Low Power Issues-Cummins ISL 370

jc2 · July 13, 2016

Intermittent Low Power Issue.

Just before leaving on July 5th for a (5) week trip through the northeast,(Maine, New Hampshire, Vermont) and ultimately to our first SKPS rally in Essex Junction, Vt, I had the yearly engine maintenance done on mh which included engine oil change/oil filter, engine fuel filters(2), etc. It ran fine and was very responsive on the first day out. Shortly after continuing on the second day, I stopped and fueled at a Flying J just east of Indianapolis and about 1-2 hrs later I started to notice that the mh seemed to intermittently run with less power when climbing some of the hills on I-70 then felt like it was ok for awhile. I added several bottles of Power Service Fuel Conditioner but long story short, It has continued to do this, at times has absolutely so pick up and does not appear to be getting any better. My thoughts are the following but not necessarily in any order of importance:

1. Fuel filters might be junked with who knows what from "bad fuel" at Flying J?

2. I have had to apply the brakes hard several times en route because of some drives not paying attention, a couple of real quick traffic lights, going down several 5-7% grades using the engine brake and coach brakes together(I have noticed that the coach will "sometimes" not pick up very much speed when going down a long hill and other times will requiring using the engine/coach brakes together.

3. Bad/weak lift pump-new was installed in June 2012 and coach has always running very good before this trip and after beginning.

4. My gut feeling is either fuel filters or sticking caliper.

We're currently at the Timberland Acres RV Park in Bar Harbor, Me and have a mobile tech($$$) scheduled to take a look see tomorrow.

Any one with any comments or thoughts would be appreciated.

Alie&Jim's Carrilite · July 14, 2016

Fuel Filters most likely. If it was a caliper you would smell it.

Chief 62 · July 14, 2016

I would venture to say fuel filters also. Try draining some fuel from your water separator and see what you got. You may have a bunch of algae clogging up the filters.

jc2 · July 14, 2016

Just a follow up and thanks for those that took the time to respond. Mobile tech guy came today ($$$) and felt also that it was most likely a fuel filter issue even thought they were changed about 2000 miles ago when I had the yrly engine service done. Will find out when we leave Bar Harbor next Wednesday and start working our way towards Essex Junction for the SKPS get together.

OLYLEN · July 19, 2016

if you have a boost pressure gauge check for boost after using the engine brake. If it has not been lubed(it's EZ to miss) it might be hanging up and would cause low power. I'll also go with filters as first choice.

LEN

jc2 · July 19, 2016

Thanks for the info. Changing both fuel filters helped a little but still not running like it should. The engine brake possibly not disengaging was one thing along with maybe the lift pump(?) . This was replaced in 2012 and I don't leave the engine brake on all the time. Is just activated/deactivated when going down long hills or possibly when needed in town. Maybe a vendor will be available at the SKPS rally in Essex Junction, Vt that can look at it. Basically, it just feel like there is a slight drag on the rig when going up somewhat long hills and/or when descending hills.

Can anyone describe the engine brake location? Is it some type of lever/flap that opens/closes when you activate the switch. Is lubing it a DIY job? Some things I've learned over the years but others I'm not familiar with the particulars so I ask.

Chief 62 · July 20, 2016

When was the last time the air filter was changed? A diesel is a big air pump that needs a good air intake flow and exhaust flow to perform efficiently.

Mcb · July 30, 2016

Do you have the engine brake or exhaust brake? From what you're describing if its the exhaust brake sticking (if you're motor is equipped with the exhaust brake) which is related to the VGT turbo function then I suspect it would be directly related to a boost issue with the turbo. low boost low power etc.

jc2 · July 30, 2016

Chief 62

New air filter was installed the first of last year and checked during our annual engine service done prior to leaving on 7/5/16.

McB

We have the engine brake which seems to be working as it should. Has a HD truck/rv place in N Monmouth, Me work me in after leaving the cg there and after a pretty comprehensive check from there knowledgeable cummins guy, his opinion: You've got some less than optimal diesel. Per his advice, I've added 1 couple of bottles of a fuel additive(Power Service) to the existing fuel and some to the fuel I added prior to heading towards the SKPS rally in Essex Junction, and it had stated to run like its old self. I think a couple of crappy tanks of diesel and extra long hill climbs were working against me. We left Essex Junction after the rally and are in the Niagra Falls area. Will be leaving Monday and heading to Missouri so this trip should tell.

Dale P · July 30, 2016

Did you check for engine codes ?

Loose clamp to turbo?

Smitty77_7 · July 31, 2016

Yep, bad fuel could have caused a problem like this. Maybe get another fresh tank under your miles of usage, then as added insurance, change your fuel filtered again.

I also suggest, not just for now where their is a solid concern for needing it, but also as periodic cheap insurance - to add some JF Biobor to your tank. Treat it as if you had moisture in the tank, as good chance you did with a bad batch of fuel. I added JF BIobor before storing, and or whenever traveling in humid moist regions. (Yeah for me, I also add Optilube to each tank for added lubricity.).

And just an FYI opinion on the lift pump. As you probably know, the lift pump has a duty to just feed the CAPS at start up, then it shuts off. So a lift pump going bad, would only be a problem at start up. After that, the CAPS is sucking the fuel in that is burned. Now, a lift pump with a 'leak' that you should be able to see when inspecting, could cause some air in the lines. But IMO, only a leaking lift pump could cause you in ongoing performance problem while the engine is running. (But, not an expert, and could be wrong:)!)

One other opinion on Air Cartridges. Each time you, or a shop, opens the canister - the risk of 'dusting' is raised. So my policy is to never open the canister, without putting in a new air cartridge. Mine is done every two years, regardless of the restriction gauge readings. Only one time, after about 15K miles on our trip from San Diego to Alaska, did I have a restriction gauge even slightly beginning to show reduction in air flow. That cartridge was pretty dirty on the bottom 1/3, where the air intake feeds in. I attribute that to the air intake being about 3-4' behind the tag - with the drive and tag tossing up dirt and dust as we ran down the road, even the paved road as we were very early in the season, and I believe I helped clean the road of dust for those to follow:)! I also carefully wipe out the inside to the canister, and take a flashlight inspect as far up into the feeding the engine tubing as possible, looking for signs of dust. (None so far.) And of course a yearly outside inspection of the tubing and hose clamps.

Smitty

sseibert3 · August 1, 2016

It is possible that you might be a little sucking air through a crack in a fuel line. We know many people that own coaches made in the late 90s and early 2000 that are replacing some fuel lines. Your being a 2004 probably not likely but don't know the type that Newmar uses. FWIW.