1998 V70 xc awd fuel pressure

[farmshop]

the local Volvo dealer diagnosed fuel pressure loss over night as the reason for hard starting, a leaking check valve at the pump. They want $1500 to replace the pump which works fine. Car runs well once started. Why can't I install a Russel check valve inline between the injector rail and the pump to hold pressure when stopped?

[rmmagow]

Wouldn't it start fine if you let pressure build up? Maybe keyon, keyoff, keyon a couple of times in the morning? I always thought it bled down overnight anyway. The real test is to see if you still have pressure about 20 minutes after shutdown (I think). Quick drop to 0 yeah, there's a check valve issue but overnight to zero, I don't think that's really a problem. Hopefully one of the more astute folks here will chime in.

[farmshop]

Tried the key on off, NG. Does bleed off in 20 min, not every time but mostly so.

[MilehighV70XC]

You can install a check valve anywhere but the closer to the pump the better. If you put the valve in the engine bay it will lose pressure behind the valve to the pump in the tank. I put my in the rear pass. wheel well area.
https://www.matthewsvolvosite.com/forums ... =1&t=57821
I put it where the piece with the schrader valve is. I cut the hose between the valve and hard line and used some 5/8 fuel hose and a hose clamp to connect the CV to the hard line. Cut the outer rubber and then carefully cut the nylon hose off of the hard line.

[Klausc]

The check valve is to keep gasoline from flowing backwards into the tank when the pump is off. It has nothing to do with pressure. If the fuel line empties overnight, it will take more than a couple of seconds to fill the line with gasoline. So the installation of a check valve needs to be as close to the pump as possible.

It is 'normal' to loose pressure at engine shutoff, it is not normal for fuel to drain back into the tank via the pump.