At key on my fuel pressure is @ 46psi (priming)
At engine on my fuel pressure is @ 43psi (idling)
At shutoff my fuel pressure is @ 40-43psi (off)

It drops VERY SLOWLY after that.
Approx an hour later its @ just under 30psi and appears to still drop slowly
Approx an hour and 40min later its @ about 10psi
Approx 2 1/2 hours, its @ about 5psi
By morning its @ 0psi

Can someone tell me what fuel pressure should drop to at a minimum? Are these numbers normal?
i.e. - Should it drop to 0 after sitting over night? Or is this evidence that theres a problem?

 

No it shouldn't drop to 0.
It should drop maybe 10 PSI then hold.
Maybe your fuel pressure regulator is bad.
Also the fuel pump has a check valve in it that goes bad sometimes.
Are you 100% sure you have no leaks?

 

I've never heard anyone that can CONFIRM this. The VOLVO tech books say that it shouldnt drop more than a certain ammount WITHIN 20minutes.
It doesnt tell you what is allowable overnight. I know of all the possible leak points. I'm WAY beyond that right now. Just curious if someone can show me in writing where it says it should hold pressure....or if someone runs a test on THEIR PERSONAL CAR and show that it drops a bit then holds firm overnight.

 

Are you having any starting problems?

Long cranking, rough running on start-up?

What I've found that if it is leaking down, it's likely an injector leaking.

To verify, you can pull the injector rail with the injectors and fuel line attached. Just pull it about an inch away from the maniold, and feel under each injector, you shouldn't have any fuel on the tip of the injectors.

You can put a paper towel under the injector tips, turn the key to the on position to energize the pump, turn it off, and watch for and drips on the paper towel.

This problem will normally show up as a long cranking and rough running when the engine is warmed up.

B

 

yes that is my symtoms. I did all the tests already. only thing I found possibly is a less than perfect flat seal where the injector meets the rail. I'll probably replace them all soon.

FYI -

Official response from 2 Volvo Shop Formen :

Completely normal for a 96 850 to drop to 0 overnight.
Idealy it would hold around 10-14psi, but its completely normal of a car that age to drop to 0 by morning.

These numbers are normal:
Approx an hour later its @ just under 30psi and appears to still drop slowly
Approx an hour and 40min later its @ about 10psi
Approx 2 1/2 hours, its @ about 5psi
By morning its @ 0psi

If theres a real problem, the pressure will drop a lot faster.

Good to know! B)