Official Cummins QSC-500 Thread

I’m sure many real world procedures. What I would recommend is that you change your racor filter elements first...per the procedure outlined in those attachments you posted is fine. However, Run the engines a bit before changing the spin-on fuel filter on the engine. The reason is when changing the racor filter elements, it tends to dislodge ‘stuff’ and you want your older on-engine filter to catch that ‘stuff’. Then go ahead and change that on-engine spinon filter. Do not fill that filter with fuel though. Install it dry and then prime your system.

Tom

Why am I thinking bad injector ? Would explain running fine at idle …

Rob

Bajturner - Do you happen to notice excessive crank times at start-up on that port engine? The engine should fire up in 3 to 5 seconds. Longer crank times could point to a bad injector.

Rob - I too think it could very well be an injector issue. Somewhat easy to run through the balance of troubleshooting of the fuel and air systems and if all clear on those, it starts pointing more specifically at the potential of it being an injector.

bajturner said:

...... Let them warm-up, left the dock, and idled out. .......

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Lots of great troubleshooting tips so far, keep us posted on how further testing works out.

Just one other bit of advice, diesels usually not all that happy sitting at idle with no load. Not sure how long you let them warm up at dock, but I was told start up, check initial oil pressures/verify water flowing out exhaust, then start tossing lines. We spend no more than 3 minutes at dock with engines running, usually its 2. Then idle until temps start to climb up to say 100, to fast idle to 130+ and then good to go with slow startup (assuming your out of no wake zone by then).

Same thing on way back, slow decrease in speed to idle, secure lines (maybe not even all of them and shut down), idle time at dock is less than 1 minute unless I am alone, then it might be 2 minutes while I secure the bow and get back to shut down.

Tman said:

Bajturner - Do you happen to notice excessive crank times at start-up on that port engine? The engine should fire up in 3 to 5 seconds. Longer crank times could point to a bad injector.

Rob - I too think it could very well be an injector issue. Somewhat easy to run through the balance of troubleshooting of the fuel and air systems and if all clear on those, it starts pointing more specifically at the potential of it being an injector.

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It started a little rough in the morning on Friday...fired immediately, but then stumbled up to rpm, with a fair bit of black smoke. Boat ran on-plane no problem, but the port engine was showing 100% load when the starboard was showing about 65%.

When I started them to return to the marina Saturday evening, however, it started perfectly. No smoke or anything. No stumbling or hesitating. The boost pressure was near zero while idling out, in sync with the starboard engine. I was thinking everything was sorted out. As soon as I gave it some throttle, though, it started stumbling again and took a while to recover to a smooth idle after I took it out of gear. I shut it down about 2 minutes later.

swaterhouse said:

Lots of great troubleshooting tips so far, keep us posted on how further testing works out.

Just one other bit of advice, diesels usually not all that happy sitting at idle with no load. Not sure how long you let them warm up at dock, but I was told start up, check initial oil pressures/verify water flowing out exhaust, then start tossing lines. We spend no more than 3 minutes at dock with engines running, usually its 2. Then idle until temps start to climb up to say 100, to fast idle to 130+ and then good to go with slow startup (assuming your out of no wake zone by then).

Same thing on way back, slow decrease in speed to idle, secure lines (maybe not even all of them and shut down), idle time at dock is less than 1 minute unless I am alone, then it might be 2 minutes while I secure the bow and get back to shut down.

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It didn't warm-up for very long. There were people on the dock having dinner so I didn't want to disturb them...maybe 4 to 5 minutes. Left the dock on slow idle. Switched to normal/fast idle once I cleared the dock and continued for about 10 minutes. Temps were climbing up at that point. Everything was running smoothly at this point...

Bit of an update. Filters all replaced and diesel conditioner added to tanks. I am an hour away from my boat so my marina is in charge of solving this problem. While they are open to my suggestions, they also have their own protocol and favourite products. Here is the diesel conditioner they used:



Seems to meet most of the recommendations in Franks article. Anyone have any experience with it?

Here are the filters that were taken out:


I am not sure which one is port and which is starboard, I have asked the tech. There was no sign of microbial growth, and so far as I know, no water in the separator.

The one from the port has had about 620 gallons through it, and the starboard about 460 gallons. Is the reason for the difference is to do with the new boat owner learning how the generator feed / return valves work!

