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Opinions needed - Performed Optical Bump

dbrannon79 said:
I wonder since when I pulled the one on my IP apart messing with it and it has a rubber check valve in it that it might be going bad. By me messing with it and reinstalling it maybe had a little to do with bringing fuel pressures back up. I did notice this evening taking a trip into town idle pressure was slowly fluctuating a lb or so but was still up at 7-1/2 to 9 sitting still. I didn’t really think much about it.
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Don't know if that glass, Torlon I could see maybe - they are usually white. They are resistant to algae sticking on them. They are also used on transmission valve body plate repair kits where steel balls dimple the plate. Like https://www.thetruckstop.us/forum/members/ak-diesel-driver.2334/ said - that "gunk" that will clog the valve - that is algae growth from too low a fuel pressure giving it space to grow. At the shop on a rebuild they were taken off and soaked in biocide and tested, but they always start to open around 10 psi, but if you got a db2 one on there I could see it opening at 5 psi because on a db2 higher pressure changes timing. It only means your DS4 won't much get above 5 to 9 psi housing pressure. On a db2 that is how the cold start solenoid works. The wording is poor by stanadyne but the theory is it is closed at 5 psi because where you turn off the key the fuel shut-off solenoid (round one standing up on the front of the IP) stops fuel flow and vacuum traps 5 psi of fuel in the IP for the next start.

Pressure is a funny thing you can have 10 psi and not be delivering a large volume of fuel measured in gallons per hour. Those OEM solenoid buzz pumps spec 25 to 35 gph, and 12 psi for say an EP1000 but the reality is they could be pushing 1 gph and still show 7 to 11 psi pressure.

Axial inline pumps like I use are a true motor driven pump and spec at 55 gph flat low and high and pressure 15 and 30 psi low and high. A regulator to hold it at 20 is just right. It will pump reliably, consistently unless the motor stops which is what mine did after five years of service.

No one but GM uses those ridiculous buzz solenoid pumps really in automotive use and calls them pumps. They are good for low speed fuel transfer like from tank to tank (axillary to main or main to genset on an rv, etc) but pretty much that's all. If you watch one doing that and see them slow down while pumping you will get the picture. They work OK for a lift pump for a mechanical IP like a db2 which can draw fuel without being damaged, but for a DS4 that is death for the fuel solenoid and pmd. Like https://www.thetruckstop.us/forum/members/will-l.12781/ said they are "junk" and that goes for even brand new.

You don't hear from most guys who have gotten away from those solenoid pumps because their problems have ended with use of a true motorized pump - be it canister like an P4601hp or an inline axial like I use. To be honest the p4601hp once did 18 psi but now everything is going to hell in a hand basket so now they spec 9.5 to 16 psi 100 gph capable.

I would replace that check valve and make sure it is for a DS4. Trouble is they are 50 to 100 dollars and some places sell the db2 valve for the DS4 again. Look for specs. If you can't find one and yours is working to close on backflow leave it in there and get a good real lift pump system. Unless other things are screwed up like your waste gate system you said had issues most of your problems will end if you get it timed and koko set. ( again mine is - 1.25, and I think MrMarty51 said his was - 1.48)
 
Fyi, a db2 -low on inlet pressure will wear out head and rotor just like the ds4. Ford put out a bulletin on it, but because they have a 3/8 inlet line as stanandyne originally designed the ip to have, they handle the lower pressure better because there isn’t as big a pressure differential going into the transfer pump. GM is the one that spec’d stanandyne to reduce the db inlet size to 5/16 to help with their stupid lift pump. Smaller line means less head pressure required and bumps pressure up since volume is constant output in the LP

Remember that whole lift pump was because the mechanical lift pumps (6.2 era) would rupture the bladder and fill the crankcase with fuel. So when they stopped that one they came up with a bandaid lift pump and just using the fuel lines from the gasser trucks
replacing the fuel filter with electric lift pump. Then continued to use that crappy thing into the 6.5. Although stanandyne went with it, there was a lawsuit between gm and stanandyne which stanandyne won and gm ate the cost of the first few years worth of ds4 over the 5/16 line and something like 80% of the db pumps over it.


Amazing how the db ip outlasts by nearly 3 times average life in a ford than gm- hmm, gear drive helps some but according to stanandyne the 3/8 line was responsible for majority of the longer life in the fords.

