Trouble in paradise. I've spoken of the neighbor's '03HO Cummins. My guess is he's up around 120,000 miles but it's down now. He delivered a trailer to Philadelphia and broke down solo, returning from the run. Truck is a some dealer in central Pa. while he returned with a rental car.


My guess is the lift pump, from what he described. No power on any grade but good speed on the level for a little while. Fuel filter did not seem to fill properly after he removed it for checking. Towed to a dealer that says it's in 'limp mode' but no codes were thrown as to why. Neighbor told me this dealer could not find their diagnostic tool and kept no Cummins parts in stock. That's why he rented the car and came back.


When I hear more I'll post. This would be the second lift pump I hear of failing on the common rail system, if that is the case here.

Keep us up to date Capt.

He needs to get with Schied diesel in Indiana. This is a known problem with them and Schied has a good aftermarket pump (stanadyne) that works. It is the pump I used for my GM. schieddiesel.com


Genohttp://www.dieselplace.com/forum/smileys/Hug.gif

Hoot


You need to look into this. Put a fuel pressure guage on your truck an when the press starts to run low it is the pump going bad and will starve your injectors whitch will lead into more problems. Schied Diesel is big in cummins.


Genohttp://www.dieselplace.com/forum/smileys/Hug.gif

Hoot


You need to look into this. Put a fuel pressure guage on your truck an when the press starts to run low it is the pump going bad and will starve your injectors whitch will lead into more problems. Schied Diesel is big in cummins.


Genohttp://www.dieselplace.com/forum/smileys/Hug.gif

Get with it geno.... you are talking non common rail motors

Not trying to be smart Hootie po just tring to help. They are the ones that told me this and Im sure they know a hell of a lot more than you do bout Cummins. But scince you own one you are a expert huh. Sorry I tripped yo triggerhttp://www.dieselplace.com/forum/smileys/HiHi.gif


Genohttp://www.dieselplace.com/forum/smileys/Hug.gif

you didn't trip my trigger at all geno. I remember you mentioned this before. The VP44 pumps in the pre-03 non common rail engines have a tendancy to self destruct when not fed fuel. Not that case at all with the 03-up common rail engines they use the same CP3 pump as the Dmax which doesn't have those issues.

Just keeping you old farts up with the timeshttp://www.dieselplace.com/forum/smileys/Hug.gif

wrong hoot they have a lift pump, hey I could care less just tring to help


Genohttp://www.dieselplace.com/forum/smileys/Hug.gif

When Dodge went with the Bosch system they stuck with the smaller diameter fuel lines and kept the electric lift pump.

What's this about starving injectors? I thought you were eluding to the VP44 pumps going bad when the lift pumps went. Sorry if I misinterpreted.Edited by: hoot

Well guys, I hate to drop this in on you, but I just smoked my main injector pump. The truck died like you turned the key off. After all the tests it is the main pressure pump, not the lift pump, the main pump.


In my opinion, if you are going to tow heavy like I do, with a fueling box, you need to put a pusher pump of some kind on your truck to keep the fuel pressure from going to zero on long hills. If running on cruise control, the truck is going to try to hold the speed and the box is going to tell the injectors to get after it and I don't think the lift pump can keep up. The injectors will empty the main pump of diesel which is it's lubricant and fry it. Again, this is my opinion, but I have heard of people with fuel pressure gauges on their trucks and they have said under full power runs with a fueling box they can pull the fuel pressure to zero. Coments???

Eb,


That would allude to the lift pump having only adequate capacity by design. The talk of a better lift pump would then make sense.


I hope to know more tomorrow. Leaving for a Lake Ontario fishing trip around 2 pm. It will be a Sunday night return to find out the issue if I don't hear from him tomorrow. Of course, this dealer may not have any answers just yet.

Well guys, I hate to drop this in on you, but I just smoked my main injector pump. The truck died like you turned the key off. After all the tests it is the main pressure pump, not the lift pump, the main pump.


