I have a fass 95 that was put on in October of 2013. After about a month my fuel pressure will start bouncing all over the place. I call fass to do some troubleshooting and they send me a new ball and spring for the return line to the tank. I am on my 3rd ball and spring in this short time. It is not my daily driver. I only average about 5000 mile a year with most of them being summer miles. The first couple of times that I have change the ball and spring I had to take the diesel bath. This time my return line was dry. Is the pump working properly? I don't understand what is going on. I plan on calling them tomorrow but want to see if anyone else has had this problem or might know what is going on. I am running it off of the factory module. Do I need adraw straw? Tired of dealing with this thing. Thought they were reliable.

Edited April 6, 201410 yr by rseabur

What type of gauge do you have?

What type of gauge do you have?

 

His signature says he has an Edge Juice, so I'd guess it's a CS or CTS monitor. If it is, I'd be leaning towards a bad sending unit for the fuel pressure gauge instead of a bad lift pump?

 

Does this happen when the fuel tank is full?

 

FASS pumps are probably the best on the market, and if/when they do have a problem, FASS has great customer service and they'll take good care of you.

I have the Cts. I have replaced that sensor twice. I did not do it this time as I am trying to figure out what the problem is. The pressure is all over the place with tank full or empty. With new spring I put in today pressure is fine at 18. Why the dry return line today? Is that a pump issue? Spring was changed before truck was started today. I cant see getting 3 bad sensors in a row from edge

I cant read signatures on my phone. I would use a mechanical gauge and see if it follows

Is it normal for the return line to the tank to be dry before the first start of the day? It has never been any other time.

Well there is nothing keeping it in the line. I have never checked. Try the gauge first and go from there

I know nothing to hold the fuel but it is all up hill to the filler neck. Loops out of pump, over frame, then down frame and up to neck. Just thought was weird the first two spring changes had fuel spilling everywhere and this time nothing.

Not sure about the dry line, but I'm with MoparTech, test with a mechanical gauge.

Would a bad overflow valve on the Vp have anything to do with this? Meaning the bouncing pressure guage

Edited April 7, 201410 yr by rseabur

Very unlikely. I dont think I have ever heard of one going bad. First, get a mechanical test/pressure gauge on there to verify that your electric sender isnt just bad again. Then, if the pressure still bounces on the mechanical gauge, you can go about figuring out if it is the pump that is going, or something else.

I am going to try to get a mechanic guage on this weekend just to see how it compares to the edge. I am pretty sure electric sender is fine since it doesn't bounce with the new spring and ball that was installed this past weekend. Holding 17 to 18 all time for now. But got a feeling it will start acting up again in about a month. I guess that is why they sent me 2 springs and 2 balls this time. I have did the bucket test awhile back and that was fine. Hard to trouble shoot when it is acting fine at the moment.

If the electric sender was bad why would pressures be good for a while after the spring and ball changes? Have heard to put a 2' piece of greese gun hose on after the snubber to take all pulses out. Is that a bunch of bs?

If the electric sender was bad why would pressures be good for a while after the spring and ball changes? Have heard to put a 2' piece of greese gun hose on after the snubber to take all pulses out. Is that a bunch of bs?

 

Grease gun hose is a Internet myth you must use a needle valve and adjust the needle down for slow rise of pressure. Electric senders must be screw into a grounded fitting with a snubber or needle valve as far from the VP44 as possible. Water hammer pulses come from the Vp44.

 

Electric sender fuel pressure gauges are highly prone to failure. Mechanicals fuel pressure gauges with direct plumb RARELY ever fail. Just for the point I've got DiPricol gauges the company is long gone and still got my original fuel pressure gauge working 10 years later.

 

 

Most electronic gauges have their own ground wire so they dont ground through the fitting. And the hose helps eliminate vibrations from the engine. It isnt for water hammering

I have my sender on the end of a grease gun hose with the hose connected to a needle valve. I have none of the sensor failures people talk about.

Engine vibration I think is a bit off too. Why only fuel pressure senders? MAP sensor and Oil Pressure sensor both bolt directly to the engine and last much longer. Still a water hammer issue seems to primary problem being neither oil pressure or MAP sensors are failing from vibration. Even the grease gun hose never resolved the vibration problem because the vibration is the fuel as there is like roughly 2,500 pulse per minute (~42 pulses per second) as the VP44 opens and closes just at idle.

 

Put you hand on the fuel line going into the pump you can even feel the pulses in the rubber hose.

I have the push loc tee cut in about where my factory filter housing was. Currently running a snubber. So I believe I am far enough away if vibrations from motor are an issue.  So....I sould take the snubber off and run a needle valve???

 

Engine vibration I think is a bit off too. Why only fuel pressure senders? MAP sensor and Oil Pressure sensor both bolt directly to the engine and last much longer. Still a water hammer issue seems to primary problem being neither oil pressure or MAP sensors are failing from vibration. Even the grease gun hose never resolved the vibration problem because the vibration is the fuel as there is like roughly 2,500 pulse per minute (~42 pulses per second) as the VP44 opens and closes just at idle.

 

Put you hand on the fuel line going into the pump you can even feel the pulses in the rubber hose.

I have the push loc tee cut in about where my factory filter housing was. Currently running a snubber. So I believe I am far enough away if vibrations from motor are an issue.  So....I should take the snubber off and run a needle valve?? or run both??   Is the spring and ball changes tricking the sensor some how to give me temporary readings that are good??  Thats why I cant understand how the sensor is bad.. After the spring and ball changes pressure are good and rock solid for a few weeks.  This happens at all fuel levels.  I am wanting to do some small injectors but think i need to wait until i get this pressure figured out. 

Water hammer pulses can run a long way depending on pressures and flows. But for our fuel system the stock filter can help reduce the pulses.

 

Like here is water hammer with about 116-118 PSI of pressure.

 

The reason why fuel pressure senders fail if the fuel system has valving that opens and closes that creates water hammer pulses where oil pressure is constant flow this why oil pressure sender don't fail as often as a electric fuel pressure sender.