fuel pump/lift pump issue?

[Solar1]

Hello folks, hope someone can give me a few hints and answers here.

It has been awhile since ive worked on any fuel system issues with my 96 ram.

420k miles. have put in 2 lift pumps as well as a couple in tank pump sending unit assemblies
on the truck over the years.

so yesterday, after a hour drive on the freeway, i shut the truck off, 2 hours later went to restart, and the engine cranked fast but acted like it was out of fuel with air in the lines.

im trying to remember, but i believe that if the lift pump is removed and line are disconnected, when i turn key on, the fuel pump in tank should pump fuel out the disconnected line, indicating that the in tank pump is working.

Im not getting that, so is my in tank pump bad?
I can confirm that there are no fuel line leaks noticeable.
one thing i did notice prior to this issue was that the truck seem to be losing a little power and i found myself pushing the accelerator pedal more than usual to maintain freeway speed.

if anyone has a quick procedure to troubleshoot, please do share.
im not thinking straight these days and i need a bit of help with a plan.

i can share that i did attempt to manually pump the lift pump and it would not get hard (pressure buildup) and I did try to bleed air....i got some fuel, but no air and it did not bleed with pressure, just a light fuel flow.


thanks

 

[DavidC]

Unless someone added a pump in the tank there is none, just the mechanical on the engine.

 

[Solar1]

thanks, like I said, im not thinking straight these days...I thought there was a pump in the tank as well. its been awhile sine I installed a new sending unit and I must be mistaken. That brings me back to my issue. I have purchased a new lift pump and with install it as soon as I get a new elbow hose. it seems then that the lift pump gave out, seeing as I gould get no air bubbles while attempting to bleed, as well as no fuel pressure squirting out the bleeder. yes? by the way, I for got to mention that I found the short elbow hose collapsed, but after move it around and restoring position and then bleeding I still got ne pressure

 

[DavidC]

Yes, it could be the pump. I believe it is a diaphram which could have gone south. I believe there have been instances where the supply on top of the tank module developed pin holes.

 

[Justinb]

There could be several issues your facing. There is a return valve on the fuel return line on the injection pump that is a serviceable item. And, the stock fuel supply and return lines at the fire wall area is prone to leaking and letting air into the system. Unfortunately the trucks is getting old and you will probably have to replace all the fuel lines, lift pump, and make sure you look at the top of the fuel sump at the tank for problems there too. everything is made from the factory with really cheap plastic flexible quick connects and they get brittle over time and break and leak. you can get some high quality AN push lock aluminum fittings and quality rubber fuel hose thats diesel compatible and replace everything. I bought Vibrant performance fuel fitting and they had everything including banjo fittings that worked with everything on the 12 valve cummins. if you are interested i can send you pictures.

 

[MHalloran]

thanks, like I said, im not thinking straight these days...I thought there was a pump in the tank as well. its been awhile sine I installed a new sending unit and I must be mistaken. That brings me back to my issue. I have purchased a new lift pump and with install it as soon as I get a new elbow hose. it seems then that the lift pump gave out, seeing as I gould get no air bubbles while attempting to bleed, as well as no fuel pressure squirting out the bleeder. yes? by the way, I for got to mention that I found the short elbow hose collapsed, but after move it around and restoring position and then bleeding I still got ne pressure

Brother where did you pick up your replacement lift pumps from? I’d like to pick up a new one too. I’ve been experiencing problems with my fuel system recently. I have a 96. My lift pump was replaced last maybe 20 years ago. Still same one in. I’ve been losing power as I’m driving too. The more I push accelerator the weaker/ slower it gets. Going up a hill? Forget about it...Came to a stop sign twice & it stalled. It restarts easy enough. I’m cleaning up fuel solenoid, replacing the relay & swapping the fuel filter too for starters. Too cold out today so maybe tomorrow I’ll do more. Maybe another member here can chime in if he sees this post. Let me know how it goes my friend....oh & I had replaced my fuel lines with diesel marine hose also. Should do yours maybe too.

 

[Solar1]

advance auto with the 25% discount code.

