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View Full Version : No boost after sc replacment



shadow357x2
07-10-2006, 05:33 PM
OK, First I did the search thingy abd only came up with this http://www.sccoa.com/forums/showthread.php?t=71310&highlight=supercharger
Didnt see any answers so here it is.
As you all know I lost a supercharger on my trip to Alabama last week and finally got it home and replaced it

Belts aint slipping
pulleys are turning
No bad crank
plenty of vacuum
new plugs,wires (not the problem but listed anyway)
everything sealed.
replace the actuator (didnt fix it)
Now thats out the way heres the story, After sitting all night and starting it in the morning I have plenty of boost but no control over the vents (defaulting to defrost) after about 1 minute or 2 the vents are operating properly, BUT now we dont have any boost at all. Up under the hood I can rev it up and the bypass valve will open only about 1/4" , As I mentioned I have 0 boost with the vac line on, I can pull over and take the vac line off and I get full boost to it. Finally I am lost on this thing anyone with any ideas to this?

20" vac at idle 0 boost with line on
18" vac at idle 14 boost with line off



S

Tickler
07-10-2006, 07:42 PM
Clearly you have a vacuum hose / routing problem. Where is the hose for the bypass valve plugged in?

shadow357x2
07-10-2006, 07:50 PM
Its coming off the main vac tee between the abs unit and the fender. Always has been there. Thisproblem didnt arise until I changed out the sc and also the same symptoms after another replacement this afternoon.


S

Tickler
07-10-2006, 07:59 PM
Still sounds like a hose issue to me, theirs a bunch of vacuum only lines and check valves for the heater controls, you may have plugged something in in the wrong spot. Try plugging the bypass valve in right after the throttle body, but before the blower. Vacuum hose troubles are my favorite, cause they always cost under $5 to fix :).

shadow357x2
07-10-2006, 08:19 PM
Ill try it in the am tired of messing with it today. Actually Im kinda zoning in on the rear of the unit as that is the only area I totally took the lines out and the only other one that came off during the r&r was for the actuator. But now that I think about it those 5/16" hose only fit one way.
I agree its a vac issue due to the fact of how it acts, seems like its keeping too much and not coming out of vac fast enough(at all)

S

Phillio99
07-11-2006, 12:35 AM
make sure the lever isn't jammed keeping the valve open all the time.
Phil

shadow357x2
07-11-2006, 11:41 AM
Already checked and replaced the actuator.

Seems to me that maybe a checkvavle somewhere is on the blink, just my opinion though.
Checked the actuator manuallytoday witha vac pump and it holds good and when you release the vac it returns as it should. Still stumped on this one. Maybe the one wants its oldsc back instead of the ones Im putting on it:rolleyes:


S

Tickler
07-11-2006, 04:28 PM
Would it be possible for you take a picture or draw a diagram of where you have everything plugged in?

shadow357x2
07-11-2006, 04:41 PM
yea I can do that. Ill post back in a little while

Heres the link to them http://s105.photobucket.com/albums/m240/shadow357x2/ too big to post here.
S

shadow357x2
07-11-2006, 05:22 PM
If you need more specific let me know....
S

David Neibert
07-11-2006, 05:41 PM
http://i105.photobucket.com/albums/m240/shadow357x2/Picture030.jpg

Move the hose end that's plugged into the big vacuum hose to another vacuum source. Tee into the cross talk tube if you have to.

David

shadow357x2
07-11-2006, 05:45 PM
Ill give that a try and see. It just seems odd that this happened only after a replacement. I did notice though that after unplugging the vac hose that I did gain about 2 more lb of boost, unless its just my fuzzy eyeballs...I take it you mean to go to this hose right? http://i105.photobucket.com/albums/m240/shadow357x2/Picture019.jpg



S

ThunderDave
07-11-2006, 06:29 PM
I'm, not sure, but I think David is talking about the smaller plastic tubing that's running across the upper ic tube. I could be wrong though. I was once before. :rolleyes:

shadow357x2
07-11-2006, 06:43 PM
Thats what I meant is taking that hose (the one over the IC) and going to the hose here http://i105.photobucket.com/albums/m240/shadow357x2/Picture019.jpg
just wanted to make sure.


