First off 2001 QC 4x4 automatic SWB - totally stock with no performance stuff or anything

Last month I got to replace my injector and lift pumps, in doing that the lift pump was moved to near the tank rather than on the engine. I thought it might be nice to not do this again soon and so installed a fuel pressure gauge Friday last. I am using the Vulcan hose to a Westek sender/gauge ( I did make a mistake and bought the 0-30 psi gauge vice the 0-15).

Now I am confused...at rest power off the gauge reads about 2 needle widths below zero, ~-3psi, upon initial start at idle it was reading 8-10psi and under load it dropped down to 3-4 psi. the specs I saw called for `10 at cold idle so i figured it was ok. I drove ~300 miles it set about 3 days and then coming back yesterday it read about 5-7 psi at idle, 4-5 psi under trailing throttle and 0 to half a needle above 0 under load.

So my questions are:
Is this right?
Does this tell me that my 3 week old lift pump is going toes down?
Is my gauge/sender going or is already toes down?
If I buy another lift pump and swap it out have I already ruined the injector pump?
and if this is normal/ok what good is it? Does the fact that I do have positive indicated pressure at idle and under trailing throttle mean that I really do have adequate head at the injector pump suction?
If I get the sender for the 0-15 psi gauge will I have better rsolution in the gauge by x2ish?

Thanks, I am supposed to do a 3000 mile round trip over Memorial day and I'd rather not have to deal with a dead truck in rural Alabama at 0300 on Saturday night of a holiday weekend...

 

If that is your accurate fuel pressure then no, way too low.

Was it a stock replacement? I had three die on me, one of them causing me to loose the VP44 in short order on my 2000. I went with a walbro pump kit after that, held 18psi all day with heavy mods.

I would first off not run the engine at all, I don't think a gauge would cause that much error to show 0psi under load. That looks like a dead lift pump.

I wouldn't worry about the resolution difference, you don't need to know to a half psi, the 30psi gauge worked great for me, and in your position I would upgrade the LP now, so you might need the higher than 15 psi gauge.

If you have the money the FASS or Airdog systems are great, I went with a walbro pump that doesn't filter like those do but just a hi perf. pump and new lines. I don't think glacier diesel sells the kit anymore but might be able to find it.

 

Thanks Alpha
I plan to verify the accuracy of the gauge first thing so I know if I need to talk to NAPA for the pump or Geno's about the sender/gauge. I did go by NAPA today and told them about it and they are happy to warranty the pump of course but I'm almost wondering if it's worth the bother....

I did some very preliminary looking at alternatives today but that pesky job kept gettin in the way so I'll do some serious looking tonight. Do you recall wich pump you chose? I assume you did the new recirc line and pressure switch as part of it right? Did you get your stuff through Glacier?

Thanks for the info, I didnt want to hear that but inside I knew that was the problem...

 

Don't bother with the oem part, regardless of warranty, you'll end up replacing it many times but gamble each time whether or not it starved the vp44. And if you plan any performance mods later you'll need it as well.

I believe it was the walbro 392. Had a return line yes, rubber lines with barbed push fittings. Easy install. search GFS 392 for some more info

 

cool, thanks I was mostly at the same conclusion myself, thanks for the info

 

yep, lift pump was nfg out of the box so it was changed out and now have 13-15 psi at idle and I havent been able to open the throttle enough to drop below 10. wonder how long this one will last

 

Not to throw a wrench in your monkey but just so you know, the VP is ONLY cooled by fuel. For this reason, the VP has whats called an overflow valve on the outlet fuel fitting of the VP. This overflow valve has a small 3/16" hole in it (for an unknown reason). The overflow valve also has a factory setting of 14-16 psi so that excess fuel at that psi or more can pass through the VP which isn't used by the engine. Any amount of fuel pressure below the factory setting of 14-16 psi means that the only amount of fuel passing through the VP specifically to cool the VP is just the small amount that flowing through that little 3/16" hole.....which is not nearly enough to provide any cooling. Its been thought for years that 10 psi at WOT is enough but I chose to never let my fuel pressure get below 15 psi.

 

trust,

you can get a raptor fuel pump for about $350. At least you have a gauge, chuck the oem pump for a reliable pump.

