Engine/Transmission (1998.5 - 2002) I suspect a lot of money has been wasted on Lift Pumps

[LTustison]

It wasn't the additional pressure, but the additional FLOW above what the vp44 is using that provides the cooling. Thats what the shop manual says.

 

[scotty1]

I have been trying to unravel the mystery of the fuel supply for both the 2 gen and 3 gen trucks.



I have also spoke direct with engineering at Cummins and Bosch.



Here is what I feel is being overlooked in the quest for pressure... VOLUME.



Increase your pressure, decrease your volume. There is a balance that has to be maintained or 'regulated'. This will vary from truck to truck and modifications. Regulating this can be with a better GPH pump, a regulator, larger lines etc. The other key ingredient is fuel temperature. If you are running high fuel pressures, there is a good chance you are returning more heated fuel to the tank then normal and as the tank gets lower, there is less dissipation of the heat. I had a temp of 180F in a 1/4 tank after a long run. Cooler denser fuel is better but there again, theres a balance that has to be maintained.



DC, Cummins and Bosch meet in the middle so to speak, to try and match what they can in the most affordable way... reference bean counters too.



I am currently testing a pump that is rated at 160 GPH at 0 resistance/psi at 12 volts or 188 [I think its 188, might be slightly different] at 14 volts.



I am gradually lowering the pressure from a start point a few months ago of 20 psi/idle. I am now at 15 psi/idle and with the power mods I have on the 04, its is actually running smoother. The pump is cooler too... as it is working less. Less stress on the pump will equate to longer life of the pump.



I cannot pull the psi any lower at 15 psi/idle then when it was higher. As long as there is a positive pressure and a good volume, we should be ok.



I am going to lower the psi/idle to 12 today. I am towing heavy on Saturday and will see how this works. Even though I am confident in this pump, I am carrying a spare. Its helps reduce the pucker effect. LOL



Scotty

 

[rweis]

Over in the DTT website in the discussion about the RASP the thread talks about anything over 12 - 14 psi input to the VP will cause additional heat to be generated in the VP. Not sure if they meant heat to the fuel or heat internal to the VP or both. But it is fairly clearly stated that their RASP bypass is set at 12 - 14 psi because Bosch says that is the optimum input pressure. More pressure than that then heat begins to build.



Now the question of flow. Because of the ease of measuring pressure everyone measures pressure. IS THERE A WAY to measure FLOW easily and reasonably economically?



In the Northern catalog back in thehydraulic section they have a hydraulic flow meter. Measures up to 30 GPM @ 5000 psi, measures GP MINUTE. You can get it with a thermometer. BUT if I understand our fuel system we are talking 45 GP HOUR, not minutes. It would take a totally different scale than the Northern flow meter.



The flow meters must be out there somewhere, but I have never heard of them mentioned anywhere in the TDR threads.



Bob Weis



Oh, as an aside - I am going to take a 2500 mile trip towing my 13k 5er. The concept of fuel temperature and VP cooling would that point to fillups at the 1/2 full tank mark, rather than the 1/8 normal check tank mark. The VP will be working fairly hard, higher fuel flows, so higher fuel temperatures? or lower fuel temperatures?

 

[Gary - K7GLD]

"Now the question of flow. Because of the ease of measuring pressure everyone measures pressure. IS THERE A WAY to measure FLOW easily and reasonably economically?



In the Northern catalog back in thehydraulic section they have a hydraulic flow meter. Measures up to 30 GPM @ 5000 psi, measures GP MINUTE. You can get it with a thermometer. BUT if I understand our fuel system we are talking 45 GP HOUR, not minutes. It would take a totally different scale than the Northern flow meter.



The flow meters must be out there somewhere, but I have never heard of them mentioned anywhere in the TDR threads. "





Seems like time passes, gears turn, and we start re-inventing the wheel...



Here's an old thread many of us have seen - but too soon forget - it pretty well addresses the ever recurring issue and debate concerning flow vs pressure, and the "value" of larger fuel lines and fittings where the VP-44 is concerned:





https://www.turbodieselregister.com/forums/showthread.php?t=11672



Be sure to pay SPECIAL attention about half way thru that thread, as readings are displayed concerning fuel flow thru the VP-44 as pressures and line sizes are altered...



Here's a teaser, just to motivate some of you to read the WHOLE thread!



