Well I took my truck to the dealer today for a few problems and fuel pressure well I thought it was low I have a briar hoppers fuel pressure gauge and was reading 12 at idle 7 cruising and 5-0 WOT. The dealer says fuel pressure is only checked at idle and 2500 rpm not under load by the book so me not believing them I went to a cummins diesel shop and they got the ISB manual out and thats what it says no less than 10 psi at idle nothing about testing under a load. So why does the instructions with my gauge say to test it under load and the cummins manual says not to help please thanks all.
-
TDR Magazine subscribers receive more than the magazine! You also gain additional forum privileges!
Details here: TDR Privileges
Subscribe to TDR Magazine here: https://www.tdr-online.com/
Engine/Transmission (1998.5 - 2002) Dealer test's fuel pressure different
- Thread starter Smills
- Start Date
Attention: TDR Forum Junkies To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.
Thanks, TDR Staff
- Status
I have often wondered this to. To me, Idle would be a critical indicator. Full load could be a very debatable question. Is full load at 2500 rpms In neutral? Or 2500 rpms at 80 mph? Or 2500 rpms at 80 mph with a 10000 pound Trailer? All of these conditions would give you different fuel pressure readings would they not? Anyway I think you can see my point. The more I read about lift pumps and fuel pressure the more I get confused? Sometimes I wonder if DC and Cummins even know, Like the point you just brought up? Another beef I have is if you flow fuel through the fuel system doesn't the injection pump get lubricated? Seems to me that theres not much difference between 6 or 8 psi as long as your flowing fuel. Sometimes I think this lift pump thing is exaggerated? Any way I'm more and more confused
Last edited:
I think no one actually knows at which point the pumps should be changed. I had only 11k miles and changed mine and got nearly exactly the same pressure readings after all the fuss. If you have SOME pressure at WOT then don't worry about it.
My new pump shows 8 to 12 psi at idle and no less than 5 to 6 psi at WOT. I am not changing another pump until I think it is time, then I will put in the original and order another spare.
Thats my opinion and I am sticking to it!
My new pump shows 8 to 12 psi at idle and no less than 5 to 6 psi at WOT. I am not changing another pump until I think it is time, then I will put in the original and order another spare.
Thats my opinion and I am sticking to it!
Well thanks for your guys help still havent found a good answer. I wonder were black mtn. diesel gets there info they sent me with my briar hopper fuel gauge of idle not being less than 11or 12 cruising not below 10 and WOT not below 7 or 8.
By the way I think that the briar hopper gauge is not worth 55 bucks its just a cheap hose and a cheap gauge and know my gauge is full of diesel because I dont think its designed for liquid.
Hope I can get some good info so I can throw it in the service managers face he was being a real a hole today.
shane
By the way I think that the briar hopper gauge is not worth 55 bucks its just a cheap hose and a cheap gauge and know my gauge is full of diesel because I dont think its designed for liquid.
Hope I can get some good info so I can throw it in the service managers face he was being a real a hole today.
shane
Have to agree...
... with emarsh and Pitbull. If you are seeing positive fuel pressure at all levels of operation you should be fine. My pressure has always fluctuated from 6 to 12 PSI, post filter, idling in the driveway or on a 1600 mile round trip pulling about 6k. I don't worry about it, thats what I use my gauge for, to monitor that I have positive pressure to the injection pump. Have Fun, Jim G.
... with emarsh and Pitbull. If you are seeing positive fuel pressure at all levels of operation you should be fine. My pressure has always fluctuated from 6 to 12 PSI, post filter, idling in the driveway or on a 1600 mile round trip pulling about 6k. I don't worry about it, thats what I use my gauge for, to monitor that I have positive pressure to the injection pump. Have Fun, Jim G.
The problem with your theory of 'Don't worry about it if you're seeing positive pressure' is that the VP44 may in fact be PULLING that fuel and creating the pressure, thus a)putting a strain on the injection pump and b)the pump not getting enough lubrication because it's not getting the 'extra' fuel it's supposed to get to lubricate it.
The information we have from members on these boards who have either gotten the word personally from the STAR line or from the DC reps (mech or service writer) who've spoken to the STAR line says the FP should never drop below 7 or 8 psi (some contention about that number) under ANY circumstances.
Remember the fuel being fed to the VP44 is both being used to feed the engine as well as the excess fuel lubricating the pump. Therefore there is a difference between 'some' pressure and what the STAR line says is minimum pressure. If you don't have the minimum pressure doesn't it stand to reason the VP44 is suffering for it?
Anywhere in the 3-5 psi range at WOT would seem to indicate that the pump is heading south and performance will only worsen from here out.