 

I would check to see if you have any kinked hoses or a plugged suction screen on the fuel pick-up screen. Seen it happen a few times. The stock lift pump from cummins is the same as the carter HP fuel pump you can get from NAPA for less than $100.

Ya the stock pump doesn't last too long. My first year owning the truck I when thru five lift pumps all under warranty. Got tired of visiting the dealership and just bought a fass 150 system. Been on the truck running fine for almost ten years now.

 

pump is cooled by fuel,a reason to never let fuel get less than a 1/2 tank,the hotter outside temp. the more fuel in tank is important.

 

great input guys, thank you, my plan is to go to a better pump asap and would have preferred to do that now but the timing is terrible both in time to change and funds.

Curious about the NAPA pump under $100 though, they soaked me $295 for the pump that failed, the new one was no charge. If I could get an equivalent for 1/3 the cost I'll take a spare to get me through the next week while I'm on the road. Do you have a part number by chance Mike?

knowing what I know now I would have not bothered with the replacement pump and gone straight to one of the better aftermarket ones. Price ranges are quite variable, as are the various brand recommendations. One man's POS is another's jewel it seems.

1/2 tank is my routine minimal, at least I try to keep it above 1/2 tank just to make sure there is adequate head for the lift pump, didnt seem to help for that reason though, I do understand about the temp and will continue to keep it as full as reasonable. I'm n the road non stop over Memorial Day weekend and I know my bladder wont let me go more than half a tank so that will make it easier. lol

Is there any issue with seal failure if you run too high a pressure at the VP suction? Doesnt seem like there should be but I read something about that somewhere. Wonder why Cummins designed the system to run at ~10 psi if that doesnt allow adequate recirc for cooling, curious.

Thanks again for the input, this has been quite an education, a very expensive education...

 

You even asking is better than most who dont know or care to know.....
But nonetheless.....here's something I wrote which kinda sums it up. Its really long so I'll just copy it since I posted it on another Cummins forum.
_________________
From 1994-1998 Cummins had used the proven oil cooled mechanical P-pump but unfortunately the mechanical P-pump was no longer efficient enough for the new emissions regulations being placed on diesel engines, and also Cummins was looking to increase power levels over a wider range of RPM’s as well. What Bosch and Cummins were working on was the mechanical/electrical Commonrail injection design but they weren’t going to make production time line for the new emission regulations so Bosch gave Cummins the fuel cooled mechanical/electronically controlled VP44, which in turn kept the ISB emissions compliant until the CR system was able to hit production in 2003. This whole ordeal meant that the VP44 was one thing and one thing only…..temporary. Even though this was a viable and great alternative, sadly the VP was plagued with inferior mechanical internal parts, poor quality control, and lead free solder in the FPCM (VP’s computer). In addition to the lead free solder, Bosch also mounted the FPCM directly on top of the VP where the high heat location causes the lead free solder to deteriorate over time, causing poor electrical connections in the computer. So in saying all that, there are people asking how much R&D did Dodge, Cummins, and Bosch actually do when they mated the VP to the ISB or was it slapped together without much concern for optimal long term reliability? Obviously, given the high number of VP failures not long after introduction…..the only answer can be…..not much. Which then has people asking the other question, which is, if Dodge, Cummins, and Bosch couldn’t seem to stop any failures at the dealers over the past decade then how much does Dodge, Cummins, and Bosch actually know about the VP, or what it needs to run reliably? Again…..obviously not much. So then you have to ask yourself, are you going to rely on a tag, sticker, or manual which “claims” to have the correct specification data for the VP44 or are you going to listen to the guys who’ve spent the last decade committing themselves to keeping the VP working?

On a good note, over the years of production, Bosch did update the VP with premium internals and used far better quality control…..but because of our “go green” society, unfortunately they still use lead free solder in the FPCM. Other than that, if you’re wondering why Bosch or Cummins hasn’t come up with a real solution for the VP? Well just remember what I said earlier…..that the VP was “temporary”. So since the VP is old world thinking and the diesel world has moved its sights to bigger and better stuff, why would Bosch and Cummins ever remotely consider dealing with any issues that us 2nd gen VP44 truck guys are still having to mess with? I’m sure Bosch nor Cummins had anticipated the high number of problematic issues they'd face with the VP but I'm also sure that neither Bosch, Cummins, nor Dodge had a clue that the VP44 would be the real beginning in aftermarket diesel performance goodies. Because the VP was so easily tunable and was capable of producing hundreds of HP at literally the flip of a switch, or the addition of a box, it became wildly popular. Unknowingly though, did any aftermarket company or consumer fully understand that what they were doing was setting up the VP for guaranteed failure when adding aggressive fueling/timing boxes combined with a crappy unreliable lift pump along with a crappy limited fuel line system. As you can see, given the number of negative hurdles placed in its way, the VP was predestined to not be reliable. This is where years of aftermarket research comes in.

