2002 XC70 D5 fuel system issues

[henrijeret]

It would be interesting to figure this out. Lost my job and with no money - need to make sense of it without a huge bill from a workshop.

The car is a 2002 XC70 D5 120kw (power has been modified to be higher with a computer)

My problem:
If the tank is full then the car runs fine. Only if I need to accelerate hard, then a significant delay is present (I have owned a volvo with the same motor and everything, the difference is there clearly). Also have seen a report of low fuel pressure when checking codes a couple of times.

After I drive for ~300km without refueling, then the car occasionally shuts down. After sitting for a couple of minutes, then it starts up and I can drive to a fuel station (one time even 70km away).

Recently climbed a steep hill on the highway and the car stopped when I reached the top. After again waiting for a moment - it started right up again and I was able to drive home just fine.

Starting the car after these shut downs is like the fuel lines were empty. Takes a while to get going

Some repairs done recently
New motor (used) and pump (new new) installed 2 years ago.

I have been driving like this refueling after every 200km for a while now. But the hill climb and engine shut down motivated to get to the bottom of this problem once and for all.

I cannot see much wrong visually. There are some small specs of some kind of dirt here and there when I took the fuel out. Could there be a blockage?

It seems like everything runs quite fine as long as the fuel level is above the pump housing edge. Is the car is struggling to get fuel from the bottom of the tank from the other side?

[reggit]

When was the fuel filter last changed? That often gets neglected and blocked causing issues - it's located under the car just infront of the rear wheel on the right side of the car (drivers side in the UK).

If transfer piping was at fault, the car would run OK until just under 1/4 tank of fuel left.

[Longhouse21]

As Reggit says, but could it also be a weak or inoperative in-tank fuel pump?

[henrijeret]

Sure hope it is not the in tank pump as it is not old and do not want to buy another one.

I inspected the lines in the tank and all seems fine . Will check the fuel rail pressure sensor and the PEM unit also. Will do the filter also. It is also2 years old now.

One question though on the inner workings of the fuel tank though.

I added some fuel that filled up the passenger side tank, did not spill over to the driver side yet. But then I ran the pump - should it also transfer fuel to the driver side or not?

[reggit]

Ok, question - are you in a left hand drive car?

When you add fuel, assuming the tank is low, it will fill the right side of the tank first, until it’s just around 1/8-1/4 full, then it will spill over into the other side.

The pump is on the right side of the tank with transfer piping to scavenge fuel from the bottom of the left side of the tank.

I thought only petrol cars had a PEM, may be wrong though.

I’ve heard of issues with the PEM on some cars, but have no experience. There will be information on here though if you search.

It’s also worth swapping out the fuel pump relay on the CEM, in case that’s going faulty.

[henrijeret]

Would a loose + terminal by any chance cause intermittent stalling (with no lights on the dash)? :P Just noticed that my battery terminal is too small for the connector to hold on properly. It does stay on, but loosely.

I have a left hand drive car yes.

[reggit]

Originally Posted by henrijeret

Would a loose + terminal by any chance cause intermittent stalling (with no lights on the dash)? :P Just noticed that my battery terminal is too small for the connector to hold on properly. It does stay on, but loosely.

I have a left hand drive car yes.

A loose battery terminal is likely to cause many strange running issues. First job is to rectify that problem.