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Volvo 780 still No start, well It started once 700 1990

The fuel pump relay is in the center panel below the radio.
The rsr, Radio Suppression Relay, which is actually the fuel Injector relay, and on a turbo also powers the coil, is black, has a square plug, and as I said is on the inner left fender above and behind the battery. That's where it is on my 4 turbo cars, and all the others I have seen and/or worked on.

The 4 white ceramic item is a resistor for the low impedance injectors that most or all turbo's use. I have never heard of one failing.

Search for lucid's 'Start-run sequence'. It's the best thing out there for your issues.

Oh here, I found it. IMO, print this out and keep it in your car.

============================================

"Start-Run Sequence LH2.4 or REX

1) During starter cranking, the Crank Position Sensor sends timing pulses to Ignition Control Unit (ICU = EZK or REX)

2-a) The ICU uses these CPS pulses to trigger the Power Stage (aka Ignition Amplifier), which initiates spark from the coil.

2-b) At the same time, The ICU also propagates the pulses to the FI ECU, to allow FI operation (no ICU pulses means no FI operation).

3-a) The Fuel Injection (System)* relay (previously energized at Key On) powers the AMM, IAC, ECU, Injectors, and Fuel (pump) relay coil + side.
* The System relay is in the white case with the Fuel relay.

3-b) When ICU pulses are received by the FI ECU, it "energizes" the Fuel relay by grounding the relay coil (– side) to run the fuel pumps.

When all these things work, the engine runs until the Ignition is switched off, which in turn shuts down the FI system.

Determining whether or not there is spark at the plugs (2a) — and whether or not the plugs are getting gas (3b) — makes a good no-start "starting" point.

For example, if 2a fails due to a bad Power Stage/Amplifier, there will be a no-start with gas-wet plugs. If 2b fails (practically never) symptoms will be Fuel-related: a no-start with spark at the plugs, but plugs remain dry.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63. "






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