In my opinion, if you are going to tow heavy like I do, with a fueling box, you need to put a pusher pump of some kind on your truck to keep the fuel pressure from going to zero on long hills. If running on cruise control, the truck is going to try to hold the speed and the box is going to tell the injectors to get after it and I don't think the lift pump can keep up. The injectors will empty the main pump of diesel which is it's lubricant and fry it. Again, this is my opinion, but I have heard of people with fuel pressure gauges on their trucks and they have said under full power runs with a fueling box they can pull the fuel pressure to zero. Coments???

Speculation is my comment.

What was the cause of high pressure pump failure? Describe "smoked". I know there is a history of pump failures... usually caused by leakage.

For the CP3 pump to "smoke" by fuel starvation you would have to explain how Dmax gets away with a vacuum draw setup and negative values under load.

As we speak, the number one cause of high pressure pump replacements in the Dmax and the Cummins is bad seal... leaking fuel. Since the pump is located external on the Cummins, the leak is visable and easily diagnosed. Also much easier to replace than on a V8 Dmax. (Take that http://www.dieselplace.com/forum/smileys/HiHi.gif)

The CP3 pump has the capability of drawing fuel on it's own, without the lift pump. Now if the lift pump becomes a 100% restriction when it fails, the engine would simply shut down... just like a DMax would with a clogged filter or air leak in the fuel stream. No pump failures reported after those events. It's pretty obvious to me Bosch designed this pump to run on zero to negative values or under pressure. I agree it needs to stay wet but I don't think the engine would ever be running a dry pump.... It can't run with NO FUEL.

I don't think the injectors can "empty" the high pressure pump. Once they have released all rail pressure, fuel is still loaded in the rails and pumps. The injectors cannot "suck" the fuel out of the rail. They only open and close. And when they open, they are under extreme pressure in the cylinder. They use high pressure fuel to open. Without the pressure, they simply won't open, even when commanded. I also doubt the ECM will command injection without pressure at the sensor. In the case of massive fuel starvation the engine will immediatly shut down.

Now a weak pump... should cause obvious performance issues. I agree a fuel pressure gauge is not a bad idea to monitor the junky lift pumps. But I don't see how a weak pump will damage the fuel system. Remember.... high pressure common rail is an entirely different animal, dynamically and hydraulically.

I'm considering a FASS system. If only they would send me one... I'll do an install article at no charge!!!!http://www.dieselplace.com/forum/smileys/Big Smile.gif

geno.... sorry for being jumpy on the subject. I agree it's important to monitor the lift pump and I will be heeding your advice.Edited by: hoot

I can not say for sure it was "smoked" (burned up) only that it was complete pump failure. The pump is supposed to put out around 26,000 lbs per sq in and it was putting out zero. No fuel coming out at all. The lift pump was working as advertised. I know that the diesel is the lubricant for these pumps. I can't answer your questions as far as the D-Max goes, I know nothing about them. What I was putting up was my thoughts on the subject. I will be putting a FASS system on before I put the Edge box back on. I contacted them and they said to send it to them and they would ck it out. I have done that. I don't think there is anything wrong with the box. I tow very heavy and still to my way of thinking the main pump was starved for fuel. Right or wrong, I am going to put a FASS system on. It certainly can't hurt.

The hp pump is controlled by the RPCV (Rail Pressure Control Valve). It's mounted to the pump with a electrical plug connected to it. It controls fuel rail pressure. If something is wrong with it or the feed from the computer is bad, you will have issues but if I remember correctly... no voltage causes full pressure. Full voltage drops pressure. Just thinking outloud. But that doesn't rule out a bad RPCV entirely. Could be stuck. Also there's a pop off valve that could get stuck open... sometimes blamed on pressure boxes. That valve is not designed for continuos use so the pressure boxes could damage it. So basically what I'm saying is it's quite possible there's nothing wrong with the pump assy itself. Somebody hooks up a pressure gauge... or reads some info on the Tach II, it reads zero.. they replace the pump an tell you it was bad.

