Engine/Transmission (1998.5 - 2002) Campaign lift pumps are junk too!

[ThrottleJockey]

Ok here are my questions. How does the vp44 get primed with the mechanical 12v lift pump? How about the fuel pressure, isn't it too much? And how about flow, is there enough? I too have thought about the camshaft swap and everytime I do someone asks me these questions.



Gary

And why can't the RASP perform this same function?

 

[Fishin Guide]

Ok here are my questions. How does the vp44 get primed with the mechanical 12v lift pump? How about the fuel pressure, isn't it too much? And how about flow, is there enough? I too have thought about the camshaft swap and everytime I do someone asks me these questions.



Gary

Okay. Prime on the VP44. The mechanical pump pushes a huge volume of fuel even while cranking. But the VP has enough fuel internally to actually get it started. My truck showed 8 psi before the truck actually lit off. Also, the VP has a bleed hole in the overflow valve. So, it does not hold pressure on the system.



How much fuel pressure is too much? I spoke with many people at length about that issue before doing the cam. Keith at DD has posted they have had no problems even running pumps as high as 50 psi. My setup runs around 20-25 psi.



How much fuel do you need? There is enough fuel from the mechanical system to support over 800 HP on fuel only. That's what I have been told anyway. I know for a fact that it will support 700HP.



Dave

 

[Silver Bullet Ram]

How much does this cam cost? And why we are on the subject of fixing problems, someone needs to figure out how to get these front wheel bearings cheaper.



Gary

 

[obert]

Also, you are not running the volume of fuel that a BOMBed truck consumes.

Yeah... . Less than 30hp/cyl versus 50 or so on my modest pickup.









But the Irony of the day... ... ... did maintinence on the work truck today, started pumping the primer and got a squirt of fuel out of the boot around the plunger. And it took quite a while to get a good idle.





BUT even though the MECHANICAL LP is dying, Id say a little over 320000 miles was a pretty good ride. My first cater elect. only went about 65000.

 

[Texas Diesel]

A question for you with the manuel, er manual, uh MECHANICAL LP's.



How is your idle? When my (latest) LP was going out, the pressure would fluctuate and cause an eratic idle.



Since the mechanical LP is camshaft driven (1/2 crankshaft speed) it seems there would be nothing but pressure peaks, especially at low RPM like idle.



Any comments?

 

[Fishin Guide]

A question for you with the manuel, er manual, uh MECHANICAL LP's.



How is your idle? When my (latest) LP was going out, the pressure would fluctuate and cause an eratic idle.



Since the mechanical LP is camshaft driven (1/2 crankshaft speed) it seems there would be nothing but pressure peaks, especially at low RPM like idle.



Any comments?

My idle is as smooth as it ever was with an electric pump.



Dave

 

[Texas Diesel]

Is the valve timing different for the 12V camshafts?





This sounds like the answer I have been looking for...



What kind of PSI do you read? I read 22-30 from someone else.



Tnx

 

[Fishin Guide]

Is the valve timing different for the 12V camshafts?





This sounds like the answer I have been looking for...



What kind of PSI do you read? I read 22-30 from someone else.



Tnx

The 12V cam is completely different than the 24V. So, the only similarity between the aftermarket 24v cam to the 12v cam is the pump lobe.



The valve timing, lift and duration are all specifically designed for the 24v. And yes, the aftermarket cams vary these parameters from stock to reduce pumping losses as well *** control cylinder pressures and intake/ exhaust timing. Another key in cam design in these flat foot tappets is rate of lift and lift profiling. Let's just say some more work has been done to look at the entire picture by some more than others.



The cam and 12V lift pump is becoming a much more popular option as CTD owners seek a way to fix it and forget it.



Dave

 

[Fishin Guide]

Oh, pressure s vary from setup to setup. Many folks report 19-22 psi at idle, 25 at WOT and 22-23 at cruise. This all has to do with the amount of fueling you are running vs. rpm vs. load.



I was toying around with a custom fuel pressure regulator, but discovered I do not need it. The factory VP44 overflow valve is retained, so hard starts are not an issue as the mechanical pump has to build pressure on every start. The factory overflow has an air bleed hole to help the electric pumps get fuel back to the front of the VP after a filter change, ect.



I can tell you that the mechanical pump works well enough that I do not have to bleed the injector lines to get the truck started after an injector change.



Dave

 

[horned Toad]

Does anyone have a link to the supplier of the 24v cams with the lift pump lobe? Is there a complete kit or do you have to source all the parts?

 

[Fishin Guide]

Does anyone have a link to the supplier of the 24v cams with the lift pump lobe? Is there a complete kit or do you have to source all the parts?

Any of the F1 dealers should be able to help you out. Check out F1 Contact list for more info.



The kit can be bought anyway you want. Cam only, cam and springs, with or without the 12V lift pump and I believe Don M is working on a fuel line kit that will also be available as few different options.



I am currently tring to figure out a tank module mod that will allow larger lines without a bulkhead fitting under the tank and reduce all restrictions. I'll send the info out to Don via e-mail when I get done.





No piece mealing required with F1 products.



Dave