Engine/Transmission (1998.5 - 2002) Running two lift pumps in series

[Wolfgang]

Has anyone tried running to lift pumps in series. Does this help the line pressures? I have had a problem since day one with my pressures at the VP44 going to 3 at WOT. I have replaced three lift pumps with out any change. So I have been thinking why not run two. Any ideas.

 

[Steve St.Laurent]

Yes, tons of us are running like that. Here's a thread I started way back in June of 2001 on my setup - https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=19767 . I had 4 lift pumps die between 24,000 and 60,000 miles (bought the truck used with 24,000 miles on it) and now have 125,000 on it and haven't replaced another since the install. Some guys are worried about high input pressures to the VP44 causing problems - mine runs at 20 psi peak. I talked with the DC and the Cummins engineer responsible for our trucks and both said 22 psi was no problem other than possible hard to start problems. A bosch rep at the TDR nationals on the other hand last year said any more than 12 psi would cause increase wear on the VP44 - but he didn't have any answers when I mentioned that the newer stock lift pumps put out 15 psi when new. Noone has reported a VP44 failure with a pusher pump setup yet. There have been a couple of lift pump failures even with the pusher but literally only a couple - and a bunch of us are running this setup. JMHO



BTW, the pusher pump back at the tank is a low pressure high volume (7 psi, 150 gph) version of the pump - it's not the same. With the same pump the pressures would be even higher.

 

[Wolfgang]

Steve I have seen the posts where they have put pumps back at the tank. What I am talking about is taking one of my old lift pumps and putting it in series with the existing pump. Does this raise the pressures? Since they both put out the same pressure. Sorry if this is a stupid question but I really don't know

 

[Steve St.Laurent]

Yes it will raise the pressure. The stock pump is a 15 psi pump. In my case for example I'm running a 7 psi pusher with the 15 psi stock pump (both are carters, just different pressures) and I see 20 psi and no less than 16 psi at WOT. I've seen some use two stock pumps in series and they are up around 28 psi. You can get the 7 psi carter like I'm running for less than $100 from summit or jegs so it's cheaper than buying a 2nd stock pump anyways.

 

[CFAR]

Steve,



Great info what part # is the 7psi pump?

 

[csutton7]

think about this for a minute---yes many guys are running this combo, but if one pump dies you're toast in the water--unless you can plumb it for a quick fix if one dies you'll be slightly ticked----I'm running one single pump and have been since July 2001---of course I punched a hole in the bottom of the tank too so I'm 1000% gravity fed all the time----this my friend is the secret----but since most guys won't do this---I'd buy one good pump (do your research) and put it back by the tank and have fun--carry a spare at all times also-even with the dual setup, if you go that way----good luck... chris

 

[Diesel Freak]

You could also run two pumps in parallel.



Idling fuel pressure would be still about 14-15 psi, but WOT pressures would only drop half as much compared to a single pump system.



Put a check valve on the discharge of both pumps, so if one fails you still have one pump to get to your destination on.



geez, I am full of ideas

 

[Gary - K7GLD]

NO reason why the fuel supply should cut off if one pump in a seriesed 2-pump setup fails - lotsa guys run around for tens of thousands of miles with failed lift pumps, and never even know it until they change their fuel filters, and then can't prime the system because the LP is dead... The mechanical LP built into the VP-44 seems pretty capable of overcoming a significant amount of obstruction in the line - including having to suck fuel thru at least ONE failed LP - and as far as an added one, here's what I did to my added Carter 4600 pusher:



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I added a control-valved bypass AROUND the pump to slightly reduce overall system psi - and IF that pump fails, the suction opens the valve to let nearly normal flow AROUND the pump. Others copying my setup simply eliminated the valve, used a plain 1/4 inch line, and get nearly the same operation with less complexity - which is what I will do with the new spare I carry...

 

[moon]

csutton7, how did you punch a hole in your tank and what fitting did you use?

 

[Mad Bomber]

Pusher pump

Steve I had a LP failier at 36K. I have a 7lbs 100 gallon carter pusher. I do belive that the L. P. was weak when I put on the pusher pump. As the L. P. failed I noticed that with the pusher was still getting the fuel though. I think that the pusher gave me a little more time before totally failing. With a new lift pump I am seeing 20 to 22 LBS at idle,WOT I get to 18LBS. Eric

 

[Wolfgang]

Gary KJ6Q



Where did you install this setup and are you by passing the stock filter setup with the fram filter or just using that as a prefilter

 

[csutton7]

yelloweyes---90* bulkhead fitting cut down---slowly hand drilled thru and then I used two poly washers(one for each side) and made a washer out of sheetmetal(for the outside so as not to suck everything thru when tightening). . here's a pic... chris



http://www.diesel-central.com/photogallery/view_ad.asp?Ad_ID=90