ISL 400 running rough

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ISL 400 running rough

August 03, 2020, 02:49:27 pm

A week ago we took a trip up the coast to Santa Barbara. It's about 150 miles each way. About 50 miles into the trip the engine started running rough. The occurred just after coming down the hill of the Sepulveda pass on the 405 as we were transitioning onto the 101. Under load at low RPMs it was fairly rough and kicking out white smoke and causing a good amount of vibration in the whole coach.

We pulled off and I changed the primary fuel filter. We continued on with out improvement but when running at 1800 to 2000 rpm it was smooth enough that I felt ok to continue. At our campsite I changed the secondary filter. Again there was no improvement. We made it home avoiding traffic times and manually shifting to maintain higher than normal cruising RPMs.

It sounds as if it is missing on one cylinder. It is a very uniform cadence in the sound. There is no check engine/stop engine indicator. I also looked for trouble codes and found none. I have a diagnostic connector but do not have VMSPc yet. I am able to query just using a terminal program.

The only other thing to mention is that I did install a resonator about 800 miles prior to this occurring but I don't think that has anything to do with it.

Any ideas of what else to check before I take it to a shop?

Re: ISL 400 running rough

Reply #1 – August 03, 2020, 02:57:07 pm

Start it up cold, wait for a few minutes then pour water on the exhaust manifold. One of the ports will look different from the other 5 not steaming. It sounds like an injector has failed. Many other possibilities but, that is my thought.

Re: ISL 400 running rough

Reply #2 – August 03, 2020, 03:15:36 pm

If you don't have one, buy a IR gun at Harbor Freight or possibly Home Depot. When you start up, shoot the exhaust manifold right at each exhaust port. Easy to see the difference in temp. This also works on a warm engine.

White smoke is typical of fuel being injected but not exploding/burning. Like cold weather starts in the moring.

Any unusual noises when you are back by the engine when running?

Could be a bad injector, wires, injector pump. Is yours a CAPS?

Pull oil filler cap and check for blowby while running. Outside possibilities would be low compression in that cylinder because of valve failure. Does the engine turn over evenly when you crank it in the morning?

No, resonator is not a factor.

Pierce

Re: ISL 400 running rough

Reply #3 – August 03, 2020, 04:46:08 pm

I have an IR gun so I can check that. And I can look for blowby.

It is CAPS per parts.cummins.com. My fuel pump part number is 4076443.

It starts in around a second and seems to crank over evenly but hard to tell in that brief time. I recall it seemed to crank over evenly when I changed the fuel filters and had to crank longer.

There is definitely a miss that I can hear when back at the exhaust. Sort of a hollow sound each cycle. Maybe I can record it.

Re: ISL 400 running rough

Reply #4 – August 03, 2020, 04:57:05 pm

A tool like a ProLink or Cummins reader will be able to pin it down quickly. Hopefully, only an injector. Not cheap items like the old injectors but better than an ECU or main injection pump.

Low supply from the lift pump is a possible suspect. They have a higher than average failure rate and should be looked at soon as low delivery amount can damage the main pump. Again, a plug in tool will be able to read fuel pressures, etc.

Keeping fingers crossed for you.

Pierce

Re: ISL 400 running rough

Reply #5 – August 03, 2020, 07:09:11 pm

If you had a silverleaf setup, would you be able to pull the same information as the other tools listed above?

Re: ISL 400 running rough

Reply #6 – August 03, 2020, 08:22:07 pm

Pull out the oil dipstick and check that the oil color looks normal and the oil level is normal, which it probably will be. It's an easy check.

Re: ISL 400 running rough

Reply #7 – August 03, 2020, 08:29:50 pm

Quote from: Eric & Alena + 3 – August 03, 2020, 07:09:11 pm

If you had a silverleaf setup, would you be able to pull the same information as the other tools listed above?

The Silverleaf and Bluefire are readers and tools in the fact that they can read from the ECU the data from the sensors installed in the engine. So, they are tools but tools-lite.

The Pro-Link 9000 and it's modern versions plus the Cummins shop tools are actually able to not only read the data but test the injectors, automatically or manually and make changes in settings in the ECU. Not change the horsepower. For instance, I can test my injectors at 600 rpm idle and at 1000 rpm and I can do it manually or let it do it by itself and then show me the data. The 1000 is nice as I can use it for a fast idle. A pain in the rear as I don't like to keep it plugged into the diagnostic port all the time.