Over the past 10 years or so there has been a multitude of knowledge gained from consumer input and aftermarket testing. What did everyone find out? First they found out that if the OEM lift pump quits (which Dodge insisted come attached to the engine delivered from Cummins) then the VP runs dry or at dangerously low fuel pressures and it didn’t take long to also figure out that the OEM lift pump was seriously unreliable. It wasn’t a question of is the OEM lift pump going to fail but simply when was it going to fail? That led people to find out that when the VP has little to no positive head fuel pressure from the fuel pump, the VP’s internal plastic diaphragm vibrated back and forth, eventually causing the diaphragm to crack. That crack or tear then causes fuel to improperly pass which disables the timing piston from achieving full fuel timing advance, which results in loss of power and, over time, eventual mechanical failure. This knowledge sparked off a huge wave of fuel pump combinations, setups, contraptions, etc….. If you can think of a fuel pump set up, it was probably tried by someone. It didn’t take long for the aftermarket world to realize what people were doing…..or trying to do, which started the introduction of aftermarket fuel pumps which were able to deliver more reliable fuel pressures to the VP. But…..even though we were now getting more reliable fuel pumps, it was then learned that fuel pressure alone was not the answer. The VP needed fuel volume as well as fuel pressure. And it had to be a lot of fuel volume too because the next thing learned was that heat was the enemy to not only the VP internals but the VP’s computer as well. Remember, the ONLY thing cooling the VP is fuel…..period. So if there isn’t an excess amount of fuel passing through the VP, at all times, then there’s nothing pulling the heat away from the VP. Also, as most people already know, computers don’t like heat and anything over about 160* starts affecting VP’s computer longevity. Don’t forget…..the VP is directly bolted to an engine that not only is running at 190*-205* but that everything is tucked in a nice hot engine compartment with 200* radiator air blowing across everything. Long story short, this is where running large diameter fuel lines with a good quality higher pressure; higher volume aftermarket fuel pumps come in. Understand that pressure and volume is also NOT the same thing so running a high pressure low volume fuel pump will not do you much good, which is why guys don’t care to run pumps like the Airtex. The Airtex is a high pressure pump with small volume lines which can’t deliver enough volume. It’s like holding a garden hose with the valve all the way open and then screwing a high pressure nozzle on that same garden hose. You’ll get more pressure but the volume will drop. Increasing the supply fuel line to ½” will increase the volume as the fuel pump pumps at the proper pressure. That increase in volume acts to help the fuel pressure stay more constant because there is more volume than the engine uses, whereas if the fuel line is smaller then fuel line volume will deplete faster, causing pressure to drop.

So getting to the point, the current consensus is that fuel pressures should be no more than 20 psi at idle and no less than 15 at WOT. Why the need for all that pressure? Well because the VP has what’s called an Overflow Valve at the outlet return line. That valve is factory set at 14-16 psi before it fully opens and allows a good flow of fuel to pass through the VP, which means that if you keep the fuel pressure at or above that 14-16 psi then you constantly have fuel passing through the VP. And if someone for some reason thinks that’s too much pressure then also understand that the OEM lift pump specs were already around 15 psi from an inadequate lift pump, so we’re not far from what was factory intended, but that we simply now have more constant pressure, more reliable pressure, and more volume. The three things necessary to keep the VP running. I won’t go into why the OEM lift pump is inadequate and can’t sustain reliable fuel pressure/volume, but just know that it is.

