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Been going through fuel lift pumps like candy from my point of view. 

Going to start a replacement process of the fuel line, lift pump and filters starting tomorrow now that I have procured all the needed parts. Going to replace the 1/4 in.  line from the last fuel filter going to the injector pump.- increasing the size to 5/6 in. line and install high flow banjo bolts, that restrict fuel flow from the first fuel filter output all the way to the injector pump input. 

Will be taking fuel pressure reading after each part is replaced and get some flow rate readings, if my friendly mechanic will let me borrow the flow meter fro a few hrs. 

I did call Cummins and did not get any real base line information on how long or how many miles there pumps should last. Thinking they have some test stand information and should be running spot checks on the new units being supplied.

However, going through 5 of them in 120,000 miles does not make sense as they drop below the specified 10 PSI minimum specification in the engine repair manual . When my big 8.1 L gas powered truck will go 125,000 miles on each pump. I'm not much for making the parts department richer.

Rich.

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Rich,

Yes, that sure sounds excessive.  Be sure to note if there is any air in the system, which can certainly cause low fuel pressure.  A loose hose clamp or crack in those OE fuel lines from the tank bare close inspection.

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53 minutes ago, wolfe10 said:

Rich,

Yes, that sure sounds excessive.  Be sure to note if there is any air in the system, which can certainly cause low fuel pressure.  A loose hose clamp or crack in those OE fuel lines from the tank bare close inspection.

Point taken Brett ! A clear portion of line inserted into the system around the fuel filter area should cover that.

Thanks! Rich. 

Note, Got all the brake hardware under the brake drums replaced an it was obvious it needed some TLC - The rollers where not roiling well and that does not make for nice even braking.

Rich.

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Brett, Things looked like what one would expect nominal humid weather would produce regarding the level of rusting.

Kind of had a rebuild job on the coach after I made the deal to buy it. It had been taken on a trip to Alaska and the owner never washed the calcium chloride of from under the coach and it needed some extensive work replacing the steel and support system from the main frame assembly down that supports the stowage area, the heater, fresh water bay, battery trays and inverter. I would not undertake that kind of task now! A number of years have passed, but it really was in excellent condition otherwise with very low generator hrs. and only around 17,000 miles.

The DW loves the floor plan and is in no rush to change after going through a few hundred over the years.

The Dealer made his money on my Gas unit - that they basically just roiled.

Rich.

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Rich, When I was converting mine one thing that Cummins pointed out was their pump wasn't designed to draw fuel the distance of a DP. Fass makes a direct replacement to the Cummins pump for a 5.9L. If you want grab the parts and head south to PA, I've got room in the driveway with Water and electric. We can go Rambo on that and convert it over.

http://store.fassride.com/shop/diesel-fuel-pumps/dodge-replacement.php

Not sure if yours is set up like a Dodge, the link is above.

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To all,

I am a novice on the subject of the fuel system on a diesel MH. Let me see if I have this straight. I have a 2002 Cummins 400 ISL 8.3. I have a Lift Pump in the Fuel Tank that pushes the Fuel to the High Pressure Pump, which feeds the Injectors. The lift pump is just a booster for the high pressure fuel pump. Am I any where close to understanding it?

By the way, in route to Indianapolis we had to have our High Pressure Pump replaced in Joplin, MO. We were there for 4 days. The great mechanics finished up on Saturday at 1:45 AM. Just as I paid my bill the tech came in and said we had a leak but that they would stay till it was corrected. I said no. Go home and come in Monday and then fix the leak. (They are closed on Sat. and Sun.) They did, found a very important "O" ring had fallen out. Put it all back together and we headed out. Runs like a top. Thanks to the Staff and Techs at Cummins Service Center, Joplin Missouri. 

Herman

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Herman,

Couple of points:

The Cummins ISL is 8.9 liters. The C is the 8.3 liter Cummins.

Fuel pump is NOT in/at the tank, but on the passenger's side of the engine.

Yes, some have added a pump up front to push fuel back, as the OE lift pump was more designed with trucks in mind than motorhomes (i.e. a few feet from fuel tank to lift pump, not a many YARDS).

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Thanks Brett, I am fully aware of the high pressure pumps location. Saw the pump and it's location when it was being replaced.  There is an oil port from the cover the pump mounts to that supplys oil to the pump. In the case is a recess for the "O" ring. Either the tech didn't put it in or it fell out during reassembly. The Service Mgr. Knew immediately what the problem was on Monday morning. He said he puts a large amount of grease in the recess to hold the ring in place. 

On my 8.9 ISL, is the lift pump in the tank? 

Herman 

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Passenger's side of engine forward of the injection pump.

Have someone turn the key to ON (not start) while you are back there.  The fuel pump/lift pump will start and run for 30 seconds or so.

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On 7/30/2017 at 2:00 PM, DickandLois said:

Been going through fuel lift pumps like candy from my point of view. 

Going to start a replacement process of the fuel line, lift pump and filters starting tomorrow now that I have procured all the needed parts. Going to replace the 1/4 in.  line from the last fuel filter going to the injector pump.- increasing the size to 5/6 in. line and install high flow banjo bolts, that restrict fuel flow from the first fuel filter output all the way to the injector pump input. 

