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-   -   Cummins ISC lift pump replacement (https://www.irv2.com/forums/f123/cummins-isc-lift-pump-replacement-280226.html)

imnprsd 12-08-2019 09:59 PM

Stock Lift Pump Vs. FASS Pump Types
 
4 Attachment(s)
A) Your stock lift pump from Cummins is a "Carter-type" lift pump that draws (sucks) fuel from the fuel tank for 30 seconds after you turn the ignition key on. If you were to measure the fuel pressure out of the lift pump you would see +15PSI out of the lift pump while it is NOT running. And then after the engine starts... and about 30 seconds later, the fuel pressure in the line will change from positive fuel pressure to negative fuel pressure when the CAPS "Low Pressure Gear Pump" is running.

So ~30-45 seconds after your engine starts, the "LOW PRESSURE GEAR PUMP" (which is a section in your CAPS pump if you review previous pictures I have post) takes over and draws (...sucks) fuel from the fuel tank all the time the engine is running. If you were to measure this vacuum pressure you would see -4 to -5PSI of vacuum pressure.

Cummins specifies the CAPS injection pump requires a minimum of -5PSI to operate efficiently.


SUGGESTION: For less than $25 you too can measure your vacuum pressure in your fuel delivery system easily by adding a vacuum gauge to the top of your fuel filter block. (Assuming you have a plug on top.)

All you need is a M10 x 1/4"NPT-Female reducer so you can mount a vacuum gauge on top of your filter block. Then all you do is remove the plug and insert the reducer and oil filled vacuum gauge on top. (See picture.) Then you can test the quality of your vacuum gear pump while the engine is running! And you can see if your engine is operating at -5PSI or not??? Here's the Amazon links:

https://www.amazon.com/Filled-Pressu...34&s=hi&sr=1-8

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

At best, I'm guessing the highest fuel pressure will be -5PSI.

...So when I measured only -4PSI (at 1800 RPM) I had to ask, was there some error in the gauge (maybe) or was it reading accurate?

NEXT QUESTIONS: Were my old 2004 fuel lines sucking air into the lines, and if so was that affecting the vacuum pressure?

Should I go to a huge expense and have those fuel delivery lines replaced as some people say fixed their fuel delivery issues? (Answer: Not if I could help it! I told myself.)

Note: My Freightliner Chassis has no access to the top of my fuel tank so in order to replace my fuel lines I would have to drop my fuel tank. (Monaco/Spartan Chassis owners do have access to the top of their tank and so they might be able to replace the fuel lines more easily. So I have heard.)

FASS TO MY RESCUE!!!

B) When you install a FASS TS (electric) Lift Pump you now have an stronger fuel pump sucking fuel from the tank; and it will supply an constant output of +15 to +18PSI of POSITIVE fuel pressure to the CAPS injection pump. Thus ensuring your CAPS pump will NEVER be starved of fuel again. And this is the main purpose of by-passing your stock lift pump.

As for any air getting sucked into the fuel delivery lines? Who cares! The FASS TS Pump is an "Air Separation Pump" that will return air and unused fuel to your fuel tank via its fuel return line. (PROBLEM SOLVED!) And all the while FASS is pumping it's also filtering the return fuel to the tank. And that will virtually eliminate your algae concerns... if you have any? I did. So once again I say: "FASS TO MY RESCUE!"

CLARIFICATION: FASS also makes just a 95 GPH Adjustable Pump, but that pump lacks many of the FASS TS Pump advantages. Namely no filtration, no air separation, and no "fuel polishing/fuel return" but it does supply positive fuel pressure just like your the TS pump does.

The installation with the Adjustible Pump is easier vs. the TS pump, but not much less expensive.

You can also find older FASS Pumps (with large filters) available on Ebay for $499/$599, but you need to check if these are the older 2018 model. And we recommend you call FASS to better understand the additional advantages of buying the newer Titanium Series "TS" Pumps launched in March-2019.

https://fassride.com/shop/product/fu...-d07-095g-kit/

Note: If you find a FASS Titanium Pump on Ebay that has "large filters" you should know this is last year's model. And there were changes FASS made in March-2019 you should call FASS to ask about so you can decide if this older pump will work for you just as well as the new Titanium Series "TS" Pump?

