Moparts

Diesel lift pump (long)

Posted By: poison_ivy

Diesel lift pump (long) - 08/31/11 04:58 AM

Just bought my first diesel. Found a great deal on an '02 with 41,000 miles. Runs great and looks like new. A friend checked and found out I have low fuel pressure,(6-7). I bought a FASS DDRP to replace the lift pump. Discovered the truck has a retro-fit in tank pump. Can this be removed and the FASS be mounted on the rail? Service rep at the Dodge dealer says the in tank setup can't be removed because it's now tied into the PCM. I located an original fuel level sending unit module to to put back in, in place of the in tank unit. What headaches am I going to encounter in this swap?
Posted By: calrobb2000

Re: Diesel lift pump (long) - 08/31/11 07:02 AM

hi
use the new pump , trash the one in tank , buy more mopar parts with money you save from not needing a new injection pump !
Posted By: fox

Re: Diesel lift pump (long) - 08/31/11 01:06 PM

Yes, get rid of the sad in-tank pump. It won't work together.

I have an 02 also. It has amused me for 10 years now to watch dodge spend $1,000 to almost fix something when all they had to do was buy it aftermarket!!! And, for $500.
Posted By: JohnRR

Re: Diesel lift pump (long) - 08/31/11 01:19 PM

Where did you measure that 6-7 psi pre filter or post, not that it matters much because that is still too low even with a clogged filter.

Change it out and don't look back.
Posted By: teflon

Re: Diesel lift pump (long) - 08/31/11 05:07 PM

Cummins is more interested in fuel FLOW than fuel pressure. Pump output is measured in mL for a 20 second period.
Posted By: a12rag

Re: Diesel lift pump (long) - 08/31/11 09:37 PM

I have an '02, 6spd, 2wd truck with 55k miles on it now . . . did the lift pump earlier this year (about 5k miles ago) . . . have pressure gauge on before I changed the lift pump. It was factory original Carter electric on left rear of engine . . . your in tank lift pump must have been changed out at some point, pretty sure they had the Carter Electric mounted on the block.

I went with the FASS stock replacement pump . . . however, I just replaced the injection pump after getting the dreaded dead pedal syndrom and the 0216 code (injection pump timing error) . . . truck is running fine again . . . nothing that $2.5k couldn't fix ! Ha ha ha . . . that was me doing the lift pump myself, and then having a shop do the injection pump.

The shop recommends a fuel additive to counteract the ultra low sulphor fuel out there now !!! . . . fyi !

Cheers

Mark
Posted By: fox

Re: Diesel lift pump (long) - 08/31/11 10:26 PM

I know that. But if you understand flow, the pressure drops then volume does too!
They are directly proportional.
Posted By: poison_ivy

Re: Diesel lift pump (long) - 09/01/11 02:27 AM

Spoke with a mechanic at a different dealer today that said they have NEVER had a retro fit pump come back with a failure. I'm just not sure if I'm just worrying too much. This truck runs fine and is all I need. Total combined weight when I'm towing to the track is 14,720. I'm told that's not bad for a diesel. I've gone back and forth with this for a couple of weeks. I know most guys want more hp and torque, but for the most part I'm satisfied with what I have. This is my first diesel, and everyone I talk to says you need to do this and do that. I don't need a monster truck. I just want something reliable and dependable. With that said, am I making too much about this?
Posted By: JohnRR

Re: Diesel lift pump (long) - 09/01/11 06:36 AM

Quote:

Spoke with a mechanic at a different dealer today that said they have NEVER had a retro fit pump come back with a failure. I'm just not sure if I'm just worrying too much. This truck runs fine and is all I need. Total combined weight when I'm towing to the track is 14,720. I'm told that's not bad for a diesel. I've gone back and forth with this for a couple of weeks. I know most guys want more hp and torque, but for the most part I'm satisfied with what I have. This is my first diesel, and everyone I talk to says you need to do this and do that. I don't need a monster truck. I just want something reliable and dependable. With that said, am I making too much about this?



