Results 1 to 10 of 10

Thread: Supercharger butterfly valve stays shut

  1. #1
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17

    Supercharger butterfly valve stays shut

    Edit: SOLVED! The vacuum solenoid by the clutch reservoir had failed so I bypassed it with some plastic tubing. Thank you KMT for pointing me to this thread: http://www.sccoa.com/forums/showthre...valve+electric
    ALSO, the title should be "Stays Open." I didn't know how the actuator functioned as well as I thought I did.

    I need some pointers on where to look for issues in the vacuum system in an 89 SC. The supercharger hasn't worked for as long as I've been around (dad owned it before I was born and I don't ever remember it working) and since it's mine now I'm determined to find the fault and fix it. I bought an analogue test gauge and here's what I've done so far...

    -I can open and shut the valve with some slight resistance, but I suppose that's just how stiff the actuator is.
    -I took the hose off the actuator and did the finger-vac test on the single port it has. I can hold the actuator in the open position by first opening it then blocking the port, so that rules that out as a fault.
    -I hooked the same line up to the test gauge and what I found doesn't seem right. The in-car gauge goes right to 20 In HG after 3 seconds of starting the car like it should, but the test gauge took it's sweet time crawling down to 20 In HG in the span of a minute. Since the line was presently connected to the test gauge and not the actuator this means the valve for the supercharger intake is stuck open, meaning I'd get boost. I blipped the throttle and surely enough I made some boost according to the internal gauge. The test gauge, however, didn't even twitch

    This is about all the further I got since all the other lines are buried under the lower windshield plastic and I don't have a garage to work in yet for another month, so I'm mostly tinkering on it on sunny days. Going back to point 3 though is yes if I start the car cold and hammer it within that first minute it does get boost and tally-ho I am flying away, but as that minute goes by the valve opens more and more. I could just leave the system disconnected and always have boost, but I see people say that would lead to some combustion issues?

    tl;dr version I have a vacuum leak, so my supercharger works but the valve gets pulled open after a minute of running. Where do I look?
    Last edited by FurryWrecker911; 10-28-2018 at 08:35 PM. Reason: Problem Solved

  2. #2
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    >I can hold the actuator in the closed position by first closing it then blocking the port
    You mean opened position...

    That valve is a bypass, preventing boost from building when it's open. It opens when there is vacuum at the diaphragm that operates the lever that pivots the plate. Vacuum is present at idle and goes away as the throttle is opened.

    With the engine off, is the bypass fully closed?

    When you start the engine, do you see that vacuum pulls it fully open at idle?

    When starting the engine and letting it idle, how much vacuum do you see on the gauge in the dash?

    While driving the car, at full throttle, how much boost do you see on the gauge?

    With the engine off and the bypass closed, can you move the lever and manually open the valve fully, then let it close, with it sticking in either position?
    Last edited by KMT; 10-27-2018 at 09:24 PM.

  3. #3
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17
    Edit: Just saw you changed your reply. I'll correct this in a bit...
    Edit 2: Fixed.

    With the engine off, is the bypass fully closed?
    -Yes, it is closed

    When you start the engine, do you see that vacuum pulls it fully open at idle?
    -Yes, it slowly pulls open over the course of a minute. It's not instant at all, and according to the test gauge the system isn't pulling an instant vac. The dash gauge says it's instant though.

    When starting the engine and letting it idle, how much vacuum do you see on the gauge in the dash?
    -20 In HG instantly. Giving it throttle causes it to rise then stop once it hits 0.

    While driving the car, at full throttle, how much boost do you see on the gauge?
    -0 under normal circumstances. It wasn't full throttle, but the most I've been able to get after starting with a cold engine was ~7-8 PSI, then after 30-seconds to a minute it's back to 0 PSI via the bypass opening itself.

    With the engine off and the bypass closed, can you move the lever and manually open the valve fully, then let it close, with it sticking in either position?
    -Yes I can. It's a tad stiffer than a throttle body but I assume it's supposed to be that stiff.
    On that note: If the engine was just run then it takes about a minute for the vac to let off in order to be twisted by hand.
    Last edited by FurryWrecker911; 10-27-2018 at 09:33 PM.

  4. #4
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    Sounds like the bypass is sticking.

    See my edits above.

    While I wait for you to digest my edits, I'll mention the spring in the vacuum pot on the bypass...

    Engine off (lever up), bypass closed. Closed bypass allows boost to build.

    When you manually move the lever, engine off, you're pushing against a spring inside the vacuum pot. The lever is moved by the spring on one side of the diaphragm, and vacuum on the other, acting against the spring.

    With the engine running and throttle opened, there is no vacuum at the pot, on the bypass, and it closes...lever up.

    With the engine running, at idle, vacuum pulls against the spring and the bypass opens....lever swung down. Just like if you move it manually when the engine is off.
    Last edited by KMT; 10-27-2018 at 09:43 PM.

