Engine/Transmission (1998.5 - 2002) I have new info on 24V LP issues...

[nps]

no matter what pressure you can only force so much fuel through any certain size line.

Agreed at pressures much higher than seen in the CTD fuel delivery system, but the theory about the pickup tube being the 'most restrictive part' doesn't hold water in my mind because it is upstream from the pump.



If the pickup was the weakest link, then it seems you would hit a wall where you couldn't build any higher pressure at the VP inlet no matter how many pumps you put on. Also, under high demand you would always see the VP inlet pressure drop to zero or a vacuum for lack of fuel flowing through the pickup tube. This doesn't happen at 300-350HP.

 

[steved]

Agreed at pressures much higher than seen in the CTD fuel delivery system, but the theory about the pickup tube being the 'most restrictive part' doesn't hold water in my mind because it is upstream from the pump.



If the pickup was the weakest link, then it seems you would hit a wall where you couldn't build any higher pressure at the VP inlet no matter how many pumps you put on.

I agree, with my FASS on, I get very little (if any) cavitation while the pump is running. The only factory fitting left between the tank and the CP3 is the in-tank pickup tube.



I was able to hold 25psi at the CP3's inlet with no cavitation of the 95/150 FASS to speak of...



steved

 

[cyborg]

Here is a link to the numbers from an Edelbrock pump.

Its from Essex and I have this pump.



As you can see... less pressure, more flow/volume.

Pressure equates to resistance. However, one must have a balance for the combinations out there with the VP-44 trucks and whatever power mods they have as well as the CP3's on the 3rd gens.

Lots a variables. Scotty

Uh, yes and no. This is where the application of theory goes awry.

the flow vs pressure demonstrates the theoretical capacity of the pump. At an open butt you may have zero pressure and max flow. As you apply restriction (smaller line, discharge oriface) you increase the pressure while reducing the flow. Just because you have a decrease in pressure does not mean an increase in flow. If it's because you reduced the restrictions by increasing line size.



Does diesel eat aluminim?

 

[nps]

Does diesel eat aluminim?

Hope not. Otherwise alot of problems down the road for the Duramax. :-laf

 

[WyattEarp]

My thoughts exactly on that nps... if it does eat aluminum then i would hate to be the duramax owner driving down the road and the pistons come through the hood and over the cab because the diesel ate the heads up LMAO...

 

[cyborg]

Hope not. Otherwise alot of problems down the road for the Duramax. :-laf

I read that last night and it didn't sound right.



Either way a lot of problem for the dura-max down the road.

and up the road.

but mostly, on the side of the road.

 

[WyattEarp]

Well as we all know any diesel engine especially a larger truck engine with that kind of compression ration, Aluminum heads cannot work right, i agree they might work for some time but, in theory and my opinion a diesel with any aluminum in the heads, block whatever just isn't diesel... this going lightweight and cost effective methods might work for a gasser but in the long run, a true diesel man knows that aluminum in a diesel just ain't all its cracked up to be, i mean warped that is

 

[steved]

I read that last night and it didn't sound right.



Either way a lot of problem for the dura-max down the road.

and up the road.

but mostly, on the side of the road.

Well, maybe and maybe not... does anyone know for sure that the CP3 on the duramax is identical to the CP3 on the CTDs??? It might be designed to the point it doesn't need a pusher pump, whereas the CTD might actually need the pusher... make sense??



I'm not really sure I have read anywhere that the CP3s between the GM and Dodge diesels are "identical" in design and requirements.



I agree about the point on aluminum heads... didn't the DMax have issues early on with cracked heads??





steved

 

[Timbeaux38]

The high HPO dmaxes run lift pumps. .



I'm about to install some pumps from Kennedy Diesel on my truck to see if they will work well in this application as well...



Look under lift pump in the duramax parts section



http://www.kennedydiesel.com/

 

[Huff N Puff]

nps,steved is right,the pickup tube in the tank is the weak link

Agreed at pressures much higher than seen in the CTD fuel delivery system, but the theory about the pickup tube being the 'most restrictive part' doesn't hold water in my mind because it is upstream from the pump.



