Fuel system problem on a 96 850 R

[aljosa123]

My 1996 850 R recently broke down while I was driving. The throttle became unresponsive and then the car just died. First I checked the fuel rail valve - no fuel. On further investigation I discovered that the fuel pump doesn't work - no buzzing sound no matter what I did, but there was voltage (10,6V) at the fuel pump connector, so that kinda rules out a faulty relay?
After that I had my car towed home, where I took the pump out of the fuel tank, thinking the fuel pump needs to be replaced. But before I ordered a new pump, I wanted to test it, just to make sure that's the problem. I connected the pump to 12V and to my suprise it worked. Then I put the pump back in the car, connected everything and the car started without any problems.

So the problem that I now have is, that I don't know what the problem was and I don't want my car to break down in the middle of the road again.

Fuel pump is actually almost brand new (whole fuel pump assembly). It was replaced last year in april and only has about 4500 km behind, so it seems odd that it would break so soon. Does anybody have any experience with pumps from "professional parts sweden"?

Do you have any idea on what to do in my situation? Or is the only safe bet to replace both fuel pump and relay, to make sure that this doesn't happen again? Could the problem be anywhere else beside relay and pump?

Also this happened on a very hot day with low fuel level in the fuel tank (+/- 12 litres) if that matters in any way?

[matthew1]

When was the fuel filter replaced?

[misha]

You should have battery voltage at fuel pump connector.
10.6v is nothing...i would say that fuel pump relay is bad.

Pro Parts Sweden...why?
Bosch insert is around 100€.

I wouldn't be surprised if that pump is bad.

My friend had a Magneti Marelli pump failed in 2 days.

[aljosa123]

[/quote]

When was the fuel filter replaced?

Fuel filter was replaced exactly 1 year ago. I have done just 2000 km since....

You should have battery voltage at fuel pump connector.
10.6v is nothing...i would say that fuel pump relay is bad.

Pro Parts Sweden...why?
Bosch insert is around 100€.

I wouldn't be surprised if that pump is bad.

My friend had a Magneti Marelli pump failed in 2 days.

Maybe the battery was quite drained at that point...
Fuel relay is possible, but it doesn't explain why it would start working all of a sudden. Between the last atempt to start the car, and when it actually started I hadn't touched it.

It came with the car...
So Bosch is the most reliable option if I decide to replace it?

So it is possible that the fuel pump broke.

[misha]

Fuel pump relay on these cars isn't just a normal relay.
It have some chips,capacitors and electronics inside.

When it starts to misbehave it is doing just that you described.

Sensitive electronics inside is sensitive to high temperatures.When it cooled down it behaved normally.

Only new or used Volvo relay with exactly the same part number can be used.

Beware that there are 3 types of fuel pump relay depending on engine management.
They are also easily identified by colour...Red,yellow and green.
They are NOT interchangeable.

[coop]

Do you hear a buzz from under the dash when you try to start the car. If so it’s the fuel pressure relay. You can jump it to get it running but swapping it out takes 5 mins

[aljosa123]

Do you hear a buzz from under the dash when you try to start the car. If so it’s the fuel pressure relay. You can jump it to get it running but swapping it out takes 5 mins

I don't hear any buzzing besides the normal relay click (on/off).

If I go on the safe side and replace both the fuel relay and fuel pump insert, will that 99% solve my problems or is there anything else that could be problematic? Fuel filter was replaced last year so that should't be a problem, wiring problem?, fuel pressure regulator?, blocked hoses (don't know from what)? Just thinking...

[coop]

It’s worth keeping an extra relay around in the car. I’ve had issues with colder weather and bad relays