I remember having 2 ds4 replacements when I worked at the dealership rejected by stanandyne and had to take the lower pay from gm corporate. (Warranty work didn’t pay same rate as paying customers or back charging vendors). The paperwork stated the “under fueling flow factor” I blew up that part of it on a copier, keeping stanandyne’s description of GM pinching pennies causing the problem below it and had it on my toolbox side door for months in that shop. Amazingly enough customers saw it and asked so that pressed management into paying me my lost $, then I took it down. Of course I said it was just a reminder for me to stay on top of fuel pressure and flow testing during diagnostics- haha

For years having a spare lift pump in the truck to replace the bad one was a smart idea. If broke economically, might be good idea for db2 users. But ds4 owners- now that really good systems exist- buy once, cry once and invest in the Fass or airdogg. The filtering is better and is worth the investment if you can. If a pump needs a back up to be carried it is obviously a piece of garbage much like the pmd.
 
Will L. said:
Fyi, a db2 -low on inlet pressure will wear out head and rotor just like the ds4. Ford put out a bulletin on it, but because they have a 3/8 inlet line as stanandyne originally designed the ip to have, they handle the lower pressure better because there isn’t as big a pressure differential going into the transfer pump. GM is the one that spec’d stanandyne to reduce the db inlet size to 5/16 to help with their stupid lift pump. Smaller line means less head pressure required and bumps pressure up since volume is constant output in the LP

Remember that whole lift pump was because the mechanical lift pumps (6.2 era) would rupture the bladder and fill the crankcase with fuel. So when they stopped that one they came up with a bandaid lift pump and just using the fuel lines from the gasser trucks
replacing the fuel filter with electric lift pump. Then continued to use that crappy thing into the 6.5. Although stanandyne went with it, there was a lawsuit between gm and stanandyne which stanandyne won and gm ate the cost of the first few years worth of ds4 over the 5/16 line and something like 80% of the db pumps over it.


Amazing how the db ip outlasts by nearly 3 times average life in a ford than gm- hmm, gear drive helps some but according to stanandyne the 3/8 line was responsible for majority of the longer life in the fords.

I remember having 2 ds4 replacements when I worked at the dealership rejected by stanandyne and had to take the lower pay from gm corporate. (Warranty work didn’t pay same rate as paying customers or back charging vendors). The paperwork stated the “under fueling flow factor” I blew up that part of it on a copier, keeping stanandyne’s description of GM pinching pennies causing the problem below it and had it on my toolbox side door for months in that shop. Amazingly enough customers saw it and asked so that pressed management into paying me my lost $, then I took it down. Of course I said it was just a reminder for me to stay on top of fuel pressure and flow testing during diagnostics- haha

For years having a spare lift pump in the truck to replace the bad one was a smart idea. If broke economically, might be good idea for db2 users. But ds4 owners- now that really good systems exist- buy once, cry once and invest in the Fass or airdogg. The filtering is better and is worth the investment if you can. If a pump needs a back up to be carried it is obviously a piece of garbage much like the pmd.
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EXACTLY... 100 percent!! It is just that I am not willing to pay $600 and more for a fuel pump system with no spare easy to replace for a vehicle barely worth much more than 3 to 4 times that much to sell it. Most in the diesel industry know to stay clear of any 6.5 powered anything!!

The 5/16 line is a rabbit hole so the easiest fix for a DS4 is all the pressure - top end spec limit - and all the gph a pump will actually push truthfully. I had a 6.2 with mechanical pump. I didn't look before I leaped into a 6.5. My best friend 's dad was a GM engineer in the Oak Creek, WI plant. He was a double major chemical and electrical engineer. He designed the catalytic converter and I watched him weld up the prototype in his garage because his team leader at gm did not believe it would work. They were at that time using the smog air pumps which weren't working and were seizing up. He literally rented a welder, bought two rectangle stainless cake pans and a stainless pipe clean out plug and fitting and perforated stainless plate and screen and welded the two together with some baffles to make the gas flow through a bed of catalyst pellets he poured in through the pipe wrench clean out. All this because gm would not spend money on his idea. Remember what the original GM catalytic converters looked like ?? He was mixed Japanese - African American and while he was literally carrying his design group single handedly of five guys, when he showed up on Monday with it in tow - looking like a muffler to bolt on - and told them to try it. For those of us old enough to remember the first gm catalytic converters with the refill plug... well I Have digressed

I have an early vortec 1999 and ecm and harness, converted and built to 10 to one pistons and it has four bolt mains, but I am too lazy to make the swap . . .
 
