Fuel pressure increasing??

[bsnemt]

So, I've had a FASS 95 installed on my truck for over a year now. It still has the original filter and separator on it with about 10000 miles racked up. My issue is the fuel pressure gauge originally started at 17-18 psi from the NPT fitting on the FASS pump and stayed put for a good chunk of time. Recently, about 4 mo ago, the pressure gauge suddenly read 22psi and again stayed that way. The gauge is the electrical ISSPRO’s EV² Series. Now, three days ago the gauge suddenly reads 30psi and yes, it stays put!

The gauge resets with every engine start and does move ever so slightly as it normally always has. I'm just confused and concerned about why the ever increasing change in psi? The FASS pump sounds normal to me and the truck runs strong. My rail pressure gauge, also an ISSPRO EV2, works great and pressure is normal across the power band. My only thought is that perhaps the filters are dirty. However, shouldn't I be expecting a decrease in psi from the FASS pump and/or poor performance? Could the NPT sensor be bad/clogged? Wiring?

Anyway, thanks for the thoughts and ideas all...

 

[MMeier]

My $$$ would be on a bad sensor . Electrical, correct ?

 

[bsnemt]

My $$$ would be on a bad sensor . Electrical, correct ?

Yes, electrical is fine. After all it worked great for about a year. Actually it still does work well, it's just off by a few psi. Unless the FASS gets better with age !!

 

[MQuirin]

Your pressure sender is on the FASS unit itself? Is that reading pressure before or after the filters?

 

[bsnemt]

Your pressure sender is on the FASS unit itself? Is that reading pressure before or after the filters?

Yes the sensor is on the FASS in the pretapped location. My assumption (never a good idea) is that its after the filters. I say this only because of where the NPT tap is in comparison to the discharge port. Plus I got figure that post filtering psi is what everyone would want to know. Unless someone knows why prefilltering psi would be important to watch.
Thanks for everyones' thoughts...
Stay tuned, changing filters today and inspecting the sensor...

 

[cerberusiam]

You need to move the pressure sensor to the CP-3 inlet to have a good reading on your downstream filters. If you tapped the eletrical sender right onto the FASS the vibrations have probbaly damaged the sender. You need to isolate the sender from ANY vibration source or the senders suffer early failure.

 

[bsnemt]

Yep, sensor is probably shot! All new filters and removed old sensor for inspection/cleaning and now gauge is pegged at 40psi max. Thanks for alls' help!
Anyone know where else to get just the replacement sensor for the electrical ISSPRO's EV² Series gauge? Or just at the source at ISSPRO?

 

[TCDiesel]

Move it to the CP3 as cerb mentioned, this way you have another touch tone if the gear pump or COV is starting to fail. also lower your pressure below 15psi for everyday use.

 

[Yo Hoot]

Move it to the CP3 as cerb mentioned, this way you have another touch tone if the gear pump or COV is starting to fail. also lower your pressure below 15psi for everyday use.

How do you mount a sensor at the CP3 pump?

How do you regulate to 15 psi?

Thanks.

Mike

 

[cerberusiam]

How do you mount a sensor at the CP3 pump?



How do you regulate to 15 psi?



Thanks.



Mike

Easiest way is a tapped banjo bolt and a grease gun hose for an isolator. If you add the extra filtration you can tap the line form the filter base to the pump with a T fitting.



The FASS type pumps have regulators on them to set the output pressure.

 

[Yo Hoot]

Thanks. I'm chasing a fuel starvation issue.

It seems like ever since I replaced the water separator filter on the FASS with a Baldwin BF 1212 the truck is slowing starving for rail pressure I believe. I don't have a rail pressure gauge.

The symptoms are... .
Less smoke. I used to be able to produce more smoke at will.
Knock on hard accellration (fuel starve knock)... more than before.
Injector clatter and knock on hard accel on the highway in overdrive.

 

[cerberusiam]

Could just be the winterized fuel or possibly the FASS is dying. LP pressure and rail pressure gauges are almost as critical as boost and EGT to diagnose issues these trucks.

 

[Yo Hoot]

Could just be the winterized fuel or possibly the FASS is dying. LP pressure and rail pressure gauges are almost as critical as boost and EGT to diagnose issues these trucks.

I have a pressure gauge on the FASS. Reads 17-18 psi. Is that before the filters or after? What causes rail pressure drop off to change? Could the relief valve be going south?

 

[steved]

If the sending unit is mounted in the FASS, the port is post filters... unless you see a significant drop in pressure under acceleration, then its probably not the FASS.



Have you tested the cascade valve on the rail?

 

[Yo Hoot]

Thanks guys.
No I havent tested it. How do I and where can I buy what I need?

 

[cerberusiam]

I think he means the PRV on the rail. Its under the banjo bolt that hooks up the return line to the rail.



Pull the banjo bolt out and bend the injector return lin out of the way slightly. Wrap a baggy on the end so it will catch the fuel when you run the engine.



The PRV is at the bottom of the well left after the banjo is pulled. Clean it with car cleaner and blow it dry. Start your engine and run the rpms up an down a couple times to get some pressure and see if it gets wet again. If it does it is toast.