Engine/Transmission (1998.5 - 2002) Old lift pump vs in-tank lift pump

[Fishin Guide]

It was spendy Bob.



If you look at current list prices for a F1 cam at around $750 plus the 12valve pump I think I paid around $125. But I understand they have gone up some?



The only other "required" addition was the adapters on the inlet and outlet of the pump with some hose at around $20. I have replaced the entire fuel pickup system, ect. You'll need a new front seal for the cover and some RTV or Permatex to seal things up. And throw in one of $1 tabs from Cummins for the KDP.



I would say the average guy would have about 1K into a fuel fix doing what I did. I did this just to fix the failing lift pump issue. I did not count on the side benefits of the cam. In hindsight, I have no idea why I waited so long.



The cam alone was well worth doing the work.



Sounds like the FASS, Airdog, RASP guys are all pretty happy with thier setups. I am happy as well.



Dave

 

[FLynes]

Fishin, if I'm reading this right, you're saying you converted your 24V over to a 12V fueling system? What is a tab and a KDP? Was this an already tested idea or your brainchild? I agree that mechanical beats electrical any day, although both do have their own shortcomings.



Huff, I'm following your posts most closely, but I still haven't really figured out if you're pro in-tank pump or against it. Are you saying that the AirDog, FASS, etc. is overkill for the rest of the stock fuel system? Forgive the ignorance on this (I'm a recovering 3rd Gen owner), but what is this fuel module, where is it located and what purpose does it serve? Does it need to be removed, when you add an AirDog?



Bob, why would the 2nd Gen trucks need a bypass regulator with a mechanical pump setup?



Thanks for all the schooling on the subject. I am greatly appreciative.

 

[jeepit]

FLynes, If you have an intank now you can either get a Draw Straw II and drill a hole in top of fuel tank and disconnect hoses and electrical conectors or you can put the old feul canister back in and work from there.

I am planning on puttting old module back in as a strating point. Then a Draw Straw.

 

[FLynes]

Jeepit, I still have the engine block-mounted pump.

 

[jeepit]

FLynes, Ok. I should have reread your post before responding. Fuel module only needs to be removed if you have an intank pump or if you are doing a Draw Straw.

Fuel module is in tank. It has the float attached to it and fuel line goes down to the bottom of fuel module to draw fuel.

 

[FLynes]

So is this module, for lack of a better word, a pre-pump? Is it electronic? I take it the engine mounted pump needs this module in order to operate?

 

[blacksheepdiesel]

Fred,

Module is simply what Dodge calls the assembly that includes a strainer basket, fuel pick-up, suction tube, return tube and the connections on the top of the tank. The entire module simply pulls out from the top of the tank. There are two modules 1. Original factory stock module that incorporates the suction tube that supplys fuel to the lift pump OR 2. The module that incorporates the in-tank lift pump. If you have the factory module the AirDog will connect with and utilize it. If you have the in-tank pump you must install a factory module OR install a Vulcan draw straw because the in-tank pump must be removed as it is a restriction.

Help?

Godspeed,
Trent

 

[FLynes]

Got it, thanks Trent. I would have just called it an "assembly". I always correlate "module" with something electronic. Makes sense, though.

 

[Fishin Guide]

I didn't come up with the idea of teh mechanical lift pump and cam. But I did get a call asking if I wanted to test some parts. So, that's how it came to pass.



As stated, the module is the entire assembly in the tank that handles the pick up of fuel and fuel level indication. The Draw Straw in a factory module simplpy replaces one of the fittings in the top. It's mounted in rubber. You eliminate all of the factory small hose and fittings internally and replace it with a tube measuring almost 1/2". This is fitted close to the bottom of the tank and you're off to the races.



The bypass is used because the mechanical pump will make over 45psi at idle.



Dave

 

[blacksheepdiesel]

Fred,

Yep, me too! That's the difference between engineers and us common folk! (No disrespect, just poking fun a little. )

Godspeed,
Trent

 

[FLynes]

I didn't come up with the idea of teh mechanical lift pump and cam. But I did get a call asking if I wanted to test some parts. So, that's how it came to pass.



As stated, the module is the entire assembly in the tank that handles the pick up of fuel and fuel level indication. The Draw Straw in a factory module simplpy replaces one of the fittings in the top. It's mounted in rubber. You eliminate all of the factory small hose and fittings internally and replace it with a tube measuring almost 1/2". This is fitted close to the bottom of the tank and you're off to the races.



