Engine/Transmission (1998.5 - 2002) Stock fuel pressure?

[AdamFarnham]

I just finished installing an Autometer fuel pressure gage. The gage is electric, and the sender is installed on the outlet side of the fuel filter/water separator.



Does anyone know what the nominal and minimum fuel pressures are for a VP44? I've done a search, and there is no concensus on the minimum inlet fuel pressure. I'd like to mark the bezel on the gage or make a note of the "do not drive this truck" pressure. I'm not sure what the Cummins spec is.



I'm currently stock in all respects except for one tapped banjo fitting from Geno's. Since I'm out of warranty, I thought the gage would be a good investment to keep the VP44 happy. I'm currently seeing 11 psi at idle and around 5 psi WOT. Will probably do a FASS setup at some point when the $ come through.



Thanks

 

[BK]

At one point Cummins told DC that the pressure should be 10psi ( I think that went to down to 8psi at one point) and above at WOT. Max of 15psi (issue of too much fuel and some part of the VP44 not liking too much pressure. . there is a very old thread about that here somewhere).

Then it went to a flow test instead of pressure

But to tell you the truth, since to me, line size and restriction are related to flow rate and pressure, I think going with 8psi as the -if below change the pump- is good.

Want to be safer, 10psi - Cummins original number.



5psi @ WOT is BAD.

Replace the pump.

As your load increases and your fueling requirement increases, that WOT # will decrease.

Go try and buy one or two of the $70 campaign pumps now.

Read the thread. .

https://www.turbodieselregister.com/forums/showthread.php?t=151407

Get a Geno's Vulcan 3/8" line pump relocation kit.

If you were bombing, I would say go to a FASS kit, and a big line kit and modify your fuel pickup(which you need todo to satisfy the FASS from what I've been reading on here. ). But if your not, just move the LP.



I don't see a sig line about your truck, I'm assuming it's not bombed.

The FP gauge is a must to keep the VP44 safe.

 

[MJardine]

The low fuel pressure alarm and switch included with the $70. 00 campaign pump is stated to be set at 3. 5psi falling. According to the instructions included with the pump kit this is to be connected as an input to the ecu to give a low fuel pressure fault code. I do not believe this can be accomplished with the Dodge ecu. The point is that Cummins has set the low fuel pressure parameter at 3. 5psi for this campaign kit. Interestingly enough when I checked the calibration of the pressure switch, it was found to alarm at 3. 1psi falling. It is a fixed, non adjustable unit.



MrMike.

 

[BK]

Mr Mike,



That's a good point , didn't think to look at that.

Didn't read the paper work that came with the one I ordered.



So 5lbs WOT is nearing failing (depending on accuracy of the gauge), still, get a pump, get a kit and be ready.



When good, you should be seeing at or above 10psi WOT and max of 15psi.



When my 1st one went bad (VP44 smelt funny-but truck ran well), I was 0PST @WOT and 3-5 idle. DC replaced after much :-{}.

The replacement pump spent most of it's life at 12PSI WOT - 14psi idle.

6 months ago dropped to about 10psi all the time, just recently started to be only 6 psi at start, goes to 8psi, 6 psi, works it's way up to 10psi. . levels at about 8-9psi. Goes to ~6psi with a heavy foot. I wont do WOT till I change it out.





-Bob

 

[Bob Cochran]

For sure 5 PSI is the very minimum pressure. I have to admit that I had zero for 200 miles before changing the pump and the truck ran fine!! Scary and sure hope no damage to the VP44. As for max I understand 15 PSI is it for non-bombed trucks otherwise have hard start problems. If you want be safe I say mark at 8 or 10 PSI.

 

[AdamFarnham]

Don't know why my sig didn't work on that try. Guess I need to post more often! I'm in the non-BOMBed category, as far as drivetrain is considered. The power is fine for me in stock configuration. I'm more of a longevity and reliability sort of customer. I pull a 10k horse trailer most of the time, and carry heavy stuff on a regular basis with it. Here in WA, nobody does more than 50 mph, so the extra power wouldn't do me any good.



I have to admit I'd be happier with 10 psi + at WOT. The truck has 83,000 miles on it, and has been a pain in the $ with steering, A/C and other nit-picky stuff. I've been going through it and servicing everything I can think of now that it's 5 years old. Not that I hadn't kept up with routine maintenance, but things like changing out the PS fluid, batteries, etc. Hope to get another 5 years out of it.



I like the Genos kit with pump relocation to along the frame rail. Seems easier for the pump to operate down there. The FASS also seems like a good idea. Will keep the foot off the smoke pedal a bit, and get a new pump and relocation kit in a month or so. I changed the fuel filter about 150 miles ago, so the reading is with a fresh filter. I use a vacuum extractor and suck out the debris on each change.