"well some of you guys ain't gonna like this , especially those led to believe (and those that believe it) ... the bigger is a MUST theory .



spent a couple minutes running some tests with a DIGITAL/mechnical flow meter and a MECHNICAL fuel pressure gauge , items under test ... 2000 RAM , DD2's , DD TTPM on level 2 (??) and a HOT PE , ( all levels tested the same at WOT)factory pickup , factory lift pump , factory fuel filter housing unmodified , all banjo bolts intact and unmodified except the banjo to the input of the lift pump is replaced with a 90* swept areoquip type -6AN hose end , the bolt at the lift pump had the schrader cut off and drilled and tapped to a 1/8 npt ( for the gauge) and the banjo fittings between the lift pump and the fitler housing have been drilled to 9/32nd . again all banjo bolts are not drilled out as i have on my ram ( test conducted on the DTT RAM ) .



we installed ( LaserBob is helping me and getting #2 fuel poured on his head ) a Sonnex digital flow meter ( inside ID is 5/16") in the return line back to the tank , cut in right at the trans crossmember . gph numbers are fuel returned to the tank .





DD2 , DD TTPM

FP volume

idle 11 psi 18gph



cruise 8 psi 24gph



WOT 2 psi 30gph





DD2 , TTPM , HOT PE ANY LEVEL

FP volume

idle 11 psi 18gph



cruise 8psi 24gph



WOT 0 psi 30gph





yes you read that correctly , fuel pressure went to 0 and the fuel volume back to the tank did not change from WOT with 2 psi . the truck did NOT stumble , buck , spit , fart , fall on it's face , nothing , ran like all heck at 0 psi , i will note , my truck ran the same at 0 psi with the DD3's , EZ and a HOT PE .



tomorrow we will install -8 lines and an HP carter pump , take flow readings in exact same spot and see what the results are . "



Interesting stuff, eh? There were more tests run and readings posted - check it all out!

 

[Todd T]

Well I don't even have a LP any more. I have a FASS and all my worrys are gone about having a bad LP. . I looked all all the posters here and noticed that only one showed to have a FASS installed. It is worth the piece of mind not to worry about having the LP to go out on me.

just because you've overpaid (IMO) for a transfer pump mounted on the frame doesnt mean you dont have to worry about it failing.



the cheaper alternative carter, Holley or Mallory, are frame mounted pushers and work just as described by Steve St. The Mallory's are rebuildable like Rweis, others and myself use. mine carries 18 at idle and 14-15 cruising @ 72MPH with 10K in tow. I may have thought about it failing once or twice and that is why i carry a brush kit and seals in the glove box. Plus have a better chance of picking up a total replacement on the road for the fact that it is not a one-off manufacturer building it out of hometown USA.

 

[Turbo Tim 1]

The concept of fuel temperature and VP cooling would that point to fillups at the 1/2 full tank mark, rather than the 1/8 normal check tank mark. The VP will be working fairly hard, higher fuel flows, so higher fuel temperatures? or lower fuel temperatures?

I always fill up between 1/2 and 1/4 tank and my last lift pump was still putting out perfect pressure when I changed it at 85,000 +/- miles. I had a new one and had everything disconnected to drill the banjos so I figured I'd change it. I bet it would still be working today if I left it in. My biggest concern was the corrosion on it since I'm in the northeast. I really think temperature and sucking from the bottom of the barrel have alot to do with lift pump failure.



With that said I'll probably be going with a RASP because I'll need more fuel for my HP goals.

 

[pcarlson]

I guess I wasted $360 on a FASS HP replacement pump then. I was in Omaha a couple weeks ago and the pressure gauge was lower than normal then it started fluctuating and when I went to restart the pressure was Zero. Played with it and got some pressure to come back to get me home but now I have a 0216 code and I am hoping the lift pump caused it. The install of the FASS pump was pretty straight forward and I get 16 psi at idle and cruise. Barely moves when you get on it. Impressive pump.

 

[Todd T]

With that said I'll probably be going with a RASP because I'll need more fuel for my HP goals.

I think you'll be surprised at how much fuel you actually dont need once you get to those levels. 110GPH is more than enough for 550HP with the right filter housing, larger lines and fittings.

 

[rweis]

Well, went back and re read all 13 pages.



One thought about the RASP is what is the relationship between the RASP mounting location and the bottom of the fuel tank? I visualize it as the RASP would be lower, but I might not be seeing it in my mind's eye quite right.