WHAT KEEPS FUEL FROM FLOWING THROUGH THE STOCK LIFT PUMP WHEN IT'S NOT RUNNING?

Answer: #10 in the attached schematic is a "Check Valve" that prevents fuel from flowing through the lift pump when it's not energized by the ECM.

LINK TO HOW I INSTALLED MY FASS LIFT PUMP:
https://www.irv2.com/forums/f123/cumm...mp-458337.html

imnprsd 01-07-2020 08:05 PM

If you do not upgrade to a FASS Fuel Pump...
 
1 Attachment(s)
CAPS injection pumps and systems were not designed to run on ULSD fuels.

Specifically, CAPS tolerances are very "tight" and rely on fuel lubrication and cooling for long term operation. So what can you so to avoid a Strikeout?

Strike 1: ULSD Fuel with ultra low sulfur reduces lubrication. They say bio-diesel has more lubricity than #2 Diesel, but most “hardliners” say they get less performance and less MPG. We did not find this to be the case in over 40,000 miles of driving our RV with a tow car.

Plus you never know how much bio-diesel you will get in your B5 to B20 fill-ups since you could be getting anywhere between 0%-20% bio-diesel.

Strike 2: Low Vacuum Pressure in the fuel deliver line can be caused by air leaks that reduce vacuum pressure (suction). And for 2004 and newer ISC/ISL owners, you can usually cure this by tightening those 3 lift pump bolts you are now hearing so much about!

Strike 3: Running with less than 1/4 tank of fuel in the tank. Note: The Dodge trucks call this a "Quarter Tank Problem" and it's common with their Cummins lift pumps... albeit their lift pumps run all the time and use a V44 Pump that is similar to our CAPS pump… the effects of FUEL STARVATION are the same. And when you have less fuel in your tank, your CAPS low pressure gear pump efficiency is affected by running your engine (under high demand… like climbing a grade or acceleration on a freeway on-ramp) when the fuel level in your tank drops below 1/4 tank of diesel fuel. So try to avoid this if you do NOT have a FASS fuel pump.

I also found lots of people think they got bad diesel when they fixed their engine performance problems by changing out their fuel filters. However, I think this is an early warning sign. Why? …Because your fuel delivery is falling below -5PSI of vacuum pressure to the CAPS pump and you may or may not know when this is happening.

If you get an “engine buck” then you know, but all the other times your CAPS pump is not getting enough fuel to cool itself and you are literally shortening the life of your pump.

So why does changing the fuel filters fix the problem?

...Read the attached .pdf.

imnprsd 01-16-2020 03:11 AM

"How is routing positive fuel pressure thru a leaking lift pump not going to leak?
 
3 Attachment(s)
In another thread, Rickadoo asks: ..."...how is routing positive fuel pressure thru a leaking lift pump not going to leak?"

Answer 1a: This is where the confusion starts. How?/Why? ...Most often it's not your lift pump that is leaking. It's the gasket between the lift pump manifold and the lift pump where the leak is occurring.

HOW EXPLAINED: When it comes to gasket materials, from what I have been able to glean from reading a lot about this subject from other members on this forum, the gasket material used in pre-2002 engines was not compatible with ULSD fuel. So if you have one of these older coaches then chances are your gasket has already leaked and been upgraded to a newer part number.

WHY EXPLAINED: Diesel shops like to bill for a complete lift pump and gasket replacement. And I bet you will only hear about tightening those 3-lift pump bolt on this website or some other RV forum websites. The bigger question is: Why aren't mechanics telling to first try tightening those lift pump bolts? Answer: For the same reason a plumber doesn't want to explain his craft. "...It ain't rock science, but it is a living!"

TR4 and BigLar368, who are my two best friends on this forum, because with their help I fixed my lift pump air leak in my Montana camp spot...and helped me derive the FASS TS upgrade for my 2003 Cummins ISC-350 and Freightliner Chassis is why I did NOT choose to by-pass the lift pump manifold.

REVIEW: When people say "Lift Pump" what they are talking about in general are 3 different parts:

1) The Lift Pump Manifold that has a check valve to prevent fuel from passing through the lift pump when it's not turned on.

