Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: Bshaunessy on June 29, 2023, 01:13:19
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1970 280 SL auto:
So…. who can advise the name / function of this under hood item pls? I’m wire tracing and identifying / labelling / testing all relays in an effort to sort out my Cold StartValve, Thermo Time Switch, , Warm Running Device.
This particular round relay has a brown and brown/green wire feed AND. a vaccuum supply from iINTAKE VENTURI and a vaccuum line to the distributor. Not sure how it functions but must be supplying electrically switched vacuum to dizzy for vacuum advance? I can’t find any such device on the 280 SL ( Tech Manual) wiring diagram.
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That is a two-way-valve. It’s not a relay. Your car must have USA emissions. Your throttle body provides vacuum all the time, not only at idle like early cars, and this valve shuts the vacuum on or off to the distributor controlling the distributor advance.
I think the tech manual describes the details - might be under ignition or emissions.
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Then, is it a vacuum relay? ;D ;D
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KAMPALA:
Yes, understood that this device is not technically a relay but is an electrical on/off device controlling vacuum to distributor. Unclear however, what controls the on/off signal?
I did another search in TECH MANUAL and found this reference ( no photo however) :
"Tom Sargeant: the vacuum line should connect to the two way valve in a properly functioning emissions control system. That distributor has an advance curve that requires the retarded ignition during initial idle and partial acceleration for optimal performance. Without the vacuum hose hooked up and the related emissions relays functional, you will likely be in a state of perpetual advanced timing. This means you either have a fast idle (15 or better degrees of advance at idle to achieve 30+ degrees advance at speed), or if the distributor timing is adjusted to have a "normal idle", your advance range is likely no more than 15 degrees. This means that at mid and high range speeds, you are only 15-20 degrees advanced, vs the optimal advance of 30-35 degrees at higher rpms. This means poor combustion, a rich running condition, poor mileage and generally less than optimal performance-both on acceleration and at speed. Joe, since you have been active on this posted topic, pls check me where I may have technically mis quoted."
I still do not know the name of this device nor can I find it on any electrical drawing?
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There is an emission-reduction system diagram, I think in the Big Blue Book, but don't have access right now. It shows the function of the various relays and this vacuum switch.
Hopefully someone can post that.
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https://www.sl113.org/wiki/Electrical/EmissionControlSystem
Just for the purpose of correctness:
A relay is an electro magnetic device which switches a set, or more than one set of contacts to operate other electrical equipment, either requiring a higher current or to switch multiple other devices via the one switch
A solenoid valve is also an electro magnetic device, which turns the electrical signal into a mechanical action, so the solenoid operates a plunger, which operates a valve
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That's known as a vacuum witch over valve. Vacuum signal always goes to the central port on the bottom of the valve. Switching is controlled by one of the black boxes nearby.
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Dr Benz:
Thanks for that tip…...mystery solved ( found a great description in Tech Manual / / "Emission Control System”.( I was searching ignition system and/ or distributor and/or ignition system)
(1) it’s called "two way valve”
(2) FUNCTION: cuts off vacuum for advance below 2000 rpm
(3) only on USA late model cars as part of that era emission control campaign
(4) signal comes from both nearby black boxes ( early version ECU's) : #50 "SPEED RELAY" and #40”WORKING CURRENT RELAY"…..( of course….l most intuitive!)