Liftpumps dreams and thoughts.

[rashwor]

Cummins sells a lot of these ISB engins for different applications (I think). Does anyone know if our application is the only one having this many problems with liftpumps? What about the ISC engines? Do they have the same electric liftpump? If the ISC is different and last better, can the ISC pump be fitted to an ISB engine?



I don't believe in bandaids, and I prefer to fix things the first time. Habit of the job.

 

[Steve St.Laurent]

Been there, thought of that. The ISC uses a completely different style of lift pump with two inputs and two output - no way to make it work. As to the other applications of the ISB I don't know if they are having as many problems as us but remember that the majority of the other applications are in medium duty trucks where the fuel tank is a lot closer to the lift pump. Carter's specs for these pumps call for a maximum of 3 feet from the fuel source, saddle tanks on a medium duty are probably pretty close to that. On our trucks on the other hand the tank is more like 10 feet from the lift pump.

 

[rashwor]

Thanks Steve!

Thanks Steve! I am learning a lot here and enjoying it. I want to make as many contributions as I can. I like solving problems. Those pesky ones get me.

 

[Craig DeYoung]

Has anyone looked into this module offered by Racor? It combines the fuel filter with the lift pump in one unit, and the lift pump is of roller-cell design, not a vane pump. . Don't know the pump specs or price, or any details, really. From the web site:



http://www.parker.com/parkersql/default.asp?type=2&id=27





"The new, patented Racor Fuel Conditioning Module (RFCM) was developed for application in any diesel engine fuel injection system. The modular configuration of this innovative fuel filter/water separator incorporates all of the low-pressure fuel system components into a single package.



A key feature of the Racor Fuel Conditioning Module is the durable, roller-cell electric fuel pump that offers the benefit of consistent fuel pressure and delivery regardless of engine speed.



Applications include all diesel engines used in a wide-range of operating environments: on-highway, off-highway, marine, agriculture and stationary. "

 

[Steve St.Laurent]

That's one that I don't believe has been tried. I tried to find it on their price list but couldn't. Some of their prices are WAY out there - their fuel filter/water seperator assemblies seem to be in the $200-$300 range, it looks like the ones with fuel pumps are in the $1000+ range - couldn't find that one specifically though.



-Steve

 

[Un-Hemi]

Easy, Steve, don't frighten everyone off Racor. I've been pricing their stuff and the filter/separator I am interested in is less than $200CAN (good guy price) with the water sensor, no heater. That's about $130US.



This Fuel Conditioning Module could be quite different. Unless there is more information posted tonight, I'll be phoning Racor in the morning.



Tom

 

[csutton7]

TT-I'm fairly sure that Craig is talking about a pump and filter that's an all in one component and that Steve is right in that it will be pricey--not sure about $1000, you are talking about a filter/water separator w/heater---I've been using one for 10 months now, the Racor R90, so far so good---it has 3/8" or 1/2" ports and can be mounted in any direction as long as it's horizontal---I mounted mine in the factory location by fabbing a bracket-----when I bought it it was more expensive than $130, but was under $200..... chris

 

[rashwor]

E-mailed racor / parker.

I emailed racor / parker yesterday and asked them about the specific unit mentioned earlier in this post. Here is the reply they sent back:



Mr. Ashworth, the aftermarket fuel condidtioning module you are asking about does not have a continuous running pump. The pump is designed to operate when a button is pushed on the control panel. We do make a continous running model, however it is designed for specific applications.

We may offer a kit in the future to fit the your application, however it

will depend on volume and of course demand. I have copied one of our

account managers. He may be able to tell us if this pump failure is a

common problem. On a similar note, the pump may be failing due to

inadequate filtration. You might try installing a Racor 660R30 fuel filter

water separator between the tank and the pump. Any questions, please let

us know. Thanks, TH



Please provide us a permanent fix, Racor!

 

[Un-Hemi]

Thanks for the update, rashwor.



Of course, obviously, when the pump in this RFCM does quit, it will be quite expensive to replace the whole assembly. Better to have a separate pump and filter anyway..... and a FP gauge.



Tom

 

[weatherbyman]

Electrical After tank pump

Why can't a booster pump be used to pressurize the inlet of the lift pump with fuel, to make sure it doesn't have to do all of the work?



Can one be installed right after the fuel tank? Would this thrash the lift pump?



Mike

 

[Steve St.Laurent]

Mike - that's exactly what I and many others are doing. here's a link http://128.242.249.86/forums/showthread.php?s=&threadid=19767 . I have 40,000 miles on that setup so far and see a minimum of 16 psi at WOT, previously I went through four stock lift pumps in 60,000 miles.

 

[A Johnson]

Rashwor, back to your original question. Can the Isc lift pump be retrofitted to the ISB? I beleive so, although I have not thought this through completely. It would take a little work and enginuity( however it's spelled) as you would need a place to mount it and some plumbing changes. The Pump itself would not last any longer in my opinion as it is the same motor on the pump.

It tends to last longer on the ISC engine because it only runs for two minutes at engine start up and then shuts off. This is a function of the ECM so if you did put it on an ISB it would run continously and hence the same life expectancy. The advantage to the ISC lift pump in my humble underated opinion is that it has a bypass built in it and if the motor were to fail the vp-44 would be able to pull fuel from the tank and not burn up due to fuel starvation.

Also remember that you want less than 5psi inlet pressure during engine cranking or you can get into hard start situations due to the way the fuel flows inside the vp-44. With more than 5 psi it can hold the shoes that ride on the high pressure pumping camring, off the camring, resulting in no high pressure fuel to the injectors.

To those that are putting aftermarket pumps on, I commend you and hope some one finds a good solution to the lift pump issue. I think it will take some time before there is a definate answer as to which setup is the best. AJJ

 

[15w40]

If your stock lift pump fails the way mine did, the pusher pump will not help gain a longer life. My original lift pump started to show erratic pressure readings and lower pressure at idle and at WOT. I found that the internal spring that is used to set the max pressure at about 15 psi had fatigued and caused the spillover valve to recirculate the fuel within the pump and lower the pressure. This valve consists of a spring and ball valve that is used to limit the maximum pressure, protecting the pump if it is deadheaded. Because the pump runs at 5000 RPM and is a 4-vane pump, the spillover valve ball and spring are constantly vibrating at about 300 cycles per second. After about 50K miles (or less) the spring gives up. Some people have been lucky and have seen no problems with more than 100K miles.



Adding a pusher pump will create a positive pressure at the input to the factory lift pump but will not help with the spillover valve failure. If you think about how this all works you can see why. The lift pump is capable of creating almost 30 psi of pressure if the spillover valve is disabled. The spillover valve is set (when good) to limit the outlet pressure to be about 15 psi greater than the inlet pressure. This is true whether there is a negative pressure at the inlet (stock situation) or with a pusher pump creating a positive pressure. If the pusher pump is making 7 psi, for example, the (good) lift pump will add another 15 psi for a total of 22 psi. The spillover valve is working just as hard as it was with out the pusher pump installed. The lift pump life should be the same as before.



I should also add that my experience with the lift pump problem came from tearing apart one that shows low, erratic pressure and may not be the only way these fail. If you see fluctuating pressure readings from minute to minute, it is most likely caused by the spring in the spillover valve.

 

[swalls]

ISC pump

The electric lift pump on the ISC runs for only 30 seconds after ignition is turned on. The main difference is the ISC injection pump contains a huge spur-gear type transfer pump that maintains a minimum of 180 PSI, at WOT & max load, in the pumping chambers of the two cam-operated delivery pistons. This gear pump is so strong that it routinely sucks a non-essential plastic check valve out of the electric lift pump outlet port. (You find it laying in the top of the fuel filter, it has no effect on the engine's operation. ) If the dinky VP-44 had a decent transfer pump, the electric lift pumps on the ISB would only have to run for 30 seconds also. The mickey-mouse internal fuel transfer pump used in the VP-44 seems to be inherited from the older Robert Bosch pumps, the CR & VE series. It wasn't much good on those series either; has a long history of wearing out and losing transfer pressure. Also had an extremely nasty habit of developing a bad diesel fuel leak into the crankcase, because it was located in the very front part of the injection pump, and the pump drive shaft seal is all there was to keep fuel in and keep oil out. Anyways, I doubt that the ISC electric lift pump would live very long running full time. The "fail-safe" dual lift pumps in parallel setup seems to be the only thing working right now, due to the poor reliability of the OEM pumps. Unless somebody comes up with a better solution, I will be putting one on my 98. 5 before I do any towing.

 

[PRout]

Originally posted by 15w40





Adding a pusher pump will create a positive pressure at the input to the factory lift pump but will not help with the spillover valve failure.



The spillover valve is working just as hard as it was with out the pusher pump installed. The lift pump life should be the same as before.

What about eliminating the original lift pump & using the one from Enterprise Engine, or that type?



Dont we just need a good quality reliable pump thats close to the tank?



How about 2 in parallel w/ a manual bypass valve & switch/relay to send the power to the backup pump in case 1 quits out in the boonies? Hopefully you'd have a pressure gauge to know before the VP44 is affected.

 

[15w40]

Shortshift, you hit the nail on the head when you wrote, "Dont we just need a good quality reliable pump thats close to the tank?" I think this would solve problem but after reading this forum for several years, the reliable pump seems to be illusive. It is hard to believe that Cummins could not have seen this problem when in trials with the ISB engine. I can only think that when bench testing this engine, fuel was supplied from a source not using the Carter lift pump.



One idea that I will try out soon is to eliminate the pressure pulsations created by the lift pump and also by the Bosch VP44 inlet pump. These rotary vain pumps both create fuel pressure pulsations. My idea is to install a pressure damper at the output of the lift pump. This damper would be similar to a hydraulic accumulator except designed for a pressure of 15 to 20 psi. By soaking up the fuel pulsations, the spillover valve spring would not be constantly vibrating and should last forever (well almost forever). The problem is it might take several years of driving before I get my answer.