S

David Neibert
07-12-2006, 12:13 AM
Ill give that a try and see. It just seems odd that this happened only after a replacement. I did notice though that after unplugging the vac hose that I did gain about 2 more lb of boost, unless its just my fuzzy eyeballs...I take it you mean to go to this hose right? http://i105.photobucket.com/albums/m240/shadow357x2/Picture019.jpg



S

Yes....the easiest way to fix it is just cut the cross talk tube and put a tee in it and attach the hose for the bypass valve to the tee. Stick a plug in the hose where the bypass valve hose was attached.

David

shadow357x2
07-12-2006, 04:39 PM
Ok Smarty Pants (Dave):D That seems to have done the trick from what Im seeing here in the yard. Goosing the throttle and the actuator is instantly opening. Havent road tested yet but looks to be fine. Thanks alot.
Now that was a quick fix and I really apreciate it from the bottom of my heart , I have another question . Apparently you have either had this problem or heard of it before. Have you ever found out what the culprit was? I am noticing more vacuum from the cross talk hose than from the original one, BUT vacuum didnt seem to be the problem, taking it away was. Could it be a check valve somewhere or what
Heres what I did , not very professional looking but did the trick.
http://i105.photobucket.com/albums/m240/shadow357x2/DSC00037.jpg
http://i105.photobucket.com/albums/m240/shadow357x2/DSC00038.jpg
http://i105.photobucket.com/albums/m240/shadow357x2/DSC00040.jpg Oak stick from a donor tree "PRICLESS"


Thanks again
Phil

David Neibert
07-12-2006, 04:44 PM
Looks pretty professional to me...however I would suggest swapping that chunk of wood out with a bolt. Put some zipties on everything and your good to go.

I'm not clear on what problem your still having with the vacuum....please spell it out for me.

David

shadow357x2
07-12-2006, 04:45 PM
Yea I already did replace it, I just did that as a joke....



S

ThunderDave
07-12-2006, 05:02 PM
So you came off the tee and ran it over to where the line coming from the firewall use to connect at the vacuum bypass diaphram and blocked off the line at the firewall?

David, is the vacuum stronger at the crosstalk tube than it is at the line near the firewall?

shadow357x2
07-12-2006, 05:14 PM
I made a replacement hose for here http://i105.photobucket.com/albums/m240/shadow357x2/Picture020.jpg
and endup with this http://i105.photobucket.com/albums/m240/shadow357x2/DSC00037.jpg

Then blocked off the line here http://i105.photobucket.com/albums/m240/shadow357x2/DSC00038.jpg .
Seems to be alot more responsive now than it has been for awhile now also, dont know if its my imagination or not. But it works now.Total cost = about .75 and a handy dandy oak stick :p


BTW I took the stick out :p

Just got back from the 2nd test drive, I dont know what the difference is but this thing has never had this power since Ive had it, barely into the throttle and the wheels are breaking. I would like to know the secret here also. Maybe this has been a problem for me for awhile and didnt notice it. The only thing (Im assuming here) is that the original position of the vac line doesnt provide a quick enough release of the vac to go into boost. Might be hose break down or what ever. Im not advertising this as a mod just what it did for me in my time of need.

S

Tickler
07-12-2006, 05:39 PM
Damn, I'm good.

shadow357x2
07-12-2006, 05:46 PM
Damn, I'm good.


:D :D :D :D

David Neibert
07-12-2006, 06:32 PM
So you came off the tee and ran it over to where the line coming from the firewall use to connect at the vacuum bypass diaphram and blocked off the line at the firewall?

David, is the vacuum stronger at the crosstalk tube than it is at the line near the firewall?

The bypass valve uses vacuum to hold it open...apparently that wasn't a problem. The problem was when putting the car under a load the vacuum drops to near zero. At about 1inch of vacuum the bypass valve should start closing and be fully closed at zero. For whatever reason Phil's was holding vacuum where he had it hooked up, not allowing the bypas valve to fully close or very slow in closing. Might be a stuck check valve, might be a kinked line, might even be plugged into the wrong location.

I knew the crosstalk tube would have a good vacuum signal because it's close to the throttle body, connects directly to the inlet plenum and it's easy to tap into, so that's why I suggested it.

David