2) The Lift Pump Gasket

3) The Lift Pump.

So, back to the question: "...how is routing positive fuel pressure thru a leaking lift pump not going to leak?

Answer #1b: Fuel does not flow through the lift pump when it's not turned on by the ECM. So no fuel will leak out.

Improvement: Since you now have a "positive" fuel delivery system, then air cannot be leaked (sucked) into the fuel lines.

Therefore, even if the Cummins fuel pump fails, so long as it does not physically leak, in theory, then you should be able to just leave it in place.

REVELATION #1: So why would anyone pay $1,500 to replace a Cummins Lift Pump when for a few more $$$ you can install a FASS TS Pump? Or you can buy the FASS TS Dodge 95GPH Kit for $700 and with $200 in other parts you can install it yourself.

REVELATOIN #2: The type of RV chassis you have will most likely determine the FASS TS Pump installation and location.

In my case, Freightliner Chassis fuel tank is not accessible from the top. So it would be a real PITA to install a FASS TS Pump in my chassis unless I allow fuel to flow through the Lift Pump Manifold.

REVELATION 3: Every will tell you that you should not route fuel through the lift pump manifold, but no one can prove this is a bad idea.

My testimonial is that I have driven 8,000 miles with +15PSI of fuel pressure flowing though the lift pump manifold and I have have absolutely no problems whatsoever. I never changed my stock lift pump or gasket. And my feeling is this: If the CAPS injection pump can pass +15 PSI of fuel RETURN pressure thru the lift pump manifold, then why can't I pass +15PSI of fuel pressure through the other side of the lift pump manifold to the #3 filter... which provides positive fuel pressure to the CAPS injection pump.

CONCLUSION:
If you can by-pass the lift pump manifold easily then do so. TR4 and BigLar368 have a different chassis than I do. ...I know BigLar368 has a Spartan chassis and an inspection door on top of his fuel tank, so that's a real plus, but I can't remember what chassis TR4 has? It's not a Freightliner that I'm sure. Maybe a Roadmaster?

Note: My Itasca-Freightliner also has a Independent Front Suspension (IFS) so there is no room by the fuel tank for a FASS up front. ...But frankly, I would not want to locate those FASS filters under the coach anyway. And it's a myth that you need to mount the FASS pump near the fuel tank.

Maybe just like it's a myth you need to by-pass the Lift Pump Manifold. I did not! All I did was remove my primary filter and install a FASS TS Pump in its place. (See picture.) And in my Freightliner Chassis it was real easy to mount the Dodge FASS Kit hardware to my chassis frame. Almost like it was meant to be there!

So I chose to mount the FASS TS Pump in the engine compartment, where I have easy access to those 2 FASS fuel filters, but I also need to point out that I have a side radiator.

So these are all factors you might want to consider before you make your plans to upgrade to a FASS Titanium Series Fuel Pump. It's a great upgrade, because it protects your CAPS injection pump from premature failure. (See previous post I have written on this subject.)

If you has a Spartan or Roadmaster Chassis like BigLar368 and TR4 and want to by-pass your lift pump manifold then follow the "pink" highlighter in the diagram below. If you have a Freightliner Chassis then follow the printed flow diagram "as described."

I hope these Revelations help you make up your mind. Upgrading to a FASS TS Pump is highly advised in my opinion and my engine has never ran better!

Jump over to this thread for more information about why and how I installed my FASS TS Pump in my Itasca "Horizon" with Freightliner Chassis:
Cummins ISC - Engine Starts But Then Quits & Why We Upgraded To FASS TS Pump!!!!

Ray,IN 02-08-2020 05:46 PM

Quote:

Originally Posted by imnprsd (Post 5026568)
Yeah, but your Lift Pump only runs for the first 30 seconds that you start your motor and then it shuts down.

But lift pump purpose is the prime the injection system so the low pressure gear pump can take over and suck fuel from the fuel tank.

The FASS fuel pump runs constantly while your engine is running... that's the point!

