The problem re-appeared but is gone again...

I began investigating the dash switches and sunroof area and did not find anything odd. Shortly afterwards, the problem re-appeared... maybe coincidental, maybe not.

While the pump was powerless, I confirmed that I get 12v across the #2 fuse even when the pump is not working. I pulled and re-inserting the #2 fuse and confirmed that the pump relay "clicks".

I went back to check power at the pump and was initially unable to get a power reading from the main lead (recall that power is only sent there for about 30 seconds or so).

I rigged up my multimeter so that I could see it from the front and confirmed 12V at the pump connector when I switched the ignition.

Unfortunately (for diagnosis), as soon as I plugged the pump back in, it started running again. So I can't be sure that there isn't a problem between the fuse panel and the pump...

Interestingly, I noticed that the female end of the connector was slightly blackened - as though it was shorting. maybe something, maybe nothing


What I did find was that the connector at the pump was not secured to anything and that the rear shock mount right next to the plug was completely shot - the rubber separated from the mount. I had a good spare, so I replaced the mount and re-secured the plug to the body with a zip tie.

I am unsure how long the rear shock mount was bad. Since buying this car a year ago, I've now had to replace all four shock mounts. The driver's rear mount was really bad and squeaking horribly. I replaced that side when the car was "immobile" last week. I did not realize that the passenger side rear mount was also bad until I got the car back out earlier this AM.


A Working Theory...
I suspect that the busted shock mount right next to the pump connector *may* be a factor. There's not a clear 1:1 match but there are some physical similarities in three of the events...

The stall this AM was after I went over a bump exiting the drive-thru's parking lot. There was a big "hump" at the license office parking lot too. The stall that happened in early February was as my wife was exiting the highway and stopping. All of these environments would be stressing the shock mounts. A completely broken mount would be shifting around. if the wiring was being contacted by the shock mount, it might have cause a short that tripped the overload relay...

The weirdness with the sunroof also seemed to happen while braking or driving on rough streets.

Not everything matches. The re-appearance half an hour ago while I was testing the panel switches doesn't fit. I couldn't find any obvious evidence of physical damage to the wires or connectors by the broken shock mount. I don't think that the sunroof power is anywhere near the fuel pump power or the rear shock mount. Until early February, rough streets and braking from highway speeds had never caused any issues with the fuel system.

Thanks to a link to the Volvo Wiring schematics from B.B., I was able to confirm that the sunroof and fuel pump share a common harness connector up near the passenger A-Pillar. It is plausible that the sunroof and pump electrical problems are related.