Engine/Transmission (1998.5 - 2002) LP woes......Again? Kinda long.

[klaybus]

After about 20k miles or less I'm seeing erratic pressures. I just replaced the fuel line going to my westach sending unit with a clear line & noticed the following.

Prior to changing the fuel pressure line out I noticed running around town & on the freeway pretty much constant 16 psi but when I got caught at a stoplight after a few minutes my pressure would drop to like 10-11 psi. I assumes my sending unit was going bad & have ordered a replacement unit. The sending unit is on backorder so I thought now would be as good a time to relocate it as any so I relocated it & installed the clear tubing. What I have found is when the guage drops to 10 psi it is truly dropping! I look at the clear tubing & it is no longer as full as it is when it shows 16 psi... . FAULTY LP?

I remember reading something about a internal bypass in the LP? Is this true & it's opening when it's not really needing to? Or in fact does it need to open when at idle & as soon as the accelerater is touched it closes when a greater fuel demand is required?

I got rid of my banjos & stock fuel lines & fittings about 6 mos. ago when I replaced the LP & have never seen better pressures but all of a sudden this scenario has started... ... Any comments or suggestions... ...



Thanks!

Clay

 

[Mad Bomber]

Clay do you want to barrow my FP gauge? When ever I get a wierd reading on my FP gauge I always stick on the tester one.



BTW I've found anytime that I start getting wierd readings on gauge that's the beginning of the end for that LP.

 

[klaybus]

Clay do you want to barrow my FP gauge? When ever I get a wierd reading on my FP gauge I always stick on the tester one.



BTW I've found anytime that I start getting wierd readings on gauge that's the beginning of the end for that LP.

Not what I wanted to hear Eric! Yep... . I'll go by Phils & give his a shot. (Rips) I just can't believe this thing is on it's way. I wonder what kinda warranty this thing has if any.....



Clay :{

 

[Mad Bomber]

Stock LP DO have some sort of warranty CRS sorry. I just thought of another cause. I had to drop the tank and cut the screening out of the pick up assembly. At that point you MUST have a screen before the pump. A Fass does this VERY well too.

 

[ChrisOlson]

hey klaybus



I to have a 99 dodge CTD less than 70000 miles total I am on my 6th lift pump yes I am mildly bombed I kept waiting for the 1 lift pump that would last I am real good at changing them out now like mad bomber said once you start fluctuating its just a matter of time. I have been watching the posts about RASP and I think that is my next step.



and as mad bomber also said I always carry a pressure tester with a quick connect on the non filterd side of the filter only once was it my sendind unit the wire broke off???

I fixed the wire and victorious it was not the lift pump until 2 months later than it was the lp darn things RASP is in my future

 

[Gary - K7GLD]

After about 20k miles or less I'm seeing erratic pressures. I just replaced the fuel line going to my westach sending unit with a clear line & noticed the following.

Prior to changing the fuel pressure line out I noticed running around town & on the freeway pretty much constant 16 psi but when I got caught at a stoplight after a few minutes my pressure would drop to like 10-11 psi. I assumes my sending unit was going bad & have ordered a replacement unit. The sending unit is on backorder so I thought now would be as good a time to relocate it as any so I relocated it & installed the clear tubing. What I have found is when the guage drops to 10 psi it is truly dropping! I look at the clear tubing & it is no longer as full as it is when it shows 16 psi... . FAULTY LP?

I remember reading something about a internal bypass in the LP? Is this true & it's opening when it's not really needing to? Or in fact does it need to open when at idle & as soon as the accelerater is touched it closes when a greater fuel demand is required?

I got rid of my banjos & stock fuel lines & fittings about 6 mos. ago when I replaced the LP & have never seen better pressures but all of a sudden this scenario has started... ... Any comments or suggestions... ...



Thanks!

Clay

YUP, sounds like cavitation - low fuel flow + high PSI = a tendency for the LP to start cavitating (air pocket and bubbles in fuel) - then once the engine speeds up and fuel demand/flow is increased, normal PSI is often restored. The PSI threshold for cavitation to start varies somewhat, but from what I've seen, it begins at around 16 PSI or so. You can easily duplicate the effect with a removed LP by connecting it up with clear hose in a loop in/out of a container of diesel fuel, and then slowly close off the pump outlet hose by pinching it. As the PSI increases, cavitation starts, and LOTS of air bubbles will be seen in the fuel line - and falling PSI if you also have a guage in the line...

 

[klaybus]

Cativation

YUP, sounds like cavitation - low fuel flow + high PSI = a tendency for the LP to start cavitating (air pocket and bubbles in fuel) - then once the engine speeds up and fuel demand/flow is increased, normal PSI is often restored. The PSI threshold for cavitation to start varies somewhat, but from what I've seen, it begins at around 16 PSI or so. You can easily duplicate the effect with a removed LP by connecting it up with clear hose in a loop in/out of a container of diesel fuel, and then slowly close off the pump outlet hose by pinching it. As the PSI increases, cavitation starts, and LOTS of air bubbles will be seen in the fuel line - and falling PSI if you also have a guage in the line...

Yep,

theres definately some cativation... . Gary, any suggestions or is this the beginning of the end for this LP? I'm kinda interested in the Enterprise Engine Pusher Pump setup but not real sure. Any input anyone? Not looking for super high pressures or HIGH prices just interested in being able to maintain 15-16 psi.



TIA,

Clay

 

[Gary - K7GLD]

Well, if cavitation IS occuring, merely swapping in a new pump won't cure the problem, unless it happens to run at a lower PSI down below cavitation PSI - you need to determine a method to lower the PSI slightly - perhaps there is a restriction - or possibly you will need to install an inline fuel PSI regulator that returns fuel to the tank at PSI above a certain level - say, 14 PSI or so.



Are you adding anything unusual to your fuel that might aggravate cavitation? Mine was doing this a couple of weeks back when I added too much used engine oil to my fuel, but returned to normal once I added clean new fuel to the tank to dilute the oil content.

 

[MichaelRubin]

After about 20k miles or less I'm seeing erratic pressures. I just replaced the fuel line going to my westach sending unit with a clear line & noticed the following.

Prior to changing the fuel pressure line out I noticed running around town & on the freeway pretty much constant 16 psi but when I got caught at a stoplight after a few minutes my pressure would drop to like 10-11 psi. I assumes my sending unit was going bad & have ordered a replacement unit. The sending unit is on backorder so I thought now would be as good a time to relocate it as any so I relocated it & installed the clear tubing. What I have found is when the guage drops to 10 psi it is truly dropping! I look at the clear tubing & it is no longer as full as it is when it shows 16 psi... . FAULTY LP?

I remember reading something about a internal bypass in the LP? Is this true & it's opening when it's not really needing to? Or in fact does it need to open when at idle & as soon as the accelerater is touched it closes when a greater fuel demand is required?

I got rid of my banjos & stock fuel lines & fittings about 6 mos. ago when I replaced the LP & have never seen better pressures but all of a sudden this scenario has started... ... Any comments or suggestions... ...



Thanks!

Clay

I have taken a lift pump apart before and it is a type of gear pump, but the "teeth" of the gear-like mechanism can slide in and out from the center, maybe one of them is getting stuck occasionally.



I would replace the LP, the injector pump electronics will overheat if it isnt supplied with enough fuel flow to properly cool it. You can buy a LP on www.EBAY.COM for about $120. 00



I would not add a Pressure regulator as the other person suggested, the injector pump requires the full flow of the fuel to cool the electronics and for lubrication. If you restrict the flow with an in-line regulator on the return line, you may slow the fuel flow and cause injector pump overheating.

 

[Gary - K7GLD]

I have taken a lift pump apart before and it is a type of gear pump, but the "teeth" of the gear-like mechanism can slide in and out from the center, maybe one of them is getting stuck occasionally.



I would replace the LP, the injector pump electronics will overheat if it isnt supplied with enough fuel flow to properly cool it. You can buy a LP on www.EBAY.COM for about $120. 00



I would not add a Pressure regulator as the other person suggested, the injector pump requires the full flow of the fuel to cool the electronics and for lubrication. If you restrict the flow with an in-line regulator on the return line, you may slow the fuel flow and cause injector pump overheating.

The stock Carter is not a gear pump, it is a rotating vane pump. It looks like THIS inside:



#ad




The stock pump is capable of about 80 GPH at rated PSI, the VP-44 at MOST will flow about 45 GPH, including internal cooling bypass fuel - so in anything CLOSE to normal scenarios, too LITTLE flow isn't likely, but just the reverse seems the problem here, since it APPEARS that when there is minimal fuel demand, system PSI is forcing the LP into cavitation - and exactly HOW will merely replacing one pump with another just like it eliminate the basic cavitation issue?



As far as an inline pressure regulator causing flow problems down to a dangerous, VP-44 threatening level, again, we're only talking about dropping PSI a couple of PSI in a pump that is capable of about DOUBLE the volume the VP-44 can possibly use at maximum demand...

 

[MichaelRubin]

I used the improper terminology for the pump, I didnt know what the "vane" things were called. I saw mention of Air bubbles in the pump in one of your earlier posts, where does the air come from? Isnt air in the fuel system a major problem for a diesel??? If his pressure is dropping, restricting the flow with a pressure regulator isnt going to help??? I could see worn "vanes" getting stuck on the inside portion of the pump and this would cause a drop in pressure. I still dont believe air would cause the problem.

 

[MichaelRubin]

By the way, cavitation is caused when liquids in a pump drop to a pressure below their vapor point and form gas bubbles. How does the LP cavitate during low demand times, when the pressure is at its highest??? This makes no sence!!! Where do you assume the air is coming from?

 

[PKleine]

Maybe it isn't cavitation, perhaps it's stalling from too much back pressure during periods of low demand (like idling). I've had these symptoms with two lift pumps now. It seems to come with the hot weather and go away in the cooler season with the pervioius pump. Oops gotta go... w. o. r. k.

 

[Gary - K7GLD]

Liquids, water for example can be drawn in a vacuum about 22 vertical feet, after that, all you suck is AIR. Where does the air come from in a totally closed environment? Dunno - I just an ordinary fella myself, and no, I don't know all the finer details of where the air comes from when a LP starts cavitating either! But I *do* recognize cavitation when I can clearly see it demonstrated right in front of me, regardless of whether it is caused by too much PSI on the output side, or to much suction on the input side.



As to my suggestion on the regulator, why are you assuming the regulator MUST automatically provide an added significant restriction to fuel flow? Regulators come in various sizes and flow ratings, and most of us are smart enough to install one big enough to NOT unusually impede fuel flow, but only to bypass the few extra PSI that aggravate a tendency to LP cavitation.

 

[diesel DOG]

Mine is doing this agian and it is the lift pump I guess what a POS this truck has become

 

[Gary - K7GLD]

On my '02, I have installed a Carter 9 PSI or so pusher back by the tank, down on the frame rail to force-feed the stock LP - it's what saved my hide while I was experiencing cavititation for a couple of weeks when I had over-oily fuel in my tank - the lower PSI pusher continued to function properly and push fuel even after the stock LP had essentially "vapor locked" from cavitation at it's higher PSI.



While that was going on, I gathered enough standard brass hardware store fittings to make my own bypass regulator to avoid future problems of that nature - but now I think I have a better idea!



I have a brand new spare Carter 9 PSI pusher I carry in my truck's toolbox in case the main one fails - I think at some point I will simply totally remove the stock LP or just run a hose around it to bypass it, and install my spare Carter pusher down on the frame in series with the one already there.



They both operate at a PSI well below cavitation threshold, and operated in series will deliver nearly the same PSI as my current setup. They should also operate a bit more"relaxed" in that mode, since at lower PSI, they are less stressed - and BOTH will be in a pusher configuration at a lower point in the fuel system - should be an added plus.



And in an emergency, all I'd hafta do is remove the stock LP bypass hose, and restore it to service.



Sounds like a plan!

 

[JCoffey]

Gary,



I have looked at your album showing your pusher setup and wonder how you have it hooked up electrically? Do you turn it on and off manually or is it tied in to the stock system? Please elaborate as I am looking at duplicating your setup on my '02. I have gone through 2 Injector Pumps and 3 Lift pumps in 175,000 miles.



Thanks,

James

 

[Mad Bomber]

I've done too worked well for 2 years https://www.turbodieselregister.com/forums/showthread.php?t=34843

 

[Gary - K7GLD]

Gary,



I have looked at your album showing your pusher setup and wonder how you have it hooked up electrically? Do you turn it on and off manually or is it tied in to the stock system? Please elaborate as I am looking at duplicating your setup on my '02. I have gone through 2 Injector Pumps and 3 Lift pumps in 175,000 miles.



Thanks,

James

I bought a Cummins short LP power extender cable to more easily tap into by soldering a pair of wires across it to power the coil on an added Radio Shack relay with 20 amp contacts, and use a pair of those contacts to then power the added pusher pump. That wiring harness then easily connects in between the stock LP and it's normal power connector - lots easier than trying to connect into the shorter harness that connects to the LP - the added relay then mounts to the firewall like this:



#ad




The power lead that now feeds the added pusher is connected directly to the battery thru a 10 amp fuse. In this way, both the LP and pusher are still controlled by the computer, but the added pusher load is not attached directly to the computer, so no danger of overloading or damaging it.



40,000 miles and 3 years, no problems to date, other than my self-inflicted oily fuel fiasco, and THAT disappeared once normal fuel purity was re-established...



Good luck