Fuel pressure drop when sitting

[JerEazy]

I did some searching first but I want to confirm once more before diving in.

1990 e30 325i - there is no pressure in the fuel line after sitting over night. But there is still fuel in the fuel rail. This leads me to think a check valve issue. But in the later models the check valve should be in the fuel pump, and the fuel pump is new OEM. Is there somewhere a check valve should be? Or should I install and inline one?

FPR and injectors are new as well.

[roguetoaster]

You can add one at the outlet of the pump if you want. I did that on several cars that had newer pumps, but bad check valves for whatever reason.

If you search for HB check valve you should find it, and 5/16" is the most common size that will fit. Just understand the pressure ratings and material compositions listed of the unit you go to buy before you slap it into a fuel system.

[TobyB]

There are lots of places fuel can go- the regulator's easiest to check,
but my 'leak-o-meter' would be rather suspicious of 'new' injectors in this
globally outsourced age.

t
old is not better, but new can be crap.

[JerEazy]

Appreciate that. The additional reason I doubt injectors is it was a problem before them and is still a problem now. So there is absolutely a possibility. But when I remove the fuel I let to the injector rail (or FPR) there is no pressure. But the rail is still full of fuel. Will add a check valve and see

[JerEazy]

dupe post. Sorry

[Gaspa_14]

I had the same issue with my 87 325e. Turns out it was accouple things. 1: I had no check valve 2: my fuel lines were leaking (new metal hard lines fixed it) 3: Fuel pump did not prime. Mine did not prime the fuel pump when the ignition was on, so I had to wire alittle button that would prime the pump when held. (next to the cigar lighter) Make sure no fuel is leaking from your hard lines/rubber hoses all the way up to the fuel rail.

[digger]

if the fuel pressure rises quickly when you jump the pump relay to run the pump then it doesn't matter very much if it very gradually leaks down over time. If the lines are leaking down alot then it would take some time to repressure which is a major leakdown which would cause starting issues