MH with ISL 400 HP Surges

[BIGNASTY]

Just a question about the Motorhome ISL Cummins.

If the MH has been sitting overnight when I start it up it surges from 800 RPM to a low of about 500 RPM the needle bounce makes it difficult to be exact on the low-end RPM. It surges 4 times then runs smooth as silk at 700 RPM for the rest of the day with stops with no further Surge upon starting. It seems that a period longer than 8 hours is when the surge happens. Its done this for as long as I've owned the MH. I did have it into a Cummins Shop in Little Rock to reflash the ECU and recalbrate the system for more HP and larger tires so the RPM & MPH worked correctly, while it was in they also ran a fuel pressure test, injectors test and said that everything was like it should be for a ISL with 35,000 miles. I forgot to ask about the Surge. I have had several RV Park Mechanics tell me that its anything from Normal to a Multitude of other non educated guesses, I had a 1693 TTA that did the same thing until it was said to run the air out of the fuel system, It naturally wasn't the HPCR system that's on the ISL. Other than that it runs beyond expectation for a mid sized motor.

ANY IDEAS?


BIG

 

[mweiman]

Look at all your fuel hoses for any sign of leaking. Sounds like it is sucking air somewhere. I have had several ISM's do the same thing. Does it have some type of fuel heater or extra filtration system? Could be an o ring or something on that.

 

[BLNRAY]

ISL has an electric lift/primer pump that runs at key on for about 30 sec.,can you hear it when you turn the key on? put a pressure gauge on the outlet side of the secondary fuel filter,key on you should 5-10 psi from lift pump at start it should go 70-125 psi.

 

[mwilson]

ISL has an electric lift/primer pump that runs at key on for about 30 sec.,can you hear it when you turn the key on? put a pressure gauge on the outlet side of the secondary fuel filter,key on you should 5-10 psi from lift pump at start it should go 70-125 psi.

I was wondering if it had that as well. Learned a while back how those work on the "C" series.

Big, give me your Engine Serial Number and I'll look it up.

 

[BIGNASTY]

Received a return call from a bar-buddy at home that's a pretty good wrench for the Cum-a-part dealer in Missoula. He said the same as Mr. BLNRAY the 12v elect. lift pump that supplies fuel to the Low Pressure Mechanical fuel pump has a Check valve on it. Most of the time if it fails the Mechanical will suck the fuel from the tank it just needs to spin the motor over for a bit longer to draw the fuel past the lift pump and check valve. He's only seen a few of the check valves go bad but his theory is that the reason it surges is that the 12v lift pump draws fuel for 30 seconds as its supposed to and the check valve is letting fuel drain back out of the line between the Lift pump and Mechanical Fuel pump over a period of time when the motor is shut down and no pressure is in the line, the line and mechanical pump has enough fuel in it to start the motor but until the air is pushed out it has THE SURGE, hence the long time before the surge is experienced. He asked if I had checked the motor for leaks? which I did, I keep a clean motor for that very reason. On the RV versions of this motor there is no fuel filter between the 12v lift pump and the Mechanical lift pump crud in the tank usally is drawn into the 12v lift pump clogging that up before taking the risk of contamination in the HIGH DOLLAR mechanical fuel pump. I had installed another fuel filter water separator in the system the line between the 12v lift pump and the Mechanical low pressure fuel pump is where he had me tap into for the Davco 382 fuel water separator, filter. Figuring that he wasn't sure if the 12v pump would have a problem drawing fuel through the filter but when the 12v pump shut down and the Mechanical pump was drawing the fuel from the tank that it would surely have enough to draw the fuel. Its my understanding that once the motor starts and the 12v lift pump stops that the check valve directs the fuel straight to the Mechanical pump and my installed safety fuel/water sep.

I hope that this sounds right I had to read it over at least 20 times. Monday I'm running to Asheville NC to the Cummins Dealer for a new 12v lift pump, he suggested that I just change the pump and check valve as a unit just to make sure.

anyway it ran GREAT as he said it should have even with the check valve and or the 12v lift pump going bad. once its running the 12v pump is out of the picture.

Thanks For your responses and will let you know how it works out Monday.

Smoky Mountain National Park is OUTSTANDING!!!


BIG

 

[Wayne M.]

I believe you should be near the visitors center. Stop in there, it's nicely run and well stocked.