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The return fitting check valve has no effect on inlet pressure. Housing pressure and inlet pressure are independent from one another.

Inlet pressure is the result of the lift pump pushing fuel into the transfer pump area. The transfer pump is the resistance that creates the pressure.

Housing pressure is created two ways. 1. fluid under transfer pump pressure being pushed out the vent wire in the head and rotor and into the housing. 2. Fluid under transfer pump pressure pushing past parts like the head and rotor or advance piston and into the housing. Then the resistance of the return fitting creates housing pressure.

If the pump has an extremely high return rate and low transfer pump pressure there is a good chance that its worn to the point where the transfer pump is pushing too much fuel past internal parts causing inlet pressure to drop trying to keep up with the high return rate. You would have to spin it on a test bench to confirm that though...
 
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@royunion
I have the timing on My 2000 K3500 set at -1.43.
Before it was at -.53 and would puff some white upon a real cold startup.
After advancing the timing, it puffs but little smoke, starts quicker but does rattle a little more. Nothing undesirable though.
 
I received the IP inlet fitting in today with the 3/8" barb so I can put back the larger fuel line. got that installed, while I was at it I remembered I had a small air regulator that I use for pressure testing cooling systems. so I pulled the return port fitting from the IP and attached it to the small regulator. used my air compressor and very slowly started opening the valve. at about 2psi the return fitting started to let air pass through it. at about 5psi is seemed fully open (didn't go any further) . pulled it apart to get some photos of the inside. but I'm thinking this one ether is from a DB pump or it has possibly failed. once I put everything back together i ran the LP to prime the air from the 3/8" line and checked for leaks. When I started the LP I immediately noticed that fuel was slowly pushing through the IP into the clear return line!! While the LP was on pressure was holding at 10 psi and no leaks, I cranked her up. pressures were steady at about 7-1/2 to 8psi. revving would drop pressure to about 5 or 6, I think I saw it briefly get down to 3-4 psi accelerating on the way home from work. The conclusion I'm drawing up is the LP can't keep up the flow with the IP passing so much fuel through the return causing psi to drop under higher rpm or engine loads.

here is what I'm thinking or wondering...

1. The LP is able to very slowly push fuel through the IP and out of the return line with engine off = possible worn out IP although it seems to run fine? (runs much better now that LP has pressure to IP)

2. The return fitting isn't holding much of any pressure = possibly have the wrong fitting or it's just bad? Photos below showing the clear glass ball in the top section of which I can blow by mouth both ways. bottom section has a rubber check valve that does not allow back flow ( checked with 5psi, air passes out not in)

Questions on how to check IP if return valve is okay... by disconnecting the return line and feeding it into a jug to measure output flow at say idle (600 rpm) how much fuel should I see in a given amount of time or is this a way of testing for a failing IP?

here are the photos I took with my phone.
new IP inlet fitting, much larger inside diameter.. yay!
IMG_1848-1.jpgIMG_1849-1.jpg

IP return fitting
IMG_1851-1.jpg

Upper and lower section
IMG_1854-1.jpg

notice the upper section, the camera makes the BB look like a silver ball, but it's clear like glass.
and the lower section has a rubber seat with a tiny plastic check valve, you can see the tiny metal spring from the bottom side through the plastic cross hatch which I didn't take a photo of.
IMG_1857-1.jpg
 
Thats the correct return fitting for the DS. The DB fitting is one piece.

The return flow rate for a DS4 is 300-600cc/min at 1500rpm. A higher than normal spec would indicate internal parts wear.

A DS4 will flow up to 75cc at 3400rpm (untuned) with a 950cc/min return rate. Thats just over 30gph of inlet volume needed to keep up with it. I'd double check your lift pump volume too.
 
I stand behind my previous post - I would replace the valve with a proper DS4 return check valve. The actual Stanadyne part numbers for the DB2 versus the DS4 is different. These 6.5 engines most likely all have had the IP swapped or rebuilt at some point. It is very quick and easy to put a DB2 valve in a DS4 rebuild. As I previously mentioned the Stanadyne DS service manual is clear at page 1.8 section H what the spec is.

This fuel pressure discussion has gone on and on even here on this forum in other threads and people always compare the DB2 to the DS4 and they should not be.

