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Old 12-05-2015, 06:29 AM   #1
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ISC 8.3L Lift Pump

Missed a bullet!
Started the MH for warm-up and then did a last minute walk-around before leaving for a week-end rally. Noted a slow drip from the engine area. It was diesel and appeared to come from the right side of the engine above the starter (blocking view). Cummins Engine manual indicated the lift pump was in that area. To troubleshoot, we dried the area and turned the key to on and could hear the lift pump operate and shut off after the normal 30 seconds. Everything was wet again! Called the maintenance folks... The mechanic was successful in viewing and confirming the lift pump leak. Figuring a gasket leak we decided to remove the pump and install new gasket(s). Only 3 bolts so should be easy. From under the MH I hear "you're not going to believe this!"... One bolt took 8 full turns to TIGHTEN. The others took 3 & 4 turns respectively. NO LEAKS.
Hal & Ginny Miller '04 Beaver Santiam PRT40
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Old 12-05-2015, 06:35 AM   #2
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You were lucky. My lift pump failed while we were in Destruction Bay, Yukon Territory. Had to have the pump flown into White Horse, and be towed the 180mi. to Inland Kenworth in White Horse. To say the least it's a story we'll be talking about for some time to come.
2000 Dutch Star Pusher
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Old 12-05-2015, 10:32 AM   #3
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Good time to buy a Lotto Ticket too! Glad that worked out so easy for you.

Being and 04, do you know if your ISC is the CAPS or Common Rail? If CAPS, these do get pricey if they fail. As you know, the Lift Pump just runs that short period of time until the engine starts and then the CAPS takes over, pulling the fuel into the pumps and pressurizing them out to the individual injectors. It is that fuel flowing thru the pump that both cools and lubricates the this very expensive CAPS...

As we were hoping to add a bit more power to our ISL370(400 flashed) CAPS era engine, I elected to also replace our Lift Pump. (Had some problems on the ECM reprogramming, and due to time, could not remain longer as the company was trying to sort things out. Time differences between Eastern Canada, and then also to Germany, made each cycle of programming about a two day turn around. Still thinking I'll go back to the shop, and let them take the time they need to get things reprogrammed, sometime in 2016.)

I elected to bypass the Lift Pump, and went with the FASS pump, not the full two filter system, just the electric fuel pump. This keeps a positive fuel pressure feeding the CAPS at all times. Would have covered potential higher demands from the remapping/programming of the ECM, and I knew owners that were on their third Lift Pump, though to be fair, usually the Pre ULSD Lift Pumps replaced with a newer unit and gasket, took care of things.

If your Lift Pump does go out, worth considering going the bypass route.

Smooth sailing for you, and don't forget to thru a party with your Lotto winnings!!!
07 Country Coach Magna Rembrandt 45' ISX600
Roo II was our 04 Country Coach Allure 40'
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Old 12-11-2015, 06:56 AM   #4
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As mentioned, the ULSD is the problem. I tightened my bolts to keep from being stranded, worked for the 1500 mile trip home. Tightening the bolts my solve the upper end problem, the pump is also prone to developing leaks from the electrical connection area. You now have the option to replace at your leisure, which is what I did.
Jim and Jennie, Cats=Bittles and Potter, 2000 Dynasty 350 ISC
2013 Silverado 4x4 Towed with R1200GS in bed.
PROV23:4 Do not wear yourself out to get rich; have the wisdom to show restraint.
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Old 12-11-2015, 12:53 PM   #5
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two years ago, my lift pump leaked. called a diesel shop, they quoted $500 including a new support assembly as they told me the gasket was no longer made. well, i did find the gasket online for $6. when it arrived, i pulled up the bed to change the gasket, and noticed the 3 bolts being loose. tightened them up, no leak any more.

last month, i noticed the drips again. repeated the process, all was good again. just keep an eye on it. enjoy the trails.
Steven & Polly
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