floydfowler Report post Posted September 10, 2020 Our 2001 Holiday Rambler Imperial with cumming ISC 350 has warning light flashing on randomly. I occasionally had similar problem last year when on long uphill pulls and solved it by replacing the ambiant air sensor. I have a Scan Gauge code reader connected and last year I was getting codes 94 and 98 which Cummings Customer service indicated problem with the sensor. Now I saw code 98 very briefly and then no codes stored. I replaced the sensor again but now get the light flashing on randomly even when not pulling uphill. I noticed a slight loss of power when the light flashes on and the boost pressure drops down some and right back to normal. I have changed both fuel filters with no improvement. Engine starts and runs normally for hours and then the light will flash on once or twice and then back to normal. Any thoughts? Share this post Link to post Share on other sites
rayin Report post Posted September 11, 2020 Hello FloydFowler, Ray Fowler here. We have the same engine. A rather common problem is the fuel lift pump develops an air leak at the gasket area. There are 3 bolt heads on top the pump, tighten them. Since this pump only runs for around 30 seconds to 1 minute, then the main fuel pump(injector pump) take over and sucks fuel all the way from the fuel tank, through the filters; if the lift pump is leaking air it cannot be seen. The link below explains how to install a fuel pressure gauge on the primary/fuel water separator fuel filter, it should read -5 negative fuel pressure unless the lift pump gasket is leaking. I discovered my lift pump was leaking when I spotted diesel fuel on the concrete garage floor. This leak drips onto the starter motor, which IMO can cause an engine fire rather easily. Two different diesel shops told me when either the injector pump or lift pump fails, the other is destined to also fail; so they usually replace both at the same time. I experienced this last summer. I had the lift pump replaced last spring afterwards discovered those 3 bolts were loose. In July the injector pump fuel distributor module failed 300 miles from home. It took Cummins Great Plains weeks to get a re-manufactured one installed due to the pandemic-induced shutdowns. They said when the lift pump sucked air it caused the injector pumps 12V fuel distribution module to fail; That bill was $5,000. Read this thread for more insight into this fuel issue. I hope this is somewhat helpful. Share this post Link to post Share on other sites
floydfowler Report post Posted September 11, 2020 Ray, Thanks for all the information! I followed all the threads and now my head is spinning. I will start with the pump bolts and keep my fingers crossed. We purchased this used motor home with 30,000 miles three years ago and I don't know about any previous issues but we did have quite an issue with algae and clogged filters. We had an on the road engine failure on our first trip that was due to completely clogged primary filter. I treated the fuel tank with biocide twice and have used Clear Diesel and Diesel kleen at every fillup since. I change the filters every 10k miles or so and have not seen one clogged in the last 40,000 miles but do occasionally see some small particles in the clear bottom of the primary filter. I have never seen any particles in the water separator filter. We leave on a three week trip in two days so I am feeling pressure to get to the problem .. Also thinking about changing the lift pump gasket. Thanks again for your input. Share this post Link to post Share on other sites
floydfowler Report post Posted September 11, 2020 Does your pump look like this? I was expecting 7/16" bolts based on info from the thread. Anyway, these three bolts are tight Share this post Link to post Share on other sites
floydfowler Report post Posted September 11, 2020 Also, I noticed the electrical connection you see in the top of the photo has nothing plugged into it.??? Share this post Link to post Share on other sites
hermanmullins Report post Posted September 11, 2020 From the look of the plug nothing has been plugged into it for some time if ever. Herman Share this post Link to post Share on other sites
rayin Report post Posted September 12, 2020 Good to hear the 3 bolts are tight, yes that is the same lift pump. I'll have to look at that plug on mine to see it it is also unused. It will be a while, I'm having heart issues again, gotta take it easy for a few days. If the lift pump gasket is leaking, there will be signs of fuel below the gasket, (on the motor) where it leaks out when the engine is shut down. Share this post Link to post Share on other sites
wildebill308 Report post Posted September 12, 2020 Ray, take care of yourself. Bill Share this post Link to post Share on other sites
