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Opinions needed - Performed Optical Bump

Will nailed it!!! If a company is selling you a back up lift pump with their pump... then they must be selling a junk product.

I will put money on it that this guy sells these pumps and is trying to sell the OP a snake oil product.
 
Rockabillyrat said:
Right I get that part. But he said in a previous post that with 16-18 psi of inlet pressure the solenoid doesn't have to work as hard because of the increase in inlet fuel pressure.... but the fuel solenoid is controlling fuel under pumping pressure. So unless your starving the transfer pump the solenoid will be unaffected by the increase in inlet pressure. Also return fuel volume has a set flow rate that is controlled by the condition of the pump, the vent wire, and the return fitting. your not going to increase flow rate through the pump by increasing inlet pressure. I'm just not seeing the point to 16-18 psi of inlet pressure.
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I think the best way for anyone to understand it the OEM solenoid pump specs which are now 10 to 14 psi for most all of the ep158, ep1000 for the 2000 and up vehicles that have same interchangeable IP and the previous years were in earlier years 7 to 9 psi cannot see there was a problem. The problem is as said by me and WillL is they do not work or work at that spec for long. See Will's post at https://www.thetruckstop.us/forum/threads/opinions-needed-performed-optical-bump.49575/post-609863

You have to understand filling the transfer pump full on every revolution will happen fully on a higher pressure and high gph capable lift pump pushi g to the inlet than with one with fake or dying unreliable specs.

The spec for THE DS4 Ip always was 5 to 18 psi. No solenoid push pump can ever attain or reach that and like Will said GM in its penny pinching lost a lawsuit on the issue, so the DS4 Service Manual shows cleary why the higher pressure is needed. At page 1.3 on the right hand paragraph right below FIG 1.3 the color IP cutaway it says the transfer pump fills from Inlet pressure. But at high speeds it won't completely fill if the pressure is low - there will be cavitation. 16 to 18 psi has the best chance of always filling that full on every revolution stroke.

The manual is clear how the throttle works and describes a "pulsed" meaning "pwm" operating nature of the Fuel Solenoid Driver aka PMD. Anybody in electronics knows it is a bad idea to use a Power Transistor as a high speed switch. It will get hot and fail - especially under a 100% duty cycle pulling amps to a solenoid.

Reading the section on how the fuel solenoid works is vague that it depends on signals from the ecm and engine feedback but this is a vague way to say a heavy foot operates the pwm circuit more agressely. Similarly if the transfer pump is slightly starved on each fill rotation there will be less fuel to inject and to pressurize the housing with.

The pmd is not a good solution but since the IP can take 18 psi Inlet pressure closer to max spec anyone who drives a 6.5 will you they would never have believed the real world difference.

Those that have it basically stop trying to help and convince others due to attitudes like this.

People tend to repeat and believe usually the wrong story, it is not how does the 16 to 18 psi make the difference, the real story is that the spec low on early 94 to 2000 DS4 units and then they GM saw they were wrong but no OEM solenoid pump would ever go that high so it was raised to 10 to 14 psi but still the manufacturers told a lie and pumps won't do that pressure to the IP Inlet either. So the 6.5 public now dwindling has and is being lied to and they are believing the spec lies. Those OEN solenoid pumps get weak fast and never meet gph spec anyway. That is why 16 to 18 psi from a real pump makes a difference.

I have said what to do... it is the IP spec limit. It works great.

IF someone cannot understand the theory transferred to real world results not only I say but lots of others who are or have driven the real and felt difference, then theory is not something they may ever get, but the real world result does not lie.

Anyone can put together any pump system that pumps 16 to 18 psi to the IP regulated, but no other system provided three pumps and a regulator and I have a trouble free 6.5 to drive.

Doubting Thomas's abound it seems, but no diesel mechanic worth anything who reads how the DS4 works would ever think feeding it anything but the max spec on fuel is not a good idea.
 
Will L. said:
Ok, so the one person here that knows about this “sure cure lift pump” carries a spare pump with him. Again I go back to my earlier statement that ANY part to make an engine run that SUCKS SO BAD that it is logical to buy 2 and carry a spare- is a total piece of crap and in no way should be introduced to a truck. If you are dead broke and scavenging parts from a junkyard (which I been through) then yes, get 2,3, even 4 of the junkyard parts that cost $3 each so you can make it to work and earn enough money to buy something worth while instead of worth less.

PMD- best reliability mod we did in the fleet was adding a second one where the driver could easily swap over and continue his route, mounted off the dash in front of the a/c vent worked well until winter and the heaters were on DUH! Haha. The couple thousand trucks I saw go through that outfit all going to junkyard after crashes or sold in excess of 200,000 miles, with many that were attempted being pushed to the 500,000 mile mark with a dollar limit of when to cut it loose of course like any fleet would have.
So now MOST everyone has learned heat soak from the engine bay after engine is shut off drives the temperature north of 140f and does damage to the pmd even with engine off. And a heat sink works both ways- it sheds heat when pmd is hottest, and when pmd is colder the ambient engine heat goes right into that heat sink and nicely warms the pmd - Hence my DUH moment of pmd infront of vent. So we learned outside the cab and engine compartment was the best option. BUT STILL THE PMD SUUUCCCKKKKSSSSS!!! Thats why you need 2. If someone made a pmd that was $300 and never any more money need be spent, most would do it. Yeah- thats 2 lifetime warranty units...
So $400 later a sure cure kit really isn’t a cure because if one pump dies, and they are so sure it will die that it comes with a spare- the next will die. Then you get to buy more. SMH

spend the $400 on a pump like the fass even if that is only most the price- buy once and cry once. Choosing to add an expensive but not top shelf part makes no sense to me. Fass and airdog at least are world wide known suppliers that have good reputation and guys that have ran half million miles plus with 1 pump.

And Yes Rockabilly- you are on point. And 2 degree colder fuel doesn’t help the ip.
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FIVE years it ran without a problem. A spare is because you cannot walk into a parts store for replacement, and still I have not used the emergency spare.

I have pointed out real world truths. And when certain people told the world what COVID was going to do, they got this reaction too. It is a stock OEM lift pump that looses its warranty because it is not installed on the vehicle the part number goes to. Five years was plenty of time for me to get my money 's worth and a replacement spare is just as smart as as spare pmd. They do the same thing - strand you dead on the road. The way I saw it I got an OEM replacement solution at close to wholesale cost.
 
I will agree that higher inlet pressure does help feed the transfer pump especially at higher RPMs. The down fall to a rotary pump is because of its design it has a hard time fueling in the higher RPM because it shares the same pumping chamber for all 8 cylinder unlike a inline pump that has more time to charge the pumping chamber for each individual cylinder. But If 5psi is starving the transfer pump at higher RPMs like you claim then transfer pump pressure would drop at higher RPMs. But factory spec under 5spi of inlet pressure is 143-157psi at 3400RPM... that sounds like the transfer pump isn't starving for fuel at 5psi.

But your not understanding the charge cycle correctly. Transfer pump pressure pushes fuel into the pumping chambers and will move the plungers as far as they can for that RPM. At idle there is more time to fill the pumping chambers so the plunger move out father. At higher RPMs there is less time to fill the pumping chamber so it moves the plungers a less. The plungers will vary the fuel volume inside of the chambers based on how much fuel can be pushed into them on the charge cycle... there is no way air can enter the system in the pumping chambers and cause cavitation like you stated earlier.

royunion said:
Wrong. See https://www.thetruckstop.us/forum/threads/opinions-needed-performed-optical-bump.49575/post-610023
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Prove me wrong!!!
 
Rockabillyrat said:
I will agree that higher inlet pressure does help feed the transfer pump especially at higher RPMs. The down fall to a rotary pump is because of its design it has a hard time fueling in the higher RPM because it shares the same pumping chamber for all 8 cylinder unlike a inline pump that has more time to charge the pumping chamber for each individual cylinder. But If 5psi is starving the transfer pump at higher RPMs like you claim then transfer pump pressure would drop at higher RPMs. But factory spec under 5spi of inlet pressure is 143-157psi at 3400RPM... that sounds like the transfer pump isn't starving for fuel at 5psi.

But your not understanding the charge cycle correctly. Transfer pump pressure pushes fuel into the pumping chambers and will move the plungers as far as they can for that RPM. At idle there is more time to fill the pumping chambers so the plunger move out father. At higher RPMs there is less time to fill the pumping chamber so it moves the plungers a less. The plungers will vary the fuel volume inside of the chambers based on how much fuel can be pushed into them on the charge cycle... there is no way air can enter the system in the pumping chambers and cause cavitation like you stated earlier.



Prove me wrong!!!
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I did not say "air" was entering - though it could be, and I also said the transfer pump was "slightly starved". Read the section on the Fuel Solenoid and if you cannot see how the energized cycle is lessened or increased by fuel demand as engine rpm I cannot help you read and understand technical literature.

You are arguing semantics. The spec from GM is now 10 14 psi. I say the pump can take 18 so feed it 18 with a regulated motorized pump. That is all.
 