No , that fuel pressure is TOO LOW , do you want to have to replace the injector pump $$$ ??? , then leave it as is ...
Posted By: DPelletier

Re: Diesel lift pump (long) - 09/01/11 06:43 PM

Quote:

Quote:

Spoke with a mechanic at a different dealer today that said they have NEVER had a retro fit pump come back with a failure. I'm just not sure if I'm just worrying too much. This truck runs fine and is all I need. Total combined weight when I'm towing to the track is 14,720. I'm told that's not bad for a diesel. I've gone back and forth with this for a couple of weeks. I know most guys want more hp and torque, but for the most part I'm satisfied with what I have. This is my first diesel, and everyone I talk to says you need to do this and do that. I don't need a monster truck. I just want something reliable and dependable. With that said, am I making too much about this?



No , that fuel pressure is TOO LOW , do you want to have to replace the injector pump $$$ ??? , then leave it as is ...





Don't believe the dealer; if I had a penny for every time I've heard the "we've never encountered that" story, I'd be a rich man. Funny thing is that often the issue (like this one) is well known to be VERY common.


Dave
Posted By: 383man

Re: Diesel lift pump (long) - 09/01/11 07:09 PM

I can tell you this since I worked for a Dodge dealer for 23 years. Every time I saw a tech replace a low pressure lift pump mech or electric if they did not replace the inj pump it would be towed back in a few days to get the inj pump replaced. The fuel has a return line at the injector pump and the extra fuel would go thru that line along the side of the inj pump back to the tank and that fuel would help cool the inj pump. And every time the lift pump went bad they ended up needed the inj pump either right then or within a week or so. Now after we started putting the low pressure pump in the tank as long as the inj pump was also replaced I did not see them come back. So it definetly helped and worked better with the in tank pump but it is not as good as most after market kits. Ron
Posted By: DPelletier

Re: Diesel lift pump (long) - 09/01/11 08:21 PM

Quote:

I can tell you this since I worked for a Dodge dealer for 23 years. Every time I saw a tech replace a low pressure lift pump mech or electric if they did not replace the inj pump it would be towed back in a few days to get the inj pump replaced. The fuel has a return line at the injector pump and the extra fuel would go thru that line along the side of the inj pump back to the tank and that fuel would help cool the inj pump. And every time the lift pump went bad they ended up needed the inj pump either right then or within a week or so. Now after we started putting the low pressure pump in the tank as long as the inj pump was also replaced I did not see them come back. So it definetly helped and worked better with the in tank pump but it is not as good as most after market kits. Ron



Ron,

Yep; I can buy into all of that. My comment was on the generic "we've never seen that before" spew when the parts are on national back order because it happens so often! Think, 2nd gen clockspring or AC blender doors!

The VP44 is VERY succeptible to damage from low lift pump pressure. In the case of the OP, the pressures he's seeing are still too low and I'd rely on the pressure gauge over the "the updated pump is never a problem" sentiments. It simply is NOT worth the risk.





Dave
Posted By: JohnRR

Re: Diesel lift pump (long) - 09/01/11 08:53 PM

Quote:


The VP44 is VERY succeptible to damage from low lift pump pressure. ...





Dave



HOGWASH ....

I ran my truck out of fuel more times than I care to admit , I did it so many times I figure out how to prime it without having to crack lines, went thru 3 lift pumps, one died completely and I drove the truck for 3 months with the VP pulling fuel thru a dead lift pump, I lost the voltage signal from the ECM. The original VP died at about 220k miles and that was in my opinion because of the low sulfur fuel ... coupled with the 3rd 14psi pump only pushing 5psi...

Posted By: DPelletier

Re: Diesel lift pump (long) - 09/01/11 10:15 PM

Quote:

Quote:


The VP44 is VERY succeptible to damage from low lift pump pressure. ...





Dave



HOGWASH ....