I cant remember which one I brought...they had a couple brands
I think it was the CARQUEST unit
my short term memory is poor

 

[MHalloran]

advance auto with the 25% discount code.

I cant remember which one I brought...they had a couple brands
I think it was the CARQUEST unit
my short term memory is poor

thanks I’ll check it out. You mentioned you purchased a couple of them in past. They both from advance do you recall? There are variations out there. Depends on what you wanna spend. We do know our fuel system is of importance to quality start up & run time.

 

[Solar1]

Both from Advance Auto.

I just checked.
First replacement was a Delphi brand, I installed it at aprox 250K miles.
Im now at 462K miles and just bought the CARQUEST unit.

I think the dephi was fine. I figure almost 250k miles on the Delphi is an acceptable expectation of life.

 

[MHalloran]

Both from Advance Auto.

I just checked.
First replacement was a Delphi brand, I installed it at aprox 250K miles.
Im now at 462K miles and just bought the CARQUEST unit.

I think the dephi was fine. I figure almost 250k miles on the Delphi is an acceptable expectation of life.

I just did a search for a Delphi. Prosource Diesel has them. Delphi brand. $70.

 

[GAmes]

Don't let the link source fool you. Joe G was a valuable member of the TDR when he wrote and published this info paper.
https://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html

As an FYI, I have never had to replace a genuine Cummins lift pump with less than 300k on it.

 

[MHalloran]

Don't let the link source fool you. Joe G was a valuable member of the TDR when he wrote and published this info paper.
https://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html

As an FYI, I have never had to replace a genuine Cummins lift pump with less than 300k on it.

I had mentioned I had replaced my lift pump in past. First swap was done at dealer with about 1000 miles on truck. They found fault in it when I brought truck back to them with an issue. That one has lasted up to now. Truck has 240k miles on it presently so I guess since I have solenoid out & am gonna change filter I can do a lift pump swap somewhat easier if these 2 items are temporarily out of the way. A little more room to access the area might I say? Just waiting on a slight increase in outdoor temps to go diving into this job further...

 

[honobiahunter]

I didn’t see if you’d figured out the problem yet or not. But have you verified that the FSS is pulling all the way up? My truck would crank and crank and I finally thought to check the FSS and sure enough it wasn’t pulling all the way up. The boot had deteriorated around it and after a through cleaning it started working fine

 

[Solar1]

I determined that the lift pump was bad, and so was the FSS relay.
Yes, I verified the FSS solenoid is pulling up hard and fast, but I I'm not sure about all the way...is there an adjustment?
I found the relay was intermittent and after I replaced it, I found the fuel pump was not pumping. So it was by coincidence, both the lift pump and an intermittent relay.

By the way, I too, also had a lift pump replaced under warranty early in the life of the truck. I would need to dig out the shop records, but I seem to remember the original pump quit at around 40k miles.

With the new lift pump and the relay replaced, the truck starts great now, but I now notice a lack of high throttle range. In other words, the accelerator pedal is dam near hitting the floor to achieve about 80mph top speed. The truck was capable 100mph before (not that I ever drove it in that range, im just saying that top speed is now about 80mph.) Fuel economy is about 19mpg.

Im not sure what to check at this point. It is complicated because before the fuel issue, I had the throttle linkage break and also lost the throttle return spring, and, I also had to replace the accelerator cable as I found that to be frayed and hanging up. With all new linkage, spring and accelerator cable ( and the lift pump) all seem ok except for the limited top speed issue.

Although I did set up the throttle linkage exactly as detailed in the service manual. I wonder if maybe I have something adjusted wrong, thereby limiting the top end speed due to a linkage restriction.
I have not been able to get back on this issue due to health issues recently, but I will need to address it.

I'm open to any thoughts you folks may have as a starting point to check this condition.

 

[GAmes]

Yes, the FSS has an adjustment. If the rod is too long the lever does not pull full up which results in a decreased amount of fuel available to the p-pump.

