I have a nice +12v square wave going from my PMD/FSD toward the IP, but very little diesel is getting to the injectors. I have good fuel pressure going into the IP. Is there a way to diagnose if the IP is bad, or the FS? How do you remove the FS from the IP ( after removing the 2 long screws on top of the FS?
Thanks,

Somehow, I overlaid your message GMCTD.

I already tested with another good FSD ( it came off my daily driver), and still no fuel. I measured the resistance of the FS and it shows the same as my good FS ( .06 ohms). I thought about removing the fuel lines to the injectors, and puting +12 volts on B and gnd on F of the FSD harness, effectively opening the FS all the time, then bump the engine with a cloth over the IP to keep from spraying fuel. How about that?

When the F sol dies the starting gets real hard as the plunger isn't opening. You have to remove the pump, remove the head from the pump, and then install the fuel sol
tightening it to the head and then chech travel. It should be set at .005" for proper C times.

I misread your post - then corrected, then deleted, preferring to leave the most correct answer to TDG.

In previous posts, he has recommended not attempting any R&R of the Fuel Solenoid, on or off vehicle. As has DieselPro.

The FS will draw over 25amps - where my meter pegged out - with +12v applied, so I would not recommend your suggested procedure.
Not sure what the result would be - it would severely jack with the fill-pump-spill routine.
Similar results if the poppet was broken.

Just not much way to operationally test the thing, without a Tech-II, or maybe a SnapOn MT2500.

Possibility the Fuel Shut Off solenoid is defunct, or the inlet filter screen is stopped up, blocking fuel flow into the housing?

What exactly is this thing doing? Hard start? No runny?

Will not start. I could check the return lines to see if fuel is flowing through the IP.

If not a problem with the Fuel Shut Off solenoid -

Try dis-connecting the Optical sensor, see if it will start on the Crank Position Sensor.

Reconnect, then try dis-connecting the Crank Position Sensor, see if it will start on the Optical Sensor.

Either way, it should start in Backup Mode.

Would tell you if a hard failure in either is causing the no-start.

Eliminate ESO solenoid from the picture entirely, unscrew it, remove the snap ring and pull the armature out of it, then it can't stop fuel from flowing into the pump.

Very difficult to tell that you have very little fuel, cranking spec is only 36cc in a 1000 strokes, so you'd be looking for 36 thousandths of a cc every squirt, impossible to eyeball, besides, what the pump can squirt out means nothing to what it can push past an injector at opening pressure.

Truck is a no starter you say? Try GMCTDs advice first, unplug optic sensor and try, you will be in extended crank mode, like 15 sec before it will even try to start. Supply pressure is good? Batteries? Starter? Need to hook up to a scanner and see if there's codes stored. You won't be able to diagnose FSOL problems with a multimeter, need to check solenoids performance, resistance won't tell you anything except that the magnet in the solenoid should still be good.

Can you give us a little more info on how all this happened?

Eliminate ESO solenoid from the picture entirely, unscrew it, remove the snap ring and pull the armature out of it, then it can't stop fuel from flowing into the pump.


OK My stupid question time, Whats the ESO solenoid?
how you disconnect it. ? Where's it at

Electric Shut-Off Solenoid, often confused for the Fuel Solenoid, its the tall steel cylinder on top of the pump. Its simply a plunger at the bottom, when de-energized, the plunger falls and blocks the inlet to the transfer pump and engergized it pulls up to allow fuel in.

ESO was swapped with my daily driver and did not change either truck. I will try disconnecting the optical then the crank position in the morning. The orginal fault was,
driving down the road, a pop noise, then a miss, then when it was parked it has not started again ( 8 months ago). By the way, Texas Diesel Guy, I disconnected one injector line on my truck ( which works ok) and turned it over with the PMD disconnected, and I can not see the spray of fuel, but it gets wet all around the injector. That's why I tryed the same thing with this truck.

