Cummins CAPS System Redesign

[jleamont]

Back home now. Did some more work today on this fuel system modification. I hooked up the fuel pressure gauge which is between the 2nd filter and the fuel injection pump. The factory design is strange when the lift pump shuts down in 30 seconds and the injection pump takes over. Monitoring that factory design on a gauge is scary. Sitting in the drivers seat with the engine running and watching the gauge fall to 3psi is gut wrenching. Almost complete and ready to make the final connections. Should be complete this week weather permitting. 

[jleamont]

Forgot to mention; fuel temps were running 20-30 degrees hotter than ambient with the fuel tank bay almost sealed off. I think I will add a cooler with a thermostat switch. We ran it from PA to AL, AL to New Orleans, back to TN, then to PA average ambient temps was in the 90's at the time. At one point I opened the fuel cap and got a fog of steam , I got my heat gun and shot it into the tank, fuel temp was 118 degrees, seems a bit high to me.

Any thoughts?

[dickandlois]

I have wondered how hot Diesel fuel gets when stored in above tanks? When it gets dropped into the station underground tanks it will cool to around 55 to 60 degrees in our area. Can not offer any real good information as to what the underground temps are in the South West during the summer.

Got to ask if your tank was full when you took the reading?

Always use Bioside  during the summer and the coach is setting for a length of time. Kind of cheep insurance to prevent or reduce the odds of the black slim formation.

Running with more then half tank and moving should keep it a little cooler and that sure helps keep the injector pumps running a little cooler.

Rich. 

[jleamont]

Rich, I checked the temps at 1/2 tank. I fill at the 1/2 mark. I always used additives now.

[wolfe10]

4 hours ago, jleamont said:

Forgot to mention; fuel temps were running 20-30 degrees hotter than ambient with the fuel tank bay almost sealed off. I think I will add a cooler with a thermostat switch. We ran it from PA to AL, AL to New Orleans, back to TN, then to PA average ambient temps was in the 90's at the time. At one point I opened the fuel cap and got a fog of steam , I got my heat gun and shot it into the tank, fuel temp was 118 degrees, seems a bit high to me.

Any thoughts?

Sounds like time for a fuel cooler (AKA transmission cooler) in the return line.  If in the air flow, doubt you would need a fan.

[jleamont]

Brett, I ordered this one http://www.jegs.com/i/Derale/259/15850/10002/-1. I spoke to their tech support department, they told me it would be a good fit for Diesel Fuel.

I have no space to add it to the coolant package, I do have a large spot to the side of it and behind into the engine bay area. I'm not crazy about the fan (more work to install) but if there isn't adequate air flow I will need to create it. I cant seem to locate a thermostatic switch low enough to auto turn it on, so I am thinking the mud flap might shove air upwards while driving and it will be enough to keep it cool (so maybe there is a reason for the flap on my coach.... Flap sits behind where this will be mounted). If not I will install the fan on it that it comes with and wire it up. Really thanking myself for pulling one 8 conductor trailer wiring harness down the spine when I replaced the fuel lines in 2014 just incase I needed it. So far it has come in handy.

My plan is to mount it toward the front of the coach on a 45 degree angle forward of the filter in the picture (it is soon to be leaving). I'm guessing that there is air flow coming up from there as the flap is mounted just beyond that. Besides, if it ever leaks it wont spray fuel onto the engine.

I think the coach name will have to change to Frankencoach

[wolfe10]

Yup, with that cooler, all you will need is an additional hose from where the fuel return line connects to the engine  to the cooler and then perhaps an extension hose to connect cooler "out" to the fuel return line.  Suspect you will change the hose fittings on the cooler to match the engine's return line style fittings.

[jleamont]

All connected and working.

I will install the fuel cooler when it arrives. At this time we have no more long distant trips planned so temps shouldn't be such a concern. Call me crazy but it seems to idle smoother 

 

[jleamont]

Photos posted in the gallery here;

 

 

[manholt]

Rich.  Underground temps are 57 degrees.  In the South, you just have to dig deeper than in the North!  Water lines are reverse, N deeper, because of cold.  In the South, about 18" is the norm!

Carl

[jleamont]

Fuel cooler installed. If you look closely you can see my mudflap, I'm hoping it will direct air up and into the cooler.

[manholt]

I see a tiny little green thing that I think is grass & mudflat ! Big Fan! 

