04 XC70 Could it be the fuel pump?

mikeamondo · Post by **mikeamondo** » 22 Jun 2014, 10:41

Ok... my apologies if this wrong forum procedure, but I'm starting a new thread on my son's XC70 issue because I'd like to ask specifically about the fuel pump and discuss specifically the ways in which they might fail, where as the original thread has focused on electrical.

Here's the original thread if you're interested.

So two people, both experienced to some degree, have now suggested the fuel pump for my son's problem. The car will run fine, he drives somewhere and parks when he comes back to the car it will not start, or it will start and run a couple second and dies. Later, it will start again. Some lights may or may not appear on the dash... different each time. A scan at a local shop showed no stored codes, and of course, it did not replicate while they had it.

So... here's a bit of new info. My son has never filled the tank since he bought it. And the previous owner (not a dealer) had it full when he test drove it and full when he delivered it. The problem first appeared after he drove out that first tank of gas and dropped below a quarter full. A friend of his... a long time Beemer enthusiast / mechanic / and somewhat specialist in European cars, suggested that the fuel pump is WEAK and after he drives a bit, a vapor lock will build up in the tank. Upon restart, the pump does not have enough pressure to overcome the vapor lock and the car fails to start. Later, the vapor lock subsides on it's own and the car starts.

This is EXACTLY how Subaru pumps often fail. We've had two old Subies that ran just fine as long as you did not let the tank get low. It needed the extra pressure of a few gallons of gas in tank to keep running. Below 1/4 it would die and not restart. Fill the tank... fired right up. In both cases the new fuel pump fixed it.

Do Volvo fuel pumps fail in this way? He will be driving the car around today, trying to replicate the problem. When the car does fail to start, he will open the tank to clear any vapor lock and try to restart. I will post what he finds out, but in the mean time.... does this idea make some sense?

Thanks!
Mike

mikeamondo · Post by **mikeamondo** » 22 Jun 2014, 13:22

Update... So Andy took the car for a drive, parked her and shut it down. As in the past, she would not restart. He opened the fuel tank and closed it again..... and she fired right up.

So... fuel pump?

Post by **jimmy57** » 22 Jun 2014, 13:47

No way to guess this one. A fuel pressure gauge will tell you.

mikeamondo · Post by **mikeamondo** » 22 Jun 2014, 14:12

where would we get one, and is it easy to put it on and check? It would be great to have some confirmation before we tackle the job. We will be visiting my son and I'd like to help him with it, but we only have one shot on one day.... If it's something he can do before we get there, that would be great!

Post by **abscate** » 22 Jun 2014, 21:28

You can't do a snap diagnosis on a problem like this, and the first thing to throw out is well-meant advice from others. If one doesn't know to suggest a fuel pressure test to diagnose a "fuel tank vapour lock" then you need new counsel.

You can get a fuel pressure gauge at AdvanceAuto or Autozone. Check pressure at the fuel rail both at turn on and after 20 minute rest to check for pressure leaks.

mikeamondo · Post by **mikeamondo** » 23 Jun 2014, 18:12

Thank you for your input. I'll have my son pick up a fuel pressure gauge asap and check the pressure. What are good values and what numbers would show the pump is weak?

Also... will any of the ones available at Advance work on the Volvo?
And finally.... got a picture of the test port?

mikeamondo · Post by **mikeamondo** » 23 Jun 2014, 19:23

Ok... sorry if this is a stupid question, but I've never used a pressure gauge before. The units available in-store at Advance & AutoZone are only 15 psi. 100psi units are available online. Then I see a youtube video showing an 04 XC70 at idle and the gauge showing 50 psi... and what the heck are the 7 Bar units about? Bars? Ugh. You've gotta be smarter than the tool and I'm coming up a bit short.

Which gauge will work to check the pressure on this 04 XC70? What number should we see? What is too low and would indicate the pump is bad?
Thanks!
Mike

Post by **jimmy57** » 23 Jun 2014, 22:57

Harbor freight has them as I recall. The pressure should be approximately 50 psi on that car. If it will not run the pressure would have to drop to 20 or less as it would still try to run with reduced fuel pressure, i.e., idle but stall when put in gear or throttle depressed.

mikeamondo · Post by **mikeamondo** » 24 Jun 2014, 04:24

So, any of the gauges that show up to 100 should have a standard connector that fits the Volvo?

Post by **abscate** » 24 Jun 2014, 05:07

mikeamondo wrote:Ok... sorry if this is a stupid question, but I've never used a pressure gauge before. The units available in-store at Advance & AutoZone are only 15 psi. 100psi units are available online. Then I see a youtube video showing an 04 XC70 at idle and the gauge showing 50 psi... and what the heck are the 7 Bar units about? Bars? Ugh. You've gotta be smarter than the tool and I'm coming up a bit short.

Which gauge will work to check the pressure on this 04 XC70? What number should we see? What is too low and would indicate the pump is bad?
Thanks!
Mike

Mike ..don't sweat the bar, unless you are a lawyer.

1 bar is 1 unit atmosphere pressure or 14.5 pounds per square inch

You might also see kPa on your gauge which is kilo pascals, another unit of pressure set by Swedish Imports.

All data on my 2005 reports fuel pressure should be 375-395kPa and should not fall below 200 kPa 20 minutes after shutoff of engine

1 bar is 100 kPa