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Old 12-12-2019, 07:43 PM   #1
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DP Lift Pump 'Upgrade': Or rather addition....

Our New to us 2008 Itasca Latitude with Cummins 6.7L ISB seemed a bit 'low' on power IMO. It's rated at 340/700, but......there is no way this rig is making anywhere close to that.

After a thorough investigation and 'shot gun' diagnostics of changing the Fuel Pressure sensor, Cascade overflow valve, Fuel Pressure relief valve, and Fuel pressure regulator valve I found very little fuel volume was reaching the fuel rail. After a 20min drive there should have been MASSIVE fuel volume and pressure in the fuel rail when I removed the sensor just 15min after parking, but there was just a light trickle of fuel.
I eventually replaced the CP3 (High Pressure Fuel Pump) thinking the gear driven vacuum pump was damaged from 12 years of use without proper fuel pressure.

The old CP3 was disassembled and found to be 'just fine'. The CP3 is unique in that it has a gear driven syphon pump that pulls a vacuum from the fuel feed line. This feature is designed to NOT be a primary 'lift pump', but a backup in the event of a lift pump failure. The CP3 vacuum pump can pull enough fuel to get your rig to a repair shop. The fuel line on this Freightliner chassis is 5/8" OD and runs from the fuel tank near the front of the chassis to the engine where the CP3 is mounted. Well over 20ft.
Anyone that researches lift pumps (or sump pumps) knows these pumps have a limit as to the volume they can 'pull' given the length and ID of the line. They can 'Push' insane amounts of fluid, but pulling (sucking) is an issue.

After contacting Freightliner and Cummins it was determined that a Lift Pump was 'required' for the 6.7L (according to Cummins) and Freightliner never installed one. According to Freightliner it was a 'cummins issue'. The 5.9L had a lift pump mounted on the engine, the 6.7L does NOT and requires a lift pump (ideally internal to the fuel tank).

Long and the short of it is a gear driven pump sucks poorly, hell any pump that has to pull from 20+ft away thru a 5/8" hose is not going to do well. So, an AFE lift pump was ordered. As I've dealt with the 'other' aftermarket lift pumps before, I was looking for something a little higher in quality.

The AFE pump is a gear driven setup (ideal for longevity) with an internal pressure regulator that is adjustable from 10-20psi. (perfect for this Cummins). Flow from the unit is 3x what the engine can use. This gives us plenty of 'head room'.
The pump is a brushless motor and therefore takes far less amperage to run.

I received the AFE pump today and am VERY pleased with the quality of parts. (No I have not yet installed it).

The pump comes with a mount, with Riv-nuts (these are great) for mounting, 12+ft of 12AWG wiring using REAL Deutsch connectors, in-line fuse, TE relay, 4 different 'add a fuse' (for 4 different fused setups), and of course instructions.

I'm looking forward to installation and 'testing'.

Of course I will be dropping the fuel tank to ensure there are no obstructions on the pickup and that it is properly sealed to ensure no air is getting sucked into the system. (that I am NOT looking forward to!!!)
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Old 12-14-2019, 09:21 PM   #2
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This FASS fuel pump might be what you seek. https://www.ultrarvproducts.com/UP95...scription=true
If increasing peformance is in your future, this upgrade kit is available:https://www.ultrarvproducts.com/ISB-...scription=true

If you wish, FASS has a Titanium series pump with 2 fuel/air seperator filters incorporated, but it a separate item.
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Old 12-15-2019, 10:08 AM   #3
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lift pump

The cp3 is used on most Duramax engines,5.9 and 6.7 cummins in Dodge trucks since 04 ,none have a lift pump.Usually a Fass or Air dog kit can be installed when your looking for 800 hp
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Old 12-15-2019, 11:10 AM   #4
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Quote:
Originally Posted by Ray,IN View Post
This FASS fuel pump might be what you seek. https://www.ultrarvproducts.com/UP95...scription=true
If increasing peformance is in your future, this upgrade kit is available:https://www.ultrarvproducts.com/ISB-...scription=true

If you wish, FASS has a Titanium series pump with 2 fuel/air seperator filters incorporated, but it a separate item.
I had a FASS setup on one of my Diesel Fords. The unit FAILED within 3000 miles while on vacation 1000 miles away from home. Lucky for us the 7.3L Ford was capable of sucking fuel into the engine and we limped it home.
FASS did NOT stand behind their unit and refused to do anything about it.
I sent the unit back, certified mail and disputed the transaction, which took 4 months to settle.

NO WAY will I ever use another FASS pump.
Besides, the AFE is superior in a few ways if you look into the details.
#1 no unnecessary filters. Why add filters when our rig has 2 already?
#2 Brushless motor which draws far less amps than standard and will last far longer (perhaps the FASS titanium is brushless, I do not know.)
#3 pump design. The AFE uses the same 2 driven bronze gears as the CP3.
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Old 12-15-2019, 11:30 AM   #5
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Quote:
Originally Posted by ronster View Post
The cp3 is used on most Duramax engines,5.9 and 6.7 cummins in Dodge trucks since 04 ,none have a lift pump.Usually a Fass or Air dog kit can be installed when your looking for 800 hp
CP3 design for the 6.7 is NOT the same as the 5.9 which has a built in 'lift pump'.