floydfowler Report post Posted September 12, 2020 Ray, thanks for the additional info. I see no sign of any fuel around or under the pump or on the engine. I too hope you will take it easy and wish you the best of health! Floyd Share this post Link to post Share on other sites
rayin Report post Posted September 13, 2020 I'm still here, finally got my heart under control. My BP was 209 over 94 yesterday, I finally figured out I was having a severe asthma attack, back to back nebulizer treatments seem to have remedied the problem for now. Anyway, I'll try to look for that unused electrical connection tomorrow Floyd; unless things go bad tomorrow. Share this post Link to post Share on other sites
manholt Report post Posted September 13, 2020 RayIN, as Bill said, X2 ! Share this post Link to post Share on other sites
floydfowler Report post Posted September 13, 2020 Ray, forget about that electrical connection and take care of yourself. 209/94 is very scary! I've driven it 40k miles that way so I think it will be just fine. Share this post Link to post Share on other sites
floydfowler Report post Posted September 19, 2020 UPDATE Changed both filters again (at 3,000 miles) and found small black particles in the primary (FS 1242, 20 mc) filter but nothing noticeable in the second (FS 1022, 10 mc) filter. Drove it about 5 miles and the light flashed once then off and now 600 miles later still no problem. I am now sure I just have a dirty/algae fuel issue and have been thinking about adding a second FS 1242 in parallel to get more filter capacity while I work on getting the fuel cleaned up. Also just noticed that the primary filter is before the lift pump and the second one after the lift pump. Sure would be great if that fuel contamination is my only issue. Share this post Link to post Share on other sites
wildebill308 Report post Posted September 19, 2020 19 minutes ago, floydfowler said: Drove it about 5 miles and the light flashed once then off and now 600 miles later still no problem. I am now sure I just have a dirty/algae fuel issue and have been thinking about adding a second FS 1242 in parallel to get more filter capacity while I work on getting the fuel cleaned up. Also just noticed that the primary filter is before the lift pump and the second one after the lift pump. Sure would be great if that fuel contamination is my only issue. I would run Clear-Diesel Fuel & Tank Cleaner by Power Service. https://powerservice.com/psp_product/diesel-kleen-cetane-boost/?utm_source=rr&utm_medium=ppcc&gclid=CjwKCAjw2Jb7BRBHEiwAXTR4jWqBg9eyzIUm45S-qtCjndE7Jrb3XCV_bOUuxM07wr-TDZIcom9sQhoCF9YQAvD_BwE I would have a extra set of filters when I did. I run Diesel Kleen in every tank full. Bill Share this post Link to post Share on other sites
floydfowler Report post Posted September 19, 2020 Thanks Bill. I failed to mention that I use Clear Diesel and Diesel Kleen at very fill-up. I am going to hit the tank again with BIO KLEEN DIESEL FUEL BIOCIDE as soon as I can find it. I have a bottle at home but I'm on the road now. I used my spare filters last week in Tenn. and stopped in Knoxville at the Cummins Dealer and bought two more sets. (Very nice folks and two minutes off I-40). Side note: Last summer I stopped at an Advance Auto in Oklahoma to pick up some Clear Diesel and they had the 80 oz. bottles on close out. I bought all they had (6-80 oz. bottles) for $0.05 / bottle. Clerk was surprised but said "oh well, that's what the computer shows". I almost ran to the car to show my wife the receipt. Best I can find now is about $30 / 80 oz. Share this post Link to post Share on other sites
rsbilledwards Report post Posted September 20, 2020 Generally Walmart has a very good price on it all the time. I too have an inventory of it since I use it in the Ford 7.3 ltr. There it is good for 100 miles a 40 gallon tank city or highway. Share this post Link to post Share on other sites
rayin Report post Posted September 20, 2020 This year I used Biobor in our MH tank, first time I ever used such product. Just one of the bottle jiggers treats my 125G tank. MH's only been driven 600 miles this year, I figured it may prevent a huge headache in the future, even though I always top-off the tank the day of storage. Biodiesel in long-term storage presents a different problem. Share this post Link to post Share on other sites
wildebill308 Report post Posted September 20, 2020 21 hours ago, floydfowler said: Side note: Last summer I stopped at an Advance Auto in Oklahoma to pick up some Clear Diesel and they had the 80 oz. bottles on close out. I bought all they had (6-80 oz. bottles) for $0.05 / bottle. Clerk was surprised but said "oh well, that's what the computer shows". I almost ran to the car to show my wife the receipt. Best I can find now is about $30 / 80 oz. I would have taken that load to the car and gone back and asked them if they had any more in back. Ray it is always easier to practise prevention than clean up the mess if you get infested. Bill Share this post Link to post Share on other sites