 

[Solar1]

That could be it, I will check my service manual for a procedure.
Thanks

 

[Solar1]

checked the measurement per the service manual which states 2.64" from bottom of solenoid mounting bracket to the top of the adjustment nut...I measured 2.625.
I would say that is close enough that it should not be creating a problem.

 

[MLee]

For your Throttle problem, you might search for the measurement that is needed in the linkage. If its to loose you'll have these symptoms. The end sockets have a tendency to ware and gets out of adjustment. I believe Genos garage has some of these parts now.
I have found that the batteries need a good charge/connections to pull the solenoid up to start also. Its just a group of things that need to be maintained.

 

[MHalloran]

I determined that the lift pump was bad, and so was the FSS relay.
Yes, I verified the FSS solenoid is pulling up hard and fast, but I I'm not sure about all the way...is there an adjustment?
I found the relay was intermittent and after I replaced it, I found the fuel pump was not pumping. So it was by coincidence, both the lift pump and an intermittent relay.

By the way, I too, also had a lift pump replaced under warranty early in the life of the truck. I would need to dig out the shop records, but I seem to remember the original pump quit at around 40k miles.

With the new lift pump and the relay replaced, the truck starts great now, but I now notice a lack of high throttle range. In other words, the accelerator pedal is dam near hitting the floor to achieve about 80mph top speed. The truck was capable 100mph before (not that I ever drove it in that range, im just saying that top speed is now about 80mph.) Fuel economy is about 19mpg.

Im not sure what to check at this point. It is complicated because before the fuel issue, I had the throttle linkage break and also lost the throttle return spring, and, I also had to replace the accelerator cable as I found that to be frayed and hanging up. With all new linkage, spring and accelerator cable ( and the lift pump) all seem ok except for the limited top speed issue.

Although I did set up the throttle linkage exactly as detailed in the service manual. I wonder if maybe I have something adjusted wrong, thereby limiting the top end speed due to a linkage restriction.
I have not been able to get back on this issue due to health issues recently, but I will need to address it.

I'm open to any thoughts you folks may have as a starting point to check this condition.

Yes the lift pump I have in place now has 235k miles on it so I ordered one from Prosource. I figured why not because I’ll have easier access to spot it’s in while other parts are out of way.
Solenoid can be adjusted as GAmes says but let me ask you this. If you can hit 80 mph now, how much faster do you really need to go man? I know you said you used to hit like 100 but let’s remember, the truck isn’t a young spring chicken anymore . IMO, our trucks aren’t built for speed, more for strength & torque. Just get it running right & reliable. To me that’s the most important factor.
Was your throttle cable original? Years back there was a TSB on these cables for a fraying issue. Dodge had a revision for this. I had replaced mine. No problem since then.
About 19 mpg you’re getting? I’d say be happy with that for a truck that weighs about 3 tons. I’m getting 19-20 mpg with mine too. It’s also a 1996 year built truck.
I can understand your being hindered from working on your truck due to a health issue. Don’t push yourself. I also have a health issue which is MS. At times it’s tough for me to work on mine too. I’ll do a little then I’ll need to take breaks. My body tells me how much I can do before I regret it. Stay well bud. I’ll keep you guys posted as I progress on mine. .......Mike

 

[Solar1]

Of course I don't need to go 100mph. Never did except once awhile after I bought the truck new, just to see what it was cable of. I realize the truck is no spring chicken, nor am I. I do pamper the truck as best I can. I was using that info as a reference.

The way I should have stated it was that now I need to damn near press the pedal hard to the floor to run freeway speed....It was never like that before. I actually get a sore ankle from driving more than a half hour now on the freeway because the pedal needs to be pressed harder/farther. Something just isn't right with it.

Yes the cable was original. It was never replaced by Dodge under warranty or Tech Bulletin. In regards the accelerator cable, I found it thru ebay from a Dodge dealer and it was in fact MOPAR oem cable.

I would be interested in a link to the Dodge tech bulletin on the accelerator cable issue, I was not aware of it. Maybe there is some info in it that will help me determine my issue here, or perhaps help me determine why the speed issue is occurring now that I replaced all the parts recently.