I ran my truck out of fuel more times than I care to admit , I did it so many times I figure out how to prime it without having to crack lines, went thru 3 lift pumps, one died completely and I drove the truck for 3 months with the VP pulling fuel thru a dead lift pump, I lost the voltage signal from the ECM. The original VP died at about 220k miles and that was in my opinion because of the low sulfur fuel ... coupled with the 3rd 14psi pump only pushing 5psi...





Yeah, but you're special! Many of us weren't so lucky. I was soooo happy the day my '01 was traded for a new common rail truck! (in hindsight, the '01 was a great truck too)



Dave
Posted By: dweller

Re: Diesel lift pump (long) - 09/02/11 10:44 PM

The in tank pump on my '02 HO has been working fine for the past 60K miles. Lift pump on the block is stock for these trucks. Mine was replaced on warranty at 90K along with a new IP. I try to keep my tank at least 1/4 full so the pump is partially submerged.

IP failures have to do with heat cycles, not so much keeping the board cool.
Posted By: Evil Spirit

Re: Diesel lift pump (long) - 09/04/11 06:17 AM

Quote:

I know that. But if you understand flow, the pressure drops then volume does too!
They are directly proportional.



If you really understand flow you understand that pressure is a measurement of restriction. Thats why pumps are rated X volume @ X pressure, as in 140 gallons @ 7 P.S.I.. Thats the reason Dodge wants to see a certain volume in a certain amount of time. A restriction between the lift pump and the injector pump can show good pressure (at the pump) but still have low volume.

I've seen cobbled together fuel systems that showed good pressure, but the small hoses and fittings wouldn't flow any real volume. If the point of the most restriction is between the carb (or injector pump) and where you are reading the pressure, you won't get an accurate read on the amount of fuel avalible, as in good pressure - low volume.
Posted By: fox

Re: Diesel lift pump (long) - 09/05/11 07:55 AM

Of course I understand flow.

My point really was that Dodge got tired of people finding low pressure at the injection pump, so they thru a curve to avoid replacing so many cheap pumps. (cheap by design)

If you have a hydraulic system and change nothing, if the pressure drops so does the voluume.
Ddoge simply twisted the talk to the customer that had low pressure and said the pressure wasn't important, it was the flow they were concerned about!
But, Bosch states 'pressure to the pump at a certain spec range. They do NOT specify the voluume. either would be acceptable. My poit is dodge tried to sell customers that if the pressure was low or zero, they still only were concerned of flow. Of course we know id pressure is a true zero there will be no flow.
Posted By: Evil Spirit

Re: Diesel lift pump (long) - 09/06/11 04:53 AM

Dodge knows that an engines fuel requirements are "volume" related and pressure is only a tool to get that volume. An engines fuel requirement is measured in B.S.F.C., or Brake Specific Fuel Consumption, which ballpark is about .5lbs of fuel per HP per hour. The engine could care less if the fuel is delivered at 10 or 10,000PSI; it wants 200LBS of fuel (about 30 gallons) to make 400HP per hour.

Asking for a certain volume takes all the guesswork out of the equasion. If the line supplying the injector pump can fill a gallon container in a minute, you have enough fuel to make roughly 780HP, or about 620HP running at the 80% duty factor a lot of fuel systems are set up at. By Dodge asking for a certain volume it takes all the custom or modified fuel system arguements out of the equasion. If a stock and unmodified fuel system doesn't meet that volume spec - that is a Dodge issue. If the retrofit Widget Industries lift pump plumbed in with Home Depot fittings only flows a pint of fuel a minute @ 15PSI - not Dodges problem.
Again my point - Pressure is a tool to obtain volume; not an accurate indicator of OBTAINED VOLUME.
Posted By: J_BODY

Re: Diesel lift pump (long) - 09/06/11 05:30 AM

Run the intank pump, it will do just fine.
Posted By: J_BODY

Re: Diesel lift pump (long) - 09/06/11 05:46 AM

Quote:

