Engine/Transmission (1998.5 - 2002) Product Engineering PE4100 installed

[Patriot Diesel]

Re: Real erratic psi's/4200

Originally posted by Bigsaint





I'll be interested in the response. I have never seen a healthy pump act in this manner ??? No one else that I know of has erratic psi's with the 4200, correct ??? Can't help but think that I got a lemon. This sucks. Tonight, on the ride home from work, the FP was idling at 14-15, dropping down to 12 and then rebounding to 16-18. Everyday I drive the truck I have different FP readings. Some days, when the grid heaters kick in, the psi's drop, some days they rise when the grid heaters kick in ??? I already checked the voltage, getting 13. 8 +/- when the truck is running, same that I had when I was running the Mallory pumps through the relay or the 4100 ????



Scott W.

Scott,



Something doesn't sound right with your fluctuating PSI's... . I think you are right... you may have gotten a bad one...



My PE4200 (one of the first ones made) has performed flawlessly. The PSI's stay constant with very little fluctuation; given the same scenario.



I typically see 18-19 PSI at idle and 17 PSI at normal cruising speeds. Under very heavy accelleration I can bring it down to about 11-12 PSI but it immediately rebounds with little or no hesitation.



Jeff

 

[cscott]

Scott



My 4200 psi is 20-22 at idle. I get a little flutter at idle 1-2 psi.



I've been deployed for a while and don't remember the pressures at wot or cruising.



My 4100 had some erratic psi for the first month then settled down so maybe it's just a break-in thing, altough my 4200 didn't do it, I don't know.



Craig

 

[cscott]

Scott



I sent you an e-mail.



Hope you get it it's kind of wierd sending e-mails from here.



Craig

 

[Bigsaint]

Thanks Jeff/Craig. I'll keep y'all updated.



Scott W.

 

[Gary - K7GLD]

I'd bet the "flutter" being discussed is the sometimes natural vibration of an object exposed to a passing fluid - as happens with air (flag waving in breeze) - and CAN also happen in fluids in the same general manner. I've seen ball check valves "flutter" in their clear assemblies inside the manifold assembly in our water softener, and have little doubt the in random cases and varying instances, the ball check valve/spring assemblies commonly used in LP application can do the same thing, until time and random conditions, such as slight changes in spring pressure or exact location of the ball check inside the chamber are altered slightly and change flow and the effect goes away...



I seriously doubt there's the slightest cause for concern.

 

[Bigsaint]

Thanks Gary, that's interesting. What do you think would cause the pump to spike up to 25 psi's at idle after a longer trip, say 20-25 miles ? Today, I took two short trips, around 15 miles each. Both times the truck had lower psi's, around 15 at idle and then would ramp up to 17-18 under heavy boost. Took a third trip tonight, maybe 25 miles, the psi's were the same. When I got home, I shut the truck down for 5 minutes. Went back out and started, at which point the psi's went right to 25 and stayed there, dropping only to 22 psi's when the grid heaters kicked on. This is the part that confuses me most.



Maybe I'm just worrying too much about nothing. The pump is running and providing more than enough fuel. Didn't get a response back from PE. I'll give it some run time before I call them again.



Scott W.

 

[Andy Redmond]

Are the grid heaters robbing any voltage to the pump?



You mentioned the voltage to the pump was 13. 8 v? Is this still a constant with grid heaters on?



Just curious, as our lights, fan / blower for the HVAC etc. dims/slows when those heaters start pulling those amps. . maybe its taking the voltage to the pump down below 12 etc. causing it not to spin as quickly, thus the psi drop.



FYI it sounds like a super pump to me.



Good luck, Andy

 

[Bigsaint]

Thanks Andy. I only checked the power at the pump once the grid heaters had stopped cycling. I would assume that the power is less when they are one as they sure as heck pull power from everything else electrical when they are on . That's the part I can't figure out with this pump. On a cold start, the psi's are at 18 psi's with both grid heaters on. Once they start to cycle between each other ( I have LEDs in the cap wired to both grid heaters), the psi's drop when they are off and rise when they are on, complete opposite of what you would typically see. Now, after a good ride and a hot re-start, the psi's are at 25 and they drop to 22-23 when the grid heaters are on, which would be normal except for why the high psi spike ???



