2003/4 Cummins ISC 350HP Sputter - Cough - Stumble Up A Grade Vs "FRESH DIESEL"

[Ivylog]

Originally Posted by Ray,IN

The FASS system also removes air from fuel(normal condition), which is an obvious benefit.

I read that to say air in the fuel is a normal condition that the FASS removes. Is that what you are saying?

[TR4]

There should be NO air in the fuel system.

Bill

[imnprsd]

If my engine starts a tad slower than I am use to after priming the system with the lift pump...

If my engine runs for ~2-3 minutes and then dies...

If I just changed both my fuel filters...

If I loosen my diesel fuel cap... re-start my engine... and then the thing runs fine... What do you conclude?

History
This happened before when the temperatures dropped from 60F the day before to 30F over night. ...But then this engine start then quit problem happened to me last week in Montana the weather was 45-60F. So I'm saying temperature is probably not a factor.

OTHER POSSIBILITIES? QUESTIONS FOR THE TEAM?

1) The only thing that is common between this engine start/quit condition today and the same thing that happened 2,000 miles ago... is that both times I only have a little more than a 1/4 tank of fuel.

So I'm wondering if the shear weight of the fuel in the tank has something to do with the line pressure delivered to the CAPS gear pump? ...And so.. if there is not enough pressure reaching the gear pump, might it be possible for the pump to starve and the engine quits?

2) Maybe my fuel line is eroding and air is getting in the line. If so, which like is more likely to fail first? a) The line to the pump or B) the return fuel line? Which one is higher pressure? Or should I always look a the line from the tank to the pump because this line is the suction line?

3) Maybe my lift pump gasket is leaking? (Doesn't look that bad, but I do see some oil or diesel fuel discoloration around one side of the lift pump. ...And I have not checked to see if the 3 bolts holding the lift pump to the manifold are loose. I will do that soon enough. I was thinking I would start my engine up a few more times with the gas cap loose and not worry about checking the lift pump gasket... unless the engine starts... then quits again.

I was hoping I was out of the woods, but based on your comments it does not sound like other people are buying into the "Diesel Fuel Cap Theory" caused by... A) Bad fuel caps or B) Stuck/cloggeed fuel tank vent.

4) Why would I see air bubbles being sucked into the primary fuel filter bowl when I loosened the drain-stop-cock? ... Or is this normal when the engine quits?

5) And maybe it's common for suction/vacuum to be created at the primary filter after an engine quits?

>>>BUT>>> In spite of all the "maybes listed above..."

...why does my engine run fine when I loosen the gas cap?

... Does this signal the fuel tank vent (on top of the tank I think is clogged?

... BTW, does this valve open when there is suction or when there is pressure?

Thank you very much for your help. I plan to have a FASS Lift Pump installed by Brazel's in Washington State when I bug-out of my summer spot in Montana in August... but I have to get there first!

Maybe with your help I will be able to do that? My fear is that my engine may run fine after I get her warmed up. So I will confirm this next week when the temperature drops, but I don't think it's a temperature issue unless that fuel tank check valve is pressure sensitive... or this condition will not happen if I have more than 3/8 tank of diesel in my tank the morning after I shut the engine down. TBD

[BigLar368]

My tank was easily accessible when I installed my FASS pump. I had to plumb in a return off the new pump so I tied it in with the vent line. My vent is nothing more than a hose coming out of the tank. There is no check valve. Just a fitting in the top of the tank with a small hose hooked up to it.

[Ray,IN]

Originally Posted by TR4

There should be NO air in the fuel system.

Bill

And Ivylog,
You are correct; however there is: https://www.parker.com/literature/Ra...iesel_Fuel.pdf
In addition to the FASS system, this is the only other such air/fuel separation system I know about.https://pureflowairdog.com/
You will note the similarities in design.

[imnprsd]

Nothing more frustrating than an engine that will not start, except for an engine that starts and then dies 1 minuet later! Ug!

UPDATE

* I started my engine today and it took longer to start, which is something I think is part of this problem??? … Then 1 minute later the engine died.