Has anyone redone the flowmeter idea since 2001? Do you think it is still idle/18gph, cruise/24gph, WOT/30gph bypassed back to the tank? Think the numbers rise because the pump is turning faster?, or some sort of internal bypass regulation? Maybe the bypass settings based on fuel needed by the injectors ie idle, cruise, WOT. More fuel needed more fuel bypassed?



The idea of hot fuel still comes up. Fuel coolers come to mind.



Bob Weis



Update, I have 52602 on my fuel system and running fine.

 

[ned flint]

ned flint UK truck

read alot of fuel lift pump threads i my self have a 2k 2500 with 110k miles on the clock i checked fp 6 psi at idle 0 at wot , changed the carter pump 15 at id 8n at wot , i didn,nt do the bump start thing i just hooked two wires straight onto the pump and on the battery bleed it through the bango no probs , also purge the fuel filter the same way, thanks for the info makes us english boys laugh, keep up the good work

 

[SnoKing]

Someone back in summer of 2001 said to pull the lift pump relay and coat the tabs with dielectric(sp) grease. I did that and pump has never changed pressure readings, however I only have 36K on the truck. SNOKING

 

[rweis]

Sounds like a good idea.



Where is the LP relay?, in the under hood distribution panel? Marked?



Bob Weis

 

[SnoKing]

Yes it is in the under hood distribution panel. SNOKING

 

[hensign]

Hmmmmm. Just a little test I did by accident that might be of interest to VP44 owners. I removed the fuel pump return line... ... well it broke. I would say I ran about 20 miles with diesel pouring everywhere, I will try to keep my fuel guage working this time. I never ran out of fuel but the VP burned up. VP was 4 months old with 10k on it as was the LP and the filter had only 400 miles on it. Again this was a broken RETURN LINE and was only allowing the fuel which had already passed through the VP to pour out on the ground.

 

[rweis]

Interesting,



One would think that "more fuel" passing through the VP would be a good thing. The 13 page thread implied that the amount of fuel going through the return line was based primarily on a rpm factor ie idle, cruise, wot.



Maybe something to do with the fuel not being able to absorbe the heat before exiting the Vp?



Bob Weis

 

[RStacy]

To OWN the world.

Lube Man why dont you test your theory out for us and run your truck with no LP, then get back with us in a few weeks while your truck is in the shop getting a new VP 44 installed. Or just keep running your pump at zero and see what happens. :-laf

I think what he is saying has credential. I think that downing someone for who has an innovative idea and is in the process of creating a new possibility for us to enjoy our truck as well as save money on lift pumps is great. .



keep goin with your thought process but don't expect anyone to buy into it until you have results/comps. I like the idea. I'm listening... ... .

 

[MurrayP]

Lift Pump

My experience with lift pumps was from a 6. 5 . What was happening was a set of electrical contacts that operate the lift pump were bad . The truck ran fine but was hard to start (cold) and air could be observed in the return line . I believe I was sucking air into the system through the Fuel Filter seal when the engine was running and the lift pump was not working.

I do have a intermittent problem ( once every 6-12 months) with my 1998 24V where-by it will just up and quits . This happen after running a considerable length of time ---hours ---- and then out of the blue it acts like its running out of fuel . Lots of cranking ... ... . #$$%^%%##%& ... and away it goes ... . anys suggestions ???

 

[litespeed]

My experience with lift pumps was from a 6. 5 . What was happening was a set of electrical contacts that operate the lift pump were bad . The truck ran fine but was hard to start (cold) and air could be observed in the return line . I believe I was sucking air into the system through the Fuel Filter seal when the engine was running and the lift pump was not working.

I do have a intermittent problem ( once every 6-12 months) with my 1998 24V where-by it will just up and quits . This happen after running a considerable length of time ---hours ---- and then out of the blue it acts like its running out of fuel . Lots of cranking ... ... . #$$%^%%##%& ... and away it goes ... . anys suggestions ???

Clogged fuel filter, clogged pickup in the tank, water and or air in the system?



Do you have a fuel pressure gauge or warning light installed in your fuel system after the lift pump and filter?



If the lift pump dies on the 24 valve Cummins, the pump it self becomes a restriction and puts too much stress on a small diaphram inside the VP44. This in turn ruins the injection pump (VP 44).



I would start with the simple things... ... Have the codes checked, check the fuel pressure, be sure the lift pump is running and supplying good pressure and check the fuel filter.



Do a search and you will read until you are blue in the face.



Regards,



AJ