The FASS TS fuel pump has two additional filters... and recycles fuel to your tank which removes. algae and other contaminants.... and that's the point

Just in case you don't have this bookmarked already, this is very interesting: https://quickserve.cummins.com/servi...0/05/iscts.htm

TR4 02-08-2020 07:16 PM

Quote:

Originally Posted by Ray,IN (Post 5140694)
Just in case you don't have this bookmarked already, this is very interesting: https://quickserve.cummins.com/servi...0/05/iscts.htm

Great find, thanks for posting! Interesting, it says to warn customers not to pre-fill fuel filters.

Bill

Mile Marker 42 12-16-2020 10:11 PM

Quote:

Strike 3: Running with less than 1/4 tank of fuel in the tank. Note: The Dodge trucks call this a "Quarter Tank Problem" and it's common with their Cummins lift pumps... albeit their lift pumps run all the time and use a V44 Pump that is similar to our CAPS pump… the effects of FUEL STARVATION are the same. And when you have less fuel in your tank, your CAPS low pressure gear pump efficiency is affected by running your engine (under high demand… like climbing a grade or acceleration on a freeway on-ramp) when the fuel level in your tank drops below 1/4 tank of diesel fuel. So try to avoid this if you do NOT have a FASS fuel pump.
Interesting info. Not sure if you are following this thread: https://www.irv2.com/forums/f115/dea...516487-23.html but he originally 2 weeks ago with a leaky lift pump climbed a 10% grade in CO with a 1/4 tank of fuel and his engine shut down. He is still in Denver trying to fix it as of today. Very sad story. When I first read it, I said to myself, "who climbs a 10% grade in 20 degree weather on a 1/4 tank of fuel"? Well this guy did. So ever since then, I have been reading as many posts as I can on this subject and 1 of them brought me to yours. Turns out that I too have the CAPS system with the lift pump mounted directly above the starter. No accessibility from the top really. Thank god it isn't leaking and I don't ever run on a 1/4 tank of fuel for very long. Thx, just wanted to share.

seaquest7 08-28-2021 12:52 PM

Quote:

Originally Posted by imnprsd (Post 5068371)
A) Your stock lift pump from Cummins is a "Carter-type" lift pump that draws (sucks) fuel from the fuel tank for 30 seconds after you turn the ignition key on. If you were to measure the fuel pressure out of the lift pump you would see +15PSI out of the lift pump while it is NOT running. And then after the engine starts... and about 30 seconds later, the fuel pressure in the line will change from positive fuel pressure to negative fuel pressure when the CAPS "Low Pressure Gear Pump" is running.

So ~30-45 seconds after your engine starts, the "LOW PRESSURE GEAR PUMP" (which is a section in your CAPS pump if you review previous pictures I have post) takes over and draws (...sucks) fuel from the fuel tank all the time the engine is running. If you were to measure this vacuum pressure you would see -4 to -5PSI of vacuum pressure.

Cummins specifies the CAPS injection pump requires a minimum of -5PSI to operate efficiently.


SUGGESTION: For less than $25 you too can measure your vacuum pressure in your fuel delivery system easily by adding a vacuum gauge to the top of your fuel filter block. (Assuming you have a plug on top.)

All you need is a M10 x 1/4"NPT-Female reducer so you can mount a vacuum gauge on top of your filter block. Then all you do is remove the plug and insert the reducer and oil filled vacuum gauge on top. (See picture.) Then you can test the quality of your vacuum gear pump while the engine is running! And you can see if your engine is operating at -5PSI or not??? Here's the Amazon links:

https://www.amazon.com/Filled-Pressu...34&s=hi&sr=1-8

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

At best, I'm guessing the highest fuel pressure will be -5PSI.

...So when I measured only -4PSI (at 1800 RPM) I had to ask, was there some error in the gauge (maybe) or was it reading accurate?

NEXT QUESTIONS: Were my old 2004 fuel lines sucking air into the lines, and if so was that affecting the vacuum pressure?

Should I go to a huge expense and have those fuel delivery lines replaced as some people say fixed their fuel delivery issues? (Answer: Not if I could help it! I told myself.)

Note: My Freightliner Chassis has no access to the top of my fuel tank so in order to replace my fuel lines I would have to drop my fuel tank. (Monaco/Spartan Chassis owners do have access to the top of their tank and so they might be able to replace the fuel lines more easily. So I have heard.)

