Hi!

I'm currently swapping in a Volvo 960 3 litre engine into a Volvo 740 -88. I was looking into connecting the Motronic 1.8 system to the old 740 fuel pump relay. Although someone said that the relay in the 740 is activated by an alternating current from the ignition coil, and since it's been removed it won't work. Is that correct? Or can I use the old fuel pump relay? I'm mostly confused since I've seen people doing swaps without mentioning the fuel pump relay, so I'd guess it still powers the fuel pump even if the ignition coil is removed. Therefore it should be able to power the Motronic ECU?

 

The fuel pump relay is activated by the ECU on an 88 740 with the LH 2.2 fuel injection system. The ECU will NOT activate the fuel pump relay unless it sees pulses from the distributor. These are the same pulses that go through the power stage and subsequently to the coil. This keeps the fuel pump from running unless the engine is turning.

Long story short is that there is no "alternating current" running to the fuel pump relay. I don't see why the Motronic ECU could not power your current fuel pump relay as long as you know how to wire it up correctly.