As far as testing it at idle or under load, forget about the dynamics of moving that beast of yours and how much fuel it takes to do that; do you not think the greatest test is under load, regardless of load, or would you like to do your MPG calculations while you are revving the engine in park or neutral in your driveway? Under load (either getting under way or WOT) you will see a pressure fluctuation and less pressure than you would at idle; the idle reading is useful only as a benchmark and is obviously easy enough for the engine to maintain even with a 'dead LP', it's only when you're under power or at WOT using Briar's gauge that you will see what is actually happening as far as fuel delivery to the VP44 under load, and when the LP is bad or going bad you will see radically different numbers than what you'll see when the LP is new out of the box. What's that tell ya?
The problem with your theory is that you will be stressing the VP44 in increments and total failure will most likely not show up until you're out of warranty (and SOL!) having to foot the $1300 (minimum) and up to $3k+ for a replacement.
All that being said, do what makes ya happy!
Just my . 02 worth.
zman
The information we have from members on these boards who have either gotten the word personally from the STAR line or from the DC reps (mech or service writer) who've spoken to the STAR line says the FP should never drop below 7 or 8 psi (some contention about that number) under ANY circumstances.
Remember the fuel being fed to the VP44 is both being used to feed the engine as well as the excess fuel lubricating the pump. Therefore there is a difference between 'some' pressure and what the STAR line says is minimum pressure. If you don't have the minimum pressure doesn't it stand to reason the VP44 is suffering for it?
Anywhere in the 3-5 psi range at WOT would seem to indicate that the pump is heading south and performance will only worsen from here out.
As far as testing it at idle or under load, forget about the dynamics of moving that beast of yours and how much fuel it takes to do that; do you not think the greatest test is under load, regardless of load, or would you like to do your MPG calculations while you are revving the engine in park or neutral in your driveway? Under load (either getting under way or WOT) you will see a pressure fluctuation and less pressure than you would at idle; the idle reading is useful only as a benchmark and is obviously easy enough for the engine to maintain even with a 'dead LP', it's only when you're under power or at WOT using Briar's gauge that you will see what is actually happening as far as fuel delivery to the VP44 under load, and when the LP is bad or going bad you will see radically different numbers than what you'll see when the LP is new out of the box. What's that tell ya?
The problem with your theory is that you will be stressing the VP44 in increments and total failure will most likely not show up until you're out of warranty (and SOL!) having to foot the $1300 (minimum) and up to $3k+ for a replacement.
All that being said, do what makes ya happy!
Just my . 02 worth.
zman
Zimman, I understand what your saying to a degree. However, there have been several members who have changed there lift pumps because they thought they were going south, only to find out they have the exact same pressures with the new ones. I think thats what confuses people. This is not so cut and dried as I wish it was. Yes if you only have 3 lbs of pressure at wot, I would say you may have a problem. . But at 5,6,7 is the lift pump bad? Everyone must monitor there trucks and each one is different. Fuel pressure gauges are a must. I just think there is some gray area here to. I will keep reading and learning as much as I can. 
Unwarranted Attack and Attitude
"Well thanks for your guys help still havent found a good answer. I wonder were black mtn. diesel gets there info they sent me with my briar hopper fuel gauge of idle not being less than 11or 12 cruising not below 10 and WOT not below 7 or 8.
By the way I think that the briar hopper gauge is not worth 55 bucks its just a cheap hose and a cheap gauge and know my gauge is full of diesel because I dont think its designed for liquid.
Hope I can get some good info so I can throw it in the service managers face he was being a real a hole today. "
Maybe he gets it from experience, from his personal knowledge, training, and the group of people he deals with personally, including but not limited to other members of this board, who do some pretty amazing things with these trucks. Have you talked with him about the guage with liquid in it, and given him a chance to know about the problem and correct if necessary or do you just fire off, which may explain why the service manager was being the way he was!!!!! Cause that is the way your post reads!!! Maybe develop a better guage assembly yourself, assemble the parts at your expense, then sell it, again at your expense until the profits comes rolling. (If you do, bet
Tom would be the first singing your praises) Haven't heard anyone attack Tom before like this, in fact all of his posts and my limited dealings with him, he has been a very standup guy. Might want to watch throwing things in people's faces, cause you might be doing some catching yourself!!! :-{}
"Well thanks for your guys help still havent found a good answer. I wonder were black mtn. diesel gets there info they sent me with my briar hopper fuel gauge of idle not being less than 11or 12 cruising not below 10 and WOT not below 7 or 8.
By the way I think that the briar hopper gauge is not worth 55 bucks its just a cheap hose and a cheap gauge and know my gauge is full of diesel because I dont think its designed for liquid.
