FPR pressure acts funny

[sebch]

Hi,

Next step in my quest for a long-lasting FPR (the "oh God that one's gone after three days, hope the next one on the shelf is the one!!" kind of quest...), I've put a Bosch FPR that says 0 280 160 213 and I hope the 13 makes me lucky! When I look around on the net, I find that this unit is rated at 3 bars. When I measure the fuel pressure on the car (engine off), I get 3.2 bars with the pump on, then when it stops, pressure goes down to 2.8 and slowly back up to 3 bars, where it remains until I unhook the gauge.

As the last rest-in-peace-FPR (3 days on the car!!) was also rated at 3 bars but was measured at 3.5 with the pump on and 3.2 with the pump off, I'm wondering if this is normal or if it's a sign of wear from the FPR?Also, could it be sth else in my fuel system that causes the overpressure?

Now another question: do I use 3 or 3.2 bars as the value for calclation my new flowrate?

Thanks, Séb

[Jim]

Regulators Failing ???? Huh ???

How are they failing ? this is really unusual , are you running a turbo ?
Maybe you have a defective "Pulsation Damper" they used to go out
pretty regular back in the 1980s .
Maybe bad "Check Valve" in the fuel pump not holding residual pressure ?

Fuel calculations are done at the pressure created with the pump running
and no engine vacuum attached to regulator (100 kPa) .

[sebch]

Hi Jim,

The to units have ben declared dead yhen I noticed fuel going up the vac line to the intake manifold... this has sth to do with the rubber membrane letting fuel throughm I guess.

I'm running the fuel system without a damper in the line, maybe I should and this could help??

Thanks, Seb

[Jim]

A Fuel Pusation Damper is mostly for reducing noise when you have
a "Roller" type pump , it's not going to solve this problem .

He's what to do , disconnect your supply and return lines from the
Fuel Rails , next get a guage with a tee fitting sized to fit your lines ,
connect your supply and return lines to this tee with proper clamps .

DO NOT SPILL ANY GAS ON A HOT ENGINE , LET IT COOL .
yes , I've done it , it's not pretty .

Start your Fuel Pump , if you get more than 3 to 4 psi then your
return line is restricted somewhere , fix it .

Roller type fuel pumps can easily create 150 to 200 psi if you
pinch off the return line .

If you don't have a problem with this test and you are using
a stock regulator , the only thing I could tell you is you'll have to
go with an aftermarket adjustable Turbo/Blower regulator .
If you do this make sure it's a "Bypass" style regulator that sends
excess fuel back to the tank and that it has a connection for
manifold vacuum .
Lots of places that sell Turbo and/or Blower Kits have these , they
quite often have Stainless Steel Diaphrams that won't blow out .