The DB2 is pressure sensitive and over 5 psi screws up the timing, but on the DS4 5 psi is the minimum pressure and is also the bench test spec pressure. It is NOT what the IP should be run at. If you are running at or near 5 psi you are running on the danger edge.

On the test stand a fuel pump is used that can push and maintain in a regulated fashion the 5 psi spec. These OEM buzz pumps do not have the power to do that at all.

In this thread the pressure and check valve issue is beat to death and Leroy diesel keeps trying to tell people 9 to 13 is ideal and 16 won't hurt. See https://www.thetruckstop.us/forum/threads/max-psi-for-a-ds4-ip.45069/

Then one of the last posts shows the OP testing the return valve. It supports the Stanadyne spec and as I said the valve opens fully around 10 psi.

The internal housing pressure has another function and that is forced immersion lubrication. Think of not enough oil pressure on a crank bearing!!

This place claims the valve is only for the DS4, https://www.udgmtruck.com/2340288 and here ssdieselsupply is selling a 6.2 valve like it is for a DS4. See https://www.ssdieselsupply.com/p190_fuel_pressure_regulatorcheck_valve.html. They say "It maintains the required 3-5 psi fuel pressure." which is just plain wrong.

Of course all of this implies you have an actual working lift pump that push spec and maintain the spec it claims to.

It is a safe bet in Las Vegas that not one single one of those OEM style solenoid pumps will do what they claim in a spec, and certainly not for long.

Remember the post of Will L where he gives history on how GM went to a smaller fuel line because the OEM buzz solenoid pumps never did work at post 162. See https://www.thetruckstop.us/forum/threads/opinions-needed-performed-optical-bump.49575/post-609863
 
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That IS a DS4 return fitting he has on that pump. I stated that in my last post. The DB2 fitting is one piece not two...

Picture of a db2 fitting
20210629_220145.jpg

It's probably your lift pump that can't keep up in my opinion.
 
I have a suppose to be remanned DS4 fuel pump that I bought from someone over here. He purchased it from SS Diesel supply.
He was sure it was the pump but it was the PMD.
Now I am thinking I need to send it off to someone that can do an actual rebuild of the pump. It was never installed onto an engine.
The new PMD that came with the pump I would never rely on, I do have another spare, Dorman, that may or may not be reliable.
 
would anyone have the Stanadyne part number for the DS4 return valve or a DS4 parts breakdown with part numbers? I can try reaching out to some of the suppliers here at work since I work the parts department here I might have some luck finding one locally!

even thought it's the correct valve, it seems it's not holding the pressure it should be.

we do mostly big rigs here but I have had some luck on parts for smaller vehicles :)
 
Here is the Stanadyne DS4 test procedure and exploded diagrams with part numbers.

31488 is correct

This test is performed usually on a Hartridge or similar stand that has the Stanadyne module ecm add on

Note the housing pressure checks at specific rpm.

Note that the test occurs at the minimum operation standard of 5 psi regulated - which means the IP operates correctly down to this pressure. I had a revision of the DS Service Manual which stated the operating Inlet pressure was 5 to 18 psi but it is buried in files on another computer.

The part is available online for about $50. See https://www.finditparts.com/products/4968412/stanadyne-diesel-corp-31488
 

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Very good info, Thank you. I reached out to a couple of the local vendors to see if they can get one, if not it's online shopping for me lol.

I also wanted to post an update to how things are going. so far I have noticed easier starting and haven't seen any more air in the clear return line. Ive also noticed that now it has positive pressure on the IP from the LP, it's easy to press the pedal and hold 1k rpm. not sure if that's just a coincidence, but it feels and drives a lot better.

back to mentioning about the wastegate system, I do need to replace the vacuum solenoid still because it doesn't cut back on boost and sets a code, but I haven't done that yet only because I don't really drive it hard enough to get into an over boost situation under normal circumstances. at least I have boost now where as before when I bought the truck, there were so many boost leaks and exhaust leaks I think when I first got the gauge installed, the most I saw was 5lb. Now everything is all sealed up :)

I think now that I have a LP that actually is working, I may go ahead and replace the boost solenoid and then run through a tank of fuel to see how my mileage is before I do any more tinkering like trying to adjust the TDC-offset closer to -1.25 to -1.54, not to mention remove the optical bump at the same time ( or should I? )
 
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