If the pickup was the weakest link, then it seems you would hit a wall where you couldn't build any higher pressure at the VP inlet no matter how many pumps you put on. Also, under high demand you would always see the VP inlet pressure drop to zero or a vacuum for lack of fuel flowing through the pickup tube. This doesn't happen at 300-350HP.

BECAUSE any pump outside the tank depends ONLY on atmosphereic pressure to get the fuel to the pump. So if the pump pushes the fuel faster than the suction line can flow it,it cavitates and frothes the fuel. If the pump is in the tank it does not have to draw it thru a long section of restrictive line,the only other way is to install a bigger line into the tank. Mopar has concluded that the old fuel module cannot flow enough fuel for 235hp.

 

[PatrickCampbell]

Any thoughts on how a bottom fuel feed helps or doesn't. I installed a 3/8" bottom fuel feed a while back and have not had any problems. I debated between tank -> pump -> filter -> vp44 and tank -> filter -> pump -> vp44. Right now I have the pump before the filter. I can't pull it below 8 or 9 PSI at WOT with a CaTCHeR and 275's.

 

[rweis]

Huff N Puff

BECAUSE any pump outside the tank depends ONLY on atmosphereic pressure to get the fuel to the pump. So if the pump pushes the fuel faster than the suction line can flow it,it cavitates and frothes the fuel. If the pump is in the tank it does not have to draw it thru a long section of restrictive line,the only other way is to install a bigger line into the tank. Mopar has concluded that the old fuel module cannot flow enough fuel for 235hp.



I think this is "one" of the MAIN issues with the 2nd gen fuel systems. One of the TDR members (CStewart) has a really good thread on taking the fuel canister apart and replacing the hardware. Special note is replacing the fuel pickups with larger diameter piping and replacing the barb coming out of the tank with a full 3/8 line. He also has CNC'ed new cannister top plugs for full flow (I got mine for $68 for both and USPS shipping).



Getting the restrictions out of the fuel system is a key issue all the way from the liquid fuel to the VP44 return line.



Bob Weis

 

[steved]

Getting the restrictions out of the fuel system is a key issue all the way from the liquid fuel to the VP44 return line.

I think this holds true for any fuel system... even the 3rd gens...



steved

 

[JWBoothe]

Is it difficult to change a faulty lp after it is moved into the tank?

 

[nps]

Is it difficult to change a faulty lp after it is moved into the tank?

No, not after you get the tank on the ground.

 

[steved]

No, not after you get the tank on the ground.

... or remove the bed... by far easier than removing three nuts, two banjos, and a wiring harness...

 

[WyattEarp]

if there is enough room between the bed and the tank to remove the pump that would be the best way, im not familiar with it as i haven't(knock on wood) had to deal with a lp issue so far...

 

[JWBoothe]

No, not after you get the tank on the ground.

Why is DM/Cummins not mounting the lp low along the frame for ease of install/removal and gravity feed?

 

[Fishin Guide]

Well, I think it's to protect the pump and to put it where it belongs. And that's pushing fuel. Submerged is best for the electric.



I think there should be a bigger, heavier duty pump and larger lines to the top of the tank. Then it would probably last forever. Although, it does not help guys that are going to heavily modify thier trucks anyway.



Dave

 

[amnewsom]

I dont think your sled puller is going to go in for a LP replacement at his local DC house. Its the guys who dont know any better (non-TDR) or those who didnt know they were going to do the in-tank on thier truck.



I have some mods, I replaced the LP on mine on my dollar, when the VP went I took it in and let them handle it. If the LP goes again I will replacement my way again. I am not going to risk draining anywhere from 10-30 gallons of diesel fuel from a tank to replace a POS stop-gap bandaid of a pump.



Next $100 in my pocket the Vulcan relocate kit is going on my truck.



Rant off.