2007 XC70 Fuel pump fuse repeatedly blows

[RickHaleParker]

And yep - it's the right headlight that went out. How could a finnicky fuse cause that?

Current surges mechanical shocked the bulb.

[mtd240]

Turns out the ‘07 is different than your ‘05 - the only fuse under that engine bay fuse panel is a 60A that controls the electric cooling fans.

[RickHaleParker]

Michael you might want to take a look at what Abscate discovered in his PEM: viewtopic.php?f=9&t=84114&p=461076#p461076

[mtd240]

Michael you might want to take a look at what Abscate discovered in his PEM: viewtopic.php?f=9&t=84114&p=461076#p461076

Awesome thanks for pointing me to his thread. The PEM was the first thing I checked actually. It's inside the car, next to the spare tire, in 2007 XCs (might have also been relocated in mine). It was in perfect shape (I opened it up).

Update: My alternator test yesterday wasn't thorough enough. Today I monitored the battery voltage after warming up the car for 15 minutes or so with all of the accessories on. The voltage slowly dropped to 12.4V - alternator couldn't handle the full load! It could hold ~13.5V with one or two less electrical loads on it, and 14.5 with just HVAC/headlights/heated seats. Seems like the alternator is on it's way out. I ordered one!

I went ahead and replaced the fuel pump anyway. The fact that its fuse was the first to blow tells me it was probably pulling a lot of extra current in the first place and is likely on it's way out too - it's a relatively common failure according to the forums. PITA to feed the new suction tube through the tank.

I guess this was a perfect storm of two things close to failure.

[mtd240]

Replaced both items. New alternator handles the load much better (batt. voltage doesn't drop as low with high loads).

But . . .

Idled the car for a half hour the first day (after replacing the fuel pump). Second day, idled it for 15 minutes (after replacing the alternator), shut it off, came back out and after a couple minutes of idling the fuel level sender threw a code and then the car stalled out and wouldn't restart. Fuel pump fuse is fine this time. Hopefully I didn't blow something else.

Any ideas? I'll run through the VIDA diagnostics for the fuel pump code (CEM 3F90).

The hardest part is, the car is at my in-laws' place. So I have to have a pretty good plan before spending the time to drive over there and work on it.

[jonesg]

Replaced both items. New alternator handles the load much better (batt. voltage doesn't drop as low with high loads).

But . . .

Idled the car for a half hour the first day (after replacing the fuel pump). Second day, idled it for 15 minutes (after replacing the alternator), shut it off, came back out and after a couple minutes of idling the fuel level sender threw a code and then the car stalled out and wouldn't restart. Fuel pump fuse is fine this time. Hopefully I didn't blow something else.

Any ideas? I'll run through the VIDA diagnostics for the fuel pump code (CEM 3F90).

The hardest part is, the car is at my in-laws' place. So I have to have a pretty good plan before spending the time to drive over there and work on it.

Only the obvious which tripped me up in the past. Check fuses with test light probe.
They can melt where it's almost impossible to see the break.

[mtd240]

Only the obvious which tripped me up in the past. Check fuses with test light probe.
They can melt where it's almost impossible to see the break.

Good point, I’ll check. But if that’s the case..where would you look next? Fuel pump relay?

[jonesg]

Only the obvious which tripped me up in the past. Check fuses with test light probe.
They can melt where it's almost impossible to see the break.

Good point, I’ll check. But if that’s the case..where would you look next? Fuel pump relay?

Yeh, older Volvo had relay problems. I recall popping a relay open and resoldering cold joints, that was the injector relay.
I don't know what relays they use now but it was a problem.
I also ran the car with low fuel in the tank, which burned the pump up, thats a very common driver error. Took me 9 stupid hrs in a snowstorm to swap the pump out.
I could do it today in 45 minutes

[abscate]

The P2 uses a soldered in relay to power the PEM which resides in the CEM under dash. You can check its output at A16 output of the CEM and then between pin 2/3 on the PEM to make sure you are getting battery voltage to the fuel pump. That will give you good diagnostics on the supply voltage.

Wow. How do I know all this stuff. If you look in my thread, I have seen further by standing in the shoulders of giants, specifically jimmy.

[mtd240]

The P2 uses a soldered in relay to power the PEM which resides in the CEM under dash. You can check its output at A16 output of the CEM and then between pin 2/3 on the PEM to make sure you are getting battery voltage to the fuel pump. That will give you good diagnostics on the supply voltage.

Wow. How do I know all this stuff. If you look in my thread, I have seen further by standing in the shoulders of giants, specifically jimmy.

That's why we're on the forum - lots of smart/knowledgeable folks here.

If the fuel pump relay is the cause, then I guess it's time for a new CEM?

Otherwise (if the fuel pump fuse did actually pop), where should I look next?