So, it seems like 3. 5 psi is the absolute minimum. 10 psi is the minimum margin and 15 psi is the goal. Most of my cruising around is at 10 psi, but going uphill with a trailer or starting out, I drop to 7 psi quickly. Will get the sender calibrated, too. (I work at an engineering company - this is easy to do).



Have to admit I'm happy with the look of the Autometer 0-30 psi fuel gage. It matches the OEM set well. Not happy with their lettering on the top of the bezel - it adds too much glare to the reading on that side at night. Very minor beef, all things considered. The OEM gages are not that great. Seems they're more interested in putting dials on the dashboard than giving the driver some good data. Most of the 'tick' marks there don't correspond to any meaningful sort of value. They seem to be adaptations of the old 'idiot light' system.



Thanks for your input!

 

[BK]

After thinking about it, the 3. 5psi from the pressure switch is probably the drop dead point and they had to worry about variations and real quick dips in pressure that probably aren't a normal problem.



You'll also have to see. 15psi is rarely acheived with a stock pump, and if it is, it rarely stays there. I think 8-10 is a good guideline, but you may find that you will be @ 10psi for a very long like I was, and now my pump is just starting to show signs of getting too weak.



I think the $$/benifit of the FASS for a non bombed truck, and the other things you need todo to help the FASS work well, aren't worth it, again for a non bombed truck.

I've read some cases (I have no idea of the % of failure rate)of the FASS pumps giving up the ghost. . may it's just all the pickup problem as I read on another thread... .



You might want to try and read the thread I referenced above and get your hands on one of the $70 campaign pumps. . it's a huge savings. . then next month get the geno's Vulcan kit.

 

[chazj]

If you end up with the new in-tank pump, the pressures will be much lower. Mine is around 7 lbs. at idle with zero psi. easily achieved at moderate acceleration.



The discussions regarding the pressures required in the VP44 cover many opinions. Some that warn about the dangers of excess pressure (which you may get by adding an additional pump) to the other extreme stating that the VP44 is designed to run at near minimal pressures. Apparently this pump is used is some applications without the benefit of any sort of lift pump.



Maybe someday we will find written documentation from Bosch stating the pressure specifications that they require for their pump. I think it would put many people's minds to rest... starting with mine...

 

[BK]

The max pressure and fact that more than zero pressure (on a stock fuel lines and electronics) were based on people doing much research into the Bosch pump and it's functions, not "feelings". . these discussions and work goes back to 99/00 time frame when the LP failures started to become very noticable. Folks had contact in Bosh, had internal schematics and explainations from Bosch. It was a lot of work from a few guys that knew what they were doing.



There was one part that had an issue with too much pressure in the VP44 and failures occured ( if my memory serves me right) and the 15 - 18 psi max became a standard.

Back in the beginning of the work that some were doing to find a better pump, they were going for some 25/30psi pressures , figuring more is better.

But it wasn't.



There is also an issue of having more than enough fuel through the VP44, not zero and not at 0psi, since there is a minimum volume needed to fuel the truck and COOL the VP44. The fuel returned to the tank carring away heat and again sent to the tank to cool. When I was at 0 WOT and 5psi, I could smell my VP44 after hard driving.

Since I didn't register any lean conditions DC didn't change my VP44, but after chaning the LP, no more burning smells from my VP44.



The VP44 can pull some fuel, but was not made to run all the time like that. It will cavitate and cause a lean condition and fail. It's a documented problem that when the pressure is too low for too long, the VP44 fails.

Your the 1st one I've heard of that has zero pressure from the intank kit... I wouldn't stand for it. It's also know that there have been bad LP (on engine) out of the box. . you may have one in your intank kit. I've been hearing 7wot - 10 idle on the tank kits, but only have seen a few on here.





The application your talking about when the VP44 has been used with out a LP, is on stand alone pumps and standby gensets, when the fuel is gravity feed. This to0 had been researched to near death back about 6 years ago, here on the Forum.

 

[chazj]

I brought my concerns to Dodge about pressure the day I had the in-tank pump installed. The "official line" from Dodge is that they now measure volume as opposed to pressure.



I don't think my Autometer guage is that far off as I have since had the FP measured with a mechanical guage with the same readings. Nor do I think that the pressures I am experiencing with the in-tank pump are far from the norm (from what I've read here).



