Fuel Relay Issues

[Austringer]

'99 V70 XC here.

So the other day the car wouldn't start. Or rather, it would start, would run for a second or two and then would die. Well that's a fuel issue thought I. Did a little reading, jumped the 15 and 87 contacts and it fired right up and worked just fine. Read that the electrolytic caps often fail so I soldered in some shiny new ones and put the module back in the car...and same problem. Harumph. Must be the coil in the relay that has failed.

Well, I was just about to head off the the dealership when it occurred to me that I never actually tested across contacts 31 and 31b. So I grabbed ye olde multitester, shoved those pins in there, and not a thing. Double Harumph!!! Putting he multi-tester across pins 15 and 87 and it reads 12V the moment the key is turned, so apparently I replaced those caps for nothing.

Now I'm puzzled. What's the next stop for the diagnosis train?

[hoonk]

The fuel system relay fails sometimes when solder joints crack where the tiny wires going to the relay coils are soldered to the fuel pump relay circuit board. You usually need a magnifying glass to see the cracks.

[Dups]

Wouldn't those be to turn OFF the fuel pump. If you jump 15 and 87 to keep the pump on always...shouldn't the others just do something different. IDK...just guessed. Has to show power at some point though.