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Old 05-29-2021, 06:09 PM   #1
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Leak determination help

While looking under the RV for leaks after changing oil, oil filter and coolant filter I noticed something leaking. I turned off the engine and scooted back under. The leak is coming from above the starter. Could have been leaking for some time but only just now noticed it. The area around the oil and coolant filters is dry (no signs of any leak). I believe the dripping is diesel fuel. It only continuously drips when the engine is running.

It seems to be coming from the area of the part in the picture (again just above the starter). There were drips on that part but I wiped it off before taking the picture. I actually checked it twice by starting the engine and both times drips were on that part.

Is that a fuel pump or part of the fuel system? What would you suggest as next steps?
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2004 Winnebago Vectra 40AD, 350HP Cummins ISC 8.3, 3000 Allison trans. Toad: 2012 Honda CRV. Living in Mt. Juliet Tennessee.
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Old 05-29-2021, 09:07 PM   #2
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I can tell you exactly what that leak is. 2 years ago my engine would start and then stall out 1 minute later. This went on-and-off for 2 years.

Solution: You just need to tighten your 3-lift pump bolts, but not too tight!

Air can get sucked into your CAPS injection pump that that is really, really BAD! So consider yourself lucky you caught this warning sign. And now you have a choice to make:

A) You can keep tightening those lift pump bolt every 10,000 miles, and that may or may not stop your fuel leak; or...

B) You can install a FASS 12V electric fuel pump and that will probably save you from a $6,000-$9,000 CAPS Injection Pump failure in the future.

Note: My CAPS injection pump failed around 84,000 miles and when it malfunctioned due to heat caused by loss of lubricity (air in the fuel line) it lost it's suction and ran dry too many times.

So installing a FASS or AirDog electric fuel pump will cure this problem.

Note: I first installed the FASS and wrote a lot about it on www.IRV2.com. So if you want more information you can search my user name on IRV2.com. ...But I did not change the fuel lines to the lift pump. So 25,000 miles later, as in last week, i too saw fuel dripping off the starter just like you and there was diesel fuel drops on the lift pump.

Sure enough, my 3-lift pump bolts were loose again by about 1/4 turn. ...Only this time I bypassed my #3 filter by creating a "closed loop" with the lift pump.

Note: A cleaner way to do it would be to remove the #3 filter and fuel lines to the lift pump and then insert plugs, but I am traveling and just swapping a few JIC fuel fittings was a lot easier and only took 20 minutes.

Now I have no fuel leaking and I'm only using the FASS Titanium Fuel Pump 2-Filters and my #3 fuel filter is not in service.

===

If you have never gained access to the top of your engine you do it by lifting the floor board between your bed and closet. This board has 4 wood screws 3" long to secure it to your raised step.

Note: You also have to work from inside your closet. Just remove the trap door and an "L-bracket" that has 8 screws holding it.

...And if you have a big air hole (gap) allowing engine hot air to get sucked into your basement AC intake register, this is the time to plug that gap!!! I used insulation and put the paper or plastic side facing the air filter.

OTHER TIPS:

* I highly recommend you add a FASS fuel pump with remote fuel pressure gauge ($150).

* This is a good time to add insulation around your engine hood. I even added insulation under the bed. Note: I used the type of insulation with a plastic backing that you buy for water heaters, but standard house insulation should be okay too.


* I recommend you add an EGT, which is real easy ($150). It will change the way you drive!

* And I recommend you put an Ag Diesel Performance Module in your ISC-350, but this is for the RV who has everything.
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Old 05-30-2021, 12:00 PM   #3
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I am updating the picture above to show how I used my old fuel lines to create a "closed loop" from the OEM Lift Pump Manifold (the Cummins Lift Pump screws into) to my old filter #2.

HISTORY OF MY FASS UPGRADE AND MY LEARNING CURVE

My ISC-350-CAPS came from Winnebago with just 1 remote mounted filter.

Then the previous owner installed a secondary filter when they had trouble with their engine's performance. This "kit" provided me with flexible hoses I used to connect to the FASS pump. (~91,000 miles)

So I removed the primary filter and installed the FASS pump, and did not touch the fuel lines to my secondary filter. Instead I turned it into my #3 filter. And my filter configuration was 20u-10u-3u.

At ~111,000 miles I notice diesel fuel drops during my walk around inspection.

I could have just tightened up my 3-lift pump bolts and that PROBABLY would have stopped the leak, but I wanted to get rid of the problem for good.

* IMO, everyone with a CAPS-1 system needs to tighten their lift pump bolts around 50,000 miles and the check them 10,000 miles later. (Use blue thread seal.)

For 15,000+ miles my fuel line out of the FASS pump ran back to the lift pump manifold and then to my #3 filter, and it never leaked.

This time, to fixt the leaking fuel problem at the Lift Pump Manifold for good, I created a "closed loop" between the OEM Cummins Lift Pump and my #3 filter.

