04 fuel pressure

[kblranch]

Installed the BD low fuel pressure sender. Light goes on if pressure falls below 5 PSI. At full throttle light flickers especially if it is not warmed up otherwise it stays off at normal cruise. What kind of pressure and flow is the canister mounted pump good for?

 

[TCDiesel]

You may drop the Pressure below 5psi with NO operational problems. . as long as it has (CP3) has adequate Volume pressure is no concern to the unit. Running excessive pressure is more likely to increase wear and eventual failure. Any lack of volume will effect performance.

 

[BIGNASTY]

You may drop the Pressure below 5psi with NO operational problems. . as long as it has (CP3) has adequate Volume pressure is no concern to the unit. Running excessive pressure is more likely to increase wear and eventual failure. Any lack of volume will effect performance.

TC you bring up a good point about excessive pressure. I run an AD100 with a cat filter before the cp3 I was wondering about the return line to the tank. But I have found Thu reading that the AD pump doesn't care about the fuel back pressure that it is returned to the system via the pump housing. So question is the above case true or is there a reason to up the return line size to relieve some of the pressure on the cp3?

 

[TCDiesel]

Feed the CP3 as much fuel as Possible...

 

[kblranch]

Thanks for the reply

 

[AH64ID]

Installed the BD low fuel pressure sender. Light goes on if pressure falls below 5 PSI. At full throttle light flickers especially if it is not warmed up otherwise it stays off at normal cruise. What kind of pressure and flow is the canister mounted pump good for?

I am still shocked they sell that part for the OEM fuel system, it's essentially a useless light that will go on long before there is a problem on a HPCR, and on a VP truck 5 psi is way too low for a light!



Bosch spec's -5 to +15 psi for the CP3. The tank mounted OEM pump is good for about 9 psi at idle, ~7 cruise at ~5 WOT, as your filter clogs WOT pressure will drop. I have heard the canister mounted pump will run a little lower, but I have never ran one. A good rule of thumb is to change the filters when WOT pressure drops to about 2-3 psi.



I would get a psi gauge, it will actually tell you what is going on.

 

[kblranch]

I carry a spare pump. If the light started staying on at cruise I figured it would be a good indicator that the pump was begining to go - better than nothing.

 

[steved]

I carry a spare pump. If the light started staying on at cruise I figured it would be a good indicator that the pump was begining to go - better than nothing.

I run (and have only ran a light), they are every bit as good as a gauge as long as you understand what they mean. Not to mention a light flickering/glaring at you is typically BETTER at grabbing your attention when a problem arises... we get complacent with gauges. I have ran a light for over 500k now, I have not had a single instance where a gauge would have been any better than a light... in most cases, I would not have even paid the gauge any attention when the light was screaming "problem".



The only thing one needs to know is how the light is powered... if its powered by the pump relay (like a FASS or AirDog), if that relay fails you won't see a light illuminate. I typically wire mine in to stand alone, and they flicker at start up to let you know the light works...

 

[AH64ID]

I carry a spare pump. If the light started staying on at cruise I figured it would be a good indicator that the pump was begining to go - better than nothing.

Not really, it tells you nothing other than your psi is at 5 or lower, and like it's been said that's nothing to worry about.

I run (and have only ran a light), they are every bit as good as a gauge as long as you understand what they mean. Not to mention a light flickering/glaring at you is typically BETTER at grabbing your attention when a problem arises... we get complacent with gauges. I have ran a light for over 500k now, I have not had a single instance where a gauge would have been any better than a light... in most cases, I would not have even paid the gauge any attention when the light was screaming "problem".

The light doesn't scream problem thou, 5 psi is perfectly acceptable.

You have no real indication with a 5 psi switch on a system that can operate with any pressure as long as it has flow. In the winter a 5 psi light would be on solid for me for 10-20 miles every time I start (and that's with the dual 300w heaters, was worse before), but the flow is fine the fluid is just cold, but with a light you don't know if your starting to gel, have no pressure, etc.

To me it's just as useless as the 6 psi oil pressure switch on the block. If you see a light you think there is a problem, but on this system 99% of the time it won't be an issue, but you will be wondering what is wrong.

 

[04blackcherry]

It would seem that flow to the CP3 is more important than pressure, if the Bosch spec is -5 to +15psi. Does anyone know the flow rate (volume) thru the CP3? In my limited knowledge of the pressure vs flow equation; if flow increases, pressure decreases. The CP3 could be happy with less pressure as long as the it gets enough fuel.

In my day job I work with pneumatic motors. We have some that use 100 cfm at near 90psi static pressure. Our air system will always provide the 90psi and 100 cfm flow. The motors will not perform properly if the flow is reduced or if the supply to the motor is too small and not capable of 100cfm flow.

There is a pressure drop at the motor as it tries to draw more air. So I guess if your pressure guage is at the CP3 it could indicate a starving pump... or not. It could just be indicating more flow.

So I've run myself in a circle. How much flow can the CP3 use?

 

[cycletech]

fuel pressure

I have an 05 2500. . My fuel pressure between the factory fuel filter housing and cp3 is 6-7 psi at idle. The big concern is volume of fuel. . I last check volume to CP3 and it was 550ML with in 10 seconds. . I believe this is within factory specs for cummins. I was told not to be concerned with psi b/c you can have plenty of psi but volume could be down.

 

[AH64ID]

I haven't been able to find the exact specs for the OEM LP, but I believe it's around 35 GPH at 8 psi. There is a bypass in the tank that keeps the output pressure to ~ 8psi. At 0 psi I got about 90GPH from my stock pump.

 

[kblranch]

Ordered a new lift pump from Genos and going to see if there is any difference with a new pump. Maybe go with the dual setup. Like being able to replace the pump with out dropping the tank.

 

[04blackcherry]

It becomes clearer... It stands to reason that if the LP is capable of 90GPH @ 0 psi, as the demand from the CP3 increases the LP will provide more flow as the pressure drops. As long as the CP3 doesn't need all 90GPH, all is good.

 

[CKelley1]

do not worry about fuel pressure worry about filtration

 

[kblranch]

I would think both fuel supply and filtration would be important.

 

[rbattelle]

Not really, it tells you nothing other than your psi is at 5 or lower, and like it's been said that's nothing to worry about.



The light doesn't scream problem thou, 5 psi is perfectly acceptable.

True, but if you have a system that was producing, say 10 psi normally and is suddenly producing 5psi or less regularly, then you are likely to have a problem.



While I agree with Steve that a light is an attention-getting device, I argue that a light alone isn't very useful. You need a gauge so that you can look at trends over a long period of time.



I don't have a light, but my gauge flashes if pressure falls outside a range that I programmed.



-Ryan

 

[AH64ID]

True, but if you have a system that was producing, say 10 psi normally and is suddenly producing 5psi or less regularly, then you are likely to have a problem.

Yes, but on a system that can normally bump down to 5 in the normal range it's not a problem.



If you had a AD or other system that was 15 at idle, 10 WOT and a 5 psi light then sure it's a little more useful, but still only tells part of the story.