Cummins ISC - Engine Starts But Then Quits & Why We Upgraded To FASS TS Pump!!!!

[imnprsd]

Geordi: How about calling a diesel generator repair shop who performs fuel tank cleaning all the time. (Google it or check the yellow pages in your area.)

Maybe you should get rid of your Diesel fuel if it's that disgusting?

Do you have a drain plug on the bottom of your fuel tank like I have?

Sailchessi... I forgot to tell you that I ended up replacing my entire CAPS injection pump because I had no confidence in the Cummins, Colburg, Oregon shop to overhaul it. I was suck and could not drive it also I took the only path I felt would work and that was to buy a CUMMINS approved CAPS injection pump.

Note: You an join their Cummins Club for $100 and they will take 30% off their parts price.

Cummins probably gets their parts out of a Mexico overhaul shop, but at least they will warranty it. In the end it's close to the same price Thoroughbred Diesel charges for a CAPS pump.

I would take your engine to a Diesel Injection Shop who is not afraid of overhauling a CAPS pump. They can replace your accumulator if that is what they think is your problem. This could save you money, but it could also be just a prayer.

See this video on how to do it on a HPFR system, which is very similar to your CAPS injection pump first states up to the high pressure stage, albeit your CAPS sub-systems will look different. ...Notice their is no ICV or fuel distributor, because a HPFR pump does not include these sub-systems.

https://www.youtube.com/watch?v=e2-yS05u7zQ

[geordi]

I'm not adverse to having the tank cleaned, but I've now put 500 gallons plus through these filters so the dodgy fuel is long gone. It is only if there's somehow debris / scale in the tank, but that shouldn't be an issue for long if it is getting polished by another pump and filter.

You missed my other questions and seem to have stopped reading with the dirty fuel filters, let me ask again in a shorter post.
What kind of max STOCK boost should I be seeing if things are running right?
You've mentioned several times about "three bolts" on a lift pump. Is this on the tank / in the tank / or on the side of the engine somewhere? I don't have a service manual for the engine so I'm a bit blind.

Thanks

[imnprsd]

People are starting to ask me: Is FASS-TS electric pump is a better choice over AirDog or is it the other way around?

My answer is: Both are good pumps and you can't go wrong with either. Both pumps protect your CAPS injection pump from premature failure (ECM included) by enduring good lubrication and cooling; but there are some differences that may make your choice a bit easier to make. (IMO)

What we now know, thanks to "ArkensasRV" is that the AirDog "demand flow" pump does not return very much fuel to the tank. This benefit results in an easier and potentially cheaper installation if you are paying someone to install your pump over the FASS-TS pump (Part #TS-D08-95G).

The AirDog, not the FASS, will allow you to "T" into the CAPS fuel return line at the Lift Pump Manifold (aka Fuel Supply Manifold) and that may save you ~$150 in labor costs.

The FASS-TS pump is cheaper, but you need 38' of fuel return line, and a few different parts, so the total cost of the FASS solution is about the same as the total cost for the AirDog. Therefore, we need to look for other differences to help us make up our minds; and I think this may be it:

FASS "constant volume" pumps requires you to return a lot of unused fuel to the tank, which may be a good thing. (I am still evaluation this.) However, for now, we know with the FASS setup you will need to run 38' of fuel line at $3/ft or ~$120; plus the additional 1-2 hours of time it takes to install a fuel filler-neck "Y" adapter into your fuel filler neck...

...unless you have a Spartan Chassis with access to the top of your tank and you elect to drill a hole in the top of your tank and go that route.

In my case, my Freightliner Chassis does not allow me access to the top of the tank so I chose to return the FASS fuel to my fuel filter neck, which you can read all about here:

https://www.irv2.com/forums/f123/f12...mp-458337.html

Of course, the first time you do any custom modifications it takes more time and you hope you don't make a mistake. ("Measure twice, cut once," as they say.)

FUNCTIONALITY

The AirDog will vary fuel pressure to meet the demand flow of your CAPS injection system; and that means your fuel line PSI will drop as your fuel filters fill-up.

In fact, you can get a AirDog 10-PSI sensor that will trip a LED light (you can put on your dash) to signal when it's time to change your fuel filters, if this is important to you, but you will need to spend time running wires and installing the LED. (This is optional. And IMO, I would prefer to install a liquid filled fuel pressure gauge on top of my fuel filter for only $20.)

