My 1st Volvo, 3 in the family
 

Was in ther salvage yard scavenging some parts and I noticed on the XC70 (like I have), year unknown, an electrically driven centrifugal pump in the drivers side area right behind the bumper. What is it for?
My Volvo is a 2001 XC70 (big change from the Chili Red Mini rag top that came before it that was destroyed by a texting driver who escaped) and it sometimes deosn't start and gives me the message 'start prevented, try again.' What does that mean? Other than it didn't start.

What year Volvo was in the wrecking yard? Without some sort of reference, can't give you an answer.

Alternate cause of start prevented
 

I want to offer another possible reason for ‘Start Prevented’. I went to my trusted, independent Volvo service garage and he told me to get all those extra keys off my key ring, that extra weight can damage the mechanical locking mechanism, but not the electronics. (Private planes have had fatal crashes for that very reason, the heavy keys damaging the ignition switch.) He also said to only use a single key in the ignition. Then, I got to thinking. Besides house keys and such I also had three keys on the key ring with ‘near field’ chips in them. Pondering this, when I put the key in the ignition with the other chipped keys ‘near’ the antenna in the ignition switch the the car’s computer sent out the signal to activate the chip and verify the correct key. But, that signal also activeted the other chips so the computer got 4 responses as the other keys chips were activated. So, the computer got confused and prevented starting. Since then I’ve rearranged all my key rings and now use a single key in all my vehicles, keeping any other chipped keys away from the antenna. As a result I’ve had no starting problems since, whereas before it happened about every third attempt to start.