Volvo 850 power loss under hard acceleration Topic is solved

Jaumme · Post by **Jaumme** » 19 Jan 2019, 03:52

My 1993 Volvo 850 t5 is losing some power in hard acceleration when you go full throttle the car pulls normally for about 2 seconds then hesitates a lose the power it keeps pulling but like half the power. I checked the vacum lanes from the turbo thenintercoler piping and its ok the tcv works properly but I unplugged it and thest drive the car and just did the same thing. The car has 63k kilometes. No codes and no engine light the car runs of except for that, if u accelerate gently the car keeps going but if u go hard on throttle it does that, what shoud I look for?

Post by **abscate** » 19 Jan 2019, 07:33

Please don't use text talk on MVS

It does sound like your turbo is the fault if disconnecting the valve doesn't change operation

There is a diaphragm in the turbo valve which can develop leaks. The other thing to check is the waste gate adjustment. I'll find and link to it.

WhatAmIDoing · Post by **WhatAmIDoing** » 20 Jan 2019, 17:30

Have you kept up with regular maintenance, i.e. sparkplugs, cap and rotor, fuel filter?

Jaumme · Post by **Jaumme** » 26 Jan 2019, 03:53

Yes i did, yesterday i tested the fuel pressure and im getting 2.15 bar with ignition and 1.75 bar with the motor running if u accelerate y can clearly see the pressure going down, y tested disconecting the vacum Lane of the fuel pressure regulator and with the motor running un geting 2.35. so o guess fuel pump os weak? Or What sugest?

Post by **Clemens** » 26 Jan 2019, 16:07

did you relace the fuel filter? if yes, the pump might be on it's way out

Sommerfeldt · Post by **Sommerfeldt** » 27 Jan 2019, 04:56

Clemens is right - 1.75 bar is far too low. Your pump is supposed to deliver at 3 bar, so even your baseline is almost 1 bar low. Check your fuel filter - or just replace it outright. Can't hurt. If it doesn't help, you need to pull the fuel pump and see what's going on. An okay pump without the armature isn't too expensive, and you really can do the job in about 90 minutes if you've never done it before (plus YouTube/MVS research time

).

- S

Jaumme · Post by **Jaumme** » 27 Jan 2019, 05:11

I replaced de fuel filter and the pressure keeps the same, i already ordered a new pump

Jaumme · Post by **Jaumme** » 28 Jan 2019, 07:42

Today i tested fuel pressure again with a diferent gauge, this new gauge shows 2.5 bar with the engine running and while driving atte Max load It Falls to 2.10 bar at 5000 rpm.
When the power losing occurs the pressure keeps at 2.5 bar. What shoud i look for now?

Sommerfeldt · Post by **Sommerfeldt** » 28 Jan 2019, 07:53

You’re still a bar short. I’m not sure what kind of injectors you have in there, but your ECU is expecting a certain flow rate at a certain pressure. If the pressure is down, fuel flow is low, and then power will be down. For example, some models of x70 came with blue injectors, some with white. Those were basically the same injectors, but operated at differing pressure, making the flow significantly higher in one than the other.

Did you swap out the pump already, or are you still waiting for it?

- S

Jaumme · Post by **Jaumme** » 28 Jan 2019, 07:57

Im still waiting for the new one, but according to the specs the correct pressure is 2.5 bar