Consequently, the AirDog “dummy light” is of no value to me. But, if drive your RV all year, and want to save money on fuel filter changes, maybe you will feel different? To say the least this is a minor benefit at best.

So what are the major benefits that would lead someone to pick the FASS-TS "constant volume" pump over the AirDog-4G "demand flow" pump?

Answer: There may be only one, and that has to do with the how much more fuel the FASS system filters as you drive.

For example: If FASS filters 10x more fuel than the AirDog pump; and if that added filtration results in STRONGER/BETTER engine performance over 3,000 miles – like I experienced -- then it follows it will take AirDog 30,000 miles to do the same thing. (Just estimates of course.) ...But if this is true, IMO, that makes FASS a better choice over AirDog... after you consider these questions:

* Do you have a dirty fuel tank to begin with?
...And what 10+ year old RV doesn't?

* Would you rather wait 1 driving season to experience STRONGER/BETTER engine performance in only 3,000 miles as the FASS system cleans your tank; or can you wait for 30,000 miles to pass to accomplish the same thing with an AirDog pump?

...Why would you?

==> So again, for my needs, I would choose a FASS system (again) over AirDog even if it costs $150 more to install; which it doesn't in my case... since I did the installation myself. (DIY)

OTHER POINTS - COUNTERPOINTS

==> The FASS-TS pump is the same pump they use on Dodge Trucks and Semi Tractor Trailors. However, AirDog offers a different “truck line” of pumps, so if you go with AirDog for your RV, I recommend you do at “ArkansasRV” did and buy the beefier semi truck model # FPII-150 or go with the FPII-200.

For now, I hope we can all agree, if you have a CAPS injection system, you will save yourself a lot to aggravation, and money, if you choose to install and upgrade (by-pass) your stock Cummins Lift Pump to either the AirDog-4G or the FASS-TS pump?

We all are seeing more and more CAPS injection pump failures as our RVs age. Who knows when your CAPS pump will go due to ULSD fuels that have less sulfur content and therefore provide less lubrication and cooling to your CAPS injection system. To solve this problem, IMO, you should install either the AirDog-4G or the FASS-TS pump asap!

[imnprsd]

I have a 2004 Itasca “Horizon” 40AD (early model) that came with a 2003 Cummins-ISC-350-CAPS injection system. The late model 2004 Horizons came with a ISC-350-HPCR injection system and I think this type of injection system lasted to 2006, but I'm not sure. And then after 2006 the HPFR system prevailed even to this day. (Can someone verify this?)

So when I installed my FASS-TS pump in the exact same place as my primary filter (before the stock lift pump)… everyone told me I had to disconnect my stock lift pump wires to the ECM, and install a dummy relay, to fool the ECM, and to keep my dash warning light from coming on. So that’s what I did. And all is working great!

…But 8,000 miles later this is what I would do different.

I installed the FASS-TS pump myself; and I think any handyman can handle this upgrade. However, I did not feel comfortable pulling down my stock lift pump wires (working blind) because these things are hidden above the starter and you have to “feel” your way around. So I took my RV to Freightliner and they charged me $350.

Therefore, this method is being propose so you don’t have to deal with your stock lift pump wires or fuel lines at all. I.e., just leave them “AS-IS” …contrary to what everyone was telling me up to this point! …and save yourself hours of installation time ($350).

PARADIGM SHIFT

* You do NOT need to by-pass your stock lift pump fuel lines or wiring if everything is running fine now.

Specifically, you CAN route your fuel through the Fuel Bock aka Lift Pump Manifold (LPM)… so just leave everything “AS IS.”

* And you do NOT need to do anything to your lift pump wires, if you employ any of these two installation approaches for turning the FASS or AirDog pump “ON.”

1) Add a toggle switch in your dash to manually turn-on your FASS pump after your engine starts.

or

2) Add a 1-minute delay “on” relay (like this one) to your FASS or AirDog relay connector. I recommend you order 2 of these relays so you have one for a back-up:

https://www.qualitymobilevideo.com/b...mpaign=BU510TD

Note: Since FASS and AirDog use a 4-pin relay connector you will need to clip-off the center of the 5-pin relay. You don’t connect this center pin on the 5-pin-relay so don’t worry about that.

THIS IS WHAT YOU WANT TO ACCOMPLISH WITH THE 1-MINUTE-TIME-DELAY-RELAY

* When you turn the key to “On” your OEM lift pump will start to prime the injection pump. Then under ECM control your lift pump will turn “off” in 30 seconds, as it should. And this will allow you to start your engine.