I don't run at Zero at WOT just notice that it would be very easy to do so even under my stock configuration as I am always backing off the pedal. Even though I don't experience the same pressures that I did with the engine mounted lift pump; the FP guage is proving invaluable to keep me from inadvertenly over-taxing the VP44.



Even though my truck is stock, the addition of guages is an expense is an investment that is proving to be most beneficial especially when towing the trailer.

 

[RHulette]

I just finished installing an Autometer fuel pressure gage. The gage is electric, and the sender is installed on the outlet side of the fuel filter/water separator.



Does anyone know what the nominal and minimum fuel pressures are for a VP44? I've done a search, and there is no concensus on the minimum inlet fuel pressure. I'd like to mark the bezel on the gage or make a note of the "do not drive this truck" pressure. I'm not sure what the Cummins spec is.



I'm currently stock in all respects except for one tapped banjo fitting from Geno's. Since I'm out of warranty, I thought the gage would be a good investment to keep the VP44 happy. I'm currently seeing 11 psi at idle and around 5 psi WOT. Will probably do a FASS setup at some point when the $ come through.



Thanks

I found out my first LP died when I did my yearly fuel filter change last year - I could not get the new fuel filter primed even though the LP was spinning. I ordered one of the new LPs from Cummins and ran it until 2 weeks ago. I got a FP gauge in February and noticed that it was all over the place - no higher than 12psi and sometimes bottoming out at 1.

I did not have a baseline of what a stock LP should put out.

At that point, I bought 2 of the $70 LPs from Cummins and matched one up with the Vulcan big line relocation kit. It stays steady at 15psi all the time. I can pull it down to 13psi if I jump on the pedal. The difference is just friggin' amazing... Smoother acceleration, much quicker from a stop light. I'm really enjoying driving it - I really didn't know what I was missing. From what I've been reading, some of the guys buying the Genos relocation kit have noticed that their screw-in adapters don't fit right. I know the Vulcan kit was a snap to install and it made me a believer in moving the LP down to the frame. It also makes it 100 times easier to change out the LP. Only time will tell if the LP lasts longer.

 

[BK]

I found out my first LP died when I did my yearly fuel filter change last year - I could not get the new fuel filter primed even though the LP was spinning. I ordered one of the new LPs from Cummins and ran it until 2 weeks ago. I got a FP gauge in February and noticed that it was all over the place - no higher than 12psi and sometimes bottoming out at 1.

I did not have a baseline of what a stock LP should put out.

At that point, I bought 2 of the $70 LPs from Cummins and matched one up with the Vulcan big line relocation kit. It stays steady at 15psi all the time. I can pull it down to 13psi if I jump on the pedal. The difference is just friggin' amazing... Smoother acceleration, much quicker from a stop light. I'm really enjoying driving it - I really didn't know what I was missing. From what I've been reading, some of the guys buying the Genos relocation kit have noticed that their screw-in adapters don't fit right. I know the Vulcan kit was a snap to install and it made me a believer in moving the LP down to the frame. It also makes it 100 times easier to change out the LP. Only time will tell if the LP lasts longer.

I bought the Geno's Vulcan kit and had an issue with the fittings, and the fittings are from Vulcan. I called Vulcan, really good guy to speak to.

He said that the plating build up in the vally of the threads is the issue, happens every now and then. Just gotta chace them with a die if you have a problem.

 

[BK]

I brought my concerns to Dodge about pressure the day I had the in-tank pump installed. The "official line" from Dodge is that they now measure volume as opposed to pressure.



I don't think my Autometer guage is that far off as I have since had the FP measured with a mechanical guage with the same readings. Nor do I think that the pressures I am experiencing with the in-tank pump are far from the norm (from what I've read here).



I don't run at Zero at WOT just notice that it would be very easy to do so even under my stock configuration as I am always backing off the pedal. Even though I don't experience the same pressures that I did with the engine mounted lift pump; the FP guage is proving invaluable to keep me from inadvertenly over-taxing the VP44.



Even though my truck is stock, the addition of guages is an expense is an investment that is proving to be most beneficial especially when towing the trailer.

The FP gauge is the one must have for a 24V CDT, every one agrees on that. .

all the way back in 99 - 00 or so. . when we were finding bad LP one after the other.



I'm sorry I thought I read that you had zero @ WOT.

Yes I too have read that they commonly are running lower - but steady and not much different from idle to WOT, and I know DC had gone to volume measurement. But all things being the same, line size, restrictions and need, it equats to a pressure. The problem with pressure, is they need to take it for a ride WOT with gauges attached, and the more your loaded the more the fueling needs and the lower the "pressure".

So once you know you have a good lift pump with your fueling needs and lines. . the pressure is a good guidline, when all things are normalized.