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Rburian · 09-29-2016, 07:30 PM

While driving up mountain grades, the turbo boost goes not seem to kick in, goes not raise above 15. No issues on straight roads or passing, I seem to also have Pacbrake issue with not holding on occasion, could this be a related issue? 2005 HR SCEPTER.

BFlinn181 · 09-29-2016, 10:52 PM

Check that the flexible boots on the pipes that connect to the turbo, inner cooler, and intake manifold aren't cracked or leaking. Sounds like you're losing the compressed air that leaves the turbo.

kerryvan · 09-29-2016, 11:07 PM

search this site for isl, there have been a few problems similar to your due to manifold leaks, egr issues, and a few other that I can't recall right now. I found them when I was researching the various cummins options and reliability. I do remember a few that discussed the boost being low.

twinboat · 09-30-2016, 04:44 AM

I suggest, if not done recently, after a good look over all of the plumbing for the intake system, that you do a fuel filter change.

Low power is the first sign of failing filters.

vito.a · 10-03-2016, 05:16 PM

I agree with twinboat. Change the fuel filters. Another good way to tell is to let up on the throttle for 2-3 seconds and then floor it. If your boost goes up to the high end you have a fuel issue.

Remember, most of these engines have a chassis mounted main fuel filter and a second block mounted small fuel filter.

bfam2008 · 10-08-2016, 08:06 AM

In my experience, if you have air leaks you'll see a lot less pressure than 15lbs of boost. As others have said check fuel system first then air filter, both of these are much easier troubleshooting points. If you still have low boost check for leaks in your induction systems.

vsheetz · 10-08-2016, 08:20 AM

Fuel filters first, then go from there if need be.

tom chelbana · 10-08-2016, 08:28 AM

Many ISC and ISL engines have 2 fuel filters and the secondary filter is sometimes not know about and it's location. Was helping a Dutch Star owner with the same issue and had over 40K miles and never had secondary filter changed and after changing fuel filter he had is power back for hills. His secondary fuel filter was located above starter and was hard to see and replace. Might check this out.

Kramer Boy · 10-10-2016, 09:16 AM

Have you checked to make sure your turbo boost actuator rod is not seized onto the boost dump valve shaft? Or broken like mine was. Had similar symptoms. Spent a few grand on this symptom. Found it myself finally.

Rburian · 10-10-2016, 04:46 PM

Thanks for all suggestions, starting with fuel filters and moving to suggestions one by one.

RIDER FAN · 10-31-2016, 06:57 AM

I have a 400 ISL in my MH. Experienced power loss on hills. Changed fuel filters and thought all was good. Next trip out same thing , down to 35 on grades that were not that steep. Ended up being lift pump , it only had approx 1.5 lbs pressure , supposed to have 5lbs to operate correctly. They are not expensive but they are a bearcat to change. Also not all , but some units have the hidden filter along frame......

vapor3000 · 10-31-2016, 08:36 AM

I went through this. I changed the fuel filter (my chassis only has one) and the problem went away. I now change the fuel filter every year with the oil filter/oil change.