I'm burnt out on this whole deal. The bottom line is that the 4200 is pumping more than enough fuel. I kicked the TST up to level 6 tonight and ran it up to 45 psi's of boost, the 4200 dropped from 13-10 psi's then immediately rebounded and feed the fueling need with 17-19 while under sustained throttle/boost. If it would just settle down and choose a consistant psi I'd be much happier, only because all of the failed Mallory pumps I observed behaving in the same manner. For now, I'm upgrading my pre-filter FP gauge to a 0-35 unit and I'll just sit back and see what happens.



Thanks again for all the responses .



Scott W.

 

[HVAC]

Pick Up?

Hey Scott, did John suggest you remove the pick up screen? He feels it's a restriction. Wonder if that's affecting your pressure readings?

 

[Gary - K7GLD]

Scott, the HIGHER pressure at LOWER voltage when the grid heaters are on sure sounds like you are having cavitation at "normal" voltage that is reduced or stops when voltage drops with the heaters on - sure would be interesting to have an adjustable voltage supply to vary, and see where the most efficient voltage and steady pressure occurs... Fuel pumps and liquids perform the same as our turbos do, there IS a maximum point in efficiency/pressure vs flow and restrictions, which once exceeded, create losses in various forms - the most common in liquids, is cavitation, and I bet that is what's happening in your case...

 

[Bigsaint]

Thanks again Gary, that would explain the erratic psi's I normally see when running cold. Seems like the longer I run the pump, the more stable it becomes. It's also very loud when providing the lower psi's, when it ramps up to 25 psi's it's very quite and smooth. Almost as if the warmer fuel causes less cavitation and better pump characteristics (sp).



Nowel, I did speak with John regarding the pick up screen. When I was attempting to trouble shoot the 4100, the 2nd thing I checked was my siphon flow to the pump. It's flowing just as it did when I was using the Mallory pumps or the 4100, very strong and solid flow of fuel when I remove the inbound line coming from the tank to the pump, at the open hose end. I explained this to John and he dismissed the thought of a clogged pick up screen.



Beats the heck outta me. I'll just watch it and try to be prepared for another failure at this point.



Only other thought I have is that the return valve in the banjo on the VP44 is sticking and releasing. Think this might cause a increase/decrease in observed fuel pressure ???? Just a thought, I have no idea.



Scott W.

 

[Ncostello]

BigSaint, there are so many variables, it would really be hard to pin point once specific cause. Its a dynamic system with many variables depending on the specific moment in time.



The flow is definately not steady, rather the flow velocity does vary with time depending on load, etc. Its easy to believe that unsteady flows are more difficult to analyze (and investigate) than are steady flows. In the case of the Cummins, the unsteady effects are periodic however, occuring time after time in basically the same manner. So at least we know the same things that cause flow differences are happening all the time... grid cycling, VP44 demanding fuel so many times per second, etc. Which is why Cummins owners get used to seeing certain things on their gauges at certain times.



There must be some point at which the P4200 and the size of the plumbing like each other... along with the temperature of the fuel and the voltages being supplied to the pump. It could be that the pump actually pumps more efficiently at lower voltages when the grids are on. Sometimes, spinning the impeller faster only makes things worse in the case of pumps. It just depends on the conditions at that particular time.



FWIW, I know our fire truck pumps put out 100% of their rated capacity at 150 psi, 70% at 200psi, and 50% at 250psi. So the higher pressures everyone likes does not always mean more flow. However many variables affect this... such as the intake water temperature and friction loss in the flow system. Our fire trucks can pump 125 GPM at 150psi or pump 1250 GPM at 150psi. It all depends how many nozzles are open and what we set the RPM's to. We also have a manually adjustable pressure relief to keep the pressure at 150psi. If the pressure goes higher, excess flow is recirculated inside the pump and intake flow is slowed. Kinda like the PE pump. Except you cant manually adjust the RPM's and pressure relief. So you get what you get and thats all you can do.



