FASS Owners, CHECK YOUR PRESSURE!!!

[steved]

Well... thought my guage was a POS... turns out the THIRD FASS SPRING is a POS... and the fourth... grrrrr!



I'm trying to keep a steady pressure of around 12psi... all I'm asking... IS THIS TO MUCH TO ASK FROM THE MAKERS OF THE FASS?????????



Here's the entire story:



Got my FASS 95/150 in Nov 2005... holding 25psi out of the box (WHY?)... bought a 12psi spring the next day to get the pressure down... had 13psi with the new spring...



12psi spring is in for less than 8k and pressure is running around 5psi by the guage (3inches from the CP3) when I arrive in NM, 2500 miles from home... have a spring overnighted to replace this failing spring (found broken in half during replacement)... got two springs delivered just to be safe, a 12psi and 17psi... replaced with the broken 12psi and pressure was back up to around 10psi... figured it was a bad/failing guage...



Well, pressure has been up and down for no reason for about 10k... finally this weekend it was down to 7psi... got a snubber to prevent another guage from dying... replaced the "failed" guage with a known working guage... still 7psi... check the old guage, 7psi... ????... so now I have ruled out the guage being bad by using a regulated pressure source to check both guages...



So, I figure I better change to the spare 17psi spring just to be sure... NOW I HAVE 24PSI!!!!!!!!!!!!!!!!!!!!!!!!



So now I will need to order yet ANOTHER SPRING to get the pressure hopefully at 12psi... is it too much to ask to have a little quality control... 25psi out of the box for a 95/150, a broken 12psi spring, a weak (failed) 12psi spring, and now a 17psi spring that's holding 24psi... ?



I guess I better get stock in DPP's spring supplier so that I can at least make money as I'll be buying a new spring every 3 months...



So if you own a FASS, check your pressure... if you don't have a guage, better check your pressure... you might have too much pressure or not enough...



steved

 

[thekidfan]

Sad to hear, really sad when you concider there new pricing increases! Yet they're still 3-4 weeks B. O.

 

[Beach]

What would be to much pressure? I have a 95gpm and just installed my fuel pressure gauge fri. It's at 20psi at idle and full throttle drop's to about 12psi and no lower! That seem's pretty good to me but I don't know!

 

[steved]

What would be to much pressure? I have a 95gpm and just installed my fuel pressure gauge fri. It's at 20psi at idle and full throttle drop's to about 12psi and no lower! That seem's pretty good to me but I don't know!

It is all preference with the CP3... I prefer staying somewhat close to stock... which is around 12psi... but I know guys on here are pushing 25ish without issues...



The VP44 is a little more sensitive... I believe what I read was 14psi ideal, 11 to 16 is OK... any less and you stress the piston (crack the diaphragm)... any more and you stress the piston (crack the diaphragm)...



steved

 

[Highfinance97]

What would be to much pressure? I have a 95gpm and just installed my fuel pressure gauge fri. It's at 20psi at idle and full throttle drop's to about 12psi and no lower! That seem's pretty good to me but I don't know!

I have a 150 FASS on my 12valve running straight to the injection pump And i believe i need atleast 25-30 PSI to the pump so i shimmed my spring using a . 065 washer, my PSI went from 15 to 27 so im happy.

I asked diesel dan if i could bump the PSI and here is his quote



"I think you can get up to around 30 PSI and be just fine. I have done some testing and found that the amperage will be under, if not, just a bit over ideal. This is about the limit of the EM-1001 (Small motor and the 150 GPH Gerotor)"



Michael

 

[BradyWilliams]

When you go over 20psi on a 24v 2nd gen. you change the pump calibration. As you keep going higher in supply pressure, you will raise the internal transfer pressure to a critical range, that will cause pump failure due to siezure. Any and all rotory pumps have a maximum pressure that it will sieze at. When you increase supply pressure more and more you will increase transfer pressure. This also happens when you keep increasing RPM. More RPM makes more transfer pressure and siezure can happen. Thanks

 

[Big P]

Isn't a cp3 pump a rotary pump also? Do the same rules about pressure apply to a stock cp3?

 

[Moose]

The CP3 is a piston pump with a small gear pump ahead of it... . With my FASS 150 I see around 20 psi at idle and have yet to pull it below 18 at WOT... .





Moose

 

[Big P]

This was taken from the service manual for my 05. Check out the last paragraph.



OPERATION

The fuel injection pump supplies high pressure to the fuel rail independent of engine speed. This high pressure is

then accumulated in the fuel rail. High pressure fuel is constantly supplied to the injectors by the fuel rail. The

Engine Control Module (ECM) controls the fueling and timing of the engine by actuating the injectors.

Fuel enters the system from the electric fuel transfer (lift) pump, which is located in the fuel tank. Fuel is forced

through the fuel filter element and then enters the Fuel Pump/Gear Pump, which is attached to the rear of the fuel

injection pump. The Fuel Pump/Gear Pump is a low-pressure pump and produce pressures ranging from 551. 5 kpa

(80 psi) to 1241 kpa (180) psi. Fuel then enters the fuel injection pump. Low pressure fuel is then supplied to the

FCA (Fuel Control Actuator).

The FCA is an electronically controlled solenoid valve. The ECM controls the amount of fuel that enters the highpressure

pumping chambers by opening and closing the FCA based on a demanded fuel pressure. The FPS (Fuel

Pressure Sensor) on the fuel rail provides the actual fuel pressure. When the actuator is opened, the maximum

amount of fuel is being supplied to the fuel injection pump. Any fuel that does not enter the injection pump is

directed to the cascade overflow valve. The cascade overflow valve regulates how much excess fuel is used for

lubrication of the pump and how much is returned to the tank through the drain manifold.

Fuel entering the injection pump is pressurized to between 300-1600 bar (4351-23206 psi) by three radial pumping

chambers. The pressurized fuel is then supplied to the fuel rail.

 

[monkeyman]

Cutting the spring is easier!

Rick