"I look at it this way, the stock lift pumps die mostly because they are "pulling" rather than "pushing"."

I don't mean to cause trouble here, but that is a fallacy. It doesn't make any difference to the pump if it pulls or pushes, provided it doesn't run dry. The pressue differential across the pump is what matters and it is the same whether the pump pulls or pushes. The motor load is the same. The forces on the pumping element are the same. No difference.

"So if I can keep it fed by the Holley (lets say 9psi), the LP has plenty of fuel, and then it up's the pressures another 6-7 psi. The Holley is in spec, the stock LP is getting fuel, and the CP3 is getting fuel."

Until the stock lift pump dies and then the Holley dies and the CP3 starves. Then you need to replace all three ! People say you can push fuel through a dead stock lift pump, but I don't know about that. And when the stock lift pump dies, your Holley is over worked because not only does it have to feed the CP3, it has to push the fuel through the dead stock lift pump.

I believe you are talking about the engine mounted lift pump here. It has a very poor service record. I would replace your setup with something before it strands you.

"As for the LP going south, so can a FASS, Walbro, etc, they all can. But if you can keep the stock LP with fuel and make its life, it will last longer."

Not all lift pumps are built the same. The things I've been talking about like % rated load, brush area, cooling, etc. all make a big difference. I would expect huge differences in the life expectancy of a carburetor type pump running at 100 or 150% of its design pressure and a Walbro (or Bosch) running at 25% of its design pressure. Night and day. Like the difference between a diesel and a gasser or more.

"how high of a pressure can be fed into the CP3 before it says "Adios" and you start to get leaks???"

Well... this is another interesting topic. The CP3 internals are fed by a constant volume gear pump. You can feed the gear pump ANY pressure you want until it blows the seals in the gear pump part of the CP3. I ran mine for a day at 60 PSI+ with no ill effects.

The CP3 gear pump increases the inlet fuel supply pressure (say 15 PSI) up to the internal CP3 pressure, which is 80 to 180 PSI, according to the 05 shop manual. So, I would say the CP3 could take at least 180 PSI before it would get hurt. The FCA controls this pressure, so even if one tried to feed it more pressure than that, the FCA will just dump it to the return line. It is probably impossible to damage a CP3 by over pressuring on the inlet.

I'll go on to say that none of the CP3 seal issues are related to over pressuring by the lift pump. Conversely, I'll go out on a limb here and say that I strongly suspect that the CP3 seal failures are due to lack of fuel supply.

There are only a few things that will take out a seal that works good for a while. Heat and running without lubrication are the two most probable. Those seals are sealing the 180 PSI pressure inside the CP3. They are not sealing 26,000 PSI.

 

Well the dealer is going to swap out the engine mount for the in-tank this weekend, then it will be feeding the holley.

 

Not to try to take anything away from what has seemingly become a holley vs walbro thread, what do you guys think of the RASP setup? Aside from the price, it seems to have some advantages in reliability/durability, however I wonder what happens if the stock lp dies, as it's incorporated. Maybe there's an easy answer - I haven't done that much research. Just seems like the rasp may be a nice setup as well.

 

"The Holley Blue come with an external regulator that is adjustable. If you don't use the regulator, it will just run "WOT", until the factory regulation limits the total system pressure.
If his system does not have the regulator(s) installed, it would 14+14=28 psi total pressure."

That will only work if the regulator in the second fuel pump is one that regulates the fuel pump output relative to the input, which I doubt is the case. If it is just a spring and a ball then the second regulator needs to be set at 28 PSI and the specs say 14 PSI is maximum.

"I agree with what your saying on the volume vs psi thing but want to piont out the 2nd gens had no where near a 3/8" delivery. The holes in the 5 banjos are tiny ( I cant remember off hand the exact size 1/8"?) so when the fuel delivery issue reared its head the fix was more in the restrictive fittings than the line."

OK. I've never owned a 2nd gen.

"It was tough to come up with anything to addapt to the factory lines other than drilling out the banjos which made them weak so a line change was eazier. I dont know what size the third gens have for fuel lines but on my second gens the steel line fits inside 3/8 rubber fuel line."

I think the 3rd gens are 3/8" on the engine. I'm not sure.

However, as restrictive as those Banjos are, someone thought they could deliver enough fuel to the pump for 250 HP at say 8 PSI.

To double the flow through the system, you have to quadruple the pressure.

So, for 500 HP you'd have to double the fuel flow or quadruple the pressure.

8 PSI x 4 = 32 PSI. This is well within the pressure capability of the Walbro.

There is a very easy way to test this. Just disconnect the return line before it goes back to the tank and route it into a 5 gallon pail. Get your stop watch out and you'll soon see how much flow you have with the restrictive banjos.

This test only works properly if you route all the fuel through the filter and the relief valve is located at the pump, which I highly recommend anyway.

