Pictures of a Disassembled Lift Pump

[TPlasek]

My 2000 with the original lift pump recently died at 80k. I took the pump apart to see what caused it to fail. This is what I found...



I had lift pump that produced 7 psi when you turn the key on and drops to 0 after the motor starts. Toady I took the top cover off my lift pump. I saw the 4 blades of the vane pump. I can not find any defects with the vanes or the housing that the vanes spin in. I pressure checked the relief valve and it opens at 12psi, so that was not the problem. The brushes had lots of life left in the but the center portion of the electric motor, the part where the brushes ride, was very worn. I wished I had a way to fire up the electric motor and do an rpm, current, and voltage test, but I do not have the tools to do so. It looks like in my situation the motor portion of the lift pump has failed and not the pump portion. My question is, could this problem be caused by low voltage or vibration??? Does the pusher pump / larger fuel line ease the load on the motor thus making it last longer???



I had to trim the pics down to be able to post them on this site. If anyone want the high quality originals, just email me.



This is a picture of the lift pump with the cover removed. You can see the 4 vane rotor pump.

 

[TPlasek]

This is the motor section with the top pump portion removed. I was suprised to find that the motor portion is designed to be full od diesel...

 

[TPlasek]

This is a picture of the bottom of the pump section that sits on top of the motor. The output is on the right side. The output goes to both the VP44 and the hole you can see lets the overflow go down into the motor section. The ball on the left is the spring loaded relief valve that puts the unused pumped fuel back into the inlet side so not to overpressure the system. My spring opens at 12 psi.

 

[TPlasek]

This is a picture of the rotor and the vanes removed from the pump...

 

[TPlasek]

Although a little out of focus, This is a picture of the center shaft that connects the motor section and drives the pump. You can see how worn the portion is where the brushes rub. This was the only visable problem I could find with my pump. I would like to know if this is a voltage problem, too much spring tension on the brushes, or too much stress on the pump. I am turning this section down with a lathe and I am going top try to put everything back together to see if it works on a test jig.

 

[Shovelhead]

Great detective work.



Keep us advised.

 

[Diesel Freak]

Great Pics!



The Commutator looks very worn... use a dressing stone once you get it turned down. . or if you do not have a stone use 1000grit emory cloth to polish it. once done check the spaces (insulation) between the segments for possible high spots, and cut them down to allow the brushes to ride smoothly on the commutator.



When I took my old lift pump apart, the pump end looked great... . no apparent damage at all... . it was just not producing satisfactory discharge pressure. It ran slower when it cycled prior to starting, and once warm, pressure just got lower on a weekly basis... .....



I think you have hit on something here... . the problem may not be with the pump end, but possibly the motor... . once the commutator gets worn this bad, the brushes do not sit flush with the segments, and hot spots develope in the points where the majority of the current passes from the brush to the commutator segment... the end result is more wear and voltage loss from the high resistance connection which causes a higher current draw... ... the end result is the brushes and commutator continue to wear at an increased rate intill failure occurs.

 

[RoryTek]

Allthough I don't have a 24 valve here is a suggestion. If you can hook up an amp and volt meter to the pump and watch what is going on during running conditions you might see something going wrong. Of course you will need a baseline. So maybe someone will hook up a meter to a brand new setup and lay down the their baseline.



Just make sure it is published here.

 

[abledog]

Great post Thanks for taking the time to investigate what has turned into quite a problem for a few of those with 24V motors. Please keep us informed.



Thanks

Terry

 

[JR2]

At our las Alaska Bombers meeting we did the same thing. We found a failed lift pump on a guys truck and tore it apart. Once we checked the vanes we removed them and then powered up the pump with 12v. It spun up fine and we stopped there. The guy was going to return the pump for a warranty claim so we did not go any further. I may check with the guy and see if he still has it. It may be worth checking and seeing if it had the same problem as yours.



Now if we could just figure out a soloution.







By the way... great pics

 

[badams1]

I have a question here about the motor brushes. Are they cooled and luricated by the fuel? Great thread, thanks for the excellent info. -- email address removed --

 

[TPlasek]

Badams,

To my suprise, the motor section of the lift pump resides in a bath of diesel oil. The pump will continue to push the excess diesel fuel through the electric motor section and circulate it back into the inlet side of the pump. So unless the VP 44 is using all the diesel that the lift pump can pump, the lift pump motor with have a continous flow of diesel to keep the motor cooled and lubricated.



I can't get to the lathe until monday. I will try next week to clean that comunicator up and see if the pump comes back to life. I will then compare the voltage and current draw to my new one that is on my truck. I'm still not sure why the communicator was so worn relative to the brushes. The brushes looked like they very little wear. One note. . there was a lot of spring pressure holding the brushes on the comunicator. More then I thought necessary(IMHO)!!

 

[illflem]

TP, a lathe may be an overkill, just put the shaft in a drill chuck to spin it and use fine emery cloth on a popcycle stick. Also use a scribe to make sure the separations in-between the communtator sections are clean. Motor shops sell an abrasive stick that is made to clean the communtator while the motor is running, not possible in this situation but could be used with a drill. I have to do this quite often on one of my chopsaws to keep it running.

 

[Rockcrusher]

Originally posted by TPlasek

Badams,

To my suprise, the motor section of the lift pump resides in a bath of diesel oil. The pump will continue to push the excess diesel fuel through the electric motor section and circulate it back into the inlet side of the pump. So unless the VP 44 is using all the diesel that the lift pump can pump, the lift pump motor with have a continous flow of diesel to keep the motor cooled and lubricated.



I can't get to the lathe until monday. I will try next week to clean that comunicator up and see if the pump comes back to life. I will then compare the voltage and current draw to my new one that is on my truck. I'm still not sure why the communicator was so worn relative to the brushes. The brushes looked like they very little wear. One note. . there was a lot of spring pressure holding the brushes on the comunicator. More then I thought necessary(IMHO)!!

Sounds like the brush material is too 'hard'. The should be "sacraficail" and go before the commutator.

I have amp meters etc and will try to take readings on my truck. / Its new so maybe can get a baseline as suggested.

Will post the results.

 

[dseabaugh]

I would like to know where all the 'debris ' from the commutator is going? Diesle fuel is non conductive to it is alright to have it in the pump other than the increased load and temperature (?) it may cause. Isn't it posssible that the commutator on the armature is causing a windage and making it more or less run dry?

 

[Diesel Freak]

Originally posted by dseabaugh

I would like to know where all the 'debris ' from the commutator is going?

look in the bottom of your fuel filter housing next time you change your filter

 

[tgbol]

Your pictures don't show the connector between the rotor and the motor shaft. There is a plastic insert with a slot that the shaft goes into. When I took mine apart the plastic came out in 2 pieces. The shaft was turning in the rotor. The rotor was still turning but I only had 3# pressure.