  5. #5
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17
    I just made edits to my own based off of your edits.

  6. #6
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    It should swing open as soon as the engine fires and runs, and you should be able to pivot the lever manually with just the resistance from the spring in the diaphragm.

    If you move the lever manually (engine off) and let go, you shouldn't be able to count to one before the spring moves it back against the stop.

    Could be worn and/or gummed up bushings. If it was out of adjustment, it could stick closed, but then you'd see boost all the time. If the diaphragm was leaking, same thing.

    Can you confirm the vacuum pot is secure against it's mount?

    Note: And since we're talking about an '89, some of them came with a wired valve to keep boost from building in reverse. See: http://www.sccoa.com/forums/showthre...valve+electric
    Last edited by KMT; 10-28-2018 at 09:21 PM. Reason: note on '89s

  7. #7
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17
    Alright, so with the vac line disconnected and the engine off, testing it by hand the actuator holds open when under vacuum (via the finger test) and it does slam shut in under a second when released from vacuum. I don't see how it can be the actuator if it's working as you're describing it. If it's connected to the vac lines with the engine running, THEN it starts behaving erratically which leads me to think it's a vac issue elsewhere.

    I'll admit I had no idea how an actuator worked internally until you spelt it out for me. Thank you big time for that c: . That being said, with what you told me combined with the testing I did says it isn't the actuator.

    What's a "vacuum pot"?

    Also I followed that link you posted and I may try jumping my lines tomorrow as suggested in that thread to see what that does. I was tinkering with that piece too trying to figure out the next place to test for vac/boost, so that should be a quick patch-together tomorrow morning and I'll see what happens then.

  8. #8
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    >I had no idea how an actuator worked
    Bypass can be a slightly confusing concept on our cars until you wrap your head around it, so don't feel bad

    These cutaway photos may help:

    Name:  engine2.jpg
Views: 48
Size:  33.7 KBName:  engine1.jpg
Views: 49
Size:  54.3 KB

    A 'vacuum pot' is a 'canister' aka can, or pot, with a vacuum port.

    Ours is the round can, that houses the diaphragm and spring, that the vacuum line goes to, that has the rod coming out the other side, that pushes/pulls the lever, that is on the end of the shaft, that passes thru the housing, that holds the plate, inside, similar to a throttle plate, or as you originally named as the 'butterfly valve'. Sorry, I assumed anyone that used the term butterfly valve knew what a pot was in this context

    You can test yours by applying vacuum and seeing if it leaks (irrespective of what the lever, shaft and plate assembly does). It shouldn't. If it does, try placing a want ad here for a good used one. If the bypass plate's shaft is sticking bad or the shaft is bent, or loose in the bushings (risking a vacuum leak), it might not be worth keeping and you may want to source the pot and the bypass assembly at the same time.

    About the electric part of the '89's valve, note that Ford decided better in 1990, and removed it completely thereafter. I suspect they are unobtainium now, so I wouldn't object if you found a way to offline that part of it. That may be your only issue, and the other hardware is fine, otherwise.
    Attached Images Attached Images    
    Last edited by KMT; 10-28-2018 at 09:19 PM. Reason: verbiage

  9. #9
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17

    Solved

    KMT I owe you big time!

    That thread you pointed me to solved my problem. I mounted the test gauge just before that solenoid and surely enough it was 1:1 with the dash needle. I went to PepBoys and picked up a variety pack of vacuum adapters and linked the pre and post lines of the solenoid together. BOOM! Making around 8 PSI under load now! So that's what it feels like to be sucked into the seat...

    Also the cut-aways you posted REALLY help in understanding how air circulates in the system. I'm still studying them to get a full understanding, but it's a big-up from knowing "air goes... somewhere, and car goes faster." :V
    Now the next thing to work on is figuring out why my temp gauge fluctuates as much as it does. It might need a 4th coolant flush. lol. 8 years of garbage in the lines.

    Here's a picture of the bypass I did:
    Name:  Bypass.png
Views: 33
Size:  759.2 KB

  10. #10
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    Good job, glad you sorted it out, thanks for the update & pics, and since this thread is marked solved, I guess I'll save comments on the temp gauge for a later thread.

    Ken
    Last edited by KMT; 10-28-2018 at 09:16 PM.

Similar Threads

  1. Supercharger Bypass Valve
    By Silver R in forum Non Technical Forum
    Replies: 10
    Last Post: 04-12-2010, 12:12 AM
  2. WTB: Supercharger Bypass Valve Actuator Hose
    By Silver R in forum Want to Buy
    Replies: 5
    Last Post: 03-04-2010, 02:11 PM
  3. Supercharger Bypass Valve Actuator
    By Michael Mattix in forum Want to Buy
    Replies: 8
    Last Post: 07-17-2006, 04:48 PM
  4. supercharger bypass valve + vacuum line
    By 90coug in forum Want to Buy
    Replies: 3
    Last Post: 08-17-2005, 12:55 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •