Lift pump failed at 46,650 miles...how about you?

[JVantreese]

Well I knew that the fuel pump on the 4. 5 year is a weak point. Today I was turning on to highway and old red just died like i turned the ignition off. I managed to coast most of the way off the highway and tried to figure out what was going on. I tried to start it and it fired up but died as soon as I gave the "gas pedal" a push. I then noticed that my fuel pressure gauge was sitting at zero rather then the 7 lbs it normally would be at. I then started the engine and decided that I could idle the 1/2 mile down the road to garage that I have used before. Due to the "improvements" that this truck has I decided not to go to the local dealer where they would pull the plug on my extended warrentee. My selling dealer, which is 100 miles away, knows of my mods and is willing to overlook anything that is not directly connected with the mods.



I had a spare pump from Geno's so it was a fairly simple job for the non dealer to fix my problem. The old pump use to show pressure of 7 to 8 pounds that would draw down to about 5 pounds with heavy throttle. The new pump runs about 10 lbs at idle and moves up to 15 lbs with a little increase in the RPM's. I would think that the pump should drop pressure with more throttle. The only reason that I can think of the higher pump pressure at higher RPM's would be more juice from the alternator. Your viewpoint on this would be helpful.



I would appreciate input as to what pressures other have with the OEM pump and what milage if/when the pump failed. I have ordered another pump from Geno's and will put in the recently vacated spot of my boony box.

 

[ASchwartz]

Mine went at 86, 584 miles. My pressure gauge is setup to read pressure post filter. I saw, depending on outside temp (colder produced less pressure), pressures between 10 to 15. When I'd throttle her up it would go to zero. I ran the bypass kit for about 500 miles before I installed the walbro. The truck ran great with no lift pump. Even made it out to Glamis and back.

 

[Bessler]

If we had Generators it would be the case, but Alternators put out the same current at idle or high RPM. Had the same thing with a warranty lift pump 8 psi some times @ idle till 1500 rpm then kick up to 15 psi. Than some times stayed @ 15 psi from start till shut down. Dislike watching fuel pressure constantly wondering if it was going to drop? now carry that as my spare. Interested to know the truth about the fluctuation of pressure.

 

[jelag]

We've changed all our trucks over to the in tank pump and have had no problems... .

Our current oldest truck now has 200K mile with the pump in the tank with no problems...

Hope this helps...

 

[JJPage]

We've changed all our trucks over to the in tank pump and have had no problems... .



Our current oldest truck now has 200K mile with the pump in the tank with no problems...



Hope this helps...

Do you actually have an "in tank" pump? The "warranty replacement" pumps, that Dishman Dodge had an outside repair shop install, was very similar to a Walbro, mounted on the inside of the frame rail.



You probably do your own work, so that would not be the case, but I hear this " I have an in tank retro-fit", and I check it out, and it is on the frame rail!



I am so glad I do my own upgrades.

 

[jelag]

JJPage

All of my lift pumps failed out of warranty... and we installed the kits. .

Dodge has a kit that includes the wiring harness and new tank unit... . this is an in tank pump like what is installed on the 05 and up trucks... mounted in the tank float system like most cars... Our 08 5500 has the same pump... .

We have installed additional filters to protect the engines... . a 10 micron and a 2 micron on a custom built assembly... . and for a friend we tested the fuel pressure(none of my trucks have a fuel pressure gauge on them) after the filters... . it was always good...

I don't have a clue what Dishman is installing... I've never seen a frame mounted system from Dodge but they might of changed... after all the kit that we've got, you have to pull the tank and that adds time and labor... if all you had to do was break into the line you'd save all that time... .

BTW with the old style lift pump on my 04 (before the change to the intank pump) we had installed a helper pump... . when the engine mounted lift pump failed, the helper pump was still running but what ever failed in the lift pump caused lack of fuel flow and the truck was stalled on the side of the road... . I naturally assumed that the if the lift pump failed that the helper pump (frame rail mounted) would push fuel through the failed pump... .

The helper pump was a Holly Red pump, suitable up to 17 psi and something like 50 gal per hour... ... more than enough pump... I assumed it had died as well when the lift pump failed... opening the line in front of this pump and turning on the key found lots of fuel but a bad lift pump...

 

[ASchwartz]

I naturally assumed that the if the lift pump failed that the helper pump (frame rail mounted) would push fuel through the failed pump... .



The helper pump was a Holly Red pump, suitable up to 17 psi and something like 50 gal per hour... ... more than enough pump... I assumed it had died as well when the lift pump failed... opening the line in front of this pump and turning on the key found lots of fuel but a bad lift pump...

When the lift pump fails it seizes and becomes a blockage.

 

[JVantreese]

If we had Generators it would be the case, but Alternators put out the same current at idle or high RPM. Had the same thing with a warranty lift pump 8 psi some times @ idle till 1500 rpm then kick up to 15 psi. Than some times stayed @ 15 psi from start till shut down. Dislike watching fuel pressure constantly wondering if it was going to drop? now carry that as my spare. Interested to know the truth about the fluctuation of pressure.

I know that an alternator will attempt to put out equal power at most RPMs but I believe they are designed to meet their maximum output at a given RPM range. Going above or below this range will prevent maximum output. I have noticed that if a car is jumped due to a low battery, the headlights will brighten when you add some RPMs. I am not an electrical engineer so I would welcome input. My opinion is just life experience from the school of hard knock. I had attempted to get my truck to run and used the starter quite abit before changing the lift pump. I figured my batteries were less then fully charged and would be using most of the alternator output. It will be interesting to see the pressure output after I get a chance fully recharge the batteries from a longer trip.

 

[jelag]

The alternator on a vehicle will not provide enough current at idle to supply all the electrical demand..... on some winter evening turn on the lights and heater to full blast... you'll see the volt meter drop below 14 volts and approach 12... . the lights will dim and the blower speed will decrease... once the engine rev's to say 1100-1200 depending on load the alternator will catch up and the recharge of the battery will start...

It wouldn't be economical to provide an alternator that would supply sufficient power at idle... . too much HP draw... . too large... etc... .

A battery is rated at amp hour draw... . the old school of rating batteries... . this is an SAE standard for simple comparison of batteries... . we used to submit batteries for testing at 3X's the AHD for load testing... than they went to CCA (cold cranking amps) and that load test was 1/2 the CCA... .

The key here is if you know the amp hour draw... lets say its 100... . than it (the battery) will supply 100 amps for 1 hour, or 10 amps for 10 hours or 1 amp for 100 hours... with this in mind, you safely charge a battery the same way... . a 10 amp charger will take 10 hours to bring a flat 100 AHD battery from fully discharged to fully charged... . Another term for AHD that I use... and more correctly so is AHR (amp hour rating) AHR or AHD as I like to think of it... . is easier to use and understand when you start talking about starter draw, load, and charging...

Your starter of course draws maybe 300 amps for a few seconds... way over the normal capacity of the battery... . if you've drawn both batteries to say 50% and they are 100 AHD batteries it will take a 10 amp charger 10 hours to bring both back to fully charge condition... .

NOW if you run your truck and the alternator produces say 30 amps more than the needed draw of the system... its going to take your alternator about 3 1/3 hours to recharge those 2 batteries mentioned above that are down to 50%... .

I hope this answers some your questions... I tried to not get too involved but relay the information...

 

[JVantreese]

Ok so if I understand what you are saying, then, a low battery at idle could give the lift pump low voltage which could give us a lower pressure reading on my gauge. When I kick up the RPMs the voltage would increase letting the pump work a little harder and increase the pressure. Am I interpreting ths correctly?

 

[Bessler]

I understand the Batt & Alt cycles, after the pump started to drop to 8 psi & jump back to 15 psi I replaced it with a pump from Cummins 12-13 psi constant. This pump failed after 16K. Reinstalled the 8-15 psi pump, it continued to cycle 8-15 psi. Went back to Cummins who wholesaled me a new pump for the one, installed it 12-13 psi. If current cycling was the case the other two pumps should have done the same? I belive its within the pump its self.