So we know the reason why we shouldn’t run any less than 14-16 psi but the reason why no more than 20 psi is because the return lines are only 5/16”, and its thought that trying to shove more pressure/volume through the small OEM return fuel line is unnecessary and could possibly cause fuel pressure to build up behind the VP as fuel isn’t allowed to escape fast enough on its way back to the fuel tank. If the VP’s overflow valve is set to 14-16 psi then more than likely that’s the proper window of working tolerances that we should care to stay within the high side of. But…..just note that there is currently zero proof indicating that running overly high fuel pressure harms the VP. We just know what low fuel pressure does. Also, in saying that, there are guys who feel that 10 psi is just fine for WOT. All I can say to that is, it’s their truck and if it works for them then great.

Of all that, the only problem no one’s been able to solve is what happens to the VP after the engine is shut off. That’s because there is no longer any fuel passing through the VP, and after about 20 minutes of sitting, the hot engine then heat soaks the VP until the VP is the same temperature as its surroundings…..which is far more than 160*. That intense heat is not so much harmful to the VP’s internal mechanics but is very destructive to the lead free solder used in the VP’s computer…..which some say turns the computer into what’s been called a ticking time bomb. So the computers working time frame is not measured by how many miles are on the VP but in actuality how many “hot starts” it’s had to endure…..and shutting the truck off for around 20 minutes or more puts the VP’s computer through one hot start. The computer can give signs of future problems or it can simply just fail like you just turned the key off. That’s the electronic failure.

Then, if you going to ask why is there so many stock trucks still running around with OEM lift pumps on low fuel pressure and their VP’s haven’t failed. Well, there’s a lot to say about that, starting with….. Do we “really” know the facts about that particular truck or even if the owner knows much either? Maybe, maybe not. But we know that driving style, how many times the truck is shut off and restarted, how hot the average weather is where that truck is driven or when the truck is driven, is the truck a highway runner or a grocery getter, how many times has the truck been run out of fuel, what’s the fuel pressure been throughout all the miles, is there an aggressive timing/fueling box tapping the VP’s wire, etc….. Proving more that constant running is best for the VP…..There’s a recent thread out about a magazine article talking about a hot shot driver who has racked up 1.8 million miles on his 2001 Dodge Cummins……….with the stock VP44. There are also other remarkable things in that article but the fact that he still has the factory VP is amazing at the least. Maybe if there was a way to run a controlled test with controlled trucks then maybe we would have more definitive answers to many of our questions but remember that there are less and less VP44 trucks on the road, and who’s going to take the time, money, and effort, to perform such a test for everyone else’s benefit and what aftermarket company is going to produce something that may only draw the attention of a few consumers who want to keep their VP44 truck? No one…..which is why it’s merely up to the few who care to keep pressing on to find how to make the VP last forever, and what they have found out is working. The new VP’s are great pumps and mating them with good quality fuel pumps with proper fuel lines has proven to be a very reliable setup. But…..that doesn’t mean that just by installing a good quality aftermarket fuel pump is going to keep your stock or old VP from failing either. Mostly because the old stock VP’s (as noted) were inferior and are prone to simply wearing out, and most of the time people only choose to install a new aftermarket fuel pump “after” they realize that their current fuel pump is either not working or not working well, which means that the VP’s probably had to endure dangerously low fuel pressure conditions for many many miles. At that point, the damage has most likely already been done and adding a working fuel pump won’t fix previous damage or reduce the number of hot starts racked up on the computer.

There are many more items to touch on with this subject but this is as much as I care to type in this post and I’m sure others will jump in and respond too, which brings me back to my first sentence..... This thread is destructive to the knowledge gained of the VP44 by trying to make it seem that all the testing and experienced shared has simply been a waste of time and effort. But, it’s your truck and no one’s stopping you from listening to others who continue to down play all the facts I just listed. As you have read, there are no “definitive” answers about the VP in print from either Bosch, Cummins, or Dodge which is why you won’t get any answers you’re looking for in this thread. Just also know that there isn’t a single type of fuel injection pump which hasn’t failed. They all have their quirks. The VP got a bad rap for the most failures but as you have read, there’s lots of reasons why that was the case. Maybe I helped you and maybe I just confused you even more.

 

Wow, lots of good info!

 

Where are you in NM by the way trust? Born and raised in Los Alamos and the Jemez Mtns.

 

Thank you. I'm located in the "real" northern CA. Some Californians like to call anything north of Santa Barbara north. I noticed that you're in Alaska. Beautiful place and I even thought about moving up there to get away from CA backwards thinking enviromentalists and overtaxing legislation but I cant get the rest of my household to go with.