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.
- S
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Volvo 850 power loss under hard acceleration Topic is solved
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Re: Volvo 850 power loss under hard acceleration
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.
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Re: Volvo 850 power loss under hard acceleration
Spesc say 3 bar and 2.5 with vacum aplied yo the fuel pressure regulator
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Re: Volvo 850 power loss under hard acceleration
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
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Re: Volvo 850 power loss under hard acceleration
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.
- S
"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.
- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.
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Re: Volvo 850 power loss under hard acceleration
-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.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
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Re: Volvo 850 power loss under hard acceleration
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
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.
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Re: Volvo 850 power loss under hard acceleration
No Codes, And allí vacum la es And intercooler pipong are ok
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Re: Volvo 850 power loss under hard acceleration
Here we go again...Sommerfeldt wrote: ↑Tue Jan 29, 2019 6:28 am ...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

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.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
- misha
- Posts: 4575
- Joined: Sun Dec 07, 2008 4:09 pm
- Year and Model: '97 850 2.5 20v
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- Has thanked: 66 times
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Re: Volvo 850 power loss under hard acceleration Topic is solved
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
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- Posts: 37
- Joined: Sat Jan 19, 2019 2:50 am
- Year and Model: Volvo 850 T5 1993
- Location: Valencia
- Been thanked: 2 times
Re: Volvo 850 power loss under hard acceleration
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
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