Engine/Transmission (1998.5 - 2002) New Lift Pump Pressure's

[RADdodge]

Hey Dave, you didn't by chance graph the psi/flow/current draw of the Carter pump did you?

 

[15w40]

It took me a while to plot the data but here is the flow rate vs. pressure for a good Carter Lift pump running on 12 volts.



#ad




I hope the link works.

 

[RADdodge]

Good Job...

Beautiful!



That graph says it all. Distills what many have tried to say on the forum for some time. Thanks Dave.

 

[GeneralMachine]

Good Job

Like the chart also all the info.

Harv

 

[zimman20]

RadDodge- I like the idea of disconnecting mods to see what the effects are. I believe I had done this already but I'll have to do it again to confirm now that I have the permanent gauge mounted in the cab. At this point I've got 15-16 psi at idle, solid 10 psi and can't get it any lower at WOT with my EZ. I'll have to get back to you on that!



I'm having a hard time understanding the above graph, however. The LP can deliver 80+ gph at 0 PSI? Am I reading

that correctly? I also don't understand the inverse delivery factor, that the higher the PSI being generated by the LP the lower the volume being delivered by the LP?



We were talking about the DEMAND of the VP44, that the higher the demand from the VP44 the more volume would be drawn/utilized by the VP44 and it may lower the PSI reading at the inlet of the VP44, but that was demand; the above graph refers to SUPPLY, and I'd think that would curve the other way, the higher the PSI being SUPPLIED by the LP the greater the volume being pumped.



Does it make sense that the LP could provide a higher volume of available fuel at close to 0 PSI? Now I AM confused!



Mag- You might think you'd get a vacuum at the inlet of the VP44 at idle if the LP was dead, but you don't; the VP44 manages to draw enough fuel to create a pressure reading that can be read at the Schrader valve at the input to the VP44. It's surprisingly high, my readings would be drawn right down to <0 (vacuum) when under throttle with a dead LP, but read 7 psi at idle. The problem is the strain that this would seemingly put on the VP44 as it is not supposed to be DRAWING fuel, it should be being SUPPLIED with fuel by the LP.



Good thread, IMO.





zman

 

[GLASMITHS]

Zimman20

Go turn your garden hose on without the nozzle attached. See how much water comes out-but no or little hose pressure. Now re-install the nozzle and see how much flow you don't have; yet higher pressure. It appears that the filter and VP44 raises the pressure, yet in the process slows down the volumn.



So from this graph you could expect around 30-35 gpm from a good pump. ??

 

[zimman20]

Good analogy, I can get that one!

 

[GeneralMachine]

Prssure With dead lp

Hey zemman20 Im not sure about cummin's but cat's have a return line orfis, that restrick's fuel back to yhe tank, if our cummin's has some sort of return orfis then that would be why the vp could build some fuel press with a dead lp? you think? Harv