My engine usually starts-up immediately, but the last two starting efforts I had to back the key off after cranking for 10 seconds. And on the second attempt the engine started. And I think it’s getting harder to start the more I try.

* Before I started my engine today I left my fuel cap loose. And since the engine died … I can take the "fuel cap theory" out of the picture.

BigLar368: You said in your 2004? Monaco RV (with a Cummins ISC & lift pump) you tied your vent tube coming out of the fuel tank to the return line of your FASS pump. Is that correct? …What was the little vent line connected to before you added the FASS pump?

* I will now proceed to tightening the 3 bolts that hold the lift filter to the fuel manifold by accessing this area through my bedroom. However, I think my problem maybe elsewhere. TBD

COORELATONS

1) My engine is not starting as easily as before. So now I have to go through several attempts to start the engine before the final attempt (2x, 3x or 4x is a charm) keeps the engine running.

2) After several attempts to keep my engine running, I assume the engine is getting warm… so if my engine starts and keeps running… do you think that engine temperature is a factor? I.e., whatever is causing my engine to die after 1 minute, could that be related to the engine temperature? Is there a sensor involved that would electrically affect the engine running?

...I know I'm reaching but I'm running out of maybes and what-ifs!

[imnprsd]

So I accessed the top of my engine and inspected the Lift Pump Manifold (through the bedroom).

At first I just saw a 15 year old Lift pump with lots of dusty-grime around it. But with closer inspection you can see discoloration under the top layer.

What ever the source of the grime that condition has been leaking for some time..

Questions:

* Is this area is prone to this sort of build-up?

* If you trace the discoloration on top, where this grim is coming from?

* I'm guessing vapor is leach out of the 3 lift pump bolts, because after I tightened them 1/2 turn that I believe (hope) fixed my engine quit problem. What do you think?

So I think the solution to everything I have been concerned about in this thread was solved when I tightened down the 3 Lift Pump Bolts. (...with not too much torque).

To verify this: I twice started my engine and she kept on running!

Of course I will double check this condition tomorrow and again in 1 week. So if you don't hear back from me then you know this was the problem!

I would like some opinions on the discoloration coming from and/or surrounding the fuel lines. Do you think this is a sign of a deteriorating fuel line or bad connector or just blow-by from the vapors leaching up the 3 loose lift pump bolts?

Many thanks to everyone! This forum is the best!

PS
While I was in my engine compartment I noticed the Charge Air Cooler Pipe Clamp broke. This is the second time that happened. (See picture.)

Any thoughts as to why this is happening? And might this breakage have to do with raising the coach? I.e., Does the radiator and charge air cooler raise with the coach body or does it remain rigid with the engine?

[BigLar368]

BigLar368: You said in your 2004? Monaco RV (with a Cummins ISC & lift pump) you tied your vent tube coming out of the fuel tank to the return line of your FASS pump. Is that correct? …What was the little vent line connected to before you added the FASS pump?

My vent line was just a fitting in the top of the tank with a small hose attached to it hanging down on the side of the tank. The FASS pump does not "dead head" fuel into the injection pump. It bleeds off excess pressure back to the tank. This excess fuel is returned to the tank via the vent hose. The fitting in the top of the tank may be a roll over style fitting or one way fitting meaning if the RV were ever to be upside down then fuel would not leak out. One more thing.....the injection pump also returns fuel back to the tank and I believe that line(s)/hose(s) runs through the stock lift pump. I left my stock lift pump as it came from the factory other than unplugging it and disconnecting the feed line from the pump to the secondary filter.

As far as the dirty lift pump that just diesel that's been leaking for quite some time and with the road dust build up it just makes things worse. Even though the pump only runs 30 seconds fuel is still drafted through it. The lose bolts could be letting air in that could shut the engine off.

Other than my lift pump not filling my filters upon changing them our RV never missed a beat. With that being said I wanted to be proactive and not have any problems down the road. That is why I installed the FASS pump. It's well known that the CAPPS pump is not the greatest Cummins idea thus far but we are stuck with it. Installing the pump was very straight forward mentally but was physically hard to run the new fuel line. If you do install the FASS pump I would recommend changing the fuel line as well while you are there.