Okay, a poppin' noise, that just doesn't sound nice, where ever that came from. . .

You have any stats on this truck (year, etc)/ codes maybe? If under a 95, then codes are a piece of cake.

AH K Thanks

1994 one ton. I thought about it and disconnecting the Crank Position or optical, will not tell me anything, since I have already put a scope on the FSD and found a good signal from the FSD going toward the FS. Seems like this pretty much narrows it down to the IP.

Seems weird. Sounds electrically like everything is it should be. Just wonder, if what fuel is getting there when maybe? No codes? The origin of that pop sounds a little worrisome still?

Are you new to the forum, or just new name? I see you had problems getting in during the conversion. I was lookin' back last night to see if you had any previous posts.

Without PCM control, the small surge of fuel out the loosened injector pipe would be transfer pump pressure - only correctly timed FS closure allows injection pressure.

Does pulse leading edge occur at correct number of degrees BTDC, as timed by OS referenced to CPS?

Does FS return (Black) indicate current surge as pulse energizes solenoid?

Is pulse width correct at 1.70-1.90ms?

Does Closure Signal occur, indicating FS has fully seated?

Any codes from right after original failure occured?

1. I am not too new to the forum, I had to change my user name to get back in after the change to the new software.
2. the pulse width from the FSD is 7ms, which is what I have scoped on my running truck, at idle. 600rpm / 60 sec = 10 rps, 2 revolutions = 8 cylinders fired. So every revolution is 4 cylinders, 10rps * 4 cylinders = 40 fires per second. 1/40 = 25ms, so
every 25 ms an injector is pulsed with a 7ms pulse at 600 rpm. As the rpm's increase the 7ms gets longer and the 25ms is less.
3. I do not know if the FSD pulse is in sync with the CPS, but I could sync the scope on CPS, and then look at the FSD pulse to be sure they are close.

That is what I've had in mind for a long while - create some 'break-out' harness, where the signals can be monitored and referenced with a four-channel scope - TEK 2445\similar.

CPS, OS, FSD drive, Closure, FS drive - monitor at the engine-to-IP connector, IP to FSD, then with remote-mount FSD long cable for spurious ringing, etc
Just need one more CPS harness, commit one OS to the cause for the female connector.
And some mosquito relief - they've been really bad here, all year long

Also check Closure signal against the running truck - that truck makes a very handy reference.

Gonna have a look at OBD-II this weekend - should add more questions to the puzzle.
Maybe it will answer a few.

BTW - glad to see you're back - wonder what happened to mdhorban?

What is the closure signal? Yes, I made up a harness to go to the FSD and that is how I scope it. The male end is kinda klugee, do you know how to get the correct connector for the male pins, I am sure the extension harness sold by vendors has found the proper connector.

Check here, Heath extension meets Kennedy extension, normal is to connect Heath at IP harness, I still am in test phase of Heath remote kit 6 mos no problems to report, but wanted ability to swap to spare if I had a fail, so I did not undo the Kennedy harness. I have Kennedys early harness from IP to a DSG cooler also have Heath's cooler mounted behind liscence plate on the bumper. Kennedy's harness uses weather pak sealing gaskets, Heath's is supplied with heat shrink sleeve which I haven't used yet. You should be able to easily get breakout for a scope with the setup I have using 2 vendors harnesses combined, the Heath one alone would work but pins would be down by the IP. JD I'll have my scope with 2 channels, hopefully we can get some good data.

A is drive, E is Closure status, C is Closure ground, which is similar to a cable wire length sense, I think.

Closure status indicates armature\poppet is seated

BTW - glad to see you back - wonder what happened to mdhorban?

anyone PM him or email him? He may have had similiar trobles as ray and other's who've lost their accessability to this forum.

TurbineDoc...

Your engine does not meet the 6.5 diesel minimum for dirt on an engine. Your clean engine suffers from thermal inefficiencies, and makes everyone else look bad.

