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Thread: Vacuum Systems on a Stock/OEM Engine

  1. #1
    Devout Follower Of He Who Walks Behind The Rows NightFlyer's Avatar
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    Vacuum Systems on a Stock/OEM Engine

    I've received A LOT of question about this, thus I thought that I'd put this together to better answer owner's questions regarding the vacuum operated systems on a DeLorean.

    Everyone should be familiar with this (courtesy of owner/member Luke S and his awesome website):



    It's not difficult to check, and not a bad idea to check the operation of the vacuum systems effecting fuel delivery and ignition distributor advance.

    They work like this:

    When you first start the engine cold, vacuum from the multi-port switch in the y-pipe (under the intake) is directed to the warm-up regulator / control pressure regulator (WUR/CPR). Once the running temperature reaches 104F, the multi-port switch redirects the vacuum to the solenoid hanging off the mixture unit behind the fuel distributor. When the engine is idling, the idle micro-switch is activated (closed) and instructs the solenoid to hold the vacuum there within the solenoid. When the the engine is under throttle, the idle micro-switch is disengaged (open) and causes the solenoid to actuate and release the vacuum being held there onward to the distributor in order to cause the vacuum advance of the timing.

    Vacuum advance at the distributor should only be present when the running temperature of the engine is above 104F AND when the engine is under throttle. At all other times, there should be no vacuum advance at the distributor - NEVER when the engine running temp is below 104F (whether at idle or under throttle) and NEVER when the engine is at idle.

    To confirm operation, you simply pull the vacuum lines off the WUR/CPR and the electrical distributor's vacuum chamber and/or vacuum solenoid and check for the presence/absence of vacuum during the various stages of engine operation.

    But the factory sticker doesn't show the entirety of the car's engine vacuum operated systems.

    The other two systems (that come to mind anyway) that operate off engine vacuum are the brake power booster and the HVAC mode control. Are there any others that I'm missing?

    Both systems are driven off the passenger side intake runner barbed tap. The hose that runs off the tap is immediately 't''d, and vacuum is directed to both the HVAC vacuum canister/reservoir mounted inside the driver's side pontoon (next to the evaporative control system's charcoal canister) and to a hard/steel pipe that runs down the length of the frame to a hose that terminates at the brake booster.

    From the canister/reservoir, the HVAC vacuum runs down a plastic line that's laid under the center console until it butt splices into a rubber line that terminates at the HVAC mode switch octopus.

    From the HVAC mode switch octopus, another plastic line is routed under the center console and into the driver's side pontoon, where it passes through the wall of the pontoon (roughly in the middle) near the bulkhead/firewall and out into the engine bay. This line terminates at the heater control valve, which is usually hanging by the coolant hoses somewhere in between the engine and the bulkhead/firewall behind the passenger side valve cover.

    Here's a few a explod-a-views from the parts manual to help you better visualize the routing of these systems:

    No. 17 is the steel pipe line for the brake booster:



    No. 51 is attached to the passenger side intake runner barbed vacuum tap. No. 27 runs into the driver's side pontoon to the HVAC vacuum canister/reservoir, which is No. 21. No. 19 runs through the driver's side pontoon into the cabin and under the center console to the HVAC mode switch. No. 50 is the steel pipe line, the same as in the image above. No. 29 runs under the center console into the driver's side pontoon where it immediately comes out of the pontoon (near the bulkhead/firewall) and terminates at the heater control valve in-between the engine and bulkhead/firewall behind the passenger side valve cover.



    Attached Images Attached Images
    "Driving Concours - proving it's possible with every mile!"

    --Josh S.
    #1798

  2. #2
    That doesn't look anything like my vacuum system:

    VacuumLabel.jpg

    Bill Robertson
    #5939

  3. #3
    Quote Originally Posted by content22207 View Post
    That doesn't look anything like my vacuum system:

    VacuumLabel.jpg

    Bill Robertson
    #5939
    Is your vacuum system Hoover or Dyson? Mine is Dyson!!

  4. #4
    Martin Gutkowski works for Dyson.

    Bill Robertson
    #5939

  5. #5
    Devout Follower Of He Who Walks Behind The Rows NightFlyer's Avatar
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    Quote Originally Posted by content22207 View Post
    Martin Gutkowski works for Dyson.

    Bill Robertson
    #5939
    My sister has a Dyson.

    Personally, I think my old school made in USA Hoover vacuums better than her plastic made in only God knows where Asia Dyson, but that's just MHO.
    "Driving Concours - proving it's possible with every mile!"

    --Josh S.
    #1798

  6. #6
    Quote Originally Posted by NightFlyer View Post
    My sister has a Dyson.

    Personally, I think my old school made in USA Hoover vacuums better than her plastic made in only God knows where Asia Dyson, but that's just MHO.
    Wow!! that sucks!!

  7. #7
    Devout Follower Of He Who Walks Behind The Rows NightFlyer's Avatar
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    I like how Bill's sticker is all inclusive.

    Why DMC didn't include the booster and HVAC systems on theirs is quite frankly beyond me...
    "Driving Concours - proving it's possible with every mile!"

    --Josh S.
    #1798

  8. #8
    Devout Follower Of He Who Walks Behind The Rows NightFlyer's Avatar
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    Quote Originally Posted by tom kish vin.4357 View Post
    Wow!! that sucks!!
    It really does
    "Driving Concours - proving it's possible with every mile!"

    --Josh S.
    #1798

  9. #9
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    pfffft vacuum advance, whats that? I got ya beat bill!

  10. #10
    I actually still use an Electrolux Epic canister that is from 1992. Still runs like a champ, though!

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