==> If you have a CAPS lift pump you see +15PSI; and if you have a HPCR lift pump your will see +70 PSI delivered to your injection pump.

* After 30 seconds you will start your engine normally... and your engine will start using the fuel in the lines; and if you did not have a FASS or AirDog pump your fuel line pressure will drop to -5 PSI of vacuum pressure. This is normal too.

* When the engine running, the Injection Gear Driven pump is working.

* Then 1 minute after you turn your ignition key (with the time-delay-relay installed) your FASS pump will start… and you will see +15-18PSI delivered to your injection pump... and hopefully your fuel delivery problems will be solved!

…or you can flip the toggle switch if you choose that route.

This approach will work with either FASS or AirDog pumps, but I have to say I prefer FASS, because FASS-TS pumps filters and returns ~60+ gallons/hour of fuel back to your tank as you drive; and that is ~10x-15x more fuel as you drive vs. what AirDog Pumps filters. This will really help to clean your fuel tank and one of the best things you can do for a diesel engine is to provide the cleanest fuel possible without any air in it!

Of course, the FASS-TS pumps will require you to run a FASS fuel return line to your tank vs. AirDog pumps that will allow you to “T” into your fuel return line at the engine. So you decision to pick one pump type over the other is based on your choice if installation options and other factors, like… where your primary filter is located, side radiator or not, chassis type, etc..

SIDE NOTES

FASS uses distributors (like Parley’s Diesel.com) to exclusively sell their Dodge Kit Part#: TS D08 095G. However, you need to call FASSride.com to order 30-38’ of fuel hose (at $3/ft) for the FASS fuel return line, plus a Silver 2" filler-neck Yoke, any AN8 or A10 JIC fittings you may need. …But you might not need any JIC fitting if you can re-use your existing fuel lines. (TBD)

Remember, the primary purpose of adding a FASS or AirDog electric fuel pump is to protect your CAPS or HPCR injection pump by providing ample, positive pressure fuel under all driving conditions, which will prevent premature injection pump failures costing $5k-$9K!!!

FASS and AirDog pumps ensure your injection pump is properly lubricated and cooled. And is this is where your stock fuel delivery system falls short, because a stock fuel delivery system operates under -5PSI of vacuum pressure; and this is a poor design for and RV since our fuel tanks are located 30+ feet away from the engine.

Specifically, if your engine misses or stalls or just doesn’t climb that grade like it used to – and if you find these symptoms may go away after you change your fuel filters – or you think you got bad diesel at your last pit stop -- that’s probably not the case!

The problem is that air is getting into their fuel lines or more likely air is entering your fuel system between the lift pump gasket and this is why many owners end up with premature CAPS pump failures, because they are not permanently solving their fuel delivery problem. And what's the permanent fix? That would be to add a FASS or AirDog!

…and as fuel filters do their job, they increase back pressure in the fuel line. So what happens then? ...At ~30% capacity, a partially blocked fuel filter can cripple a vacuum fuel delivery system!

And at this point your -5PSI vacuum drops to -4PSI and then your CAPS pump will eventually stall out if you are lucky. And for those of us are "unlucky," we lost our CAPS injection pump due to excessive and constant heat caused by lower lubricity in USLD fuels; and this is why everyone, IMO, should be using Howe's or some other fuel additive at least every other fill-up, if not at all fill-up just for extra measure.

I know it’s hard to pony-up the dollars (aka pay insurance) to deal with possible unknowns, but in this case, you really should and you will be glad you did.

CAPS and ECM failures will cost $5K-$9K to fix and when a catastrophic failure like this occurs, it will leave you stranded and ruin your trip! These are the facts, and so don’t think I’m trying to scare you.

…There will be very high tow bill too! …And as our RVs pass the 60,000 mile mark, we will start seeing more and more CAPS failures from people who have not upgraded to a FASS or AirDog pump.

Further, IMP, if anyone is faced with replacing your stock lift pump, this is my suggestion: Don’t let your mechanic go that route.

The common rate for a stock lift pump repair is ~$1,500; and I think that money would be better spent upgrading to a FASS or AirDog pump!

