Hi all,

I've diagnosed the problem with my '90 240 wagon as a failed fuel pump. The main relay is working as it should. A jumper between fuses 4 and 6 won't make the pump run, and the pump, when removed, won't run when 12v is applied.

But: with the ignition switch on, I do not measure 12v at the pump wires.

Typically, when you turn on the ignition switch, the pump runs for a second or two to come up to pressure. Once that occurs, does the ECU then remove 12v at the pump, waiting until you actually crank the starter? Or should 12v remain present at the pump? Am I making sense?

IOW, I'm trying to ensure that I don't also have a problem w/the ECU or the relay.

 

You will not have 12v at the pump with the ignition on.

Ecu will prime pump for a couple of seconds then remove power.

With engine cranking/running,ecu grounds the relay and restores 12v to the pump.
If your applying 12v to directly to the pump,it should run,if it doesn't,pump is bad.



Dan