carb questions

[moparvwfreak]

decided i should not hijack Bugeye's thread anymore than i already have. as i stated earlier in his thread, i had gotten the idle back where it should be. and it was dropping back to idle properly when stopping. today i took the truck out again adn guess what. it wasn't returning abck to idle AGAIN. i know its the BCDD. it seems like its sticking and just not working right.

 

now my questions.

 

#1 can the BCDD be cleaned or would it have to be replaced? i have a spare carb that i can take apart to see how its set up so i am not screwing up the carb on my truck. i am just curious if anyone knows before i go screwing something up. i like having spare parts if i can.

 

#2 would a carb for an L18 on an L16 cause any major problems except using a touch more fuel? i checked the #s on the carb against the ones in my 73 service manual and the carb i have on the truck now is one for an L18 powered 620. my spare i was not able to make the #s out. they were to far gone. so i dont even know if its for an L motor or not, what year and whatnot.

[bonvo]

there are slight differnces between the l20b and l16-l18

[moparvwfreak]

like extra vac lines, or sensorsswitches?

[bonvo]

if im looking at mine correctly (have one of each thanks zerow) there are less vac lines and according to dimequarterly the one for the l20b dumps more fuel for the bigger motor

[moparvwfreak]

ahhhh ok. makes sence. i just wish i could read the #s on my spare carb.

[datzenmike]

d i know its the BCDD. it seems like its sticking and just not working right.

 

now my questions.

 

#1 can the BCDD be cleaned or would it have to be replaced? i have a spare carb that i can take apart to see how its set up so i am not screwing up the carb on my truck. i am just curious if anyone knows before i go screwing something up. i like having spare parts if i can.

 

 

Post a picture of driver's side of your carb. Some BCDD had a solenoid that is opened by a tranny switch to vent vacuum and turn the BCDD off. Maybe all you need to do is wire this solenoid on all the time to deactivate it. If not the BCDD can be adjusted to a vacuum level so high it won't come on in the first place. Post a picture.

 

Here's one type of BCDD. Turning the adjustment screw counter clockwise will increase the vacuum level needed to trigger it. Turn out a turn at a time until it stops the high idle.

 

http://i138.photobucket.com/albums/q251/datzenmike/carbLseriesBCDD.jpg[/img]"]

[moparvwfreak]

Post a picture of driver's side of your carb. Some BCDD had a solenoid that is opened by a tranny switch to vent vacuum and turn the BCDD off. Maybe all you need to do is wire this solenoid on all the time to deactivate it. If not the BCDD can be adjusted to a vacuum level so high it won't come on in the first place. Post a picture.

 

i will do that come morning as its dark and wet right now. the switch mine has is mounted to the manifold but the one on my spare carb is mounted on the BCDD itsself. and by adjusting it do you mean up or down? i have adjusted it down already but maybe need more??? also i tapped it with the handle of a screw driver yesterday and it seemed ot actually work. hence why i asked if ti was cleanable or not. seemed like it was sticky.

[zerow]

...have one of each thanks zerow...

 

What?! That carb is still around? She was going rounds here in SoCal before her trip north! Glad she is still helping, be it the technical, parts, or old gas for lacquer value!

[Bugeye]

Post a picture of driver's side of your carb. Some BCDD had a solenoid that is opened by a tranny switch to vent vacuum and turn the BCDD off. Maybe all you need to do is wire this solenoid on all the time to deactivate it. If not the BCDD can be adjusted to a vacuum level so high it won't come on in the first place. Post a picture.

 

Here's one type of BCDD. Turning the adjustment screw counter clockwise will increase the vacuum level needed to trigger it. Turn out a turn at a time until it stops the high idle.

 

http://i138.photobucket.com/albums/q251/datzenmike/carbLseriesBCDD.jpg[/img]"]

 

THREAD JACK: sorry, neither one of my carbs look like that now im confused:blink::blink: heres what my carbs look like

[datzenmike]

i will do that come morning as its dark and wet right now. the switch mine has is mounted to the manifold but the one on my spare carb is mounted on the BCDD itsself. and by adjusting it do you mean up or down? i have adjusted it down already but maybe need more??? also i tapped it with the handle of a screw driver yesterday and it seemed ot actually work. hence why i asked if ti was cleanable or not. seemed like it was sticky.

 

Turn the tiny screw in the middle counter clock-wise, or to the left. This will actually turn it in (left hand thread:D) and turn up the setting needed to trigger the BCDD. High enough and it won't come on.

 

Yeah, take apart and maybe spray it clean. Some have a rubber hose going to them, others have an internal port to vacuum, still others have a solenoid (like the idle cut solenoid) that opens to vent the vacuum to turn it off. It's one of those emission things that has no effect on performance and when working, you don't even know it's there.

[datzenmike]

THREAD JACK: sorry, neither one of my carbs look like that now im confused:blink::blink: heres what my carbs look like

 

Looks like dwnshftr owned this! :lol:

 

Someone put a block off plate on it. It will still work as a carb.

[Bugeye]

that was the rebuilt carb my grandfather bought 15 years ago, so if i take the plate off, will the carb still function?

[Bugeye]

Looks like dwnshftr owned this! :lol:

 

:fu::lol:

[datzenmike]

that was the rebuilt carb my grandfather bought 15 years ago, so if i take the plate off, will the carb still function?

 

I wouldn't touch it or you may have a vacuum leak.

[moparvwfreak]

alrighty then. i will definatley take ti apart and clean it. i do think its sticking. had the same issue yesterday and tapping the BCDD actually helped until i shut the truck off. so i am really thinking it is jsut sticky from years of use and build up.

 

thanks guys!!!

[moparvwfreak]

well i lulled it apart and cleaned it. teh thing worked flawlessly, for one day AGAIN! i am really starting to think that the fast idle cam is getting caught. tap the gas and it drops the idle. but thats really annoying ot have to do. i have already adjusted the BCDD again down alot. so hopefully i can figure this out. it gets real old to ahve to goose it to get the idle abck down at every light.

[moparvwfreak]

all right. this is really starting to get annoying. i checked some things today. spent the afternoon adjusting the carb to get it to quit drinking fuel like a damn V10. drove it 50 miles and went through 12 tank. so now i am sitting there 1-34 turns out on the mixture screw, idleing at 800 rpm and the timing adjusted to about 5*. it seems like it runs good but backfires out the exhaust upon deceleration. even at 8* it seems to backfire.

 

i also know i have to redo the intake and carb gaskets as i thinki have a little leak. carb cleaner brought the idle up a little when i sprayed the intake. also the entire intake and carb was loose. and when i say loose i mean LOOSE!! something like finger tight??!!