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You are the one that doesn't understand how the fuel solenoid works.... have a good day I lost enough brain cells reading your BS🤣
 
I have a system that I put together when experimenting with fuel injecting my 78 MG-B roadster.
IIRC the pump is capable of 60 PSI and it has a Holly adjustable pressure regulator mounted in the system. I dont remember how many GPMs the pump is rated at but I imagine it would be more than enough to feed the 6.5 diesel. The fuel pump os a NAPA brand that was manufactured for the MPFI SBC engine.
I think that this pump and regulator is going to be My next try on My 2000 K3500.
 
Rockabillyrat said:
You are the one that doesn't understand how the fuel solenoid works.... have a good day I lost enough brain cells reading your BS🤣
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I am not going to go there. I have seen plenty of DS4 with burnt up fuel solenoids. What do you think happened when it starved trying to just keep an idle?? Have read your own motto in your profile that says "SlIgHtLy Stupid".??
 
MrMarty51 said:
I have a system that I put together when experimenting with fuel injecting my 78 MG-B roadster.
IIRC the pump is capable of 60 PSI and it has a Holly adjustable pressure regulator mounted in the system. I dont remember how many GPMs the pump is rated at but I imagine it would be more than enough to feed the 6.5 diesel. The fuel pump os a NAPA brand that was manufactured for the MPFI SBC engine.
I think that this pump and regulator is going to be My next try on My 2000 K3500.
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I used a Holly Blue knock-off once in testing. It worked but was noisy on the rail and maxed out at 14 psi, but without a regulator it surged to idle speed and the idle speed surged because of it
 
royunion said:
I am not going to go there. I have seen plenty of DS4 with burnt up fuel solenoids. What do you think happened when it starved trying to just keep an idle?? Have read your own motto in your profile that says "SlIgHtLy Stupid".??
Click to expand...

lets keep this clean. Rockabillyrat has been here to help. everyone's help is very much appreciated.
 
royunion said:
I am not going to go there. I have seen plenty of DS4 with burnt up fuel solenoids. What do you think happened when it starved trying to just keep an idle?? Have read your own motto in your profile that says "SlIgHtLy Stupid".??
Click to expand...

You just proved to me you have no idea what you are talking about with that comment.

A DS4 fills the pumping chambers 100% at idle and controls the volume of fuel to the injections with the fuel solenoid. When the solenoid is closed fuel is pushed from the pumping chambers to the injectors. Once the desired about of fuel is reached it opens the solenoid and dumps the remaining fuel back into the chamber in the head that is under transfer pump pressure. If the plungers fill to 100% at idle how in the hell is the solenoid starving for fuel???the answer is its not!! You need to read that manual some more because your just not understanding how this pump works.

A db2 is completely opposite and uses a metering valve to control the fuel volume into the pumping chambers.

With that im out. I got more important things to do then argue online with some one that doesn't understand how a DS4 works.
 
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Unless I am completely confused on my memory of the ds4, Rockabilly has that correct.

Something that hit me in reading this, quite a while back Roy and I were in disagreement over. 5/16 line being upgraded to 3/8 line- which the op here has done and long since eliminated the factory ffm. But if you are concerned with getting enough fuel into the transfer pump (something all 3 of us agree is a good thing) then that larger diameter line pushing 14 or 18 psi- whatever it is- would refill faster with the larger line. Having a larger reservoir of fuel at pressure will always fill the next chamber faster if everything else is equal (like no mods internally that affect flow). Now, I would have to do the math, but a simple calculation says set volume at pressure x is equal to same volume at pressure Y.

And remember, no pump actually creates pressure. They all create flow, and the resistance to that flow creates the pressure.
 
well said Will !

something I looked at when I got the 3/8" fitting for the IP was the filter screen fitting that screwed into the IP. I had read somewhere that others were drilling out the four small holes to a larger size so there wasn't a restriction there. I took mine and sized each of the holes and saw they were 1/8". my math might be wrong trying to factor in flow, but four 1/8" holes is the same as one 1/2" hole so I left it alone! also I didn't want to chance getting burs or metal fragments in the tiny valve at the bottom or into the IP. the inner diameter of the 3/8" fitting was almost 5/16"

but that T fitting I scrounged for connecting the boost gauge to is one of those multi size adapters that accepts 1/4 and 5/16 hose so until I remove that and get a permanent fuel gauge, that is causing a restriction!
 
