Engine/Transmission (1998.5 - 2002) Wanna fix your lift pump problems?

[Whitmore]

I titled this post to get attention , so since you are here I want to offer a fix that has worked for me but is not possible for all, I notice alot of new as well as older members here that have great concern on the L/P issue so I am trying to get some exposure here. After all the L/P issue will never go away till we re-engeneer the system, DC obviously does not care. When something fails DONT put it back the same way... ... ..... try something different.

I firmly believe that the OEM lift pump is the best pump available to us at this time but also think that the setup is the problem, NO pump likes to pull a vacumn but prefers a positive head pressure, the OEM setup is the problem, the pump is on a constant vacumn from pulling up to 2 feet and from up to 8 feet away, there is not a pump on the market that will survive this kind of application or punishment. I am sure I will catch some flack over this but IMHO a pusher pump is only a bandaid at best and with 2 pumps you then have twice the chance of failure. I know alot of members are using pusher pumps and some with success With that said once again there is only one fix for this IMO, You MUST install your L/P lower than your supplied fuel source and the less line between the fuel and the pump the better, You MUST also have adequate delivery lines to and from the pump, at least 1/2" line to be safe, some of you may comment that the inlet and outlet of the pump are like 3/8" and that is true but trust me here larger line is necessary in order to supply the least resistance as possible. If you have ever studied hydrolics than you know what I mean.



Here is what I have done to correct my OEM fuel delivery system. I purchased an auxillary inbed fuel tank, this is my MAIN supply to my delivery pump ( no longer a lift pump ) I have installed a ball valve at the bottom of the tank for maintenance purposes and 1/2" line to the pump, 1/2" line from the discharge of the OEM pump to the OEM filter housing in its original location and 1/2" line from the filter to the VP-44... ... ... ... ... ... ... ... ..... RESULTS ARE I now idle at 15 psi of pressure and cruze 75 mph at 15 psi!!! and at wot I can only pull it down to 12 psi!!! As far as fuel usage from my Cummins I have 275 injectors and a comp box, the above stated readings are with the comp on 5x5. Before this mod my numbers were cruze 75 mph at 12 psi, WOT at 4-5 psi. I now use my OEM fuel tank as a storage and transfer tank, I use a small 40 dollar pump for this task, something interesting here is at first I used the oem line from the OEM tank to the aux tank and it took about 30 minutes to transfer its contents up to the aux tank ( main feed ), I didnt like that so I installed 1/2" line and now I can transfer in 13 minutes!!! That tells me alot about fuel delivery lines because the transfer pump and its location didnot change, I simply reduced the resistance of the lines.



I really wish I had a amp load reading from the liftpump from before and after this mod. I know it is less because the pump is not working near as hard now. It no longer is SUCKING.



OK OK, I know that this setup is not for everyone but the same logic can be applied to this concept on the OEM tank as a main fuel delivery system. It is not very expensive and will help alot.



If you dont have an inbed tank you can do like Chris Sutton (I Think that who did it) and buy a bottom bung tap and come off the bottom of your OEM tank to the pump. This will give you the same concept, The fuel supply must be higher than the pump and the pump needs to be as close to the fuel source as possible.



Bottom line is if you dont want a lift pump than turn it into a supply pump.



Also I had what I thought was a bad lift pump ( crappy psi and down to 2 psi at WOT ) sitting on the bench that had 12k miles on it, just for grins I installed it and guess what I have the same readings, so now I have a spare pump for future use.





Smash this and bash this but give it thought and lets collectivly make it better yet.



cheers, Kevin

 

[mgoncalves]

Hey buddy, I hope you realize that you're going to have to help me move mine, as well as upgrade the lines some day





I think you are right on with your thinking on this.









Matt

 

[Whitmore]

More from Lsfarm Greg



The factory lift pump is being used in a location that is out of spec for the pump. The pump is designed [I believe these are the right specs] to pull fuel from a fuel source not further than three feet, and not lower than sixteen inches.



As installed in our trucks, the distance is around seven or eight feet, and the lift is between sixteen and twenty four inches. If the fuel tank is kept near full then the lift distance is minimized.



