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Forcing the fuel pumps to run by "fuse jumpering" (or jumpering 2 relay terminals) as a trouble-shooting aid does not activate the complete FI system. Even though the engine may start, it won't run well (K-Jet) — and may not start at all on LH 2.2 and 2.4
This is because both K-jet and LH Fuel relays have two (2) separate "outputs", only one of which powers the pumps. (The LH relay is actually two separate relays under that white cover.) This second output is especially important in LH systems–less so with K-Jet. Its terminal number and functions are as follows:
LH 2.2, Terminal 87-1 controls:
• AMM pin 5
• ECU pin 9
LH 2.4 (and presumably 3.1)
• AMM pin 5
• ECU pin 9
• IAC Valve voltage
• Injector voltage (RS relay on 700/900, and '93 240?)
K-Jet, Terminal 87b controls:
• The complete Lambda (O2 Sensor) System (if so equipped)
• Heaters for Aux. Air Valve and Warm Up Regulator (not essential to starting)
For a complete diagnostic relay bypass, a 3-legged jumper having flat male terminals is needed—and plugged into the relay harness socket, as follows:
Leg 1 from socket terminal 30 (heavy Red wire, fused battery +12V)
Leg 2 to socket 87-1 (or 87 for K-jet)
• Yellow-Red wire (to K-jet pumps)
• Orange, Brown wires (LH 2.2 AMM etc.)
• Red-Black wires (LH 2.4 MM etc.)
Leg 3 to socket 87-2 (87b for K-jet)
• Blue wire (K-jet Lambda sytem)
• Yellow-Red (LH 2.2 pumps)
• Yellow-Red (LH 2.4 pumps, O2 heater)
As with other jumpering schemes, the pumps run immediately. For more than a quick test, a control switch can be wired into the common leg connecting terminal 30 to the other two legs.
Comments and questions welcome...
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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