Why cant someone come up with a mechanical lift pump like the class 8 engines most have? They work pretty good and when they do fail they're like 100 bucks if that.
Whats the life span of a FASS pump? Is the electric pump going to last 1,2,3,4,5 years? 1 or 2 hundred thousand miles?
I say a mechnical pump would be the way to go. I know all things man made and mechanical will eventually fail, but it seems the electric stuff fails a little earlier than the mechanical stuff does when it comes to pumps and stuff.

 

"Why cant someone come up with a mechanical lift pump like the class 8 engines most have? They work pretty good and when they do fail they're like 100 bucks if that."

Most newer class 8 engines don't have lift pumps anymore. Some do, but most don't.

The CP3 is actually designed to be its own lift pump ala Duramax, but the filtering systems are smaller on the ISB so ONE plugged filter = bye-bye CP3.

For the most part the fuel injection systems on class 8s are easier to feed than the CP3 or VP44, which require excess flow for cooling. In head injectors generally don't need as much excess flow.

And the fuel pumps on some of those engines did give trouble. I'm thinking the gear pump on DD x-71, x-92, etc. The gears would wear out and then no more supply.

"Whats the life span of a FASS pump? Is the electric pump going to last 1,2,3,4,5 years? 1 or 2 hundred thousand miles? "

Dunno, but these Walbros are excellent, especially when only running at 10 PSI. They are cooled and lubricated by the fuel they pump. Which also means that they don't like dirty fuel. But if you pump everything through the filter (ie no pressure relief short circuit to the tank) the dirt only goes through once and then it is in the filter.

"I say a mechnical pump would be the way to go. I know all things man made and mechanical will eventually fail, but it seems the electric stuff fails a little earlier than the mechanical stuff does when it comes to pumps and stuff."

Lots and lots of trucks and cars have fuel pumps that will last literally forever. It is easy to design the to do so. The mechanical pumps worked too, but it is getting harder to mount a cam operated pump. The camshaft timing sensors go where the mechanical pump went.

Try the Walbro. It should be excellent.

BTW: I think the problem with the electric pumps being used are twofold.

First, they are low pressure pumps (10PSI) and when the filter plugs a bit they are operating at high pressure and then they burn out. The Walbro will run at pressures high enough to blow the filter lid all day long ! The Walbros are designed to run at 60 to 100 PSI for thousands of hours. Ford SD lift pumps run at 60PSI from the factory and you rarely hear of them failing. Ironically, they are a Bosch pump.

Secondly, I am not sure where the relief valve is in the stock system. I don't think those low pressure pumps have a relief valve. Thus when the filter plugs or the fuel gels the pump stalls and burns out. Then you need a new one. That won't happen with a Walbro. It will push fuel until it blows the filter lid. You won't burn out the pump. It does have an internal relief that will keep it living if the pressures get too high. But it isn't good to be operating it up at the relief pressures. Although some of us have done it, accidentally.

 

https://www.dieseltruckresource.com/...ad.php?t=78702

There is a post about CP3s being rebuildable here:

https://www.dieseltruckresource.com/...ad.php?t=86694

Putting a seal kit into a leaking CP3 should be an easy job. A shop manual is helpful with pulling the CP3.

 

Once again Superduty, Excellent writeup. All of the class 8 engines I deal with do have lift pumps still. The Cummins ISX has a wierd little electric setup that I have yet to fully understand. Our Macks on the other hand have a fuel supply system down to a science. A simple, old school science, but it works great. You have a #10 suction line from the tank to your primary fuel filter. From there you have #10 to the inlet of a gear driven fuel supply pump that is just a small version of an oil pump to give a visual. it comes out of that supply pump with #6 and goes to the secondary filter. Out of the secondary filter to a cooling plate, depending on which engine you have, and then to a common rail where all 6 electronic unit pups are pressured to anywhere between 5psi to 120 psi. It is regulated with an overflow valve at the end of the rail and returns any unused fuel to the tank. This is a very simple system and is easily adjusted for what ever pressure you would like. I dont see why we cant adapt just a pump like this to the little cummins. It drives of of the front gear train of the engine.