Note: It's not the Cummins Lift Pump that is leaking. It's the gasket between the lift pump and the Lift Pump Manifold that leaks because the 3 bolts get lose.

In my case, since was traveling when I needed to perform this fix, I just "looped" the fuel lines in place and leaking fuel problem was solved for good.

Of course, I already have a FASS pump installed. If you don't then your only option is to tighten down those 3 Lift Pump Manifold Bolts, by going-in thru your bedroom floor and 9x out of 10 that will solve your problem.

Note: If you have older model Cummins Lift Pumps you may or may not be able to tighten down your 3 bolts to solve the problem.

Why?

2003 and earlier model coaches with a CAPS pump came with different gasket material that ULSD fuel is not very compatible with. So you guys might not be able to easily fix a fuel leak.

Note: I would never spend money to put a new Cummins Lift Pump back in place. This would be the time to upgrade to a FASS or AirDog electric fuel pump and you do it to protect yourself from CAPS injection pump and ECM failure that can cost you $5,000-$9,000 to repair.

==> Go to the IRV2.com website and lean more about this subject before it's too late!

Back to my commentary... and to repeat a few things. Now I'm using the two filters on the FASS pump and my fuel filter configuration is 10u and 3u.

Note: I seem to remember FASS saying they would prefer I do not use less than 20-micron filter on the suction side, but I have been driving for about 1,000 miles now and I'm not finding any issues.

I will call FASS next week to discuss this with them.

You can put whatever fuel filter configuration you want, but I wanted to keep my 10u filter because it has the WIF sensor installed and it is a WATER FUEL SEPARATOR; and I wanted 3-5u filtration on that #2 filter. So if you have only 2 filter connections then I went with 10u and 3u.

Note: Having used the FASS pump with an additional #3 filter, and now I'm running with just the FASS pump, I think my engine runs better without the #3 filter. So if you add a FASS or AirDog pump, just use 2 filters and remove the third filter or use it to create a "closed loop" like I did in the picture below.
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Old 05-30-2021, 02:35 PM   #4
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Well well well, Imnprsd, I read your very detailed response this morning and had to give tightening the bolts a try right away. Took my three mile ride out to the MH, opened the hatches in the bedroom and closet floor and found and cleaned off the top of the lift pump. I then tightened the three bolts about 1/4 turn, until tight as you suggested. Started the engine, checked for a leak and started my happy dance. I so appreciate your help and will make sure I am watching for a leak in the future and adding this bolt tightening to my maintenance schedule.

The other solution with the FASS pump is a little above my pay grade. Right now I have ~39K miles on the MH. If I experience leaks from the lift pump again, I may go forward with the more involved solution. But I'll definitely keep it in mind. I'm sure others on the forum very much appreciate the time you spend responding and the detail provided. I will also be adding the insulation you suggested and blocking the air hole (gap) between the engine and the basement A/C intake.


Thanks so much.
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Old 06-14-2021, 08:04 PM   #5
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Papayoda: I just read your reply, because for a while there I was not getting notices of new posts. Now this is fixed.

I am so glad you were able to do your happy dance!

I know what that feels like and it is why I try my best to help other RVers out.

Credit goes to a number of of IRV2.com owners and some here on this forum, because back in the day I was stuck in my Montana camp spot with an engine that would start and then quit. The solution was to tighten those CAPS Lift Pump Bolts.

25,000 miles later my Lift pump started leaking and once again all I had to do was tighten the 3 lift pump bolts... so when this happens to you again, I would recommend you add Locktite-Blue thread sealant to those 3 bolts... one at a time.

====

Adding a FASS or AirDog 12V electric fuel pump is an additional expense, but I think if you plan on owning your RV for another 30,000+ miles you really need to make a priority to do this upgrade ASAP.

===

I also think you need to start using PS-Diesel additive with every fill-up, because our CAPS system was not designed for ULSD fuel and you need the additional lubrication the PS-Diesel additive provides.

That said, I feel better when I fuel up with bio-diesel, because you want your CAPS injection pump to get all the lubrication you can add to your system. Of course, you really don't know if you are getting any bio-diesel when you fill up, but at least you don't have to worry about all the noise coming from those who hate the stuff. These same people believe there is such a thing as Bad Diesel and that is rarely the case.

Just keep using a biocide (off Amazon) when you store your RV and don't run too small of a fuel filter. Your Cummins engine does not like small micron filters and your CAPS system will choke on algae.

Note: In my FASS system I'm also going to recommend a 20-micron Water Separator (FS-1212 or Baldwin #BF-1212) and then I will use a 3-midron or 5-micron BF7633 on the Pressure Side of the FASS fuel pump.

If you have a stock Cummins ISC/ISL then you do not want smaller than a 10-micron filter since your injection pump has to suck fuel from the fuel tank and thru the fuel filters.
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