Volvo S70 AWD Diagnostic

Post by **Ozark Lee** » 19 Sep 2009, 00:19

The fuel pump and the fuel system is a bit different on the XC / AWD series cars than a standard 850 so I am not speaking from experience.

On the plain'o 850s your symptoms could point to a bad check valve in the fuel pump. The way to tell is to hook up a fuel pressure gauge on the schrader valve, get the car to start, and run, and then turn it off. Take a look at the fuel pressure after the car is turned off. If it falls of rapidly you either have a bad check valve in the fuel pump or a bad fuel pressure regulator.

On the 850's the check valve is integral to the fuel pump assembly which means that you can't just change the pump motor itself to fix it and you need to buy the entire assembly. On the 850s the fuel pressure regulator is vacuum controlled and the diaphragm can breach and not only will it not maintain fuel pressure but it sucks raw gas into the vacuum line. If your fuel pressure regulator is vacuum controlled remove the vacuum line and look for signs of gas in the line itself, it shouldn't be there.

...Lee

pmarinello · Post by **pmarinello** » 19 Sep 2009, 12:09

misha wrote: Fuel pressure at first prime,before starting engine should be 43.5psi-max.At idle is a little lower..about 35-40psi and when you drive with a full throttle(pedal to the floor)43.5psi.

Is this correct, because tomorrow I will test the pressure at the Rail. Also what is the proper way of checking?

Post by **misha** » 19 Sep 2009, 18:57

Yes,it's correct,but everything about 35-40 psi is acceptable.

pmarinello · Post by **pmarinello** » 22 Sep 2009, 13:59

I just tested the fuel pressure with the relay jumped it was 375kpa which is in spec. and the residual value was fine. But then when I used the relay it was 340-355 which is out of spec and residual value is fine. New Relay? or what?

Post by **misha** » 22 Sep 2009, 16:28

With relay jumped...375kpa
With relay not jumped...340-355psi.

Sounds like bad relay to me,but if it's bad you wouldn't be able to start or drive a car.

I would wait for response of any of the moderators,just to be sure.

pmarinello · Post by **pmarinello** » 22 Sep 2009, 22:56

Does anyone have any idea's of what the problem may be?

Post by **Ozark Lee** » 23 Sep 2009, 09:07

Leave the fuel pump relay jumpered and see how it drives. If it behaves then the relay is your problem.

...Lee

pmarinello · Post by **pmarinello** » 23 Sep 2009, 09:28

When I jump the relay the pump runs constantly is that safe I don't want to burn the pump out

Post by **Ozark Lee** » 23 Sep 2009, 11:52

It runs constantly when the car is running anyway.

...Lee

pmarinello · Post by **pmarinello** » 23 Sep 2009, 22:10

Same thing when I pump the relay. What could this possibly be, this is really starting to kill me. I'm starting to run out of ideas.

Volvo S70 AWD Diagnostic

Re: Volvo S70 AWD Diagnostic