...So if you are faced with a stock lift pump problem, then and only then might I consider by-passing the stock lift pump as everyone says you need to do. Which is false in my opinion. I.e., if the gasket ain't leaking fuel I would just leave the stock lift pump fuel lines and wiring to the ECM "as-is" and implement either #1 or #2 installation approaches (as stated above) to deal with the ECM wiring issue; but "yes..." you do not want both the stock lift pump and the FASS pump to run at the same time. This would cause your total fuel line pressure to "sum" the two pump pressures together, which in a CAPS system might not be good if the consensus is that your CAPS pump inlet PSI should not exceed 25PSI. However,
"deadhead" pressure limits in a HPCR system may not be a problem, because these HPCR injection pumps can receive over 100PSI without a problem. Still, I don't recommend 2 lift pumps running at the same time.

FASS & AirDog has been around for decades, but it wasn’t until mid-2019 that they offered these new generation pumps became available. And you can always do the first part of the installation yourself and then drive your RV to a shop when it comes to finishing the job… if you don’t’ feel comfortable dealing with the fuel lines. …But you do the Pre-installation part easily!

Good luck!

[Burgy]

could we not just mount the fass pump up by the tank and then only buy a small section of return line, pull the power from the front run bay(MONACO), on a timer relay.
Remove the air/water filter in the rear and accomplish the same thing as mounting in the rear and buying another 40 foot of fuel line.

[imnprsd]

Burgy: If you want to use FASS you need to run a dedicated fuel return line to your tank, because it will filter and recycle 60+ gal/hr as you drive, and that's too much fuel flow to "T" into your injection pump fuel return line. (And doing so will cause your pump pressure problems.)

However, an AirDog-II-4G pump only returns 1/2 - 1 gal/hour of fuel to the tank; and therefore, you can "T" in to the injection pump fuel line located in back of your engine. This may or may not be easier. Every RV is a little bit different.

Either pump is a great choice. I just think the FASS pump will clean your fuel tank faster than the AirDog pump, but one could argue any 2-micron fuel filtering is more than sufficient to clean the fuel and remove the air... so who cares how dirty your fuel tank remains? (I guess I do, but not everyone will.)

NEXT CONSIDERATION

HPCR injection systems need to keep their stock lift pump in the fuel delivery system, because it primes the injection pump for 30 seconds to 70 psi, and after you start your engine, the HPCR gear driven pump takes over and pulls a vacuum (suction) to draw fuel from the tank.

So I'm suggesting: When you add a FASS or Air dog pump you can a) install a On-Off toggle switch in your dash; or b) you can plug-in a 30s to 60s deley-on-relay and just leave your CAPS or HPCR lift pump "AS-IS".

Up until now, everyone has been disconnecting the lift pump in CAPS system, but this appears to me to NOT be the case. I.e., their are other options.

CAPS injection system lift pump only prime the injection pump at +15PSI so you can either leave that pump in the fuel delivery line or by-pass it when you install a FASS or AirDog pump. However, you still need to either a) Disconnect the lift pump wires and install a dummy relay to fool the ECM; or b) you can plug-in a 30s to 60s deley-on-relay... and then just leave your stock lift pump to prime the system like normal.

I hope this clarifies your options.

OTHER REMINDERS

* I prefer to mount the FASS or AirDog in the engine compartment or if you have a filter bay you can check out your mounting options. Some fabrication may be required if you have a filter bay.

In my Freightliner chassis with a side radiator, the FASS-Dodge Kit mounting (steel) brackets worked perfectly; and as shown in earlier threads all I did was to drill 2 holes... and I was able to re-use my fuel lines and JIC fuel fittings.

I know ArkansasRV has a Spartan Chassis and mounted his AirDog in a filter bay and he had to remove a welded bracket before he could add is own mounts.

==> So mounting is just as important when choosing between FASS & AirDog. You have to weigh the "+'s" and "-'s" when picking.

For example, if you chassis is a PITA to run a dedicated fuel line back to the tank then AirDog-4G is the best way to go, because as I said you can "T" into your injection pump fuel return line in a CAPS or HPCR system.

If FASS is easier to mount, and you like the 60+ gal/hour "fuel polishing" benefits, and you can install a 2" Yoke in your fuel filler neck, then I would go that route if you believe your fuel tank has or had algae problems you just can't seem to rid of.

[geordi]

I talked with FASS a lot in the last few days, and their suggestion was a TS165G kit, which I have now with me and soon to install. They said it can be installed where the existing primary filter is, and all it needs is key-on power and the return line to the tank. No mention was made about messing around with the electric pump from the engine at all. If the electric pump can pass fuel when it is not running, then it shouldn't mind having fuel pushed through it to the CAPS as well.

[imnprsd]

geordi: Depending on who you talk to at FASS and Airdog, or their distributors, you will quickly find out they do not know much about RV ISC and ISL injection & lift pump systems.

