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Old 08-30-2014, 11:00 PM   #15
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I recently put a new cummins lift pump in my motorhome and I am only getting 11psi at idle and 8psi under a load. I put a digital gauge in and watch it like its my job. But I feel like it should be more than 8psi under a load.
That's not bad, from what I've been told and read 5PSI is the dead least you should ever see. I used to idle at 5PSI and it would bottom under a load, it's a wonder I didn't fry my injection pump.

The banjo bolt that retains the return line actually has a check valve in it that is supposed to regulate the pressure. I'm thinking of replacing mine as I idle at 15PSI but under full throttle and 3000RPM it gets to about 7PSI, I'm thinking I may be returning too much fuel.
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Old 08-31-2014, 08:54 AM   #16
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Quote:
Originally Posted by camping fam View Post
I recently put a new cummins lift pump in my motorhome and I am only getting 11psi at idle and 8psi under a load. I put a digital gauge in and watch it like its my job. But I feel like it should be more than 8psi under a load.
I get about the same as you with my new pump, maybe slightly higher. Your ok as long as your better than 5-6 psi under load. That is the objective. Keep a watch on it. If you get below 5 under load, change the pump again. Remember that is a long way from the tank to VP.
If you should consider a FASS or equivalent you can expect another 5 psi.

From my forum readings, not an expert, more is not necessarily better since keeping your present readings seems to be ideal for the VP44 injection pump. 8 turns into over 10000 psi in the VP44 for the injectors. You just have to have enough lift to satisfy the VP.


If mine gets weak again I will probably opt for the FASS and put it on the frame instead of the engine.

Just my opinion and I am sure forum experts have a different view.
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Old 08-31-2014, 10:50 AM   #17
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Good idea moving it to the frame, closer to the tank is better. Electric pumps don't suck very well and are far better at pushing. Supposedly if I went to dodge for a pump I'd get an update kit that puts the pump in tank and bypasses the engine mounted pump.
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Old 08-31-2014, 12:04 PM   #18
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when I bought my cummins pump I got the relocation kit from cummins and if have to do this again I am either going to get a fass pump with adjustable pressure or I am going to elimanate the pump being at the back and actually mount a fass system up at the tank. My opinion is its easier to push 38 feet than suck 38 feet and I also feel like the more furl pressure the more power you can make.
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Old 09-03-2014, 08:27 PM   #19
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When I had to replace my stock pump, went with an I believe a Fass Airdog from Blue Chip Diesel. Made a bracket and mounted the pump away from the engine to avoid vibration and allow for easier change in the future if needed. Like the idea of higher pressure and flow for better cooling of the VP44 injection pump. Also installed a low pressure warning light just prior to the stock lift pump failure.

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Old 09-03-2014, 09:09 PM   #20
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When I had to replace my stock pump, went with an I believe a Fass Airdog from Blue Chip Diesel. Made a bracket and mounted the pump away from the engine to avoid vibration and allow for easier change in the future if needed. Like the idea of higher pressure and flow for better cooling of the VP44 injection pump. Also installed a low pressure warning light just prior to the stock lift pump failure.

Martin
If my new pump weakens I might do that and mount in on the frame. I did a mod in my back compartment that includes a removable panel so I can easily get to my pump, fuel filter, and engine computer. So a frame mount would be ideal for me.
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