So, after you identify which cylinder is not firing with the IR gun, you can probably check fuel pressure with the Silverlink but then I don't have a Cummins so can't say for sure. Roger can tell you that.

The other possibility is that low fuel supply pressure may be causing a different cylinder to misfire and not the same one all the time. Does the misfire stay constant on grades when the engine is pulling harder?

With a noticeable miss, I would not wait long to have it checked. The days of pulling an injector and testing it yourself are long gone.
All the components in the fuel system are interrelated more than they used to be with much closer tolerances.

So, you might call around to see what big rig shop is going to be able to connect up to your port and what they charge to do it. Look online at Yelp or other sources close to you for recommendations.

Pull dipstick for amount and color plus smell it for diesel.

Bottom line is this may be a very minor problem or there is a possibility the miss may indicate a major problem. Checking the blowby with the breather/oil fill cap off is a good way to see if there is major pulsing blowby that would indicate cylinder damage. If it seems excessive, a shop will have a tester to put over the breather to pinpoint the amount and make sure it's within limits.

A faulty injector may be spraying a straight stream of diesel into the cylinder. While diesel is a lubricant, it's nowhere as good as the oil in the engine so you can see that this needs to be addressed. Then again, it could be an injector to ECU wiring problem where the injector is not getting triggered.

Other possibilities so do some online research with other forums. Guys out there are just waiting to give their educated (or not) opinion and I'm sure there are others who may have had the same problem in the past.

Keep us informed.

Good luck and good night.

Pierce

Re: ISL 400 running rough

Reply #8 – August 03, 2020, 08:50:06 pm

It could be your cam position sensor is failing on the primary side. If this happens sometimes when it is swapping back and forth from the primary side to the back up side to the it will cause the engine to stumble.

Mike

Re: ISL 400 running rough

Reply #9 – August 04, 2020, 01:28:14 pm

A few years ago I was having similar problems with my 2001 U270. I had the Cummins ISC350 with CAPS fuel pump. Had replaced fuel filters several times, new lift pump, finally took it to Cummins Coach Care in Avondale, AZ. They diagnosed it was the accumulator which is part of the CAPS fuel pump. They had the part, but it was an all day job to replace it, but when done we got out for about $2500 instead of a new CAPS pump for $6 coach bucks. Worked great after that.

If you do think it is the CAPS fuel pump, get it tested at a good quality Cummins Coach Care shop with a good reputation. There are a lot of diesel shops who might just recomend changing out The CAPS pump when you might be only need part of it.

Best of luck getting it figured out and fixed.

Re: ISL 400 running rough

Reply #10 – August 04, 2020, 08:37:14 pm

I did not observe any blow by fumes or smoke coming from the oil fill in the valve cover. So that's a good sign.

Running it for 5 minutes I did not measure any significant difference in exhaust manifold port temperatures. I did however notice a cold temperature exhaust leak from the manifold. It appears to be at the joint in the manifold segments but I also see that many people have had manifold cracks as well. So one more thing to have looked at. If it was just the manifold I would probably do it myself but I need the other diagnosis/fix.

I don't want to have to start cancelling monthly get away trips. I arranged to take it to a shop next week.

Re: ISL 400 running rough

Reply #11 – August 31, 2020, 08:38:37 pm

We got the coach back today from the shop.

Originally they diagnosed that one injector was bad. After replacing that, it was running better but still rough, especially when cold. They checked compression on each cylinder and #1 was losing compression. This was the same cylinder as the bad injector. After consulting me they went ahead and pulled the head. One of the exhaust valves on #1 was slightly bent and looked as if it had been impacted by the piston. There was a very slight indentation on the top of the piston but difficult to say if it was from the valve. I know I have not over rev'd the engine so we don't know what happened. Perhaps a weak valve spring? The cylinder wall was fine.

So after a new OEM Cummins cylinder head, piston, connecting rod, bearing, injector and assorted gaskets, we are back in business. Runs better than it ever has since we owned it. Either that or my mind is trying to justify the several CBs that it cost to repair. That and its hard to get out of my mind the vibration of 200 miles I had to drive on 5 cylinders.