I shy away from fuel pressure boxes. They ran a short stint early in the Dmax days but everyone quickly switched to the timing/duration boxes when they came out.

Remember... any reference I make to the Dmax usually holds true to the common rail Cummins. It uses the same system.


This picture shows the RPCV on top of a Dmax hp pump.
http://www.uscom.com/%7Ehoot/cars/duramax/gmc/headgaskets/images/DSCN4573.jpg


Here is the same deal on a Cummins "600"
http://home.comcast.net/~rs6000/dodge/600cutaway/images/DSCN4758.jpgEdited by: hoot

I've heard about this on TDR. If you use a fueling box, larger injectors, or anything else that requires an extra drain of fuel (usually a compination of more than one or a high performance box such as the TST PMCR), the fuel pressure coming from the lift pump will drop to nothing.


If this happens, it can cause the main injector pump top go out rather quickly. The lift pump doesn't have much reserve pumping capacity. I'm going to go with the FASS system before I go beyond the Edge EZ I have in my truck now to avoid this.


Just though I would pass on what I've read.

I'm back on the road again. It was the main injector pump. That is the only part replaced. To quote from the work order "no pressure coming from the high pressure pump diagnosed, replaced high pressure fuel pump, test drove OK" The pump was a remanned pump, part # R5104877AA, price $1075.00
I might be wrong Hoot, but I still feel like a pusher pump like the FASS or the AirDog will keep the main pump well supplied with fuel and maybe keep this from happening. There was a $400.00 core deposit so I let them keep it. I plan on getting a pusher pump of some kind before I put the Edge back on.
Thanks for all the coments and suggestions. If I can roll off 150k again before another major problem, I don't plan to fuss to much. Thanks again.Edited by: eb290

I've heard about this on TDR.


If this happens, it can cause the main injector pump top go out rather quickly.


David

I would like to see on TDR where a starved CP3 pump failed. Yes there are multiple posts and topics about a fuel starved VP44 pump going south in the older trucks but I don't remember reading about failed CP3's.

But I do agree something like a FASS or other lift pump would be a durability benefit.Edited by: hoot

Of course you would ask. I haven't been able to find the posts yet, but I remember two. They could have been on DTR. I'll look some more tomorrow. I know Keith from DD mentioned that low pressure could damange it, but didn't point out any particular case where it did. Here's what he said on TDR:
<DIV>Lack of fuel pressure will hurt the power and may cause damage to the CP3 pump. If you have to wait to get a pusher kit, don't drive it hard enough to pull the pressure down below 6psi.</DIV>
<DIV>__________________
Keith Lockliear
keith@dieseldynamics.com
Diesel Dynamics, Inc. (http://www.dieseldynamics.com/) </DIV>

. edited because of duplicationEdited by: hoot

"Lack of fuel pressure will hurt the power and may cause damage to the CP3 pump."

I really don't think they can back that up. But maybe they sell lift pumps or are planning to? But to decifer that statement a little more...

"don't drive it hard enough to pull the pressure down below 6psi."

tells me something is fishy in his knowledge of the CP3 pump. It is designed to operate at zero pressure. It has it's own internal lift pump. and can suck fuel on it's own if the lines were designed to allow it.

Will low pressure effect performance? I think only if supply is restricted. The CP3 can drop pump pressure to zero even when it is fully supplied. The problem occurs when it tries sucking fuel out of a failing lift pump. Fortunately it has a pretty robust gear rotor lift pump that I believe can handle fuel starvation from a cavitation point of view but I don't think the hp pump will run dry. Once pressure drops too far at the rails the truck will shut down and throw a code most likely. Even no pressure in the rails doesn't mean it's dry.

The older Bosch pump P7100 was oil lubricated but the VP44 used on the 24V engines before common rail were fuel lubed and cooled. They are sensitive to unhealthy fuel flow.