Hope I can get some good info so I can throw it in the service managers face he was being a real a hole today. "
Maybe he gets it from experience, from his personal knowledge, training, and the group of people he deals with personally, including but not limited to other members of this board, who do some pretty amazing things with these trucks. Have you talked with him about the guage with liquid in it, and given him a chance to know about the problem and correct if necessary or do you just fire off, which may explain why the service manager was being the way he was!!!!! Cause that is the way your post reads!!! Maybe develop a better guage assembly yourself, assemble the parts at your expense, then sell it, again at your expense until the profits comes rolling. (If you do, bet
Tom would be the first singing your praises) Haven't heard anyone attack Tom before like this, in fact all of his posts and my limited dealings with him, he has been a very standup guy. Might want to watch throwing things in people's faces, cause you might be doing some catching yourself!!! :-{}
zman...
... . if your post was a response to mine let me clarify. I understand just a little bit about fluid dynamics and I monitor my fuel pressure post filter to "read" the value my injection pump is "seeing". If the vp-44 were capable of "pulling"an adequate VOLUME of fuel from 10 feet back in the tank, our applications, Rams, would not require a lift pump. My "don't worry about it" point was a reference to the fact that my closely monitored pressures, are always 6-12 psi from idle in the driveway to full load, towing. Never have seen 15 psi, sometimes is under 8 psi. The point of installing and monitoring a fuel pressure gauge in our trucks is to watch for deterioration or failure, not absolute rigidity to what is obviously a poorly defined standard. Again, Have Fun, Jim G.
... . if your post was a response to mine let me clarify. I understand just a little bit about fluid dynamics and I monitor my fuel pressure post filter to "read" the value my injection pump is "seeing". If the vp-44 were capable of "pulling"an adequate VOLUME of fuel from 10 feet back in the tank, our applications, Rams, would not require a lift pump. My "don't worry about it" point was a reference to the fact that my closely monitored pressures, are always 6-12 psi from idle in the driveway to full load, towing. Never have seen 15 psi, sometimes is under 8 psi. The point of installing and monitoring a fuel pressure gauge in our trucks is to watch for deterioration or failure, not absolute rigidity to what is obviously a poorly defined standard. Again, Have Fun, Jim G.
Just a note of caution when checking the pressure at WOT. Do it on the road where the rpm's can be variable. When I had cummins check out my truck for a low power condition, the cummins tech. performed several (4) WOT stall tests th check pressure. Each test lasted about 5-7 seconds. Since then, when I accelerate from a stop, I can feel a jerk in the motion, like there is an extreme amount of backlash in the drivetrain, then the truck starts to move. It wasn't there before the tests, but it's there now. Probably screwed up either my tc or transmission. You might want to keep this in mind. 
Total bummer about Shane's gauge. A new one is being sent to him. This is a first for us, out of the hundreds we've sold, to hear of one filling with diesel fuel ! 
(My original gauge, the one that started it all, has spent 2 years surviving rain, snow, sun, and cold, in the open bed of my truck, and still works) We use top brand name parts to make the gauge, purchased from the lowest cost wholesaler I can find. It may or may not be worth what it costs. The charge that Shane mentioned includes priority shipping and bank charges for credit card use. I've always asked my customers to pay by check, it lets both of us avoid the bank fees. I haven't had one bounce yet! The TDR is full of good guys and gals...
I don't make enough on the gauge to justify the time spent on ordering & retreiving the parts, assembling and shipping them, but the requests just kept pouring in...
Several guys from Canada have asked me how to build it and where to get parts locally to build it, and I've gladly told them, as the exchange rate would be terrible, if I sold them one. I've explained in these forums several times what the gauge is made from and where I get the parts.
The general idea is to offer people a convenient way to safeguard their $40,000 investment in their truck, and protect the $1500 injection pump, seeing how so many dealers have been difficult to deal with on the lift pump issue.
(My original gauge, the one that started it all, has spent 2 years surviving rain, snow, sun, and cold, in the open bed of my truck, and still works) We use top brand name parts to make the gauge, purchased from the lowest cost wholesaler I can find. It may or may not be worth what it costs. The charge that Shane mentioned includes priority shipping and bank charges for credit card use. I've always asked my customers to pay by check, it lets both of us avoid the bank fees. I haven't had one bounce yet! The TDR is full of good guys and gals... I don't make enough on the gauge to justify the time spent on ordering & retreiving the parts, assembling and shipping them, but the requests just kept pouring in...
Several guys from Canada have asked me how to build it and where to get parts locally to build it, and I've gladly told them, as the exchange rate would be terrible, if I sold them one. I've explained in these forums several times what the gauge is made from and where I get the parts.
The general idea is to offer people a convenient way to safeguard their $40,000 investment in their truck, and protect the $1500 injection pump, seeing how so many dealers have been difficult to deal with on the lift pump issue.
- Status
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
Turbo Diesel Register
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