The problem is this: PUMPS LIKE TO PUSH, not to suck!! Positive pressure from gravity or a pusher pump will allow a pump to last as long as it can. Having to suck fuel from a low and distant fuel tank creates a 'made to fail' situation.







Greg L The Noise Nazi





__________________

 

[juicedcummins]

Whitmore, I have been running basicly the same setup as you for about a year and agree that seems to be the way to go. Your numbers on the fuel pres that you see on your truck are within 1psi of mine[could be the gauge diff from truck to truck].

The only difference is that I have a switch to go back and forth from the factory tank to aux. This gives a direct comparism on the differnts in restriction on each system. I see no difference on pres runnig the stock tank verses the in-bed. I still do agree that the little bit of head pres is a benifet to the life of the lift pump. My supply lines are 3/8 with no 90deg bends or banjo's.



I did post a while back that my lift pump was on it's way out but iit ended up being a bad sending unit on the pres gauge.



The lines seem to be the ticket along with moving the lift pump back.

 

[Diesel Freak]

Originally posted by Whitmore

NO pump likes to pull a vacumn but prefers a positive head pressure, the OEM setup is the problem, the pump is on a constant vacumn from pulling up to 2 feet and from up to 8 feet away, there is not a pump on the market that will survive this kind of application or punishment. I am sure I will catch some flack over this but IMHO a pusher pump is only a bandaid at best and with 2 pumps you then have twice the chance of failure.

I agree Kevin!



That is exactly why my lift pump is mounted to the frame rail above the transfercase support crossmember.



Idle pressure is 14-15, 70 MPH is 13 and WOT is 9 with DD3's and the Puck.



Next plan is to run twin Parallel Carter pumps... adding a little redundancy to the system Oo.

 

[Pit Bull]

Kevin, how much did your set-up cost? How long did it take to install?

 

[Whitmore]

excluding the tank ... ... ... ... around 250, its just hoses and fittings, I didnt go with the braided SS, looks was not the issue but performance was!

 

[RobbyRam]

I know it's kind of a provocative question, however, I'll ask anyway: Isn't it just a little bit cheaper to have a spare lift pump from 'Cummins' stored under your seat with the tools and instructions to install, in the 'off rare case' that your lift pump might fail, instead of all the re-routing of fuel lines and mounting points closer to the tank, etc?

I've been on the TDR since Oct 1999 and this is POSITIVELY the most 'paranoid' thread I've seen on the TDR! Mine was replaced at my request because of worry generated by reading TDR threads even though it was working fine. Had I not read this type of thread it would probably have been working fine for who knows how long.

Bob in Sacramento

 

[Whitmore]

I guess each to his own, I personelly dont like it when something is not designed right so I redesign it and implement it. I also like the dependibility from a correct system and prefer not to (less chance) of putting a new pump in on the side of the road while in my nice cloths with the lil woman sitting in there waiting on me, and the smell of fuel on the interior of my truck for the rest of its life.



cheers, Kevin

 

[Behr]

Well... . I must say... some good points brought out in this thread so far.

Kevin... I like your idea of the in-bed fuel tank... but for me and some others... . that is just not possible.

I do agree in the concept of larger fuel lines in and out of the pump... . and I am also a strong believer in the pump been used to push not pull the fuel. Back in 95 I owned a Chev pick up with a 6. 5 Diesel in it... and they had there transfer pump mounted halfway between the tank and motor but was mounted physically lower than the tank itself.



I will be in the next few weeks making some mods to mine... but definitely larger lines in and out and if I don't move the pump to the rear I will at least make sure its just below the tank.



Does anyone know if there is some kind of screen or filter on the inlet of the fuel line inside the tank... ??

 

[jmeehan]

I'd like to run an in bed tank but it won't work for me either.

I have been thinking about putting a low suction on my factory tank. I won't go with a bottom mount, I'd worry about scraping it off on something, but a side mount with a bent pickup tube inside the tank and a screen on the end of the pickup tube.