 

[BIGNASTY]

Took off old Fuel Lift Pump to take as a comparison AND DAMN GLAD I DID!! There's several different models

Seems like there was a period of time between 2004 and 2007 when they weren't sure about the effects of ULSD on these pumps. Wouldn't you know it mine was the OEM that didn't like USLD.


Anyway there was a minor design change that a 90 Degree fitting took care of for fuel line attachment to the pump.

I replaced the pump (piece of cake) and cycled the 30 second time out on the pump twice times. It fired up and the surge was still there but I feel that was to be expected since the line was open and im sure that air had entered the system. I did notice that the Davco filter/sep filled much faster with this pump or at least it seems it did. we ran the motor for awhile to make sure no fuel leaks and shut it down until tomorrow to see if this takes the surge out of the start up. The desk jock at Cummins in Asheville called in a Tech and he said that replacing the pump should do the trick. This new replacement pump is ULSD compatible so this project shouldn't need to be repeated.

BIG

 

[BIGNASTY]

I believe you should be near the visitors center. Stop in there, it's nicely run and well stocked.

Wayne

If your talking about the oconaluftee visitor center (your guess is as good as mine on how to pronounce that ???) it is a really nice center, I was especially interested in the "Corn in a Jar" display. The day we went there was some Hillbilly Banjo Pickers & singers there, I never have figured how they can play and be missing a couple of strings?? Penny & her Mother talked to the Local Cherokee Tribes people that had a show is dress.

Had some nice Elk and lots of Whitetail running around but one step into the tree line they disappeared that's some thick bush in places. Lots of hog tracks and have seen a few Boo Boo type Bears (we still have ya beat on the bears) but lots of Boo Boo Bears roam the campground at night. One lady came running out from the restroom area yelling Bear!! I lifted my pant leg and said THEY DON'T EAT MUCH!! she didn't see the humor in that. :-laf

 

[Wayne M.]

I'm happy you're having a good visit in what I call Gods country there. Yes that's the visitors center I meant. Just up the road that takes you into the mountain, and I believe the enteance to your camp, there's a large clearing where the Elk roam. Huge tourist draw.
were you able to go over the mountain yet into Tn? When you went to Asheville, did you go through Maggie Valley?

 

[BIGNASTY]

I'm happy you're having a good visit in what I call Gods country there. Yes that's the visitors center I meant. Just up the road that takes you into the mountain, and I believe the enteance to your camp, there's a large clearing where the Elk roam. Huge tourist draw.
were you able to go over the mountain yet into Tn? When you went to Asheville, did you go through Maggie Valley?

We went on a hike today 2.7 miles one way to Rainbow Falls. The trail continues past the falls for a total of 6.7 miles up to the summit of Mt. Le Conte. Some of the older or out of shape folks stayed and enjoyed the Falls, Those of us who possess big Ball's HA HA HA HA JUST KIDDING went to the summit for a really nice view of the landscape. Its some dense forest to be sure. If you don't have a compass or somehow get off trail I can see spending some time trying to find your way home.

When we went to Asheville we took 19 to 40 at Sand Hill. My Mothers house where she grew up was in Canton, then into Asheville, for those (myself included) That think the West is the land of Steep up & down grades I HAVE NEWS FOR THEM. We were in the Tacoma so it wasn't to awful bad. I learned why these are called the Smoky Mountains, FOG!! BIG TIME FOG, Calif. has some pretty tough fog in the central valley "Tule Fog" I THOUGHT that it was as bad as bad could be until we went to Asheville I xxxx U NOT I LOST THE FRONT END OF THE TACOMA


The fuel pump went well, I got up this AM and hit the key waited until the pump timed out and hit the start. It fired up without hesitation went to idle at 650 RPM WITH NO SURGE. I let it run for a bit and shut it off so we ate breakfast and went hiking for the day, when I got back I touched it off again and AGAIN NO SURGE im as tickled as a pig in XXXX.

Going to the Park Ranger Program "Bears of the Smoky Mountains" you folks do have some pretty good sized Boo Boo Bears, the people are terrified of them if they got a look at one of our Grizz bears they would have a XXXX hemorrhage for sure.

Still not used to the way people talk, I think its pretty cool that people try to get that "second syllable out of a single syllable word" Some good hearted folks, I was asked to join in at a Pick-in & Grin-in session with some banjo pickers that had a guitar (with the correct amount of strings) they are WAY BEYOND my level of picking.

 

[BIGNASTY]

Started the MH today after several days of not, Started and ran GREAT!!!!!!

 

[TFucili]

Sounds like you can declare VICTORY!