My point really was that Dodge got tired of people finding low pressure at the injection pump, so they thru a curve to avoid replacing so many cheap pumps. (cheap by design)



....actually Chrysler bought the package from Cummins, and it was Chysler that absorbed the expense of replacing all those VP's and lift pumps. It was also on the common rail trucks (03-04) that the "supplied" lift pump was also a failure prone piece. It was chrysler that came up with the in-tank pump that appeared stock in 05, but retrofit kits went all the way back to the 98.5 VP equipped trucks. I do remember hearing the the warranty cost was such that during the Diamler era they were looking hard at replacing the Cummins with a Mercedes based package. That would have most likely been the death of Dodge trucks, but it would have kept costs "in house" too.
Posted By: fox

Re: Diesel lift pump (long) - 09/06/11 01:27 PM

As I understand it Dodge supplied the lift pump. and this was against Bosches wishes as far as quality goes.

And my point is missed or distorted on the pressure issue.

We are not talking about any system other than the fuel system on the 98.5 to 2002 dodge/cummins.
If the system is left intack/ unmodified workings, if the pressure drops, so does voluume. No if and or buts here.
customers were installing fuel pressure guages and finding below spec bosch standards, and wanting to protect thier expensive injection pumps by asking for replacement of the lift pump.

dodge got tired of changing out weak lift pumps , then started telling customers it was volume that is important. YES THEY WERE RIGHT!!!
But if Bosch says 8-10 PSI is needed to get that volume, that is thier specs on it.
Some dealers tried to tell customers that they could have the needed volume with ZERO pressure!!!

IMPOSSIBLE!!!!

Also, the spec was including enough VOLUME to lube and cool the pump, not just supply the fuel required to make HP.
Posted By: Evil Spirit

Re: Diesel lift pump (long) - 09/07/11 03:13 AM

I wonder if the being able to get the proper volume (with no pressure) might have been a little mis-understood. If the line from the pump was open to run the volume test, as in aiming the line into a container to measure the volume, the pressure gauge would probably read zero, since the line shouldnt be a restriction. You could have your volume with no "indicated" pressure. I would rather see a sized restriction put onto the end of the line and you need "X" volume in a given time and still hold a minimum pressure, say 10PSI.
Posted By: fox

Re: Diesel lift pump (long) - 09/07/11 12:39 PM

Once again, you are not dealing with an apples to apples comparison!!
You just described an open system, not closed like bosch specs. ( on a diesel, you don't open a fuel line unless absolutely neccessary)
This is why pressure is the spec!!

Try this if you don't understand.
Do try to fill your swimming pool with the garden hose. Rather that walk to the pool, cut a slit in the hose at the valve to check volume. What happens? The system is open and pressure drops. You cannot check a pumps capacity without a pressure and volume spec!!!
Posted By: fox

Re: Diesel lift pump (long) - 09/07/11 12:44 PM

Quote:

Dodge knows that an engines fuel requirements are "volume" related and pressure is only a tool to get that volume. An engines fuel requirement is measured in B.S.F.C., or Brake Specific Fuel Consumption, which ballpark is about .5lbs of fuel per HP per hour. The engine could care less if the fuel is delivered at 10 or 10,000PSI; it wants 200LBS of fuel (about 30 gallons) to make 400HP per hour.

Asking for a certain volume takes all the guesswork out of the equasion. If the line supplying the injector pump can fill a gallon container in a minute, you have enough fuel to make roughly 780HP, or about 620HP running at the 80% duty factor a lot of fuel systems are set up at. By Dodge asking for a certain volume it takes all the custom or modified fuel system arguements out of the equasion. If a stock and unmodified fuel system doesn't meet that volume spec - that is a Dodge issue. If the retrofit Widget Industries lift pump plumbed in with Home Depot fittings only flows a pint of fuel a minute @ 15PSI - not Dodges problem.
again my point - pressure is a tool to obtain volume, not an accurate indicator of volume.


