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Devac Write Up.


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#16
crazy87rexsi

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what about devac a si
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#17
BigAir

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QUOTE (esty @ Feb 9 2008, 05:29 PM) <{POST_SNAPBACK}>
i wish you a lot of luck...i devac'd my 86 in feb or march and it's not run since...i bought new manifold spacers...ordered 2 new rebuilt honda carbs and put 3 known and good working weber 32/36's on the car still could not get it to run...it starts and idles but when you take it on the road when it hits about 4500 rpm's that all she wrote...it stalls, backfires etc until you back off the gas...i rejetted a weber thru the entire range of jets, etc and it's always the same problem...hiy hi rpm's and she stalls

i've never been able to drive the car as long as i've owned it ans have not been able to find anyone that's willing to work on it for me...so she sits covered in the back yard


It sounds like your distributor is not advancing properly. Make sure you did not remove the vacuum advance going to your distributor. It should go from a vacuum port above the throttle plate to your distributor. Also, keep in mind that one of the ports on the distributor is actually a ignition retard an not a advance.
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#18
esty

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QUOTE (BigAir @ Feb 11 2008, 09:26 PM) <{POST_SNAPBACK}>
It sounds like your distributor is not advancing properly. Make sure you did not remove the vacuum advance going to your distributor. It should go from a vacuum port above the throttle plate to your distributor. Also, keep in mind that one of the ports on the distributor is actually a ignition retard an not a advance.


which vac port on the dist should be connected to the carb...top or bottom and does the other (retard) just get cap'd?

#19
anassa

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QUOTE (BigAir @ Feb 12 2008, 12:26 AM) <{POST_SNAPBACK}>
It sounds like your distributor is not advancing properly. Make sure you did not remove the vacuum advance going to your distributor. It should go from a vacuum port above the throttle plate to your distributor. Also, keep in mind that one of the ports on the distributor is actually a ignition retard an not a advance.


omg omg, actual good information, is there any chance you can use the pics that i posted on page one to explain more clearly? like just refer to it. that would be very helpful.

small update on my own devac, i guessed the smoke and what not had to do with the valve cover gasket, so i took a hour or so last weekend to take off the valve cover (for the first time! biggrin.gif ) cleaned it, cleaned around the dizzy and engine a bit, there was tons of crap all around it, the engine bay actually looks clean for the first time. Then I thought to see if i could start the car and see what happens to it, so then i reach for my keys and OMG!!! i lost my keys..... how embarrassing... i've been searched for two days already so i think i have to see if i can save for a locksmith to make me one or something like that. but again BigAir if you can describe a bit more what you mean it would be very helpful.
Someday my car will look as clean and sexy as this:


-1997 318ti DD

-1989 240sx sold on CL

-1985 CRX DX, sold to Justin

-1985 CRX Si, sold to Indyman.

-1991 CRX Si, totaled in the mountains, RIP

#20
CRXfanatic

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I've devac'd several Si's, all with success. There's a gizmo in the big black box that needs to be saved, the rest goes.

QUOTE (Josh @ Feb 9 2008, 06:21 PM) <{POST_SNAPBACK}>
what about devac a si

"If Honda does not race there is no Honda." -Soichiro Honda

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#21
DarkHand

Wow I have no idea how I missed this thread until now!


QUOTE (esty @ Feb 11 2008, 10:35 PM) <{POST_SNAPBACK}>
which vac port on the dist should be connected to the carb...top or bottom and does the other (retard) just get cap'd?

The bottom one, closest to the distributor gets connected. Keep the other one uncapped though, else the diaphragm can't 'breathe', and won't be able to move.


QUOTE (anassa @ Feb 12 2008, 02:00 AM) <{POST_SNAPBACK}>
small update on my own devac, i guessed the smoke and what not had to do with the valve cover gasket, so i took a hour or so last weekend to take off the valve cover (for the first time! biggrin.gif ) cleaned it, cleaned around the dizzy and engine a bit, there was tons of crap all around it, the engine bay actually looks clean for the first time. Then I thought to see if i could start the car and see what happens to it, so then i reach for my keys and OMG!!! i lost my keys..... how embarrassing... i've been searched for two days already so i think i have to see if i can save for a locksmith to make me one or something like that. but again BigAir if you can describe a bit more what you mean it would be very helpful.


You were changing the valve cover gasket... Did you check under the valve cover for your keys? You never know!