How do these look? Is this bad, typical, nothing remarkable? I have no prior experience.
Any idea why one filter looks relatively clean on one half?

Lake test today. As of this morning, the starboard fires-up immediately while the port is still a little rough. Waiting for more details...

One more thing...is there a typical lifetime in gallons of fuel for these filters?

The filters looks clean, but the real answer was in the Racor bowl. Did you drain the bowl and catch the debris the filter had caught? What did it look like?

There is no lifetime expectancy for diesel fuel filters. How long they last is almost totally dependent upon the quality of fuel you pump into the boat, how much tank sludge/water is in it and how much water you are condensing in your tanks between fill ups. If you manage your fuel system as I recomended and use 30 micron Racor elements and OEM secondary filters then you should be able to change the filters at your annual service and have have no problems during the year.


Your engines are QSC's which are electronically controlled. The ECM controls injector timing so if your engine has a rough idle on start up, something is wrong. I am 3500 miles away from the boat so obviously we can't observe the rough idle or see any exhaust smoke, but the most likely cause of a QSC rough idle and an engine not running up to full rpm is a cylinder not completely burning all the fuel that is injected or an injector not functioning properly. Neither problem is going to be fixed until you get the engine diagnosed by a qualified Ccummins technician. The worry here is that if an injector has some carbon build up on the tip and it spraying droplets rather than atomizinf the fuel properly, you get unburned fuel in the cylinder. That fuel will "wash out" the cylinder by washing the lubricating oil off the cylinder walls and that leads to premature piston, piston ring and cylinder liner wear. If it were mine, I wouldn't run the boat until you had Cummins look at it.

Thank you Frank.

I didn't change the filters myself, so I have to rely on what the tech (not a Cummins tech) is telling me. The reply I got was:

"No water visible, black sticky sludge in housing. Lots in racor on Port side, some on stbd."

I will pass along your concerns, and if the engine is not running right at this point stop operation and get a Cummins tech to diagnose.

Like frank said . A cummins tech can come hookup and read any issues. I had a bad injector years ago. Was intermittent. Which made it even worse. Boat would run like a champ... Then it would be crippled. ( bog down , no power ) would idle down throttle back up and boom she rain great. Cummins came 2 x for this . Finally injector dumped out for good. Turns out there was a recall. Did they replace all the injectors ? NO. But they changed a few not sure the basis for the logic but what ever. So I think its more injector related from ur description

Rob

Ok, here is the latest:
- After adding the Howes to the 1/4 tank of last year's diesel, the engines were run for about 30 minutes by marina staff last week. Started fine, idled fine, ran on plane fine up to WOT. I got qualitative feedback only, no numbers.
- I went to the boat last weekend. Started up Saturday morning fine, ran perfectly. All the numbers looked good and I thought the problem was solved. Short trip (~3 miles) to a mooring and stayed until Sunday.
- Sunday, started-up, no issue, idled out, ran up on plane. Port engine started surging and hesitating.
- Monday- spoke to Cummins tech who recommended filling-up with new fuel and re-confirming problem before he comes. With travel of about an hour away, his call starts at $500.
- Yesterday: topped-up with known good fuel from a delivery truck and added 80oz of Power Service Diesel Kleen + Cetane Boost (per Frank's article).
- Went to boat this morning with service manager on-board. Powered-on engines (didn't start) one at a time with service manager in engine room listening and comparing fuel pumps.
- Port and starboard have a slightly different tone, but both ran for ~30s before shutting off.
- Started port- a couple woofs, then smooth idle.
- Started starboard- one woof, then smooth idle.
- Added some revs to each in neutral. No problem.
- Idled out of marina. All good.
- When temps reached ~ 130F, we jumped-up on plane. Both engines ran perfectly up to WOT.
- Numbers looked good, and pretty much the same port and starboard (except oil pressure): 2680rpm, 32mph, temp 176-179F, oil press 58psi p / 50psi s (Gorham Diesel survey last Sept in Plymouth, MA recorded 60psi p / 55psi s as "normal"), ~25GPH each side, man. temp 82F, boost 29-30psi, 100% throttle, 92-95% load.
- After about one minute there was a SmartCraft warning I had never seen before: 281 Cyl Press Imbalance Error (see pic), port side. Not a coincidence, I am thinking. Performance unchanged. Error cleared on its own (changed from alarm symbol to check mark), then happened again about 30s later, and cleared on its own again. Went to 80% load. Everything looked fine, 24mph, 18GPH per. Back to WOT. Numbers unchanged from before.
- Ran for about an hour at various speeds. No warnings. Flawless.

