855 T5 w/ 140k mi and ipd ECU

Two months ago, the car would not start. I noticed there was no fuel pump whir when key was in 2nd position. Checked for power at the fuel pump, 12V there, yet pump wasn't going.

Replaced pump with a used one ($125) instead of a new one ($440). Car worked fine for two months.

Then, it decided to stumble and die while driving. Would not start again, same symptoms as before. Occasionally it would run for a couple minutes though, then stumble and die again. Otherwise, would not start at all.

Checked power to pump, 12V, but nothing was pumping.

On a whim, I dug up the original pump I took out 2 mo ago, gave it 12V, and it happily pumped out bits of gas left inside and sprayed it on my carpet. :)

Any ideas what would cause two different pumps to not work right when given ample power?

You also have a main relay under the front cowl in front of the fan. It is the gray one. Further, the battery terminal tends to fray and corrode, result? No power to relay; no start for you.

Replace your Fuel pump relay it's in the Fuse box on the drivers side above the fire wall. This is a common Volvo problem. let us know if this fixes the problem. The relay cost about 40 bucks from Groton from Volvo about $80.00.

I recently changed my fuel pump. From my VW days I recognized the louder than norm buzzing sound telling me my fuel pump was about to go out. I assume this is from my wife driving it on empty or possibly the mileage. If either of your pumps was buzzing, Id say the pump is bad. (Internal bearings, un-repairable) Ive seen the pump on Ebay new for $150 from some europarts company. (Of course this was after I bought mine for $235!)

check the fpr (fuel pressure regulator)if it is not working right excess pressure will build up and jam the pump.

Sounds logical. How would I go about testing it?

to test you can hook up a gauge or take the return line off. at idle there should be a lot of gas going back to the tank. i think there is a writeup
at ozbrick.