FASS fuel system install upgrade
I've had a few that were following my work behind the scenes, I promised I would give details when it was all done and working as intended. I upgraded the fuel injection system on my 2001, U295 8.3 ISC. This was done at the same time that I was already doing my 20 year old fuel line replacement. As I still work full time this entire task took several months of effort. I only recently took the RV out for a full trip and the system performed nicely.
Why did I do this upgrade?
All Cummins ISC engines from 98- mid03 used a fuel injection system known as CAPS (Cummins Accumulator Pump System). Not exactly a proud moment for Cummins, if you have ever spoken to any Cummins techs. This system incorporated a system priming pump, known as a lift pump. The OE lift pump, a very little robust centrifugal sliding vane pump, would only prime the system for 30 seconds. After the 30 second prime, the very costly main injection pump would suck the fuel to keep the engine running. The weak link in this system is the OE Lift pump that has been known to start leaking at its mid-section gasket. Once leaking then would also suck air inward during regular running. The fluid path of diesel was the sole cooling medium for the injection pump. Any air in the stream would rob from the cooling effort, affect engine performance and also tend to cause issues with the individual injectors. As the area of the lift pump is never really under much pressure (usually under vacuum), it is not common for owners to notice a leak until maybe it's too late.
Now there have been limited reports of these injection systems totally failing in the RV market, but count-less units in the heavy truck industry. However, if you search the many RV forums out there, you will find several that have suffered costly losses. Not to include very inconvenient trip interruptions. Many of us DIY many if not all things, as well as try to prep for any potential road failure. To me, this was one of those worst case scenario things that a DIY RV owner can prep for and not at a very costly price compared to many other things.
Knowing what style/type/vintage RV I was after when I started my search, I also knew it might incorporate a CAPS setup. Once I educated myself on the issue, I also put together a plan for if I purchased a unit that had it. Sure enough, I ended up with our 2001 U295 Foretravel that with an 8.3 ISC, had the CAPS injection system. At PPI there were no issues with my pump, but about 6 months after, and a few runs, sure enough the darn thing started leaking.
There are no direct recommendations at FASS for the Cummins 8.3 in the RV market, but after a phone conversation with a company rep the recommendation was made for the Fass Titanium series, Universal Class8.
Fass TS 100G
Fass T 150G - Semi Fuel System
(I know this link says 150, but it takes you to the 100 system)
This is a basic universal kit. This kit mainly comes with the new pump, pump bracket and housing, basic mounting hardware, wiring harness, initial set of filters. The installer will need to come up with all the extras that are needed to finalize an install.
As stated. I started this by upgrading all of my entire fuel lines. Using Trident marine diesel line, replacing all engine, Generator and Aquahot lines. I did have to run a new 3/8" return fuel line for the FASS return.
Both FASS and CUMMINS recommend against tapping into the existing CAPS return line.
Some points to mention.
1.) I was able to re-use all of the original Aeroquip pushlok barbed fittings, but did need to get fittings for the new FASS fuel return line.
2.) The fuel tank, on my model has 3 fuel return ports.
a. 1 for CAPS return
b. 1 for Aquahot return
c. 1 for Generator return
3.) I combined the Aquahot and generator return into 1 return using a billet fuel system 3 way splitter block.
4.) The freed up return was dedicated just for the FASS return
5.) I bypassed the OE Lift pump, but have plumbing in place to easily pipe it back in should I need to in an emergency. I did this for 2 reasons.
a. One of the problems the FASS install prevents is any air in the fuel path being provided to the injection pump. As the lift pump body would still have this possibility due to its mid-section gasket, I did not want this in my system.
b. The OE lift pump is not accustomed to constant pressure on it. As the FASS pump provides constant pressure to the injection pump, in my situation I could never get it to stop weeping fuel even with a new gasket. Others online saw a similar issue and went the bypass route as well.
My OE lift pump is still in place and functional if ever needed, but not in the fluid path for normal FASS operation.
6.) The OE lift pump wiring harness MUST have an electrical load installed, or a Cummins engine code will go off. A standard 12vdc lighting relay will do the job.
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7.) I used existing spare Foretravel wires running from Cab to engine for FASS trigger voltage.
8.) It is preferred to use 90° fittings on the fuel suction and return, you will need to acquire/build these as the FASS kit comes with straight ones. On my RV the OE lines were 5/8", the fass fittings are ½". So as I did not have to alter the fittings on the fuel tank and secondary fuel filter, I opted to keep all my lines 5/8" and do any coupling work at the new FASS pump.
I started by doing my fuel line upgrade. I purchased several metal barbed fittings, 3/8",1/2", 5/8", that were used to assist in using the old lines to pull in the new lines. I also installed a nylon string alongside each pull just in case a barb were to come loose (1 did) I left the string in place for any future pulls of any nature. 1 string was used when I chose to pull a new multi conductor electrical line for a digital fuel pressure gauge that I mounted near the dash.
I chose to mount my pump on the back passenger side frame rail in place of the original primary fuel/water separator filter. Some oe holes were reusable, I did have to drill/tap a few new ones. You can purchase extra bracketry from FASS if you want to bolt around the frame rail. I wanted my system to look factory not like an add-on. I gave each fuel line some extra length just to make sure nothing rubs, and room to trim back at a later date if need be.