This is because their training and target market is based on fuel systems used in Dodge Ram & Chevy Duramax trucks, with a spatterings of Class 8 Semi Tractor Tailor knowledge.

If you call FASS and talk to Justin and Gene, they know about RV-CAPS engines, but they are still "winging-it".

Just this week I proposed to FASS my idea about using a delay-on-relay, and the passed it on to their R&D department, but again I doubt they will move forward with a new RV product line anytime soon. So we RV owners are on our own!

I'm guessing, when you got someone in FASS to help you, they lumped your RV-ISC/ISL application in with the Class 8 crowd; maybe because they got the impression cost was no object on your part, or you wanted the very best for your RV. Do you think that might be true? IDK. I'm just thinking that may be why they did not recommend the Dogde-Kit-95GPH (Part #TSD08095G).

...Which begs the question: Did you buy a FASS 165 GPH "Kit" or did you just buy the 165-GPH pump?

...Is it a Titanium Series pump released in mid-2019 or is it an older model?

...Does it have tall filters of short filters? The new Dodge Kit pumps come with short filters, but eventually you will want to use the tall ones, because tall filters have more filter medium than sort filters.

What I also know is that both the 95GPH FASS-TS pump or the 165GPH FASS pumps will work. However, the 165 pump will be returning almost all that fuel to the tank at idle, but that's just ~2-3 gal/min, which is manageable with a 1/2" fuel return line with no problem, but that's still a lot of fuel splashing back into your fuel tank. ...And almost twice as much fuel returning to the tank as the 95-GPH pump.

Why did your contact recommend the FASS-165-GPH pump?

Your wire harness in that 165 GPH kit may be longer, which is good if you need the extra length to reach your (ENGINE) battery bank, and your mounting brackets may be different than what comes in the 95 GPH Dodge Kit, which may or may not be better... so maybe you can send us some pictures of your installation and let us know how it goes?

* My guess is that the person you talked to... did not tell you about by-passing he stock lift pump fuel lines or electrical wires in your RV, because he does not understand RV delivered ISC/ISL motors.

For this reasons I have outlined options for dealing with your CAPS system stock lift pump, because you do not want both pumps running at the same time -- creating a "deadhead" fuel pressure to your CAPS gear pump reaching to 30-35 PSI.

==> To keep your CAPS "deadhead" PSI under +18 you want to follow any of 3 earlier mentioned options... including the option to manually turn your FASS-TS pump "ON" with a toggle switch mounted in your dash. ...which you can also do, but you have to remember to turn your FASS lift pump off.

[Burgy]

The question I was trying to pose is...

is there any reason the FASS pump can't be installed right next to the tank and push the clean fuel to the engine vrs in the engine bay. This would allow for a very short return line to the tank.

In the dodge trucks, the pump is mounted in that matter all be it a shorter run to the engine.

[TR4]

Originally Posted by Burgy

The question I was trying to pose is...

is there any reason the FASS pump can't be installed right next to the tank and push the clean fuel to the engine vrs in the engine bay. This would allow for a very short return line to the tank.

In the dodge trucks, the pump is mounted in that matter all be it a shorter run to the engine.

In my opinion this would be the preferred method as long as you have your final filter just before the CAPS pump. Bypass the existing lift pump and install the relay to fool the ECM (this is with a CAPS system).

Bill

[geordi]

Two low pressure pumps working inline does not equal a high pressure pump. That's not how that works.

There was not a significant price difference between the 95 and the 165, and who cares how much it is returning to the tank or if it is "splashing around" exactly? It's a closed loop. Yes it is the titanium signature, and yes it is the full kit, and yes the filters are 1"x14tpi which will work fine with the existing filters that I already have stocked up - so I can use them as the primary.

[Alpine36]

Originally Posted by Burgy

The question I was trying to pose is...

is there any reason the FASS pump can't be installed right next to the tank and push the clean fuel to the engine vrs in the engine bay. This would allow for a very short return line to the tank.

In the dodge trucks, the pump is mounted in that matter all be it a shorter run to the engine.

No reason at all Burgy, it'll look something like this when you're finished...feel free to pm me if you have any questions.
Mike

https://www.irv2.com/forums/f104/fas...ne-484540.html

[imnprsd]

You can mount your FASS or AirDog pump almost anywhere. The suction side will pull approximately -15PSI of vacuum which is ~3x stronger than your stock -5PSI Injection Gear Pump.