The IP transfer pump makes the rules here. If the lift pump isn't up to the job, kinked hose, or plugged filter, plugged screen... The Diesel in the fuel line between the restriction and transfer pump will boil off and you get Diesel Vapor Lock. The transfer pump doesn't care what the inlet pressure is as long as it can get flow. No flow = bubbles in the return line. Some DS4's won't even run with a bad lift pump due to restrictions... IMO DB2's did slightly better with only power loss on a bad lift pump.

Wear of a 15 psi difference on the inlet when the outlet is 150 psi is a lifetime concern. As long is the transfer pump isn't boiling diesel with a high vacuum it will deliver X volume and X pressure. Where the pressure regulators for things are referenced matter like the DB2 that's referenced off the inlet.

Dodge Cummins also went through the krap lift pump and blow the fuel cooled electronics PAIN with a VP44 that would die with the lift pump. That Cummins "We didn't learn from GM's screw up" is why we have aftermarket Diesel fuel pumps people plunk down serious cold hard cash for. (Beyond the Holley Blue and other gas hot rod stuff.)
 
royunion said:
Well as I read the whole post, I was waiting for the post where you discovered that the lift pump pressure was not good enough.

There are a number of things that matter, but the number one is good presistant high lift pump pressure. The OEM style solenoid pumps do not work at all or for long. When warm up they loose the ability to pump even more. I use the Sure Cure Lift pump solution. It comes with three pumps. One to use, one is a spare, and one is a emergency use one that is a canister style and a fuel pressure regulator that will hold and let 20 psi to be set. By the time it passes through the filter you get 16 to 18 psi at the lift pump under all conditions even wide open throttle. The emergency pump is used for mounting bracket and some hardware., but it is emergency swap use only because it only puts out 4 to 5 psi. You will hear and read that fuel pressure should be 5 psi, but that is MINIMUM psi. Even the Delco EP 158 has a spec of 10 to 12 psi though it won't hold that for long even after new.

I have an electric in cab digital readout that I use rotary switch to switch from vacuum / boost, to fuel pressure at the ip, to fuel pressure pre filter, to transmission line pressure. They all use 0 to 300 psi transducer sensors. The readout is dual display and the other is post turbo exhaust gas temperature (EGT)

It has been five years since the Sure Cure Lift Pump solution went in and recently pressure dropped to 14 at the IP. OK so what I figured I needed to change the filter.

One day it stumble started only the second time in five years. Then again a d shut off. The lift pump is really quiet so much so if the HVAC fan is running I can't hear it. I cut off the fan turned the key on and it sounded weak. Then it started on the fifth try. The next morning no start, and no lift pump sound at all. This is why the Sure Cure Lift Pump Solution comes with a spare. Checked for 12 volts at key on and swapped the lift pump which took 30 minutes, and started it right up. Now it was back to 18 psi at the IP.!!


Since I used to work with a Diesel shop that specialized the Stanadyne pumps, it is important to understand the pump expects about 12 to 18 psi to perform best. At about 10 to 12 psi the return check valve on the top of ip opens to begin to let let fuel return to the tank. The purpose of that is to keep the timing wheel tank full of cool recirculating fuel which supposed to cool the PMD that mounted on the side.

But here is where the problem started where GM wod not listen to Stanadyne that the solenoid lift pump they selected would not work for the DS4. GM did not understand the electronic nature needs 18 psi to work properly for long life. The PMD also called the Fuel Solenoid Driver or FSD is a poor ideal to use Power Transistors ( the two round things on the underside of the PMD) as a voltage regulator switch to drive the the Fuel Solenoid which is on the rear of the IP which is effectively the throttle that is actually pressure controlled. FUEL pressure controlled, and it is kept closed by a spring and assisted open by the Fuel Solenoid which driven by the PMD. The PMD is supposed to to assist only to open the plate more to increase engine speed. When there is low fuel pressure in the IP, two things happen, first there is no fuel to fill the optical sensor tank area to cool the PMD and second the the switching transistors are OVERWORKED trying to keeping the throttle plate open to try and increase engine rpm. This overheats both the PMD and the Fuel Solenoid which also shortens the Fuel Solenoid life also. So this the DS4 death spiral. The PMD relocation is a band aid. Minimum fuel pressure is also contininung the death spiral.

It is all because of the lift pump. The Sure Cure Lift Pump solution has in line axial pumps but the emergency one is a canister motor driven wet pump.

When you put 18 psi at the IP you should notice a light foot on the accelerator will make it take off and it will pull like a gas engine if everything else is right.