Using the OE Aeroquip fittings, lubed with oil, using a rubber mallet was easily able to make these work with the new Trident fuel line. On the old pushlok fittings there are no need for hose clamps, but in marine type fashion, I used tie wraps as an added band around the barb. Fittings I had to buy extra that are standard barbed, I used conventional hose clamps. The discharge out of the new pump went straight to the secondary main fuel filter that is routinely mounted on the rear passenger side of the engine. There is normally a hard "S" shaped pipe from it to the OE lift pump. I removed the hard pipe from the filter end, rolled it out of the way and capped it. DON'T FORGET TO REPLACE THE SMALL SECTION OF HOSE BETWEEN THE FILTER AND THE INJECTION PUMP. *** SPECIAL COMMENT ABOUT THIS DURING SYTEM STARTUP***
At the fuel tank, while it was out. Boy that was a chore on my unit!!!
DSD (Scott) was on the phone for moral support as I attempted his recommended pull method. However after nearly ripping the bottom "L" flange from my tank I opted for a tractor and battering ram approach, it came out nicely after that. It appears my FT had that area built on either a Monday or Friday as some of the fuel lines coming from the front of the RV were wrapped around the entire bundle vs just coming through the pass and turning. This is what was causing my not so smooth removal issue. Some reroute on the return as well as a complete bundle slide shield made it go back in with very little effort.
Using the push out approach, which was the only option I had, I was forced to remove the large fiberglass fuel tank side cover on the driver side. As my unit has this rather large metal cross member for some sort of slide support, I was forced to remove the cover by means of cutting it in half horizontally. This was not a big chore using a pneumatic body saw. Easy to remove afterwards, also easy putting back in. Now 2 sections with rubber molding over the cut edges.
Anyway on to the FASS upgrade. At the fuel tank once I identified the 3 return ports, I used a Billet "Y" type fuel splitter to tie together the 2 fuel returns (Aquahot/Generator) into 1 return.
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The fused/relayed power harness for the new FASS Pump was powered via one of the cranking battery hot posts back under the bed after the Isolator. The 12vdc trigger for the FASS relay came off of the ignition switch ON position, but I used a Foretravel spare wire to get it back to near the relay. A pressure gauge was installed near the dash (at the moment) using a provided harness and a new multi conductor cable that I pulled from pump area to dash area. I didn't want to use up all the FT spares.
The last part is to pull the wires that go to the OE Lift pump. The Cummins ECM has to see that an electrical load is present for the 30 second priming sequence that the OE lift pump used to perform. It used to detect that the coil of the pump was in the path. What you have to do is wire in a load to take the path of the old pump. What the masses use for this application is a standard 12vdc lighting relay. You take the two wires that used to go to the pump and wire them to the coil connections of the relay. Usually these are pins 85-86. The ECM sees this coil as a load and satisfies the starting condition, thus not creating an ECM error code. I myself made up a small harness to incorporate this relay and have it mounted on top of the engine easy to get to should it ever need to be replaced. Then I put shrink wrap on the old Lift pump connector so as it would not accidentally touch anything and laid it back out of the way for the hopeful never needed emergency usage. I also made a cap to protect the socket of the old lift pump.
For the test running.
I tried to use a small amount of pressure on the tank to force fuel back to an open filter on the FASS system, but after 20 minutes no fuel ever made it back there. Rather, using the FASS recommended way, ran the pump in few small cycles, within a matter of seconds the filters were flooded. I then confirmed that fuel was coming back to the tank via the new return line. After letting this run for about a minute attempted to crank the engine. But I could not get it to crank. After a few attempts I got an Engine fault code associated with fuel pressure.
***THE EARLIER COMMENT ABOUT THE SHORT FUEL LINE BETWEEN MAIN FUEL FILTER AND INJECTION PUMP NOW COMES INTO PLAY.***
No other internet write-ups on this conversion ever stated what I experienced. However, in my case it appears by replacing that small fuel line, and fuel within the injection pump draining out, I somehow got enough air into the fuel path that the Pressure transmitter was full of air rather than fuel. I had to pull the Fuel pressure transmitter from the injection pump body, and with my wife bumping the FASS pump power waited until I had fuel coming out of the transmitter port. ***CAUTION*** when you pull the transmitter there is a small stainless bushing inside of the port that I think aids in sealing off the path to the transmitter, if you do not realize this bushing is in there you could easily blow it our during the priming and lose it.
Once I cleared the trapped air situation, the engine came to life. Having all things still uncovered checked all fittings, etc for leaks, and did so several times over several short local runs.
The FASS system runs at around 20psi idle and 15-18psi going down the road. For those curious of Cummins technical specs, the CAPS injection pump is rated to accept up to 25 PSI constant incoming pressure.
I took it out on several around town 15-20 miles runs, but this past weekend we took it out for its first decent distance highway run. Here is what I have seen since having this system.
1. Smoother idle
2. Better acceleration
3. Improved MPG
FASS claims all of these as well as easier cranking. I cannot say for sure it cranks any differently than it used to, but it most definitely idles much smoother. Throttle response is much more responsive than it used to be. I used to average about 8.5 mpg, but then again never really did as accurate a test as I did this last weekend. Based on talking with other Class A DP owners, the numbers I am seeing are pretty impressive.
This past weekend. Mostly interstate or 4 lane, average speed with cruise at 62-65, not much elevation changing, occasional stop-go, we ran 350 miles on 33.71 gallons = 10.38mpg. We were flat towing a Honda CRV and we ran the generator 100% of the time, including when stopped to keep the roof air running.
I did this upgrade as stated to ensure long term reliability and minimize a potential costly loss. Not really to gain all that FASS claims you will or might see. However, aside from the reliability part, I am definately glad I did this. To me, all the extra gains makes this a very solid investment and bang for the buck. You also get the added feature of constantly having your fuel polished for air and contaminants.
I hope anyone contemplating this upgrade finds this information of value.
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Topic: FASS fuel system install upgrade