FASS TO MY RESCUE!!!

B) When you install a FASS TS (electric) Lift Pump you now have an stronger fuel pump sucking fuel from the tank; and it will supply an constant output of +15 to +18PSI of POSITIVE fuel pressure to the CAPS injection pump. Thus ensuring your CAPS pump will NEVER be starved of fuel again. And this is the main purpose of by-passing your stock lift pump.

As for any air getting sucked into the fuel delivery lines? Who cares! The FASS TS Pump is an "Air Separation Pump" that will return air and unused fuel to your fuel tank via its fuel return line. (PROBLEM SOLVED!) And all the while FASS is pumping it's also filtering the return fuel to the tank. And that will virtually eliminate your algae concerns... if you have any? I did. So once again I say: "FASS TO MY RESCUE!"

CLARIFICATION: FASS also makes just a 95 GPH Adjustable Pump, but that pump lacks many of the FASS TS Pump advantages. Namely no filtration, no air separation, and no "fuel polishing/fuel return" but it does supply positive fuel pressure just like your the TS pump does.

The installation with the Adjustible Pump is easier vs. the TS pump, but not much less expensive.

You can also find older FASS Pumps (with large filters) available on Ebay for $499/$599, but you need to check if these are the older 2018 model. And we recommend you call FASS to better understand the additional advantages of buying the newer Titanium Series "TS" Pumps launched in March-2019.

https://fassride.com/shop/product/fu...-d07-095g-kit/

Note: If you find a FASS Titanium Pump on Ebay that has "large filters" you should know this is last year's model. And there were changes FASS made in March-2019 you should call FASS to ask about so you can decide if this older pump will work for you just as well as the new Titanium Series "TS" Pump?

WHAT KEEPS FUEL FROM FLOWING THROUGH THE STOCK LIFT PUMP WHEN IT'S NOT RUNNING?

Answer: #10 in the attached schematic is a "Check Valve" that prevents fuel from flowing through the lift pump when it's not energized by the ECM.

LINK TO HOW I INSTALLED MY FASS LIFT PUMP:
https://www.irv2.com/forums/f123/cum...mp-458337.html

I know this is an old thread but I'm hoping someone can answer a related question.
I have a 2001 American Tradition, Spartan chassis, with a 8.3 ISC Cummins. I'm stuck at a campground because during my pre-trip routine of snugging up the three fuel transfer pump bolts, I stripped one hole in the bottom electric pump housing. I purchased a new pump assembly but instead of replacing the whole assembly and chancing breaking one of the stiff lines connected to it, I'd like to just replace the bottom half that the three bolts screw into. It's hard to tell if there is enough clearance to remove the bottom electric motor/housing once unbolted, but it looks like there may be. My question is will I get a steady stream of fuel from the supply side hole (fuel tank) that gets exposed once the electric motor housing is removed? I'm hoping it would it just be whatever is left in the fuel line or filters but I don't really know. All hoses and plugs currently connected to the pump manifold will remain intact. I'm placing a container to catch any fuel that leaks but my container will only hold about 2 gallons and I don't now how long it will take me to get the new one in place and bolted up. I didn't see any fuel cut off option but I'm surprised there isn't one. Sharing of any thoughts or experience would be greatly appreciated.
I would normally just have a shop do the work but around here (Cave City Kentucky) all shops that can do the work have told me they're book solid into late next week. I had to drive my toad to the Cummins shop in Nashville TN to get the pump (a very long 184 RT) so the local shops could get on t once they had an opening.
I would have gone the FASS way instead if I had more time to find someone to install it and get the parts delivered in time. Replacing the original with the newer "Improved" version was all I could manage to get installed quickly.

jacwjames 08-28-2021 04:13 PM

You will loose a little fuel but not much since the fuel tank elevation is lower then the lift pump itself.



I was having trouble with my fuel pump starting to leak so I just bite the bullet and installed a FASS pump and bypassed the old lift pump. I had to disconnect the fuel lines in & out to put a union between them and caps on the lift pump. Lost very little fuel.

