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Volvo 850 power loss under hard acceleration Topic is solved

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Sommerfeldt
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Re: Volvo 850 power loss under hard acceleration

Post by Sommerfeldt »

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
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.
Jaumme
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Re: Volvo 850 power loss under hard acceleration

Post by Jaumme »

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

Post by Jaumme »

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

Post by Sommerfeldt »

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
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.
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misha
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Re: Volvo 850 power loss under hard acceleration

Post by misha »

Jaumme wrote: Mon Jan 28, 2019 7:57 am 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.
'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
Sommerfeldt
Posts: 1143
Joined: Tue Jul 29, 2008 1:25 pm
Year and Model: 1996 850 T5
Location: Oslo Area, Norway
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Re: Volvo 850 power loss under hard acceleration

Post by Sommerfeldt »

misha wrote: Mon Jan 28, 2019 6:41 pm
Jaumme wrote: Mon Jan 28, 2019 7:57 am 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?

- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.
Jaumme
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Re: Volvo 850 power loss under hard acceleration

Post by Jaumme »

No Codes, And allí vacum la es And intercooler pipong are ok
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misha
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Re: Volvo 850 power loss under hard acceleration

Post by misha »

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
Here we go again... :mrgreen:
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
User avatar
misha
Posts: 4575
Joined: Sun Dec 07, 2008 4:09 pm
Year and Model: '97 850 2.5 20v
Location: Serbia
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Re: Volvo 850 power loss under hard acceleration  Topic is solved

Post by misha »

Jaumme wrote: Tue Jan 29, 2019 6:31 am No Codes, And allí vacum la es And intercooler pipong are ok
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'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
Jaumme
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

Post by Jaumme »

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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