I would bet that the pump actually pumps the colder diesel better at lower voltages (slower speeds, grids on) while on the other hand pumps the warmer diesel (after long runs) better at higher voltages (higher pump speed, grids off). Laminar flow and good gauge readings have to be somewhat dependent on temperature and thus viscocity.



I myself wouldnt worry about the pressure fluctuations. It too hard to analyze and be absolutely sure about the results for one particular instant in time.



I still wanna know how the PE4200 pushes 247 GPH through the system that was designed for 45 GPH more or less. It still seems to me that the pump is really working the bypass to death. And trying to push too much volume through a system can be a major source of resistance to flow. High turbulance at fittings can cause great back pressure on a system thus reducing total flow.



Sorry for the long post... maybe it wasnt all necessary... and dont get me wrong... I think your on the right track anyway with the PE4200 over the stock pump.

 

[Bigsaint]

Thanks Neil, great info .



I will say that the pump seems to be somewhat less erratic with the more miles I put on it.



Scott W.

 

[HVAC]

Another Point

When discussing the PE pump with a couple of my mechanically astute friends, we reached some common ground regarding this pressure/volume debacle. The PE is capable of 270 gph, so even if the pressure fluctuates lower, we are still comfortable that such a formidable pump is going to deliver adequate volume to meet the requirements of a modified engine. Of course we are talking about engines devoid of banjo fittings and puny stock fuel lines.



This goes back to the what press/fuel line dia. is comperable to volume/fuel line dia.

 

[Bigsaint]

I agree 110% Nowel, not that I'm mechanically astute . There is no doubt that my VP44 is not starving for fuel. I'll just keep an eye on it and won't worry so much about particular psi's, just real low or non-existant ones.



Scott W.

 

[Gary - K7GLD]

I personally think that while use of a pusher in addition to the stock LP is valuable insurance for fuel flow to the VP-44, it is ALSO serious overkill in terms of potential GPH - AND really working BOTH pumps way beyond their most comfortable flow rate - REGARDLESS of fuel lines or fittings used. I think that is also why even the added pushers suffer premature deaths - just too much pump for the actual amount of fuel that's being moved - causing excessive head pressures for BOTH pumps, and holding their workloads right up at their maximum as far as both pump AND motor are concerned...



That's why I did this to mine:



#ad




It provides "relief path" around the Carter 4600 pusher to allow it to work easier, reduce noise, drop system pressure by several PSI, and provide a flow path for fuel to the stock LP in case it DOES fail... So far, so good...

 

[HVAC]

Pressure Consistancy

Scott, did you see my question regarding the pick up screen? Did you remove the pick up screen from your system? John feels it is a restriction. I have an open 1/2" pickup without a screen on my rig. An obstruction would cause pressure to drop as the engine is run longer, and rise back up to max after being off for a period.

 

[Bigsaint]

Yep, I replied on the past page, Nowel. Thing is, my psi's go the longer I drive the truck.



Scott W.

 

[HVAC]

Up Or Down?

Scott,



Do they go up or down?

 

[Bigsaint]

Oops, sorry Nowel. Was typing a reply at work when a call came in. They go up with more miles. Tonight, when I left work it was 15F. Truck had been sitting for 8+ hours. At idle psi's were around 14 pre-filter. On the way home, they jumped between 12-17, according to the mechanical gauge on the hood. The SPA registered a consistent 13+ psi's, as you know the sample rate time comes into play with that gauge. Once I got home ( a short ten miles) my at idle psi's were around 15. I took the truck for a 50 miles ride this morning, once I got home they were at 16 at idle. The pump is very loud when the cold fuel is going through it's vanes, much more quite after a 20-30 mile ride. Seems to like the warmer fuel more I guess.



I think, come spring, I will do what CSutton has been preaching for a while now. I'll drop the tank, punch a hole in the bottom and add a 1/2 bung for true gravity feed. I really don't think my siphon flow is giving me the odd fluctuations in psi's, as it never had an effect on the 4100 or Mallory psi's, but it sure won't hurt anything but my time spent. What do you think ???



Scott W.