You should have enough room to pull the lower section off, make sure the hole patterns are the same, if you luck the new pump will have a gasket that matches the old.

shootist 08-28-2021 07:18 PM

Did you already separate the new pump motor from the pump? I think at worst you will have to pull the starter. Reaching the plug from the bottom you depress the center tab. You can't see it so find the part that moves on the plug and push it down. It will be on the top side. The wiring goes to the ecm so don't have it connected when you drop the motor. Also raise the back up and leave the nose down for lessening the fuel flow if you open the lines. And disconnect the batteries house and chassis if you go to drop the starter. Lastly if for any reason you get stuck with it doa you have to air it up with an external compressor to get under it.

seaquest7 08-28-2021 07:34 PM

Quote:

Originally Posted by jacwjames (Post 5892251)
You will loose a little fuel but not much since the fuel tank elevation is lower then the lift pump itself.



I was having trouble with my fuel pump starting to leak so I just bite the bullet and installed a FASS pump and bypassed the old lift pump. I had to disconnect the fuel lines in & out to put a union between them and caps on the lift pump. Lost very little fuel.

You should have enough room to pull the lower section off, make sure the hole patterns are the same, if you luck the new pump will have a gasket that matches the old.

Thanks for the quick reply. This is the answer I was hoping for.

Per the service tech at Nashville Cummins, the old pattern is the same. He said the upgrade was the electrical motor and the rubber gasket. He said the gasket was upgraded to work with the ultra low sulfur fuel and the electric motor was beefed up due to many past failures. He said the fuel housing/manifold that the electrical pump mounts to hasn't been changed since its original design. Looking at them the only difference I can see is the three bolts that can loosen up now have star head and the bolt it self has a course thread and a slight triangular shape (not round) and is tapered for about a 1/4 inch at the end. Im not familiar with this style bolt but it seems as though it may be some sort of self locking bolt. My new concern is that if this is the case I may have just defeated the fix for the bolts loosening up. I'll put a drop of thread lock on them before using them just t be sure.
Again, thanks for the help.

radar 08-28-2021 07:42 PM

Cummins keeps them in stock and if I remember correctly they come with everything you need including o-rings etc. Back in 2007 or maybe 2008 we had to change ours. We.changed it in a flying J somewhere around Palm Springs. I thought I would change it from below but I ended up holding the flashlight while wifey changed it from the bedroom access hole. Bit of a stretch though. Prime (with the key) many times before turning it over.

Good luck.

seaquest7 08-28-2021 07:50 PM

Quote:

Originally Posted by shootist (Post 5892422)
Did you already separate the new pump motor from the pump? I think at worst you will have to pull the starter. Reaching the plug from the bottom you depress the center tab. You can't see it so find the part that moves on the plug and push it down. It will be on the top side. The wiring goes to the ecm so don't have it connected when you drop the motor. Also raise the back up and leave the nose down for lessening the fuel flow if you open the lines. And disconnect the batteries house and chassis if you go to drop the starter. Lastly if for any reason you get stuck with it doa you have to air it up with an external compressor to get under it.

Hi and thanks for the response.
I haven't disconnected the old pump motor yet. I can see the electrical plug (a little) and I can get that disconnected. Hopefully I won't have to remove any other parts. Good suggestion on lowering the front to help lessen the fuel flow and of course killing all power before messing with the starter.
I've seen a screwdriver burst in half coming across a hot battery cable to ground. I don't want those surprises :nonono:
Thanks for the suggestions and quick response.

seaquest7 08-28-2021 07:54 PM

Quote:

Originally Posted by radar (Post 5892460)
Cummins keeps them in stock and if I remember correctly they come with everything you need including o-rings etc. Back in 2007 or maybe 2008 we had to change ours. We.changed it in a flying J somewhere around Palm Springs. I thought I would change it from below but I ended up holding the flashlight while wifey changed it from the bedroom access hole. Bit of a stretch though. Prime (with the key) many times before turning it over.

Good luck.

Thanks for the info and story. I'd like to be the one that holds the flashlight for a change :)

radar 08-28-2021 08:16 PM

Quote:

Originally Posted by seaquest7 (Post 5892466)
Thanks for the info and story. I'd like to be the one that holds the flashlight for a change :)

Yes, the advantages of being married to a retired soldier/technician. She always wants to hold the wrench. :).


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