Fuel pressure regulator question....99 volvo v70xc

[bcfischer]

Fuel pressure at the engine fuel rail is 42 psi for ME7 cars like the 99 XC

Fuel pressure at the pump after filter is 55 psi spec, before the FPR

The FPR moved around a bit on 98 99 00 models and can be left rear wheel, or on top of the tank, requiring an axle drop to access

Thank you! That helps me reconcile the various sources that spec the pump at 55PSI with the sources that tell me that pressure at the rail should be more like the low 40's.

Brian

[erikv11]

…

The FPR moved around a bit on 98 99 00 models and can be left rear wheel, or on top of the tank, requiring an axle drop to access

True that’s the overall description for p2 x70 cars but in this thread viewtopic.php?t=94869 jimmy57 says 99xc70 has it at left rear wheel, told same OP to look there.

bcfischer did you look aft of the rear wheel, and it’s not there? Definitely start there. Good idea to look now not wait another few years!

[erikv11]

Is the engine not running well and if so, what are the symptoms?

A hard negative on the running well. Right now it's not running at all. It seems that the ECM is convincing itself that it is running lean at idle and low RPM and, as a result, forces itself to run rich, causing erratic misfires (not always the same cylinder) and spark plug fouling with a black carbon. When I could get it to run, It would experience very poor power response, especially on any form of an incline, until it got to a bit above 2K RPM, where the pitch of the exhaust would change to a more normal acceleration sound and the motor would rev further more normally.

I unplugged the battery to reset the fuel trim to default and will be cleaning the spark plugs as soon as I can get the two remaining valve cover screws off that my non-Volvo mechanic stripped when he was looking at it. (I'm sure that the T-25 screws absolutely required an impact driver...).

The front O2 sensor has been throwing codes for years. I have a replacement and hope that I can get under there to swap it out. Last year I pulled the prop shaft off after it failed in the middle of the night in the middle of the UP of Michigan when my daughter was driving home from college. I'm hoping that the absence of the prop shaft makes it easier to get leverage on the O2 sensor.

My first suspicion would be a leak in one of the turbo air induction hoses. Are they squishy? Check all connections carefully.

[bcfischer]

Thanks, @erikv11! I will check that tonight.

[wizechatmgr]

Thanks, @erikv11! I will check that tonight.

When you get a moment, try checking your coolant temp sensor's resistance and see if it's in spec for your current ambient temp. Every once in a while these fail in such a way that the car will generally run extremely rich or not at all...

[Maestrours]

Fuel pressure at the engine fuel rail is 42 psi for ME7 cars like the 99 XC

Fuel pressure at the pump after filter is 55 psi spec, before the FPR

The FPR moved around a bit on 98 99 00 models and can be left rear wheel, or on top of the tank, requiring an axle drop to access

Hi abscate,
My '00 XC is at 56psi at the injector ramp.

[bcfischer]

Thank you, both @wizechatmgr and @Maestrours!

I will check that ambient air temp sensor. During one especially bad drive, I noticed that it was reading an ambient air temp higher than it has ever been in Minnesota, like 133F. The next time I started it, it still ran bad, but the ambient air temp was more normal. I have a suspicion that some errant reading is throwing the fuel mapping off, perpetuating a bad situation.

Brian

[scot850]

The air temp gauge that shows the ambient temp on the dash is not related to the engine controls. There is a 2nd identical part on the RHS of the grille under the car. In some it clips into the side of the slam panel opening for the grill, others it is on the RHS of the air guide plastic panel under the car. That is the one the engine uses to gauge outside temps.

Neil.

[abscate]

That sounds like a classic induction leak Brian. Go back and follow all the big fat pipes ftom the turbo onward looking for loose clamps, splits, etc. Inspect the throttle body connections with a mirror , finally you might have to smoke test the intercooler for splits or holes ( there is small drain hole at the bottom which is ok)