S40: Car cuts out after tank reaches 40L of fuel

[Syked69]

Hi Everyone,

I have a 1999 S40 B4204T and I've been experiencing a problem where the car will cut out after the tank reaches 40L of fuel. After the car cuts out, sometimes it wouldn't start again until more fuel is poured but other times it will start after several attempts.

Initially the problem was evident when the tank reached 20L and progressively got worse and worse. Up until now I was just pouring fuel before it got to 40L on the gauge and the car works normally with a full tank but I think it's time to fix it.

With a full tank, I've checked the pressure at the rail and it's 310 kPa as per the specifications. Residual pressure is ok too and only losing approx 10 kPa after an extended period. I've also checked the pressure at the filter and that is was approx 450 kPa which again is within spec.

When the car wouldn't run / start I checked the pressure again both at the rail and at the filter but this time the results were very different. At the rail the pressure was 110 kPa and at he the filter the pressure was 550 kPa

I've already swapped out the rear pressure regulator (fuel governor - part 30851005 which is a essentially OEM Weber RPM73) based on the troubleshooting steps in VIDA but that had no impact on fixing the issue.

I did a scan with VOL-FCR and there was a DTC and the description said "short-term fuel trim changing too quickly". I can't remember the code through.

The fuel filter was changed earlier this year and I've done about 10000 KM since.

I was thinking of changing the front pressure regulator it but it doesn't make sense that it will fail only under specific conditions.

The next thing I was thinking of doing is to take out the pump and sender unit to check for any blockages and give it a good clean or even changing the filter on the bottom of the send unit.

What are your thoughts?

[Matt86]

I'd start looking at the pump, as at least you can inspect the inside of the fuel tank as well then.

[Clan]

Originally Posted by Syked69

Hi Everyone,

I have a 1999 S40 B4204T and I've been experiencing a problem where the car will cut out after the tank reaches 40L of fuel. After the car cuts out, sometimes it wouldn't start again until more fuel is poured but other times it will start after several attempts.

Initially the problem was evident when the tank reached 20L and progressively got worse and worse. Up until now I was just pouring fuel before it got to 40L on the gauge and the car works normally with a full tank but I think it's time to fix it.

With a full tank, I've checked the pressure at the rail and it's 310 kPa as per the specifications. Residual pressure is ok too and only losing approx 10 kPa after an extended period. I've also checked the pressure at the filter and that is was approx 450 kPa which again is within spec.

When the car wouldn't run / start I checked the pressure again both at the rail and at the filter but this time the results were very different. At the rail the pressure was 110 kPa and at he the filter the pressure was 550 kPa

I've already swapped out the rear pressure regulator (fuel governor - part 30851005 which is a essentially OEM Weber RPM73) based on the troubleshooting steps in VIDA but that had no impact on fixing the issue.

I did a scan with VOL-FCR and there was a DTC and the description said "short-term fuel trim changing too quickly". I can't remember the code through.

The fuel filter was changed earlier this year and I've done about 10000 KM since.

I was thinking of changing the front pressure regulator it but it doesn't make sense that it will fail only under specific conditions.

The next thing I was thinking of doing is to take out the pump and sender unit to check for any blockages and give it a good clean or even changing the filter on the bottom of the send unit.

What are your thoughts?

The fuel level is the critical thing here , which indicates a problem in the fuel pick up area in the swirl pot . I wouldnt mess around i'd just replace the whole fuel sender/pump/pick up assembly .. Turbo pumps can play up over 100000 miles .

[Syked69]

Thanks guys. I'll order a new complete fuel pump assembly.

[Syked69]

Just thought I'd close the loop and provide you all an update. Well I changed the complete fuel pump assembly and the problem hasn't returned so I'm guessing the pump was just getting lazy.

[Syked69]

So a few months after changing the sender unit, the problem has returned. Could the new pump become faulty so soon or is something causing them to fail. I have another S40 which also has the same problem.

[DXMachina]

is there a sock or similar over the pickup that could be part blocked?

[Dancake]

I had the same issue with my S40 before I sold it. I had discovered diesel bug in the fuel filter, which led me to believe this had something to do with it. I will be treating my old car next week with Marine 16 to eliminate the bug. This will also rule out the bug as a cause if the car still stops after treatment. Did you inspect the tank when you changed the sender unit for water and sediment?

[Syked69]

Originally Posted by DXMachina

is there a sock or similar over the pickup that could be part blocked?

There is a filter right on the bottom of the sender unit as well as filter on the the actual pump itself and neither are blocked. Both still look new like I installed the sender unit yesterday.

[Syked69]

Originally Posted by Dancake

I had the same issue with my S40 before I sold it. I had discovered diesel bug in the fuel filter, which led me to believe this had something to do with it. I will be treating my old car next week with Marine 16 to eliminate the bug. This will also rule out the bug as a cause if the car still stops after treatment. Did you inspect the tank when you changed the sender unit for water and sediment?

These cars are petrol so I'm pretty sure I can rule out diesel bug? Yeah the tank looks clean enough (noticed small scattered particles) which I would have thought will be filtered by the sender unit filter but as above they're still clean. Didn't find evidence of water in the fuel.