The smoke probably wasn't from the valve cover gasket, but there's no such thing as an unnecessary gasket change on a 20+ year old car. smile.gif


QUOTE (anassa @ Jan 4 2008, 06:04 PM) <{POST_SNAPBACK}>
- In the last 4th pic (left side of mani carb) i have the two out lets circled in green, if i am correct this is the "fast idle diaphragm" should this be capped? quote from DarkHand: "With the car running, connect a vacuum hose to that fast idle diaphragm again, just the port on the right (looking at the carb from the angle in that last pic), and suck on it! While holding vacuum, blip the throttle a little. This will make sure you're off the fast idle cam in the carb by applying vacuum to the diaphragm. The left port (further from the carb) turns fast idle on, the right side (closer to the carb) turns it off. If still no luck, try holding the choke plate completely open and blip the throttle... Perhaps the choke isn't opening enough." <-- very helpful but when i tried my high idle (2800-3000rpm idle) seemed to become unsteady and go lower then higher and back and forth, so i don't really understand the correct procedure for turning off the fast idle.


Seems you've already sorted out the fast idle, but keep those fast idle ports uncapped. The diaphragm inside needs to be able to move, just like the one esty asked about. You can get stuck on fast or slow idle when those are capped. The sucking on the hose is also just a test to see if you're stuck or not, you won't need to do it all the time. smile.gif If you're really concerned about it, you could add yet another T and connect a line to that fast idle port. This will ensure that you're always off of fast idle. You wouldn't want it like that all the time, you'd have a heck of a hard time starting up in the cold, but it could be good for testing.


QUOTE (anassa @ Jan 4 2008, 06:04 PM) <{POST_SNAPBACK}>
- Now i'm wondering about the places where the remaining vac lines should be connected, in pics there are absolutely no vac lines going to the dizzy, should there? also should it be hooked onto the top or bottom place on the dizzy? like this??:


green shows the vac lines, blue the "T"


Yep, just like that, connected to the lower port on the distributor.


Seems like you're learning the all-important lesson of not experimenting on your only car... I learned that one the hard way too! When I finally got my CRX I learned more in a few weekends than I did in a few years with my daily driver Civic, because I could rip it apart in the garage and not have to have it running again by Monday morning.

Edited by DarkHand, 12 February 2008 - 12:02 PM.

DarkHand

#22
squareback

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QUOTE (CRXfanatic @ Feb 12 2008, 09:30 AM) <{POST_SNAPBACK}>
I've devac'd several Si's, all with success. There's a gizmo in the big black box that needs to be saved, the rest goes.


I've devac'd a Civic Si and a CRX Si, both with perfect success. The "gizmo" in the black box that needs to stay is round metal and controls idle, if I remember right. The other plugs for the black box get disconnected and stay that way.

Mike
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#23
BigAir

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I devaced my 85 per the instructions in this thread. I used the vacuum advance, but not he vacuum retard on the distributor. That port was left open. The car ran "OK". It did seem to be running very rich and would a have hard time starting after it was warmed up and ran at very slow speeds for more than about 30 seconds. Parking lots were my enemy. It would flood so bad that I had to wait at least 10 minutes before it would start. It also had a hard time idling at stop signs and lights. I threw in a rebuild kit and found that the power piston thing was a little bent and actually stuck. My guess is that it was just dumping gas into the motor. Between straightening it out, putting in all new gaskets and seals and finding one more large vacuum leak on the intake, it now runs perfectly. The idle is smooth from fast to slow. It's not flooding and I don't have to worry about parking lots anymore. Thanks to all that contributed to this thread.
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#24
DarkHand

QUOTE (BigAir @ Feb 12 2008, 09:38 PM) <{POST_SNAPBACK}>
Between straightening it out, putting in all new gaskets and seals and finding one more large vacuum leak on the intake, it now runs perfectly. The idle is smooth from fast to slow. It's not flooding and I don't have to worry about parking lots anymore. Thanks to all that contributed to this thread.


cool.gif

In most cases when people have trouble after a devac, the carb itself is at fault. The emissions equipment seems to hide the problems of a multi-decade old carburetor, but they become prominent without all that support equipment. Gaskets or seals that were just holding up may act completely different without the pressure or vacuum that the emissions equipment provided. Dirt and crud that was built up inside may get knocked loose and clog up a jet or passage. Sometimes, even handling the carb may damage something that's just barely working. With our cars getting older and older, a carb rebuild should definitely start being recommended when suggesting a devac. It's not the easiest thing in the world, but it's also not that complicated if you take your time, handle it in sections, and stay organized.

Hmm, a carb rebuild writeup might not be a bad idea. smile.gif

Edited by DarkHand, 13 February 2008 - 12:56 PM.

