2400 RPM vacuum retard

[dwsfca]

 Does the NO VACUUM above 2400 RPM  apply when the car is in park or neutral?

My friend has a 70-280 SL with the "061" aluminum distributor.  When I plugged in a vacuum gauge in the line to the distributor and revved it above 2400 RPM the vacuum was still there. Does it only drop off when the car is driven or should it shut off anytine above 2400 RPM?

Thanks,
Dan

[glenn]

Try running the engine with no vacuum in the intake manifold-------. ..

[Naj ✝︎]

There is a vacuum valve together with the 3 relays next to the battery.
The speed relay operates this valve to cut off the vacuum at the distributor above set rpm.

naj

[jeffc280sl]

Attached you will find a diagram of the emission system.  Pull off the connector to the 2 way valve.  At 2400 rpms and above you should have 12 volts across the pins in the connector.  At 2200 rpms and below you should have 0 volts.   If this isn't the case you most likely have a faulty speed relay.  This is the 6 pin black box near the battery.  You do not have to be driving the car to test run this test.

[dwsfca]

Thanks Jeff C. 

I appreciate the diagram.  I just really needed to know if the vacuum would change while in neutral as opposed to driving.

I will do the voltage test as suggsted.

Dan

[jeffc280sl]

Vacuum should change while in park or neutral

[dwsfca]

Jeff C,

I finally got around to checking the voltage across the pins of the 2 way valve.  Result =O volts regardless of engine speed.
 
Is there any way to test the speed relay?  Are these available and where would I find one?

Thanks,
Dan

[jeffc280sl]

If you take the connector off the 100 degree switch and ground it you should have 12 volts across the two way valve pins.  If you do then your wiring would appear to be correct  and it looks like the speed switch is bad.   The 100 degree switch is schematically connected to pin 1 on the speed relay.  From pin 1 on the speed realy 12v is switched to the two way valve either by the 100 degree switch or speed relay.   Make sure you have 12 v on pin 2 of the speed relay in all cases when the engine is running.  Some have had their relay boxes repaired at Beckman.  I think they are in Durham, NC.  Do a search on this site and you will find their address.

[Desertpagoda]

 I  have some good used speed relays around. Also distributors, vacuum valves, injectors, injection pumps, fuel pumps, orig York & sankyo compressors or adaptors, p-s pumps/brackets, manual steering box, starters, alternators, voltage regulators, relays, heads, transmissions, fluid flywheels(steel&alum) double acting solenoids, calipers, rear ends, radios, lights, alloy wheels, hub caps, trim rings, tool kits, window cranks, guages, horns ... etcetera etcetera etcetera. Call with wish list/part numbers/applications needed.  Keith 520-404-2875