I like the idea of relocating the lift pump but I wonder how far it will push the fuel? I think with a pusher pump supplying the factory lift pump you know you're covered.

 

[Diesel Freak]

here is my idea



a possible 200 GPH free flow, and 15 psi

 

[Behr]

Ok... . now I am a bit confused... .



I am hearing words like "lift pump" and "pusher pump"..... now I can see the OEM pump where it is located been called a lift pump... . because it literally has to suck the fuel out of the tank and UP to the fuel filter ... ... but if we move this same pump back to the tank and lower... . would it not become a "pusher pump"... ???



If I am incorrect..... I would love for someone to explain to me exactly what the difference is.....

 

[jmeehan]

Behr, you've got it. A pusher pump is back near the tank, pushing the fuel to the engine, and a lift pump is up on the engine, lifting the fuel from the tank.

My worry is, I don't know if the lift pump is moved and used as a pusher pump if it will have enough flow for the VP44.

 

[krs]

Yes, move the OEM pump back to the tank and it becomes a pushING pump, but the reference to 'pusher' pumps is the local description of an additional pump at the tank to push fuel to the OEM located pump. Is that clearer?



Pet theory: I think that Dodge included a fuel supply system in their spec for the engine to be supplied by Cummins as a package and that's the only reason we get the pump where it is as original equipment. They probably are delivered assembled and ready to install in one big box. Likely high level contractual stuff that no one at Dodge is empowered to alter, so we're left to our own devices. There's no other reason to put THAT pump on the engine itself and it even is at odds with Carter's own instruction for use of the pump. There is a benefit: the pump is included in the engine 100K warrant and would probably not be if not mounted on the engine or supplied by Cummins.



Whitmore - I think yours will work FOREVER!

 

[Diesel Freak]

Originally posted by 85CJ

My worry is, I don't know if the lift pump is moved and used as a pusher pump if it will have enough flow for the VP44.

It will work... that is the exact thing I and many others have done. Getting rid of the banjo fittings helps also.

 

[Whitmore]

Originally posted by Diesel Freak

here is my idea



a possible 200 GPH free flow, and 15 psi

Diesel freak, this is not a bad idea at all but I would sugest that 2 seperate lines from the tank to the suction side of the pump would be better, I have a ton of experience with what you are talking about here and what I do know is that the way you have it drawn here the strongest pump of the two will end up doing 90% of the work and the weaker one will possibly get hot and burnup, but if you had a seperate line from the tank to each pump you would have much better luck. Also I would be concerned with to much flow and washout, if you plan on using both pumps at the same time that is , or was this going to be for a spare?

 

[Diesel Freak]

What do you mean by "washout"



Actually in the parallel system, volume will not go up over the OEM system, but the pressure drop as fuel demand is increased by the VP44 will be less than if the system had just one pump.



Also, volume should not go up appreciably unless you have some serious fuel going to the injectors, or fuel pressure is high enough to lift the VP44 bypass relief.



with this system, you just have a large reserve volume of fuel available.



twin pickups from the tank would help a bunch

 

[tajensen]

Kevin



Yesterday after getting my fuel pressure down to 3 psi at WOT I started thinking. Ironically, you posted an answer to the exact question I was thinking: Should I use a pusher pump, or relocate the lift pump? Now I am confident that relocation of the lift pump with 1/2" fuel lines is the way to go. Thanks for the insight.



-Tim

 

[Whitmore]

The oem system is so I hear anyway a 70 gallon per hour and you are saying your setup will give 200 GPH, that is 3 times the flow from original design, there is plenty of mass flow there! and you should never have a heat problem or lack of lubrication to the vp but when I say concern over washout I am thinking that somewhere inside the vp something will be wearing 3 times faster because of all that flow, I have seen spillbacks at work that get used way to much and washout is a big concern, the fluid trafic can actually wear stuff out.



Aslo I would be concerened with the temp of the fuel as pumping causes temp rise, I dont think it would be to bad with what we are doing here but I would want to check it , I am talking temp of fuel at the inlet to the vp from 1 pump vs. 2 pumps.



I am just thinking outloud here