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Old 07-09-2012, 01:46 AM   #15
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I agree with Gary - K7GLD. Had ours replaced (2003 ISC) last year by the local Cummins Dealership. Over a cup of java at the rear of our coach following the repair, the up-front tech stated that lift pump replacement on our series and age ISC is common, stating that he usually does 2-3 lift pumps a week. Normally, there is nothing internally wrong with the pump, he stated....the seal(s) just fail. The Parts Manager also stated that he tries to keep an adequate supply of the pumps in stock at all times (this is a good-sized store). And Cummins revised the lift pump seal material, I believe, about 2 or 3 years ago. I don't believe a seal kit is offered any longer by Cummins, at least for our ISC....just a new pump. I have no idea if your 2008 Cummins has the newer lift pump seal material. A call to a GOOD Cummins Part Manager might answer that....or possibly a call to Cummins. They are very helpful.
2003 Fleetwood Revolution DP
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Old 07-12-2012, 11:28 PM   #16
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Do yourself a favor and put about 10gallons of 100% bio-diesel. The lubricity in th ebio will do wonders for your engine. Besides if you find someone that makes it at home like I do then you can save money and help the enviroment.
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Old 07-13-2012, 09:53 AM   #17
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Originally Posted by bgc44a View Post
Many diesels use the fuel for lubrication of the injectors and the injector pump(s). That is what the sulfer in the fuel did. If however you had a Cummins, it did not matter, because Cummins developed their engines with engine oil lube for the injector pump. Also it wasn't until the last few years that diesel engine manufacturers gave the OK to use biodiesel fuels.
That was true ONLY in the older "P pump" Cummins setups - which DO/DID use engine oil lube for the lower injection pump parts - but even THOSE still used fuel to lubricate the upper pump parts. Later VP44 type pumps depended entirely upon the fuel lubricity to lube the pump internals - and ALSO started using an electric powered lift pump that was ALSO sensitive to fuel lubricity for the expected long lifespan - thus, the increased failure rates as fuel lubricity was reduced with the newer diesel fuels.

And yes - BIO fuels ARE the best "fix" for reduced lubricity in diesel fuels - but unfortunately, many of us don't have access to those BIO fuels - I know *I* sure don't!
John Day....|'88 Winnebago Super Chief 27ft. Class A
Eastern .....|'88 KIT model 240 24 ft. 5er
Oregon ......|'02 Dodge/Cummins 2500 Quad Cab
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Old 07-13-2012, 09:56 AM   #18
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A minor point, but just to be accurate, the sulfur in diesel fuel is NOT a primary lubricant. Rather, the lighter aromatics that are removed in the desulfurization process in making ULSD are what resulted in reduced lubricity.



There is a misconception that sulfur is what provides the lubricity to fuel oil, but that idea is only indirectly correct. Although the sulfur does contribute somewhat to lubricity, the lower lubricity level of low sulfur fuel is more a by-product of the refinery processes used for desulfurization. In its purest state, crude oil would consist of various bonds of hydrogen (H) and carbon (C ) atoms linked together in chains of various lengths.

However, no crude oil is entirely pure, but always contains trace amounts of various impurities. One such common impurity is sulfur; depending upon the crude source, the sulfur content can range from as low as 500 ppm (sweet crude) up to as much as 10 fold (sour crude) that amount.

During the desulfurization process via hydrotreating, hydrogen gas is introduced to the crude under extreme temperatures and pressures. The hydrogen combines with the sulfur to form hydrogen sulfides that are then removed and ultimately converted into elemental sulfur for resale.

Unfortunately, during desulfurization, critical polar and organic aromatic compounds innate to the fuel and identified as responsible for imparting significant lubricity quality, are destroyed under the necessarily intense operating conditions. The resulting yield is a satisfactory low sulfur diesel fuel, but also one that is unsatisfactorily low in lubricity.
Source article HERE.

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Old 07-13-2012, 10:02 AM   #19
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My lift pump leak occurred in Jan 2010 at just over 56k miles. ...Cummins ISC. Actually I have no idea how long it had been leaking as we parked on a concrete drive for two nights after a few months on gravel, and I noticed the drips on the concrete when packing up.
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Old 07-13-2012, 10:04 AM   #20
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The resulting loss of lubricity is why many are using additives made to improve lubricity in ULSD. The best additives also improve water/diesel separation, clean injectors, and reduce corrosion to improve operation and performance which more than pays for the cost of the additive.
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Old 07-13-2012, 10:11 AM   #21
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there is no other fuel out there, as there is no leaded gas anymore. there are additives if you feel the need, but also no other alternative either. i have a 97 ford diesel truck, and an 05 cat diesel in my rv. no problems with either.
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Old 07-13-2012, 11:41 PM   #22
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My sister and her husband own a major steakhouse in my hometown. l have been running their grease in my airstream for two years. of course its free. but more than that i have never had a problem. Your choice is some oil company's fuel or cooking oil which has already been refined. You pay probably $4.00 a gallon. I pay nothing.
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Old 07-13-2012, 11:50 PM   #23
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One more thing...it really smells great unlike diesel fuel. I am getting 10 mpg minimum (even in the Tennessee mountains) with no smoke problems whatsoever. The only problem is that when I have my grandkids on board they are always wanting me to stop at a mcdonalds for some fries. I love it.
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diesel, fuel

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