It sounds like there are turbo and waste gate issues. The waste gate solenoid or actuator or map sensor may have issues assuming you have good vacuum. An OEM setup will never go over 10 psi. It will open the waste gate using the map sensor and waste gate solenoid. As others have said the wicked wheel will spool pressure faster but a proper system if stock will work with the ecm, timing and fuel input. pressure

I would get a good positive in line true motor driven ift pump that is dependable first. Most of the problems may go away like you realized the lift pump was not working. Also even the OEM solenoid pump from cold start pumps strong and then gets weak when it warms up.

Also my TDC offset is - 1.25 and it ran like crap until I did the key on key off procedure
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@royunion would you be able to post some photos of the Sure Sure lift pump your running on your truck?
 
MrMarty51 said:
So I too am not quite understanding the concept.
The fuel pressure from the LP is helping to hold open the shut off solenoid ?
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Fuel Solenoid at the back is not the Fuel Shutoff Solenoid which stands up on the front. So... No

The DS4 Service Manual is hard for many people to understand.

The way to understand it is the Fuel Solenoid is the throttle. The rest if the IP is the carburetor. When there is insufficient fuel pressure to keep the fuel bowls fuel when the accelerator pump goes to squirt fuel it cannot but it tries tries to stay open so a venturi effect keeps pulling what fuel it can from the bowl to keep the engine running.

In the case of the DS4 it keeps making what pressure it can and trying to operate the injectors by supplying whatever pressure it has. The Fuel Solenoid does this from the ecm telling it that it needs a specific rpm or the accelerator pedal is calling for increased fuel injection for increased rpm. The PMD does this by increasing the duty cycle to the Fuel Solenoid.

For a new pmd it will keep this up for quite a while. For an older pmd it can cause the power transistors to thermally and electrically stress and be unreliable as a switch or just fail.

An IP that has max pressure at the inlet will operate 100% as designed

The concept is simple if it can take 18 psi - then feed it 18 psi - that is what will operate it best, but in theory it is statically tested at 5 psi which is the minimum it should operate at with sufficient fuel volume but WillL at post 162 truthfully told us that the inlet for volume is too small from what GM did trying to get the OEM solenoid pump to work. Pressure and Volume when restricted by line size means you need higher pressure and volume to meet the needs of the DS4 IP design.

There should be enough bleed from the internal parts to cause a housing pressure at high speed and WOT to keep pressure in the housing to keep the spec circulating which originally to keep the pmd cool which does not get hot at high inlet pressures anyway.

But the truth is it all went to hell in a hand basket when gm put on a lift pump too small, that did not work, and did not really push pressure and volume of fuel for a new electronic design which relies on pressure to work right.

I mentioned in an earlier post how I tried AN unregulated Holly Blue knock off, and it proved what I am saying. As I a created and the fuel pump came to push maximum pressure the6. 5 ran like a rocket for a diesel at 14 psi. When I stopped at idle the alternators let the fuel pump rpm and pressure drop slightly, and so too came a loppy idle. Took it off the same day and put on the regulated system and a gauge under the hood also at the ip and have not looked back since.

In my posts are enough clue to build something yourselves, if you know the features of the OEM lift pump.

There are several ways the inlet volume and pressure is not used exclusively for injection. But when there is plentiful fuel the pressure itself causes idle without pmd involvement and to accelerate the engine minimum electrical power is needed energize the throttle as the fuel is ready for increased injection rates and tends to push through on its own. A spring and plate is setup in such a delicate balance that requires a crush ring and dial indicator to set it up.

The concept is no different from a more powerful fuel injection pump to feed more fuel to larger fuel injectors on a gas engine.

Try to run say a vortec on 30 psi of fuel pressure and see how well it runs when the injectors require 45 or 60 psi to work. DS4 usually cannot idle with insufficient pressure and fuel volume. It often will shut off because the fuel solenoid is at 100% duty cycle and cannot maintain 600 rpm.

Ask yourself where is the throttle cable on a DS4?? OF COURSE it is called drive by wire. There are several places in the DS4 Service Manual that the difference between it and a DB and you need to understand what this means in how engine speed and injection is controlled.

This where car sales people and mechanics do not try to explain engines and vehicle systems - people try to understand it the way they want to, and after several times being told no that is wrong, they get mad because they themselves don't understand.

IF there is someone in a math class trying to tell the class a wrong answer is correct - well we watched the last president do that and so no, that person is not here to help at all.

I think the OP has plenty of information to complete his project, and I am retired and this fun for a while, but now I am not helping the OP.

This has turned into a challenge for who can argue about nothing, so it can go on without me

I know what I am doing and I do not have problems with my 6.5. I think it is time I am done sharing.
 
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