Problem solved, or a problem still lurking?

Did the injector cleaner do its job and blow some crap through an injector, causing the alarm, and fixing the problem (I hope!)?

One thing of interest. I have not been waiting 30s to allow fuel pumps to charge...more like 10s. Could this cause an issue? Is 30s normal?

First, your WOT numbers look good, Port and Stbd oil pressure will vary, one filter is relocated further away than the other so pressures will be different. What numbers were you running at 2400 rpm (or what rpm was the 80% load)?

The fuel pumps always run about 20-30 seconds once power is applied to system (ignition on). If you haven't just changed a filter and don't have a fuel system leak running for more than a few seconds is probably a waste of time since they are just circulating fuel. If you have just changed a filter you want to cycle ignition on and off 10-15 times before attempting a start, that will get the air out of lines (and/or fill the on-engine secondary filter). I used to only wait a few seconds, now I wait the 20-30 seconds, I turn the ignitions on and then get other things setup/ready and by that time at least 30 seconds has gone by.

Odd the error you got was on both engines simultaneously. I would call your cummins tech and get his advice before running any further.

swaterhouse said:

What numbers were you running at 2400 rpm (or what rpm was the 80% load)?

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I took pictures of the SmartCraft screen but they are blurry and I can't read them...and I don't trust my memory! I will record numbers at a few power settings this weekend.

swaterhouse said:

The fuel pumps always run about 20-30 seconds once power is applied to system (ignition on).

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Ok, thank you.

swaterhouse said:

Odd the error you got was on both engines simultaneously. I would call your cummins tech and get his advice before running any further.

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The error was only on the port side. The picture shows both sides with check marks on both sides once the error cleared on its own. When the error is active, there is a bell symbol with an exclamation mark instead of a check mark on the port side only.

I called Cummins and they advised to monitor at his point if everything is running within spec, no smoke, etc.

Here are some more numbers from this past weekend. Both engines ran perfectly. The 100% and 0% throttle readings were taken on a different day than the 80%, 50% and 35%. The conditions were similar though. the yellow boxes were from recollection (if I could recall!).



I also have small .3gp video files in which you can hear the fuel pumps when the ignition is turned on, but I can't figure out a way to post them (they are small, a few 100 KB each). The port sounds a little sickly to me, but I am new to these engines.

Anything look out of whack here?

They all look pretty much what I get everytime out.

Its hard to interpolate but below are the cummins specs for specific RPMs, you want to be at or below these specs. Based on your numbers at 2270rpm, you may be a bit high in fuel (i.e. over loaded). I was also told you should be closer to 95% load at full throttle (i.e. the engines easily spool up to governer). Try running again at 2200 rpm, and at 2400 rpm, its in taht range that is most important since its normal cruise range. I was under the full throttle flow of 25.4 at 2650rpm but over at 2400 rpm so I removed an inch of pitch and came under with about a 2 knot loss in speed.

Cummins Specs
RPM Gal\Hr
2600+ 25.4
2400 20.1
2200 15.7
2000 12.2
1800 9.4
1600 7
1400 5
1200 3.3
1000 2.1
800 1.3

Suggest you get under the boat and take a look at the running gear. A little slime of algae or some hard growth can cause what you are seeing.

Airplane Guy said:

I have a 2006 44, on the last trip of the season , and continuing this season, I've noticed a fuel flow split starting at 2150 rpm. Port engine 14.8, Stb 12.1. No smoke from the port engine. The load was also split , at 79%, Port 62%, Stb 47%. the boat tracks straight, and after a 4 hour run and topping the tanks, both were within 2 gallons of each other. I believe I have an indication problem( I hope) and was told that the engine load uses a calculation of fuel flow. Does anyone know where the fuel flow transducers are and if they can be swapped?

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I would contact Seaboard Marine (sbmar.com) either by calling, email or post to their forums. They provide fantastic support.