ISL not performing

Your turbo plumbing could be leaking air.

Fuel filters changed and the problem started. I'd start by taking them off... should be fairly hard but you can with your hands. If it turns easily, stop and tighten it up as it was not put on tight enough. If hard, then make sure the small rubber seal is on the threaded shaft that the filter screws on to or on the top of the filter. If missing, buy another filter and use the seal from it and on the next filter change. While off, dump the fuel into a pan and see what it looks like.
You prime the fuel system by turn the key on for 30 seconds and off several times. You do not have to put fuel in the filters before putting on unlike on a Cat engine.

How long between was your coach sitting? Days? Weeks? Months?

If it had been sitting awhile, I'd guess you had gunk growing in your fuel and it subsequently clogged your filter.

In my experience (admittedly with trucks and tractors, not MHs) that is exactly the type of behavior you get from diesels with a plugged fuel filter. Usually due to the fuel gelling when it gets cold out, but there are a ton of other causes or maybe just a defective filter.

I agree that checking and possibly replacing the fuel filter is step 1.

Could be coincidence but I'd check your turbo flange and make sure all four bolts are tight. For a quick check, look for soot around that flange. If that appears to be ok, the next thing I'd do is change all the filters again. I use Speedco for less than $300 includes lube, oil and fuel filters oil etc. Since you've already had your oil changed, I'd just replace all the fuel filters. Did you buy the filters or did your 'friend' supply them? Use quality filters, always. Finally, purge your fuel line again to make sure you're getting good fuel....Dennis

The only bad thing about SpeedCo is that there aren't any in Florida.

Mine was acting much like yours.

I took it into a small Cummins dealer and first thing
he did was pull out his laptop and check my engine history
stored on the coach.


He could see when and why I had problems with fuel.

He changed both my fuel filters and its been good since.



I now carry spares as they can be a little hard to find.

You might want to check your inline fuel filter/strainer.It is located in the fuel line between the tank and engine ,mine is on the frame rail by the rear axle.

No matter how you attack this issue, it will cost you a minimum of $200.00 to take it to a shop and walk in the door. More than likely, their first move will be to change the filters. The evidence really points to bad filters. I would buy two sets of filters, change out the ones you have and see if the issue is solved before spending money at a shop.

If you're mechanically inclined at all or have someone who can help you, changing filters is a simple task and knowing how can really be a lifesaver if you're ever stuck in the middle of nowhere. Often the only issue is the strength required to remove a filter located in a tight spot.

The filters for your engine both come with an o-ring about the size of a quarter. Your filters screw onto a threaded tube and often when people remove the old filter, they neglect to make sure the old o-ring is removed from the threaded tube. They also forget to install a new one that comes with the filter.

Theoretically, you're suppose to be able to install your filters dry and then prime them by turning the ignition on and off several times. I never got this to work. I always prime my filters. This is also a simple task. When looking at the top of the filter, the diesel fuel from your tank enters the perforated area around the edges of the filter, is filtered and comes out the hole in the center and flows through the threaded tube you screwed the filter onto. Simply take your clean thumb, cover the center hole of the filter and slowly poor clean diesel fuel from a small jug around the outside of the filter until it's full. Install, wipe clean and start the coach.

If you got bad fuel or had fuel go bad, you may have to replace the filters several times to resolve the issue.

rad1 wrote:
OK you diesel experts, here's what's going on. I have a 400HP Cummins ISL in a 2005 Itasca Horizon motor home. I've had this coach for 3 years and it's performed flawlessly. Last winter I had a diesel guy in our RV park change the oil and all the filters. Upon leaving the park to travel home, the coach right away wasn't showing any power. In the past it would rev right up the the 2000s before shifting and it would pull like crazy. Now it just has no guts and it shifts at 1000 to 1500 rpm. It seems to run OK once up to speed. it will still cruise at 65 with the cruise control on, but if it meets a big hill it just dies. Stomping on the pedal has no effect, as if it isn't even connected. Also, I don't know if this is connected or not, but the turbo gauge jumps from mid-gauge (0-25) right to the max. (50) when the engine calls for power. I don't remember it doing this in the past, but then again I don't remember looking at it that closely when it was running fine. I actually stopped at a Cummins South service center on the way home last winter, but they said if it ran at speed and showed no trouble lights then it was probably OK. Although it does what they said, it's definitely not OK. Any ideas?

Use the KISS method and just change the fuel filters - my guess is, that when they were installed either you had a bad gasket or a pin hole in one of the filters - not being there to listen to the engine it sounds like a fuel issue that because it happened right after a filter change is probably fuel filter related.

Simplest easiest first thing to do - Let us know how you do.

BOL,