Will be taking fuel pressure reading after each part is replaced and get some flow rate readings, if my friendly mechanic will let me borrow the flow meter fro a few hrs. 

I did call Cummins and did not get any real base line information on how long or how many miles there pumps should last. Thinking they have some test stand information and should be running spot checks on the new units being supplied.

However, going through 5 of them in 120,000 miles does not make sense as they drop below the specified 10 PSI minimum specification in the engine repair manual . When my big 8.1 L gas powered truck will go 125,000 miles on each pump. I'm not much for making the parts department richer.

Rich.

OK, I just quoted my own post to expand on the lift pump conundrum ! Edited 6-25-2018

        I went and purchased an aftermarket lift pump and the difference is very obvious !    

After finding a way to mount the pump in the OEM location , Connecting up the fuel lines and replacing the second filter. Because it is much easier with a number of things out of the way.

Connected everything up except the 12 volt power, made a jumper cable connection (making sure the polarity was correct)hocked the pump to one of my spare batteries and listened to the sound of the motor for maybe 2 to 3 minutes and then it started to labor. Went to the drivers set and bumped  the starter - that worked -so I then cracked the engine for 20 to 30 seconds - no fire - bumped it twice more and the engine tried to com to life. 

Then I looked at all the connections and checked for any leaks on the pressure side, NO leaks is good. Removed the jumper and the power from the pump, connected the pump to its mating connector. 

 Thinking that if I had a small air leak in the 25 to 30 ft. of fuel line running from the tank back to the pump, I would need to run the pump a few times to re prime the system. The engine sputtered for maybe 5 seconds and smoothed right out, let it run for a good 15 to 20 mins. no issues. 

           Then I oped the fuel line between the second filter and the fuel line running to the injector pump. THAT move allowed to system to loose its prime, but with the pressure gauge now in place I could see the pressure reading slowly rise to 14 psi before the engine started. Ran the engine at idle apx. 750 RPM for around 5 more min. Then got my DW to watch the pressure reading as the RPM's where increased to 1900. Fuel pressure  dropped from 14 to 12 psi. 

      The thing that stands out is - the OEM pumps delivered a maximum pressure of 12 psi. that dropped to 9 to 10 psi when idling  and dropped to 7 to 8 psi. at 1900 RPM.

Let the coach set over night and bumped the starter - The delivery pressure before starting the engine hit 18.5 lbs.  Never have had numbers like that, but remember the VP-44 injector pump maximum input pressure is 20 psi if you do not want to kill them. Real good numbers again    Started the engine and the idle pressure set at 15 psi. - increased the RPM to 1900 and the pressure leveled at 14 psi. this was a no load test. So I turned on the Dash AC and the load only dropped the pressure 1/2 LB.  Will run to the Fuel pumps and top off the tank. 

       OK, Topped off the fuel tank and the fuel pump pressure increased by 1 Lb.  Nice, fuel level in the tank increased by 12 plus inches, The pressure only increased a little. That indicates to me that this is indeed a much better pump in regards to its vertical lift ability  !!

   Then to get a road test in before being interrupted for like 2 weeks. Forth of July weekend - Road trip will need to weight for a few days.

after that I will see how this miner but impressive change affects the performance on a real road test, of 75 miles and a 3/4 mile climb at 9%. That one hits coming out of a 40 MPH zone.

Rich.

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9 hours ago, jleamont said:

Rich, sounds good! What pump did you use? 

Joe, This is not a vendors forum ! LOL - So I can not offer any information or my personal views of the device.  Is that politically correct?

It is a Fass DRP series that did not include the installation Kit.

Fuel lift capability is 4 ft. and a flow rate of 90 GPH. at 15 to 18 psi. The low number does drop as the engine load increases, but still is well above the OEM pressure levels. 

Had to lower the pump about 2 1/2 in. so it would clear the frame rail.  The pump mounts horizontal so the weep hole is pointed down, if not orientated correctly, the warranty is voided. 

Used 5/16 -18 stainless steel rod to make mounting studs / jamb nuts at the pump mounting bracket an the pump mounting plate, long enough to drop the pump and clear the frame rail.  I placed 3/8 in. threaded couplings over the rod(just a nice fit)to increase the three point bearing weight area of the pump adapter and the OEM mounting plate . The pump hangs out about 3 plus inches from the brackets and I wanted to limit the torquing affect on the mount. 

The only item left to replace is the fuel input connection from a straight fitting to one with a 15 degree offset so the fuel supply  line does not rub on the top corner of the Allison transmission.

Rich.

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When I got my new to me coach 2 1/2 years ago the first thing I did was to install a new fuel system.  Had a VP44 failure on my last coach at 128K miles and was told I was lucky because they usually don't make it pass 120K.  I was told that the failure is partly due to inadequate lift pump pressure.  I replaced the VP44 and the lift pump.  I chose the complete Air Dog system.  It has a 1/2 in suction line from the tank and a 5/16 in return line.  Since I added a second tank the withdraw is from the rear tank and the return is to the front tank.  The unit has a 20 micron filter on the main line and a 2 micron on the engine feed line at 16 lbs pressure. The unit is mounted in the side compartment next to the engine and has easy access to the filters.

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Rich, that’s is similar to the Fass pump I have. Glad you decided to modify it once and for all! 

Could care less about PC also :lol:

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