Just don't mount your FASS or ADog higher than 3' above the sump in the tank... and in an RV I don't think this is possible.

Spartan owners with access to the top of their fuel tank may choose to install their FASS or ADog close to the fuel tank, but us Freightliner owners don't have this option since we do NOT have access to our tank fuel lines.

My guess is that this option maybe preferable if you Spartan Owners do NOT have a side radiator or you don't have room in your filter bay.

In any event, I'm not a fan of crawling under the front end to replace the filters, but that's no big deal since you only do it once every 2 years or so.

The bigger advantage to installing a FASS or ADog by the tank is to utilize your existing fuel delivery line from the tank to the engine primary filter. (That is if you can?) ...Is so, then you can run a short fuel return line which is included in the kit... and avoid the cost of buying 38' of fuel line required if you mount your FASS by the engine or in the fuel bay. (Cost savings of $150.)

Note: If you have an Independent Front Suspension (IFS) then you probably don't have room up front to add a FASS or ADog. (TBD)

BY-PASSING THE STOCK CAPS LIFT PUMP (Pre-2004) - YOU HAVE 3 OPTIONS

1a) Cap the stock lift pump in and out on the fuel delivery side -- and never worry about leaking fuel out of, or air leaking into, your old lift pump again. Most people recommend this option.

1b) Leave your fuel flow "as-is" and disconnect the wires to the ECM; and use a dummy relay on the ECM side to keep the dash warning light from coming on.

2) NEW OPTION: Don't do a thing to your lift pump fuel flow or to your lift pump wires... by adding a Delay-On-Relay of 30s - 60s to your FASS or AirDog relay harness... so both pumps do not come on at the same time.

3) Install a manual On-Off toggle switch to manually turn your FASS or ADog on or off. Just don't forget! ...Especially the "Turn-Off" part!

Note: Pre-2002 engines have known lift pump gasket issues that appear to be not compatible with USLD fuels. So if you still have a stock lift pump with a OEM gasket that was never changed, then I would recommend you by-pass your lift pump in it's entirety.

Note: Contrary to what "geordi" said... Your PSI will add together if you run both lift pumps at the same time. (15+15=30PSI total) ...I verified this by installing a liquid filled fuel pressure gauge on top of my #3 filter before the gear driven injection pump. ($20) This is the "deadhead" psi to your CAPS gear pump and I understand the maximum inlet pressure to a CAPS pump should not exceed +25PSI.

** I recommend everyone add a liquid filled fuel pressure gauge on top of their fuel filter block (FASS or no FASS) which shows both positive and negative scales. (See other posts for Amazon links.) Or add a digital fuel gauge you can mount under or near your dash. This is a great diagnostic tool always at your disposal.

ADDING A FASS OR AIRDOG TO A HPCR (2004-2006) SYSTEM - 2 OPTIONS

Note: HPCR lift pumps produce +70PSI for 30 seconds in order to start the engine. Therefore, you have to leave this HPCR stock lift pump in a HPCR System.

Note: HPCR systems are sometimes referred to as CAPS-II systems due to their similarities. These two pumps are similar in principle but they use completely different parts. So here are your only tow options when installing a FASS or ADog in a HPCR/CAPS-II system. (See diagram below too.)

1) Don't do a thing to your lift pump fuel flow, or to your lift pump wires, and add a Delay-On-Relay of 30s - 60s in your FASS or AirDog wire harness... so both pumps do not come on at the same time.

or...

2) Install a manual On-Off toggle switch to manually turn your FASS or ADog on or off. But with this approach you need to remember to turn your pump off after you shut down your engine. So I prefer the other options.

Here are a few updated fuel flow diagrams that may help you decide on how you design your FASS or AirDog fuel pump upgrade. Good luck!

[momcat]

Hey.....I have followed ,loved and appreciated the depth you have put into this thread or post. My Question is how long did you run your fass pump thru the original lift pmp, before you bypassed it. I have had the titanium pump on my ISL for about 3000 miles. It currently is flowing thru the original lift pump. Now after reading your plan, I am going to make the changes like your diagram shows. I won't have the time to do it before I go South next week. My current system works fine, but I just feel like yours is superior compared to mine. I have no leaks at this time. I'm sure you understand my concern. My bus is a Tiffin, 2007 allegro bus, with a 400 ISL, with 31,000 miles. Filters have always been changed too often in my opinion.I am just asking for an opinion, and know that is all it would be. Thanks again for all the effort you put into this helpful site!!!! MOMCAT