[jleamont]

Better photo of the flap

[jleamont]

Final update: drove it into the hills of Lancaster co PA for a holiday weekend getaway. NEVER have I had this much power, boost gauge at 25 in a blink coach will pull you into the seat. Idles smoother and accelerates much faster. Very Happy with this modification. 

[wolfe10]

jleamont,

Very good job of reporting-- often what works on a front engine truck may not be adequate for a longer diesel pusher.

Might be a good idea to post all the PN's of what you used (pump, additional primary fuel filter, etc). Details of wiring the additional fuel pump (suspect ignition-hot source with its own fuse), exact change in fuel hose routing, etc.

Thanks.

Brett

[jleamont]

Brett, great idea. When I get home And pull all of my data I will do that. 

[jleamont]

Ok, here is my parts list for the project and the overview on how it was completed. You will notice some of the parts listed for the modification were completed utilizing aftermarket performance parts for a Cummins 5.9L in a Dodge pickup truck. This modification is fairly common on a Dodge Ram with a Cummins ISB but since it is a DP coach with a 8.9L ISL some additional modification's had to be completed to make it work properly. The reason it worked so well on the ISL 8.9L is the parts were spec'd for a Modified 5.9L with an output of 425 HP, which is close the same spec as my ISL.

Fuel pump; Fass part number FA D08 95G link; http://store.fassride.com/detail/diesel-fuel-pumps/adjustable-diesel-fuel-pumps/adjustable-dodge-ram-cummins/adjustable-fuel-pump-95-gph-dodge-cummins-1998-1999-2000-2001-2002-2003-2004.php

Fuel pump set to 17PSI from the factory, not touched.

Davco filter; 243950RLFGD-10 (Davco model 243 Cummins filtration design with a 10 micron filter (same spec as the original primary filter, no micron changes were made), none heated, no water in fuel sensor) literature link;http://www.davco.com/forms/tech/F1215.pdf

Note; The Davco was not needed, the factory filter could have been utilized, I just wanted to be able to see the condition of the filter and the fuel flowing through it.

Fuel, one way check valve; https://www.summitracing.com/parts/sum-220194b

Note; Fuel one way check valve, not needed if I kept the factory filter housing, it incorporated a one way check valve from Cummins, since I was not using that filter housing I had to install one in its place.

Fuel Cooler; Derale # 15950. Link; http://www.jegs.com/i/Derale/259/15950/10002/-1

Relay; Standard fog light type relay. https://www.summitracing.com/parts/bch-0332019155?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-bosch-automotive&gclid=CM-66prO_84CFYtbhgodXcQHSw

Note; The fuel cooler would have not been needed had I not closed off the fuel tank bay with another coach modification (removal of the propane tank)

Fuel pressure gauge; Autometer, modified by their custom department, changed to a black face and chrome bezel to match the factory gauges in the dash. link; http://www.autometer.com/2-rail-press-0-30k-psi-fse-cummins-5-9l-4474.html

Fuel pressure gauge on pump; not needed but I wanted to see what the pump was set to and to use as a tool to see how clogged the secondary filter is (compare the two gauges to determine secondary filter condition). link; https://www.summitracing.com/parts/hly-26-502

Factory fuel pump extension wiring harness; Used to connect relay to existing fuel pump connection. Reason; the factory fuel pump only operates on startup for 30 seconds and shuts off, if nothing is connected the "Engine light" will illuminate (ECM thinks the lift pump circuit has failed). I extended the harness to my rear "coach" electrical compartment and used this harness to get the factory connection from the ECM at the factory fuel pump to that compartment. I used a standard Bosch relay on pins 86 and 85 (positive on pin 86, negative on pin 85) to energize the relay, for nothing more than to trick the ECM into thinking the original fuel pump is still connected and operating (the ECM only needs to see resistance). link; http://www.fassride.com/detail/accessories/drp-fuel-pump-relocation-kit/drp-relocation-dodge-ram-cummins/ddrp-fuel-pump-relocation-kit-dodge-cummins-2003-2004.php

Fuel system layout;

Existing Fuel Tank, one way check valve, Davco primary filter, Fass fuel pump (with Holly gauge mounted to it)(located up front of the coach next to the tank), secondary filter (OEM filter from Cummins located in engine bay, original location) "T" on outlet to injection pump with sending unit for dash mounted pressure gauge, factory hose to the CAPS pump, AKA fuel injection pump.

