Unleaded/Premium mode test

[Chalky]

Hey All, maybe my brain is failing me, but many moons ago I remember seeing a post which discussed the test procedure to see if the Unleaded/ Premium mode system was working. If I remember correctly, with a timing light connected you should see a jump in base timing when you switch from Unleaded to Premium?? Is this correct? Any further details on this test procedure please??

[MikeFleming]

Hey All, maybe my brain is failing me, but many moons ago I remember seeing a post which discussed the test procedure to see if the Unleaded/ Premium mode system was working. If I remember correctly, with a timing light connected you should see a jump in base timing when you switch from Unleaded to Premium?? Is this correct? Any further details on this test procedure please?? Hey Chris!

Yes, there is s timing diff of +6 degrees (crankshaft), fixed, when in Premium vs Unleaded. Only caveat is must not be at closed throttle (CT). Easy to have someone inside hold the RPMs at 2500 and flip the switch back and fro while a second person is holding and observing with the timing light (and Pat is tapping a wrench on the pavement!).

Also associated with the Premium position is the Boost output signal is sent to the Boost Controller (either the module or directly to the solenoid for 1985+). That signal goes through a fuse tho.

If the timing does not change, first check / replace the relays behind the upper part of the consoled, under where the radio would normally go. One relay forwards he Premium boost input signal to the EEC and the other sends the Boost output signal form the EEC to the Boost controller./solenoid.

HTH!

[Chalky]

Thank you Dr. Fleming!! I was not aware of the CT caveat. I will re-test with my co-pilot at the helm and report back. I have some NOS relays in a box somewhere, I'll give them a go!! I owe you a call, it's been a while :):):)