 

"Not to try to take anything away from what has seemingly become a holley vs walbro thread"

I didn't mean for this to become a holley versus walbro thread. I did want to compare carburetor versus fuel injection type pumps and I only have specs for the Walbro. If I had specs for the Bosch I'd be using them because it is a good pump too. It runs in the 99+ Superduties at 60+ PSI for years and years.

"what do you guys think of the RASP setup? Aside from the price, it seems to have some advantages in reliability/durability, however I wonder what happens if the stock lp dies, as it's incorporated."

I don't know anything about it. If you get us some info, like pump curves and preferrably post them in this thread as an image, I am sure it will get discussed. That goes for any other pump too.

Are you telling us that the RASP isn't self priming and that it needs a stock lift pump to feed it ? If so, I have no use for it.

 

For some reason when people think lift pump they think FASS. Why ? I can't see that it does anything that the Walbro or the Bosch don't do.

Why? I'll give a couple of my reasons. First it was recommended by Piers and everyone I talked to. I like the filtration setup and get the filters from cummins. Four year warranty a plus and the success/history of the fass pump made my decision. Yes it was expensive, but I find it a convienent off the shelf proven system that was quickly and easily done.

 

Afternoon SD...I've been reading quite abit about your Walbro pump on your Ford/Cummins. Maybe you can give me some quick advice. I respect what you've done and what you've said about the stock pump setup on the Dodges'. I have an 05' with intank pump. Is there anyway that you think i can engineer a similar setup to what you have while leaving my stock pump in the tank and operational? I agree with you that I shouldn't wait for a problem and I'd like the added insurance of the extra pump feeding my CP3. Thanks in advance if you can help.

Tony

 

"Why? I'll give a couple of my reasons. First it was recommended by Piers and everyone I talked to."

No disrespect to Piers, but if we open up a discussion on fuel pumps in general then people can make decisions for themselves.

"I like the filtration setup and get the filters from cummins. Four year warranty a plus and the success/history of the fass pump made my decision. Yes it was expensive, but I find it a convienent off the shelf proven system that was quickly and easily done."

OK.

How about getting us a flow curve for it so we can compare the pump part of it ?

BTW: for those that are interested in finer filtering, the VW TDI guys are running a big Cat 2 micron filter on their engines. I think the filter part number is 1R750. I think one can use that filter with a standard big truck filter housing, a $20 part. You guys can do the homework on this.

 

"Is there anyway that you think i can engineer a similar setup to what you have while leaving my stock pump in the tank and operational? I agree with you that I shouldn't wait for a problem and I'd like the added insurance of the extra pump feeding my CP3."

I'll leave you to sort out the warranty implications of this.

One could argue that if the stock in tank pump fed the Walbro it might live <forever ?> and could thus be left in there. How much load the in tank pump has will depend on its flow rate relative to the Walbro. However, should it ever fail, then the Walbro is going to starve. Your call.

One could drop the tank and put the Walbro in the tank. I suspect it might fit right where the stock in tank pump goes.

One could fashion a second fuel pickup for the Walbro, leaving the stock pump and pickup in tact. For regular use the Walbro (or Bosch or...) would suck from the second pickup and circulate the fuel to the CP3 and back via the bypass. If the truck ever had to go into the dealer, you could remove the Walbro, reconnect the in tank pump and remove the CP3 bypass, putting it back to stock. Except if they look on top of the fuel tank they might notice a second fuel pickup.

If I owned a Dodge and it had the engine mounted lift pump on it, I would mount a Walbro on the frame, install the CP3 bypass and be done with it.

If I owned a Dodge and it had an in tank pump, I would for sure mount a pressure gauge and watch things. If I was nervous about the in tank pump, I would drop the tank, put in an 03.5 fuel pickup and mount the Walbro on the frame.

The thing about the Walbro on the frame is that it is easily accessible. Dropping tanks is a pain. With the Walbro feeding a bypass'd CP3 I figure it will run forever at 10 PSI and I can easily get to it if it fails. I would never have to worry about fuel pumps again.

If I was really, really paranoid, I would carry a second fuel pump and tools to change it.

Over Christmas I read several posts about people being without their trucks for a few days while the dealer got them a new fuel pump. Considering the failure could happen at any time and anywhere, I'd at least want the pump mounted on the frame so that I would not be at the mercy of the dealer. Nothing against dealers, but they aren't always open. And losing the use of your truck at the wrong time can be a big pain.

Just my $0.02

 

No, and no thanks. 2 years without a hitch... the setup I run has worked well for me. If it fails I'm going mechanical.

my fault, I thought you were talking about a stock truck. It's not restriction that pulls the pressure down that far... it's just the system seeking it's point on the pump curve. Believe me when I tell you, though, that banjo bolts in the stock system are a major restriction at the 500 hp level.

No, not two holleys in series, although that would work. My pumps are in series. The internal regulator of the 2nd pump won't limit to 14 psi total... it's 14 psi above the inlet pressure. the internal regulators reference their pressure off the pressure of the fuel seen at the inlet. The check ball sees the outlet pressure on the out side and inlet pressure plus spring pressure on the inlet side. Outlet pressure will always be 14 psi or about inlet pressure unless you mess with the spring load.