Wiring layout; The new fuel pump is connected to the chassis electrical panel/compartment located in front of the driver steer tire. The Fass pump came with a wiring harness which incorporated a fuse and relay to power up their pump, which is now on a circuit that is ignition switched (key on, pump on). Pin 30 is connected to the Chassis battery lug in that compartment with the inline fuse connector it came with and pin 86 is on an open ignition circuit that was in the main power circuit board not being utilized by Monaco (also with an inline fuse I added). I had to modify their harness as it was designed to connect to the factory pump on a Dodge ram and that was connected to pin 86 on the relay, it was originally designed to power the relay from the factory ECM harness. The Cummins ISB in a Dodge operates differently, when the key is on so is the pump, my existing fuel pump circuit is not (only on for 30 seconds) so a slight alteration of their harness and I just needed a different power signal key/ignition switched to power the relay coil, which is also the reason I could not use my factory fuel pump power harness, plus my harness is located in the rear of the coach and the new pump is in the front next to the fuel tank.

Plumbing; Since Monaco in these years plumbed the fuel system with 5/8" hydraulic hose and JIC fittings I continued with this and just made extension hoses to reach the new layout. All fuel lines are only 2 years old, so replacing them was unnecessary, I just needed them to reach places they were not capable of without some extension hoses. All fittings are hydraulic hose fittings that were crimped on.  I capped the factory lines no longer needed as follows and left them in the engine bay, just tied out of the way;

Line between the OEM primary filter and OEM lift pump, capped.

Line from the OEM lift pump to the secondary filter, capped.

At the tank I added a section of hose to reach the Primary filter from the fuel tank. Another section to reach from the pump outlet to the existing line that was connected to the fuel tank (runs from the front of the coach to the rear) Another section of hose from the inlet side of the old OEM primary filter to the secondary filter inlet.

Returned fuel via the Original fuel pump; by design all excess fuel from the injection pump and cylinder head return to the factory lift pump, which in turn send the excess fuel to the tank (it is only a manifold for the points to connect to on this portion of the pump). This would normally be untouched, due to closing off the fuel tank bay, the tank does not get much air circulated around it to cool the fuel. I have installed a fuel cooler to correct this. One line from the cooler attaches to the old pump (return side of the pump) and the other connected the cooler and the existing return line from the rear of the coach to the fuel tank.

Any questions please feel free to ask.

 

 

 

 

 

 

[dickandlois]

Joe, Think I should look into offering your clerical staff a job.

Rich.

[jleamont]

Rich, thank you. It sounds much worse than it was. 

[blakeloke]

Joe,

You do absolutely amazing work from engineering, project design and installation.  Much beyond my paygrade!  I'm gonna have our mechanical guy look at your post and see if he can perform same. 

Like you, I want to insure reliability over better performance. But, I don't know what I don't know, but everything you and others have said makes a lot of sense!

Thanks for the documentation of the work!

Blake

[jleamont]

Blake, your engine should be "High pressure Common rail", not CAPS (different design) Ask your mechanical guy to look. I do know you have the same lift pump and should have the same issue pulling fuel that distance

[rvarner]

This mod sounds great.  I assume it would work on an ISC 350 with CAPS-2004 Itasca with one filter.  I know the starting pump has been replaced but just waiting for the other one to crap out. Thanks 

Rich

[jleamont]

Rich, can't imagine why it wouldn't work. You might need a different spec fuel pump based off of your HP. Are you sure you only have one filter?  

[jleamont]

Took the unit for a good run to Mt Pocono over the weekend. Have accumulated around 300 miles on it, pulled hills like a champ. I suspect the lack of fuel to the engine was why my MPG's were so good. It has appeared to drop slightly in MPG's. Trips to the beach, the best was 10.05MPG, (have to re run this in a few weeks to see) to the Poconos best was 9.49 to now 9.24. As we know fuel quality, air temps and wind all play a part on this, so its hard to tell. I am expecting a drop in economy, no complaints with that as long as the engine is getting the proper amount of fuel to be happy, I'm happy .

[manholt]

9 and 10 mpg's?  I'm lucky when I get 6.4 !!!  Is that by computer or actual known mileage vs actual gallons used?  I go by gal, miles...no gen on.

Carl