The Duramax pretty much has proved out the CP3 is not susceptible to this reduced pressure damage. The Duramax has NO lift pump... it sucks fuel all the way from the tank. People are installing 2 micron fuel filters in the suction path and running stacked boxes.... all creating major vacuum in the fuel system and starving the pump. On top of that people get clogged OEM filters, air leaks in the fuel system that cause hard starting, both because they are starving the pump of fuel.

Not sure what else we need to know unless the Dodge lift pump spews parts into the pump but I think its pre-filter.

I think a lot of guys are using the problems with the VP44 and it's fuel sarvation issues as fuel for these threads, not realizing we are dealing with an entirely different injection pump and fuel system. The CP3 pump is super simple. All it does is pump. It has no distributor rotor. and very few moving parts. Part of the beauty of common rail is the reduced mechanical complexity up until the injector.

Look at the Powerstrokes.... to go off on a tangent. They don't have a fuel injection pump at all. Part of the reason their system is as reliable as it is.Edited by: hoot

I'll back what Hoot writes above. The Vp44 and Cp3 are totally different pumps. One is an injection pump (Vp44) and the other is "just" a high pressure pump (cp3) that goes to a common rail system. About 8 months ago I purchased a text book from the SAE that was written by Bosch (Diesel Engine Management). The book goes into the details of the various fuel injection systems for diesel engines (480 pages worth). The Cummins Gen3 and Duramax fuel injection systems are very close in design. It looks as if GM shorted (or left out) the lift pump that is present in the Cummins Gen3 design. The standard block diagram for the Bosch Common Rail High Pressure system shows a lift pump. The Common Rail system more resembles a high pressure hydraulic system than a fuel injection system of 5 years ago. The block diagram for the Gen2 Cummins system looks different.


The High Pressure pump in the Gen3 and DMAX is a two stage pump. The low pressure side is a gear type pump that feeds the actual high pressure side that has 3 pistons. I have seen one of these things completely dissected over at the TTS shop. It is really amazing simple. I do not know about the Cummins lift pump, but a lot of the add on lift pumps that people are putting on the DMAX (Delco design) do not present a complete restriction when they fail. The suction on the line goes up slightly and the truck continues to operate. The stock DMAX always operates with a vacuum on the supply line. It ranges from 2 - 8 inHg (with a clean fuel filter). A portion of the fuel sucked up from the fuel tank by the low pressure pump never goes to the high pressure pump. It is returned unused to the fuel tank.


The other thing people need to look at is what pressure the HP pump is outputting. The DMAX runs up to 23k psi (it does not run at this pressure all the time). The ECM commands a pressure and the regulator tries to maintain the commanded pressure. I would think if the commanded pressure is being maintained, there must be sufficient fuel being delivered to the input of the HP side of the pump by the low pressure gear pump. This is relative easy to monitor on the DMAX (commanded vs actual fuel pressure), not sure about the Cummins.


Good luck,,,,


BTW - How are those injectors holding up?


I am seeing numerous posts on the various Cummins/Dodge forums of injector problems. Seems to be a different variation than the DMAX failures. Looks like the Cummins cannot completely escape the curse of the Bosch HPCR injectors.


Edited by: OC_DMAX

Right at 150k miles, no injector problems to this point. The only real problem has been the above mentioned pump failure. Still don't really know what caused it.

I've made two runs since I got my truck back and this morning before I started I cked codes. Guess what, I have thrown two. The first is P-0480, which is cooling fan 1 control circuit/open, I'm not really concerned about this one but the other one is P-2509. That one is PCM/ECM Power input signal intermittent. This one probably can cause problems. Anyone familiar with it? This has all come up in the last 500 miles.

The first thing I would do is go over all the connectors and make sure they're clicked in tight.Edited by: hoot

Neighbor's truck is not fixed. Dealer finds nothing wrong with the injector or lift pumps. Truck will not run. They are calling in some kind of "expert".


Looks like I'll be on the road all week doing his Albany delivery and then immediately taking one to Missouri. Expect to find out more about his problem at the end of the week.


Great reading your opinions and experiences guys. http://www.dieselplace.com/forum/smileys/Clap.gif