[imnprsd]

Here are a few pictures of my fuel lines going into and out of the Lift Pump Manifold.

Questions:

1) My return fuel line is copper. Is this normal or did the previous owner replace this line? (Because I didn't replace it and I was not expecting to find copper. Or maybe this is just a copper tube that connects to a flexible fuel line I just have not found at this time???)

2) Which fuel line is likely to degrade or go bad first? A) The suction line from the tank to the primary filter and lift pump; or B) The return line from the CAPS Fuel Pump (via the lift pump manifold) to the diesel fuel tank?

[Ivylog]

OP, 17 days ago I suggested the next step (after filters) was to check for air in your fuel system (not the BS of air normally in diesel). Stumbling and shutting down after starting are both signs of air getting into the system. For $5 at HD you can add a sight gauge before your second filter (easy to get at)...6” of clear plastic tubing, a short pipe nipple and 2 clamps added to the in side of the filter. Any bubbles after cycling the key a couple times or while the engine is running confirms your problem...finding it is the next step. Mine was a tight fitting at the fuel tank (had a big change in temperature over night) and putting it back on (after removing the dip tube) solved the air getting into my fuel system.

[mackwrench]

That fuel line is not copper. It's a flexible nylon line made for fuel systems that's brown.
I doubt that line is any issue.

The hose from filter could be, but you'd see black chunky yucky stuff in filter/pump/lines
I take it you poured out the old filters to see if anything bad in them...

Your chasing your tail, the easiest way to diagnose this is to eliminate parts of the fuel system till problem is found.

You can remove the line coming from primary filter, attach a short, 3 or 4 foot, piece of hose drop hose in a 5 gallon can of clean fuel run it at high idle for a while and see if problem goes away. If so, issue is between primary filter and tank. If not then between secondary filter and engine.


My gut is gonna be the lift pump. Is yours is original, that's a long time for one of them to last, lol

[TR4]

Originally Posted by Ivylog

OP, 17 days ago I suggested the next step (after filters) was to check for air in your fuel system (not the BS of air normally in diesel). Stumbling and shutting down after starting are both signs of air getting into the system. For $5 at HD you can add a sight gauge before your second filter (easy to get at)...6” of clear plastic tubing, a short pipe nipple and 2 clamps added to the in side of the filter. Any bubbles after cycling the key a couple times or while the engine is running confirms your problem...finding it is the next step. Mine was a tight fitting at the fuel tank (had a big change in temperature over night) and putting it back on (after removing the dip tube) solved the air getting into my fuel system.

I have to agree. In troubleshooting you have to start at the most common problem and eliminate it, them move on to the next. You’ve been given great ideas on areas to check. You shouldn’t worry about a fuel return line when you haven’t first checked for air in the system, which has been recommended by more than one member.

Don’t overthink this, start with the basics (air in system), then report back.

Bill

[imnprsd]

I can now confirm my engine starts up quickly and keeps on running!

* The solution was to tighten down the 3 lift pump bolts on top of the lift pump manifold. Hence, air was either being sucked into the system at the lift pump gasket or suction was being lost or both. So I think checking these bolts should be done... maybe every 25,000 miles.

* I like the idea of having a short clear piece of fuel line either leading to the secondary filter or coming out of it, but I'm probably not going to do that myself, but I may ask Brazel's RV Performance about this option if I see them later this summer.

* When I cut open my filters I did not see any slime or gunk, but in the secondary 10-micron filter there were a number of very small, black chunks (coffee grind in size) that felt "sandy" and crumbled when I crushed these between my fingers. Is this dead algae or pieces of my eroding fuel line?

* My original lift pump with 91,000 miles on it. Is this reaching the end-of-life?

* Why replace a lift pump for $800-$1000 when you can add a FASS pump (and keep my 2 fuel filters) for $1000? It seems to me the FASS lift pump is an upgrade so for about the same amount of money I think I would rather upgrade to a more reliable pump that may or may not be better for my engine. What would you do?

[BigLar368]

Just the parts to install our FASS pump with the built in filters was over 1K. If you pay them to install it you will probably be more than 1K. I'm not trying to talk you out of it though....I feel it's a good upgrade.