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You are describing the LH 2.0 FI circuit, so the car is an '84. Those cube relays are not failure-prone, in my experience, but given the age they may be suspect. The operation is fairly simple:
1) the System relay has constant +12 on its coil and armature (86 and 30) from the 25 amp blade fuse in the coil/battery area. The relay closes when the ECU grounds the Y-R wire on 85, which it does when it sees Key ON +12 at pin 18.
• System relay sends voltage to ECU #9 and AMM #9, when energized.
• Relay ground comes from ECU 21.
2) The Fuel relay has the same +12 (25 amp fuse) on it's armature (30), with Key-controlled +12 at its coil 86 (where a blue-red lead-off takes the voltage to ECU 18.
(Relay +12 path is Battery=>fuse 13==>blue/yellow==>3-pin plug under glove box==>blue/red==>relay 86.)
The Fuel relay should NOT energize until the ECU grounds its blue-green wire at 85. This requires that the ECU receive pulses from the negative side of the coil (Coil#1). ECU grounds relay blue-green wire at its pin 17.
•Fuel relay sends voltage to fuse 5 input and Main pump, Idle Air Control valve, and Injectors.
If the Fuel relay EVER picks with Key On, that's wrong.
But the System relay must ALWAYS pick when the Key is turned on.
The "click" at Key-On must always be the System relay, never the Fuel relay. Don't trust the sound to tell you which one(s).
Prime suspects are:
• 25 amp fuse, fuse holder, and wiring to battery +
• Fuse 13 and its contacts
• connecter at Coil#1
• 3-pin connector under glove box
• maybe wiring insulation, but usually that's just under the hood.
• possibly a geriatric relay
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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