I will try and explain how this system makes its high pressure for injection. The EUP's mentioned earlier are mounted in bores in the side of the block about mid ways up or just above the cam. Once again, more old school tech. Mack still runs an in-block cam. The EUP has a roller lifter that rides on a special cam lobe just like an injector lobe on a Detroit or similar. The EUP has a high pressure fuel line that goes to a in head mounted injector. When the lobe comes around, it pressures the fuel to between 21,000 and 29,000 psi and POP, we have fuel spray at the injector tip.

Its a very simple system that works wonders and is easily modified. I guess I am partial to the old school stuff cause it worked. I need to wake up and relize that that stuff is done and gone i guess.

Thanks for the great writeups Superduty, Keep em' coming

 

2 reasons why you can't have nice simple reliable injections systems like mentioned above.

Noise
Emissions

 

BigBlock, You hit the nail on the head. I know it all gets back to the Gov. and emissions.

 

Allright here we go AGAIN. After about 1000 miles I am getting DAMP on the bottom of the new PUMP this one is CP3S. What is the deal???????????????
This is the 3rd PUMP. We'll see if she starts dripping???

 

20 bucks says your lift pump is shot. The CP3 isn't getting any lubrication/cooling flow and thus is takes out the seals.

 

Why does everything work so good? Even if I drain the fuel filter it will cycle and run as usual.

 

There is no backpressure on the lift pump when you drain the filter. It is a false indicator. And the fuel is probably warm then. And the engine isn't operating at WOT. It might only be starving at WOT.

I can't think of anything else that would cause seals to go out in 3 different pumps.

Are they sure it isn't leaking at the connectors ? These were all seal leaks ?

I still think it is the lift pump. As soon as the cold weather hit we saw the lift pump failures and the CP3 leaks spike up. I think they are related.

 

Other thing kinda of funny is why it's a Cold weather thing and now its warmed up and this pump is new? I have heard the Dmax'z have the same problem but the fuel collects somewhere in a cavity and doesn't drop off to the engine where is visable like ours. Now the Dmax doesn't use a lift pump so how does this add up? I sniffed a Dmax the other day and it reaked of Diesel form under the hood big time.

 

Duramax CP3s suck their own fuel from the tank. Your would do the same, but you've got a dead lift pump in the line.

If dealers really want to test for bad lift pumps they should put 5-10 PSI of backpressure on the line at the CP3 before they measure the flow.

My official stance on CP3s is that they will last a long, long time unless they get starved or fed dirty fuel.

 

Also my truck lives in a heated garage?? So the fuel stays warm. Man this is a pain the a!!. Well if does starts leaking and dripping like the others I'll insist on a new lift pump. Plus when this occured (this time) there has been NO W.O.T. at all. Lift pump still???
Superduty what else might it be, or are stuck on the lift pump.

 

Those seals seal the CP3 internal fuel pressure (80-180PSI) from leaking out. I only know of a few things that make seals fail. Rough shafts, worn bearings, lack of lubrication, heat. I doubt you've gotten 3 CP3s with rough shafts or bad bearings. So what is left ?

The Cascade over flow valve in the CP3 prioritizes the fuel flow in the CP3. First it fills the pumping chambers and then it supplies lubrication and cooling to the rest of the pump. Yours must not be getting any of the later.

Stored inside ? Do you ever get a water in fuel light coming on ?

Are you running a box ?

I can't think of anything else that would take out those seals. Save something like the gear drive is putting funny sideways pressure on the pump shaft. Hard to imagine that though.

How is the fuel filter ?

Are they replacing the FCA when they change the CP3 ?

 

"FCA"? Yes I run a VA3.1 for towing at work. Just reinstalled it.