Volvo 850 power loss under hard acceleration Topic is solved

Sommerfeldt · Post by **Sommerfeldt** » 28 Jan 2019, 08:01

Hmm. Which specs are those? All the “stock” fuel pumps I’ve seen deliver 3 bar for 850s. Some X70 models have higher specs, but I can’t remember seeing lower.

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Jaumme · Post by **Jaumme** » 28 Jan 2019, 08:04

Spesc say 3 bar and 2.5 with vacum aplied yo the fuel pressure regulator

Jaumme · Post by **Jaumme** » 28 Jan 2019, 08:19

Its strange to me because the car pulls ok for 2 seconds and then u feel a clean cut un the power deliver i mean the power loss is not progresive and the car keeps pulling like a 150hp car

Sommerfeldt · Post by **Sommerfeldt** » 28 Jan 2019, 14:54

Again, I don't know which "specs" those are. The greenbook says nothing about pressure going down when there's vacuum connected to the FPR. The testing procedure for fuel pressure only says this:

"Turn ignition on. Fuel pump should start. Fuel filler
cover can be removed to determine whether main pump is operating. Fuel pressure should be about 43.5 psi (3.06 kg/cm )."

There's also further points to that procedure, in order to troubleshoot, but only says to not let pressure exceed 86 psi. Nothing about lower pressure than 3 bar being normal.

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Post by **misha** » 28 Jan 2019, 18:41

Jaumme wrote: 28 Jan 2019, 07:57 Im still waiting for the new one, but according to the specs the correct pressure is 2.5 bar

-43.5psi(3 bar)on 1st prime,without starting the engine
-around 35psi (2.4 - 2.5 bar)at idle
-again 43.5 psi(3bar) at WOT in high rpm.

Sommerfeldt · Post by **Sommerfeldt** » 29 Jan 2019, 06:28

misha wrote: 28 Jan 2019, 18:41
Jaumme wrote: 28 Jan 2019, 07:57 Im still waiting for the new one, but according to the specs the correct pressure is 2.5 bar
-43.5psi(3 bar)on 1st prime,without starting the engine
-around 35psi (2.4 - 2.5 bar)at idle
-again 43.5 psi(3bar) at WOT in high rpm.

I don't think that's entirely accurate... Pressure IN should still be 3 bar, not 2.5. Then some of that is returned when it's idling and should correspond to vacuum. So if you're never getting 3 bar, or it at some point drops below 2.5, then something's amiss.

A clean cut in power means either there is a fuel issue or an air issue. Is it not setting any codes at all?

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Jaumme · Post by **Jaumme** » 29 Jan 2019, 06:31

No Codes, And allí vacum la es And intercooler pipong are ok

Post by **misha** » 29 Jan 2019, 06:48

Sommerfeldt wrote: 29 Jan 2019, 06:28 ...I don't think that's entirely accurate... Pressure IN should still be 3 bar, not 2.5. Then some of that is returned when it's idling and should correspond to vacuum. So if you're never getting 3 bar, or it at some point drops below 2.5, then something's amiss.

A clean cut in power means either there is a fuel issue or an air issue. Is it not setting any codes at all?

- S

Here we go again...

Fpr is dictating what fuel pressure would be in the system...not the pump.
Fpr is vacuum controlled...that said....pressure varies as vacuum varies....Fuel pressure is not steady in all running conditions.
It's not exactly 2.4-2.5 bar at idle...i said it's AROUND 2.4-2.5bar at idle...BUT it MUST be 3 bar at 1st prime before starting the engine and wot on healthy fuel system...although everything around 35psi is acceptable.
You would have constantly 3 bar pressure in all running conditions ONLY if vacuum line from FPR is disconnected and engine side plugged.

Post by **misha** » 29 Jan 2019, 07:13

Jaumme wrote: 29 Jan 2019, 06:31 No Codes, And allí vacum la es And intercooler pipong are ok

Jaumme · Post by **Jaumme** » 29 Jan 2019, 07:27

i will follow these procedures today, but with the ignition pressure was lower than 2 bar And when i started the engine the pressure rised quickly to 2.5 bar