2008 volvo xc90 fuel pump relay

t.ali.eubank · Post by **t.ali.eubank** » 25 Mar 2017, 10:58

I'm trying to locate and replace the fuel pump relay on my 08 xc90 and not sure if its in the one of the fuse boxes or what. please help, i don't wan this issue to cause my actual fuel pump to go out.

Post by **cuhfs** » 25 Mar 2017, 13:47

Not sure if this will help but here is a thread I found online regarding a 2007 http://www.justanswer.com/volvo/7nruz-v ... hange.html About halfway down they start to talk about fuses and relays. Maybe someone else here has done that job before. I have not on my XC90.

Post by **jimmy57** » 25 Mar 2017, 21:32

The fuel pump relay is built into the CEM. The fuel pump is variable speed controlled by a transistor power stage called the PEM. It is a grey and black with finned aluminum that should be in spare tire well on 2008.
Why do you think you need to replace the FP relay?

FREEBUSINESSES · Post by **FREEBUSINESSES** » 22 Feb 2020, 05:45

Fuel pump relay is under hood on driver side where 6 relays are located, PEM is not the fuel pump relay.

Post by **ggleavitt** » 22 Feb 2020, 11:11

This is 2008 so either 3.2 or V8 (Denso ECM) if the vehicle is North American. PEM gets moved inside the vehicle by 2007.

As noted above, it's 12v power to the pump from the PEM by way of CEM with control via ECM (B:21 for the 3.2, B:20 for the V8). CEM (B:16) gets the power for the fuel pump from the 30+ feed A1-3 through 15A fuse 11B-F8 in the engine compartment and provides the power (A:16) to the pump. So there is a fuse under the hood for the fuel pump but no relay specific to the pump.

Long link and nothing to do with the original question, but you can see a wiring diagram here- viewtopic.php?f=10&t=83957&hilit=fuel+pump&start=10

If you could add some context to the question, might be able to help answer more accurately.

*2/22- modified based on earlier response.

Post by **jimmy57** » 22 Feb 2020, 16:31

There is a relay for power supply to the engine compartment components like coil, injector, evap purge valve, intake chamber control solenoid (V8) or intake runner damper motors (I6) that is in that fuse and relay box in engine bay. The fuel pump relay on P2 up through 2004 model year was mounted on CEM and serviceable. In 2005 the CEM revisions did away with some plug in relays in favor of board mounted relays. The ejector fuel pump on dual pump tanks comes on via the CEM relay. The injection delivery pump gets 12V then too but it is speed and thus pressure regulated through ground side by PEM to control pump speed to maintain desired fuel pressure as the only fuel pressure regulator in system is there as a back up if the fuel pressure control system has a fault. The V8 and short I6 engines all have speed controlled fuel pump in North American market versions. the 5 cylinder engine had the speed controlled pump system the last 2 years it was used in NA market versions.

Post by **ggleavitt** » 23 Feb 2020, 11:19

Thanks very much for the clarification. I see it now, there's a "second" pump (6/31) in the pump assembly for US/KOR market variant that one gets a separate feed from the REM (B:25) although I don't see a fuse called out. The electrical diagram I noted earlier is incorrect (partial) although the thread is still kinda interesting and does provide some good visual references.

So what you're indicating is that on the dual pump assembly, the ejector pump (6/31) always provides a baseline operable pressure to allow the vehicle to function but the higher and varying duty cycle pressures required for "normal" operation are supported by the PEM controlled fuel pump (6/33)?

And If I read the earlier thread correctly, the ejector pump also creates the venturi for the other side tank pickup, is that correct?

Thanks

Post by **jimmy57** » 23 Feb 2020, 19:53

Yes, on the PEM controlled pump vehicles with dual sump tanks there is that second pump operated with full 12V power just to move fuel over to the left sump ejector pump (venturi device, no "pump" to it) to create the suction that picks up any fuel on that side. The second pump looks like the standard pump but it could have a wimpier winding set and even a different pump section. I have never seen any detailed description of it. I have one I salvaged out of a failed pump module and have used it to move diesel fuel out of a truck bed tank but never attempted using it to build pressure.