Bosch didn't spec the volume!! Because it is tougher to do in a closed system. So, they use thier calculations and used pressure.
Posted By: Evil Spirit

Re: Diesel lift pump (long) - 09/07/11 02:20 PM

I said : "I would rather see a sized restriction put onto the end of the line and you need "X" volume in a given time and still hold a minimum pressure, say 10PSI."

You said: "You cannot check a pumps capacity without a pressure and volume spec!!!"

I'm not sure why you can't see I just said the same thing - it takes pressure and volume to figure capacity. I was questioning how some people are getting their results, not how the results are figured.

You said : ( on a diesel, you don't open a fuel line unless absolutely neccessary)

Yep, agreed. but how else do you verify actual fuel delivery, a Magic 8 ball? Well, first, how do you install an accurate gauge system without opening lines? Then the only accurate way I know to verify fuel flow to the injector pump is to remove the line from the lift pump and test it there. I'm not looking at Bosches test, but if it doesn't require both a pressure and volume minimum, it's worthless. If it does - GOOD FOR THEM, My point has always been a simple pressure test may be flawed due to a damaged (pinched) line, or operator installed incorrect fittings.

You said : "Bosch didn't spec the volume!! Because it is tougher to do in a closed system. So, they use thier calculations and used pressure."

That may be fine, but why not just do an accurate test and see how much fuel is actually being delivered.

And I'm only talking about this, since you brought it up : "Do try to fill your swimming pool with the garden hose. Rather that walk to the pool, cut a slit in the hose at the valve to check volume. What happens? The system is open and pressure drops." No argument there. Go a step further - take a 100' hose, run water through it with the end open. Take pressure measurements along the length of the hose. I bet they are higher at the supply end and gradually get lower as you get to the open end.

Another point - if Dodge and Bosch was so flippin smart - why didn't they put the lift pump in the rear of the truck, where it would be more effecient and not have engine heat?

At this point we're just snipe hunting and beating it to death. Anybody that doesn't understand the concept of needing more than just a pressure reading to accurately measure total flow, read a book. And that's just a general statement; not directed at any one person.
Posted By: DPelletier

Re: Diesel lift pump (long) - 09/07/11 05:24 PM

Quote:

We are not talking about any system other than the fuel system on the 98.5 to 2002 dodge/cummins.
If the system is left intack/ unmodified workings, if the pressure drops, so does voluume. No if and or buts here.
But if Bosch says 8-10 PSI is needed to get that volume, that is thier specs on it.




Correct; in the context of this discussion/issue, the pressure can be used to determine if the lift pump is adequate or not.

Dave
Posted By: Evil Spirit

Re: Diesel lift pump (long) - 09/07/11 07:13 PM

Quote:

Quote:

We are not talking about any system other than the fuel system on the 98.5 to 2002 dodge/cummins.
If the system is left intack/ unmodified workings, if the pressure drops, so does voluume. No if and or buts here.
But if Bosch says 8-10 PSI is needed to get that volume, that is thier specs on it.




Correct; in the context of this discussion/issue, the pressure can be used to determine if the lift pump is adequate or not.

Dave



On an unmodified fuel system, I'd agree with that. You can see if the lift pump meets the specs of the people (Dodge and Bosch) who designed the system that has such a high failure rate and can't agree on how to test it; pressure VS volume.

The original poster has a modified system, which appears to have low fuel pressure. At this point is the fuel pressure low enough to cause a problem? A solid probably. Best way to fix it? My suggestion would be to use the FASS pump with the relocator kit to put it on the frame rail. I would return the tank to stock condition. I would make sure that the connections that were made where the factory lift pump was originally are correct and not restricting flow. Lastly, I would try to take my pressure readings at the inlet to the injector pump if at all possible, since that takes all the restrictions in the supply system out of the picture. This may not be possible, due to the possibility of the injector pump creating a pulsation while it draws in the fuel.

My appologies to the O/P for getting off track and getting caught up discussing theory.
© 2024 Moparts Forums