Position II fuel pressure - 1999 V70XC

[bcfischer]

No. Valve stem seals have no relation to fuel pressure.

Possible causes

Fuel pump relay
Wiring
Low voltage to pump
Fuel pump/ integral check valve
Fuel filter
Leak in fuel lines

Abscate: Thank you for your quick and thorough response. Addressing your possible causes (numbered below), is my analysis generally correct in that:

1) Fuel pump relay
2) Wiring
3) Low voltage to pump
4) Fuel pump/ integral check valve
5) Fuel filter
6) Leak in fuel lines

5 (if a leak and not a clog) and 6 would result in fuel leaking from the fuel system and ending up outside of the fuel system, like on the ground or puddled somewhere in the car. [it's not leaking onto the ground, I can't see it puddling in the car, and the plastic skid shield under the fuel pump is still off.]

Either 2 or 3 (and 5 whether a clog or a leak) would result in decreased pressure both pre-ignition with the key in the key II position AND with the engine running. [The car turns over more or less normally if I wait for the fuel pump to charge up and then stop, turns over longer than normal if I just turn the key right through key II to ignition, and, after ignition, runs rock solid at 58-60psi, even at idle.]

As to 1, how long should the fuel pump relay allow the pump to run prior to shutting the pump off? Mine runs for maybe a long second. Is the relay designed to provide full voltage for a specified period and then a lower voltage (enough to hold pressure but not enough to spray gas all over the place in the case of a crash), or is it on at full voltage for a short period of time and then off until it detects that ignition has commenced?

As to 4, what is happening really kind of seems like a a failing check valve, as the pressure is dropping, but the fuel isn't leaving the system or going into one or more cylinders, resulting in a momentary super-rich condition at startup. Is the integral check valve integrated into the pump module itself(the silver part), or into the pump housing complex (white plastic tub with a filter on one end and tubes going up to the flange that is locked by the fuel pump ring as the fuel lines leave the tank)? Does the check valve (if operating properly) ever allow the system to depressurize from operating pressure after the engine is shut off, or is the system from the check valve to the fuel rail supposed to always be at +/- 57 PSI unless you depressurize the system at the fuel rail schrader valve?

Thanks in advance and in retrospect for your guidance,

Brian

[abscate]

The fuel pressure spec has both a running spec of52 psi and a spec after 30 minutes of something like 25 psi

I think there is a link to the actual spec in Elizabeths maintenance thread, at the link below in my sig, look around April 2017 for an entry on this

[bcfischer]

The fuel pressure spec has both a running spec of52 psi and a spec after 30 minutes of something like 25 psi

I think there is a link to the actual spec in Elizabeths maintenance thread, at the link below in my sig, look around April 2017 for an entry on this

Thanks Abscate! I found the entry. You have done your fair share of maintenance on that car and documented it well. I have a bad habit of finishing a project and then deciding that I should have taken 'before' pictures.

Given those specs, I am beginning to doubt the fuel relay. When I turn the key to the Key II position, the pressure gets to about 20-25 PSI and then backs off very quickly, like within seconds, down to 5-10 PSI. These are pressures at the rail.

Marvin (named by another daughter) the V70 XC is heading across the UP to Marquette for my daughter in less than a week. If I wait for the pump to prime and then stop, and THEN turn the key to the key III position, it starts predictably well, so this is probably a project that can wait until the semester ends, before Thanksgiving, (a nod to COVID) to work on. I do plan to do a transmission fluid replacement (overdue) and new front rotors to see if I can clear a front ABS sensor code/condition before I drive it out.

I have the pump housing that I pulled out with the bad pump module, I will probably rebuild it with a new module, and bench test it for pressure and check valve integrity and hope and expect that she returns the car with so little gas that it won't spill on my head when I pull the current pump out. I have decided that a spare fuel pump/assembly is a good thing to always have on hand for this car.

Take care and stay safe,

Brian

[abscate]

There are better feelings in theworld for aDad than wrapping up a college bound young lady in the Swedish Armor. I think we have some members in Milwaukee area too!

I haven’t measured my bleed down time in a while , I’m still on my original 1999 fuel pump and relay

[misha]

...If I wait for the pump to prime and then stop, and THEN turn the key to the key III position, it starts predictably well...

Then there is no problem.
The system is designed to work like that.

You need to prime it(turn the key in pos.II and wait 2sec untill fuel pump stops),then start the car.