unit (gauge didn't work) and the filter... what am I missing here??? the only other things I could think of are clogged lines or junk in the tank clogging the sending unit. Could anyone think of another solution to this problem I would really hate to have to replace the whole fuel system.
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Unread 12-08-2009, 07:50 AM   #14
Mike Romain
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Quote:
Originally Posted by theguy427 View Post
Hey guys I've been having the exact same problem with my 79 cj7 258, I know nothing of carbs so I didn't want to mess around I just bought a whole new carb but it did not solve the problem. I have replaced the sending unit (gauge didn't work) and the filter... what am I missing here??? the only other things I could think of are clogged lines or junk in the tank clogging the sending unit. Could anyone think of another solution to this problem I would really hate to have to replace the whole fuel system.
You really should start your own thread, this thread was finished so folks won't usually come back to it, I was just checking all the threads I have posted in expecting to see a thanks or oops or something.

This thread is a carry over from another one already.

As mentioned, his issue was the float level.

When you put the gas line on the new carb did you use one or two wrenches? If you only used one wrench and not a second one to hold the brass fitting in the carb steady, then you likely blew the float adjustment off the same as his is.

That brass fitting in the carb is the float needle seat and it has a thick gasket under it. If you don't hold it stable when you use a wrench on the gas line fitting, it compresses the gasket and lowers the float level radically which causes your symptoms.

The Haynes manual has all the carb settings and how to do it, but your float needs to be 1/4" below the lip of the float bowl measured down from a straight edge held across the edges of the bowl to work right.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 11-21-2010, 07:26 PM   #15
mthom5436
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The Brass fitting: Does the brass fitting adjust the float level?

I just installed a new carburetor. When I hooked up my fuel line I noticed the brass fitting was only turned half way in. That seemed odd to my so I tightened it. Was that a bad idea? If I just back the fitting out will that re-adjust the float level?
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