From 2007.5 up the Cummins 6.7 with CP3 runs an in-tank lift pump.

A very similarly designed CP3 is used on the Duramax WITHOUT a lift pump. They use the Gear driven Vacuum pump on the CP3 to suck fuel from the tank.

Keep in mind, any pump can only *suck* so much as they are limited to atmospheric pressure pushing the liquid to the pump by creating a vacuum inside the pump via gears.

29.53in/hg (1Bar) at sea level is 14.5psi. Assuming a PERFECT vacuum, this is the maximum pressure the fuel will be 'pushed' to the pump via atmosphere at sea level.
Of course these CP3 gear driven pumps CANNOT produce a perfect vacuum.
Atmosphere pressure changes, and line length/rise play a huge role in pressure DROP from tank to vacuum pump.

The real kicker is the LONG and LARGE fuel line on the RV which is the biggest variable here vs a light duty truck. It's called Dynamic Head, which is a measure of how much flow a pump can produce given the LENGTH and VOLUME of the suction line.
Most vacuum fluid pumps fall to ZERO flow before 30ft of Line length.

Our Diesel pusher has the fuel tank mounted right around the door to the unit. That's over 25ft of 5/8" fuel line not taking into account the pickup assembly.
By contrast a Duramax with CP3 has the fuel tank less than 1/2 that and uses a 1/2" OD fuel line.

The dynamic head of the RV is TRIPLE that of the Truck!
15ft of 1/2" OD fuel line (.375" ID) has a total fuel volume of 20 cubic inches.
25ft of 5/8" OD fuel line (.5" ID) has a total fuel volume of 58 cubic inches.

20ci of fuel weighs just over 1/2lb.
58ci of fuel weighs over 1.5lbs.
Pressure DROP across the system is significantly different in these 2 vehicles using the same CP3 pump.

Flow vs dynamic head is not linear, it's exponential. As the length/volume increases flow decreases exponentially.

As such, a lift pump is indeed NEEDED in our application. The CP3 just cannot suck enough fuel to feed this engine at the rated power level.
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Old 12-16-2019, 05:38 PM   #6
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Lift pump installed, set on the lowest pressure (10psi).

Rig sees more boost now, and it comes in faster, takes less throttle to stay at speed, and holds MPH better on the grades as well.

Don't get me wrong, it's still a turd (340HP 6.7), but it's at least up to spec now.
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Old 12-28-2019, 01:21 PM   #7
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Quote:
Originally Posted by ShaunAED View Post
I had a FASS setup on one of my Diesel Fords. The unit FAILED within 3000 miles while on vacation 1000 miles away from home. Lucky for us the 7.3L Ford was capable of sucking fuel into the engine and we limped it home.
FASS did NOT stand behind their unit and refused to do anything about it.
I sent the unit back, certified mail and disputed the transaction, which took 4 months to settle.

NO WAY will I ever use another FASS pump.
Besides, the AFE is superior in a few ways if you look into the details.
#1 no unnecessary filters. Why add filters when our rig has 2 already?
#2 Brushless motor which draws far less amps than standard and will last far longer (perhaps the FASS titanium is brushless, I do not know.)
#3 pump design. The AFE uses the same 2 driven bronze gears as the CP3.

Bummer you had a problem with your FASS pump, and more so your not receiving courteous assistance and support from FASS. So understand your unenthusiastic recommendation one FASS!

That being said, we've had our FASS Pump (Pump only, not their full filter system.), on our CAPS era ISL370, since October 2015. Never a problem since when Alan Sanders, at Brazel's, did the install for us. I remain comfortable knowing the CAPS is receiving positive fuel pressure at all times. If I had it to do over, and will probably add it in 2020, I'd include an inline Fuel Pressure gauge too. Having more info, is always better!

Best to you and all,
Smitty
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Old 12-29-2019, 12:10 PM   #8
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Quote:
Originally Posted by Smitty77 View Post
Bummer you had a problem with your FASS pump, and more so your not receiving courteous assistance and support from FASS. So understand your unenthusiastic recommendation one FASS!

That being said, we've had our FASS Pump (Pump only, not their full filter system.), on our CAPS era ISL370, since October 2015. Never a problem since when Alan Sanders, at Brazel's, did the install for us. I remain comfortable knowing the CAPS is receiving positive fuel pressure at all times. If I had it to do over, and will probably add it in 2020, I'd include an inline Fuel Pressure gauge too. Having more info, is always better!

Best to you and all,
Smitty
That was back in 2008 or 2009 I believe. Likely a faulty pump or incorrect clearances in the gear box that caused the failure. Just sucked to have to fight tooth and claw for a fairly expensive part failure.

Make sure to get an electric fuel pressure gauge and place it as close to the CAPS (post filters) as possible for accurate readings. At that point you'd actually be able to see a 'surprise clogged' filter.
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