DarkHand

#25
BigAir

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QUOTE (DarkHand @ Feb 13 2008, 01:43 PM) <{POST_SNAPBACK}>
cool.gif

In most cases when people have trouble after a devac, the carb itself is at fault. The emissions equipment seems to hide the problems of a multi-decade old carburetor, but they become prominent without all that support equipment. Gaskets or seals that were just holding up may act completely different without the pressure or vacuum that the emissions equipment provided. Dirt and crud that was built up inside may get knocked loose and clog up a jet or passage. Sometimes, even handling the carb may damage something that's just barely working. With our cars getting older and older, a carb rebuild should definitely start being recommended when suggesting a devac. It's not the easiest thing in the world, but it's also not that complicated if you take your time, handle it in sections, and stay organized.

Hmm, a carb rebuild writeup might not be a bad idea. smile.gif


Those are very good suggestions. The only hard part I found with rebuilding the carb was in removing the float pin. You need to do that in order to remove the needle and seat. Any suggestions on an easy way to get that pin out and back in without breaking the housing? What about that power piston? What does it do and what happens if it sticks in the compressed position?
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#26
BigAir

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QUOTE (BigAir @ Feb 13 2008, 01:58 PM) <{POST_SNAPBACK}>
What about that power piston? What does it do and what happens if it sticks in the compressed position?


never mind. I just found the answer. The power piston (power valve) opens when when the vacuum drops a couple inches below normal operation at idle. Vacuum should drop under heavy acceleration, the valve opens, the motor gets more gas. If the power piston/valve is stuck open, you will run very rich and flood your motor at low RPM's. Also, if you notice there is a spring on the piston shaft. I'm guessing you can play with spring weights to fine tune your carb a little more. I love these cars.
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#27
DarkHand

QUOTE (BigAir @ Feb 13 2008, 11:58 AM) <{POST_SNAPBACK}>
Any suggestions on an easy way to get that pin out and back in without breaking the housing?


If I remember right, I braced the thinner post with a small piece of wood and tapped it out. I think I did it backwards from the recommended way, but it felt safer that way with the wood bracing it.

Edited by DarkHand, 13 February 2008 - 03:05 PM.

DarkHand

#28
anassa

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I GOT A KEY!!!!! (thanks to "harm") and yes DarkHand i have learned the all important lesson of not working on my dd, well actually i still am in the process of learning that =]. Ok i routed the vac lines to the dizzy and one to the fast idle valve to ensure that it is turned off. First start up was miraculous: it hasn't it start up like that since before the devac. was idling around 2k but it wasn't such a big deal, then turned it off and restarted and, same thing started perfectly fine. So i thought i might as well take it around the block and see how it feels. Well the third time wasn't the charm... it started and was very rough, so right now i'm thinking that i got all the vac lines in the right place but the ignition timing is off. So i have to find out how to change the ignition timing, and that will hopefully solve all the problems. laugh.gif
Someday my car will look as clean and sexy as this:


-1997 318ti DD

-1989 240sx sold on CL

-1985 CRX DX, sold to Justin

-1985 CRX Si, sold to Indyman.

-1991 CRX Si, totaled in the mountains, RIP

#29
DarkHand

QUOTE (anassa @ Feb 22 2008, 05:10 PM) <{POST_SNAPBACK}>
Well the third time wasn't the charm... it started and was very rough

Intermittent idle sounds like a vacuum leak somewhere to me, they're a female dog to track down. smile.gif

QUOTE (anassa @ Feb 22 2008, 05:10 PM) <{POST_SNAPBACK}>
so right now i'm thinking that i got all the vac lines in the right place but the ignition timing is off. So i have to find out how to change the ignition timing, and that will hopefully solve all the problems. laugh.gif

Easy as pie! Get yourself a timing light and start here: http://www.redpepper...25/abf.png.html Hard to track down a carb problem without having your timing set.
DarkHand

#30
harm

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QUOTE (anassa @ Feb 22 2008, 05:10 PM) <{POST_SNAPBACK}>
I GOT A KEY!!!!! (thanks to "harm") and yes DarkHand i have learned the all important lesson of not working on my dd, well actually i still am in the process of learning that =]. Ok i routed the vac lines to the dizzy and one to the fast idle valve to ensure that it is turned off. First start up was miraculous: it hasn't it start up like that since before the devac. was idling around 2k but it wasn't such a big deal, then turned it off and restarted and, same thing started perfectly fine. So i thought i might as well take it around the block and see how it feels. Well the third time wasn't the charm... it started and was very rough, so right now i'm thinking that i got all the vac lines in the right place but the ignition timing is off. So i have to find out how to change the ignition timing, and that will hopefully solve all the problems. laugh.gif



glad to help. I don't post much - mostly because it's too stupid-cold here to work on the car, even in a (stupid-cold) garage. I'll definitely be referencing this thread during the next couple months while attempting a de-vac myself, and I'm definitely thankful to not be working on my DD.. note the CRX gets the garage, the DD (supposed to be my "nice car" but no longer my favorite) sits outside in the cold. :b