2003 Newmar Dutchstar cummins 350 isc loses power

If you have a laptop, buy a copy of Silverleaf sw and cable and set your laptop up on the dash. It will tell you whats going on.

Turbo boost pressure, fuel pressure (bad lift pump).

Diesel houses charge anywhere from $150 per read so it wont take long to pay for the Silverleaf and then you will have it down the road.

I had a bad connector on my turbo boost sensor. Tech read the code, replaced the $180 sensor. A month later code was back. I bought SL, set it up and figured out that the sensor wasnt bad, it had an intermittent connection. With the engine cover off I could wiggle the sensor connector and make the code come and go.

Get a scan gauge and check your boost pressure. Under WOT you should be getting north of 20, closer to 30 actually (can't remember exactly) . We had a boost sensor go on ours and it limited boost to under 20. It was a dog. It was not expensive to find or to replace....according to my mechanic.

Also check your exhaust manifold for cracks. Easy to see. Just lift the bed and look closely. We had one of those as well which caused a lower boost and subsequent lack of power. Exhaust manifold re and re was under 900 bucks Canadian including parts.

Take a look and see what you see. The crack will be obvious and its common with the ISC.

Are you sure you only have one fuel filter... Most Cummins have two. Last summer I had much the same that changing both filters and the lift pump did not solve. Away from puter so do a search by me for lift pump and more than a year ago for my $10 solution.

*Back on line so read this and what codes are they getting from the engine? Mine was computer code check... 329.
I do not believe a clogged air filter would get you down to 10 mph plus is the filter minder in the red?

If your fuel water separator is not transparent, take a sample from the drain into a glass jar. if there is crud in there you will see it in a hurry. I've seen bad fuel aplenty. So bad changing filters did no good. Hope this gets you n the right track.

Fuel and air IN, compression, exhaust out.

A diesel really is that simple.

A clogged air filter OR exhaust can cause symptoms similar to insufficient fuel. After those things have been addressed, the compression needs to be checked.

Long shot: Thermostat stuck open and engine not getting hot enough.

At this point, a professional analysis might be cheaper in the long run.

The simple fact that this showed up right after filling up is STRONG evidence that bad fuel might still be the cause.