We've only put 3000 miles on in the 1 year that we have owned it (just over 91k now). Somehow I suspect that the value issue existed but was not rendering that cylinder completely out. It was only when the injector failed that the cylinder was complete out. Maybe I didn't know how smooth it was supposed to be. It felt quite smooth on the highway. I never had a big diesel before and my only other basis for comparison is my 2006 Ford F350 with the power stroke 6.0 that always sounds like a tin can full of loose bolts at idle. On the drive home from the shop I barely knew the engine was behind me it was so smooth. Who knows...

I would recommend the shop to others. I tried them after fellow member pibutler recommended them. It is Interstate Fleet Maintenance in South Gate, California.

Re: ISL 400 running rough

Reply #12 – August 31, 2020, 09:56:59 pm

If the shop charged you $2000 for "new OEM Cummins cylinder head, piston, connecting rod, bearing, injector and assorted gaskets", you got the deal of the century. Some shops might have charged $15K

I see the OEM head alone for $2250 here: New Cylinder head for ISL / QSL Cummins Engine - 5256469 - 5347975 - 3969722

Glad it's fixed

Pierce

Re: ISL 400 running rough

Reply #13 – August 31, 2020, 10:48:54 pm

Great news on the repair, Interstate Fleet Maintenance in South Gate, California, is a fantastic outfit. I use them for all of my maintenance needs and other repairs. They recently fixed my Knoedler drivers seat and replaced the seat motor and they also fixed an air leak that was causing my secondary tank to drop pressure while parked for more than week. I could not locate the leak for the life of me, and they also replaced an air brake line that had signs of wear.

While these may sound like simple repairs, it's hard to find a shop that can accommodate a large coach for basic repairs.

Pat

Re: ISL 400 running rough

Reply #14 – August 31, 2020, 11:01:03 pm

Quote from: Pierce & Gaylie Stewart – August 31, 2020, 09:56:59 pm

If the shop charged you $2000 for "new OEM Cummins cylinder head, piston, connecting rod, bearing, injector and assorted gaskets", you got the deal of the century. Some shops might have charged $15K

I see the OEM head alone for $2250 here: New Cylinder head for ISL / QSL Cummins Engine - 5256469 - 5347975 - 3969722

Glad it's fixed

Pierce

Even $15k is a great price. My friend just had the same work done on his 2004 FT with 400 ISL at Cummins in Phoenix AZ, and he was out the door for $23,400.

Re: ISL 400 running rough

Reply #15 – September 01, 2020, 11:18:26 am

It ended up being just under $8,800. Obviously any surprise repair costs hurt but given the scope of what they did this seems quite fair. The parts are true Cummins parts and have a warranty. The head itself was $3125.

Re: ISL 400 running rough

Reply #16 – September 01, 2020, 11:21:15 am

Quote from: bpal – September 01, 2020, 11:18:26 am

It ended up being just under $8,800. Obviously any surprise repair costs hurt but given the scope of what they did this seems quite fair. The parts are true Cummins parts and have a warranty. The head itself was $3125.

Good price considering. Could have been much worse. Do you have any photos? What did Cummins give for the cause of the bent valve?

Pierce

Re: ISL 400 running rough

Reply #17 – September 01, 2020, 12:22:21 pm

Here were the photos the shop took after pulling the cylinder head. You can clearly see that the valve in question is not concentric with the valve seat and there is the scuff mark on the valve surface. I don't know what the other dings are from around this valve and the one to the right? They inspected the turbo and said it was fine so I don't think anything went into the cylinder and out the exhaust.

Re: ISL 400 running rough

Reply #18 – September 01, 2020, 02:18:30 pm

The pictures look like something came loose in the system and got eaten up by the no. 1 cyl. in my opinion. I have seen a carburetor screw do the same to an auto engine. Did they look at the old injector for missing piece?

Re: ISL 400 running rough

Reply #19 – September 02, 2020, 06:21:35 pm

I didn't ask about the injector specifically but he was not guessing that anything had dropped into the cylinder. I may have to email them and ask.

I had a mid-80s Celica GTS where a screw on the intake butterfly valve backed out and went down into the cylinder. The back of the screws were waffle stamped but it still worked its way out. It did a good amount of damage. I had a friend at the time that did a similar repair in the garage for the cost of parts and beer.

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