 

I also didn't intend to hijack the thread into a holley vs. walbro thread... my apologies for that. IRT Lightman, IMO the RASP, DonM's cam driven mechanical pump, or a custom mechanical setup is the best of all the worlds. The 12V trucks VERY rarely ever had a problem with their cam driven lift pumps, and there are numerous trucks out there with 500,000 miles and more. Even the best electrics out there are inferior to these mechanical setups. The main downside is cost and complexity of retrofitting. The main thing I dislike about the RASP on the 3rd gens is the requirement to clip the fan blades, but that's probably a minor nuisance compared to the benefits.

 

Thanks for clearing up the regulator stuff, Bansee. It was a good discussion of fuel pumps, regardless of brand. And that was the purpose in the first place.

 

Thanks for explaining it better than I could gypsyman. Superduty - more info is available on the rasp at www.dieseltrans.com and koengineering.com . Would appreciate your comments since you seem quite well versed in the fuel pump arena!

Banshee - I believe dtt has pre trimmed fans they will trade with a core charge and possibly some $, not sure if they're available yet.

I still think the rasp is what I'm leaning towards..hardly anything to wear out and no additional noise like the fass.

 

The fan was really no problem at all. Took longer to break the nut loose than to trim the blades. Make a template about 1/2" wide from some scrap cardboard, scribe the rear edge of each blade, trim with a jig saw, clean up edges with a file, re-install. Can't even tell anything was done. Less than 1 hour total...

Richard

 

If you guys are limiting your pressure to 18 PSI, then why do you need an engine driven pump ? I don't understand the need for a belt driven pump when I feel that an electrical pump could more than do the job ?

Once again, I think the perceived requirements of the fuel system are blown way out of proportion, flow wise. Go back and look at my flow numbers for various HP levels. That is all you need, actually delivered to the engine. I think the problem lies in that everyone is using carburetor type pumps rated at big GPH flows, but short on pressure. Their flow rates are falling off on pressure OR the pumps are wearing prematurely and the flow rate is dropping and that is where the problem lies. Or the pressure regulator is in the wrong location.

If the use of the RASP is to stop pressure drop as the engine speeds up/flow increases, that can be overcome by plumbing an electrical pump differently.

Put a Walbro in the truck. Put the pressure relief at the pump and set it for 20 PSI. Go to WOT. I guarantee the pressure doesn't drop.


Let me explain the pressure regulator location bit.

Lets say our engine uses almost no fuel at idle and uses 40 GPH at WOT. Lets say the pressure drop across the filter and lines is 10 PSI at 40 GPH but nearly zero at idle. Lets say our pump will output 50 GPM at 50 PSI.

Setup # 1: regulator at the lift pump.

We idle our engine and set the regulator so that we have 15 PSI at the lift pump. At idle the pressure drop across the filter and lines is 0 PSI. So our regulator is set at 15 PSI as well. Everything is fine.

Now we take the engine to WOT. The pressure drop across the filters goes to 10 PSI. Our regulator located at the lift pump is still set to 15 PSI. The pressure at the injection pump drops to 5 PSI. In spite of this our regulator is still returning fuel to the tank ! No good.

Setup # 2: regulator at the injection pump.

We idle our engine and set the regulator so that we have 15 PSI at the injection pump. At idle the pressure drop across the filter and lines is 0 PSI. So the pressure at the lift pump is also 15 PSI. Everything is fine.

Now we take the engine to WOT. The pressure drop across the filters goes to 10 PSI. Our regulator located at the injection pump is still set to 15 PSI and our pump flow keeps it there. The pressure at the lift pump is now 10 PSI + 15 PSI = 25 PSI ! There is no pressure drop at the injection pump ! Furthermore, all the fuel is going to or by the injection pump. No more starving !

Our engine gets all the fuel it needs.

Moral of the story: the regulator has to be located at the injection pump or there will be a pressure drop when the engine goes to WOT caused by the lines and the filter.

I'm telling you that a Walbro and a regulator mounted at the injection pump are more than enough to feed 99% of the engines out there. And for those it won't feed, use 2 Walbros in parallel. I'm talking about for engines over 600 HP here.

There is no need for dual pumps, replumbing trucks, replacing banjo bolts, belt driven pumps.

I guess one of the problems with the FASS and Holley pumps is that the pressure regulators are built into the pump itself. That might work OK for carburetors, but it doesn't work OK for diesels with filters and restrictive lines. On diesels the regulator needs to be positioned at the pump.

And you want it that way anyway so that the pumped fuel goes through the filter so the dirt is taken out of the tank as soon as it is pumped.


I am going to take a break from the lift pump stuff for a bit. You guys have enough to chew over in what I've written already.

Don't PM me about this stuff.