The bypass is used because the mechanical pump will make over 45psi at idle.



Dave

So, if you're replacing the factory hose internally, do you still keep the 3/8 line outside? Also, is it hit or miss how you place that Draw Straw in the tank? I can imagine that if you place it too high, you're running out of fuel early, and if you place it too low, you run the risk of blocking the tube completely, because it bottomed out.



All in all, are you happy with the conversion? Have you noticed a difference in MPG? Has the ULSD affected the system? I know it's a lot of questions, but I'm just trying to get all the data I can on this, so I don't feel so dumb.

 

[Fishin Guide]

For systems that don't need high flow, the 3/8" line is fine. The key is that by doing this mod you remove no less than 3 restrictions in the draw side of less than 1/4".



You could go to -8 lines, but most likely will never need that much flow.



To place the Draw Straw, it takes testing the height a couple of times and a careful snip. I got mine to barely bump the tank bottom with it fited off the ground. (simulate center sag). Then I used a pair of hose cutters and cut the tube at an angle. I bought a replacement locking ring and gasket before I pulled the module. I did not need either and returned both. But it was comforting to know I had it "just in case".



I didn't get any change in milage or fuel economy. This was simply to supply enough fuel to my VP to keep it happy. No issues with USLD with any of the Vulcan's products.



Asking questions is a good thing! Don't let anyone make you feel you can't ask what you need to know!!



Dave

 

[FLynes]

Ah, so you didn't put on a P7100 pump then (don't know if that's even possible with the 2nd Gen block). All you did was cam and lift pump. I was under the impression that you had totally converted your system to a 1st Gen fueling system.

 

[blacksheepdiesel]

While it is true that the factory suction tube is not the best it has been proven more than adequate when used with the AirDog. The AirDog engineers took into account the factory tube and made sure their product would not suffer adversely because of it. Don't know how, it just is. Putting a Vulcan draw straw in is mandatory if you are removing the in-tank pump (unless you have the factory module) and/or with certain aftermarket lift pumps. While you can install the Vulcan with the AirDog to me it is not worth the hassle of dropping the tank.

Godspeed,
Trent

 

[Fishin Guide]

Ah, so you didn't put on a P7100 pump then (don't know if that's even possible with the 2nd Gen block). All you did was cam and lift pump. I was under the impression that you had totally converted your system to a 1st Gen fueling system.

Nope, just the lift pump!!



It is possible to convert 24 valves to the old 12v pumps. It's not done all that much, but it has been used to make some serious power!



I don't think it's cost effective as a VP fix.



Dave

 

[Fishin Guide]

While it is true that the factory suction tube is not the best it has been proven more than adequate when used with the AirDog. The AirDog engineers took into account the factory tube and made sure their product would not suffer adversely because of it. Don't know how, it just is.

I would disagree in regards to any truck making anywhere around or over 400hp. Not just for raw flow alone, but for taking stress off the pump and reducing aeration/ cavitation issues.



I know the party line about air removing filters, ect, ect. Even if they worked as stated, I would still prefer to make the flow from the tank to the pump inlet as unimpeded as possible.



Why pull a vacuum with a pump? Doesn't make sense.



Dave

 

[FLynes]

In my case, truck is staying bone stock on HP. I just use it to tow my Airstream, Horse trailer and Bass Tracker. I'm not looking to drag race it or tractor pull it.

 

[Fishin Guide]

In my case, truck is staying bone stock on HP. I just use it to tow my Airstream, Horse trailer and Bass Tracker. I'm not looking to drag race it or tractor pull it.

I said that too!



But then again, that was about 400 HP ago. :-laf



Dave

 

[rweis]

Fishin Guide second comment is why. Target is 13. 5 psi, cam lp generates WAY too much psi.



Bob Weis

 

[Fishin Guide]

Who's target? Bosch's?



With a simple bypass in place, fuel pressure is whatever I dial it in at. I did run at well over 40 psi for over 50K with absolutely no issues however. And I am not the only one. All of the early cam/ pump swaps ran at high pressures. No one worried about it. And to date, I do not know of one case of failed VP due to high pressure.



The primary reason for the bypass for me is not to lower the pressures. It is to keep fuel moving through the system and prevernting fuel heating. I get the side benefit of additional filter as well.



Seem's there is no "right" answer as to what is too much pressure. It's well established what is NOT enough. If there is a spec, I am still waiting to see it for the high pressure side.



Dave