Please mix up 1 gal #2 diesel, 3 lbs of common dirt, 1/2 cup 90 wt gear lube and 3 tablespoons of axle grease. Add dead bugs or birds to taste. Apply this mixture to the top of the engine, coating ever available surface.

We will overlook this transgression if you vow never to let it happen again.

Tim

BIG STEENKING GRIN

:D

HEE HEE and his hands are way too clean too.

Qm I think the PMD relacement project has stalled.
GMCTD I am going to have to work with FSD-pin C. I know pin A and E come from the PCM and a positve pulse on Pin E with a negative pulse on pin A causes a +12 v pulse on Pin B. I will scope pin C, to see if it ever changes.
Turbine Doc I was hoping to buy a male connector for around $10, the Kennedy cable is $90 plus I can not tell how much the Heath cable is. Any idea where I can just buy the male connector?

I'd give Bill a call I don't know if he considers his harness propietary, explain why you want one, I think this is a Packard Weather-Pak plug, part number PED-1 I think I've googled weather pak before and found some.

Now to those who would cast disparaging remarks about my engine bay jealous i have most of my leaks under control? Actually what you don't understand I haven't shot pics of the grimey parts, plus me & Mr GMCTD are going to be doing some R&D this weekend with this L65 reflash I just got and comparing T2 tool vs MT 2500.

I got to clean it up some cause Mr GMCTD will cuss me out if I bring over a dirty engine, we were going to install that locker I was talking about in the DIY forum but I decided it's too cold to be lying on the ground to fool with that. As for the hands I just got them clean from last weeks TDI brake job, had clean dirt on them up to about 2 days ago.

Actually - the negative pulse on pin A drives the positive pulse on pin B, and the positive pulse on pin E tells the PCM to set code 35 or 36 - or not..........

Qm I think the PMD relacement project has stalled.

Can you elaborate?

Qm I have not heard from mdhorban for awhile, but then again I have changed my name. I was waiting for files from him to print a silk screen or turn over to a PCB manufacturer for one or two boards to test.

GMCTD ok, but I think your wrong here, I wish I could take a picture of the scope, but the poitive pulse on E only exits when the two conditons are met, if what you said were true the pulse on E would be the same length as the pulse on A, and that is not the situation.

The E pulse occurs after A\B when solenoid current changes drastically, indicating the armature has stopped moving, valve is seated.

PCM measures the duration between leading edge of B and the initial surge, to that current shift, which generates E, for Closure Time.

If duration is too long you get 36 (2.5ms) indicating the armature is dragging - low voltage, fuel is icy (waxy), dirty, etc

If duration is too short you get 35 (1.5ms) indicating bubbles in fuel, no fuel, etc

Those delays\deltas\durations are what I was\am interested in seeing, first hand.

That should all occur shortly after leading edge of A\B - 1.88ms avg

Did I get somethin' wrong here. . . (normal right?) Is closure time measured in mS [milliseconds] or nS [nanoseconds]?

milliseconds

GMCTD #30 I will scope again today with #30 in mind. Thanks for the explaination.

Excellent, hr - the good-vs-broke comparison will add to the data base that federal law - EPA, CAFE mandates - prevents GM from sharing with us.

Hopefully, the boys in black won't show up on our doorstep(s) some night, to shove a tracking device(s) up our collective nose(s)..........;)

You c'n run, butcha cain't hide !! !! !! ! ! ! !! !! !!

Guess we can assume you don't have the combination oscilloscope\microwave\garage-warmer - that was a 30deg ambients indicator, right?

Or, does your scope weigh #30? ;)

Anybody know at what pressure the injectors open and start spraying?

Got a chance to look at the FSD signals Sat morn, but moving the scope lead between signals - even Closure Ground - occasionally killed the engine, so we decided to wait for my harness breakout.

Did see about 2ms between FI Control A and FI Signal E, and heavy ringing on B leading\trailing edges, partially resulted from running JK's harness and HD's harness in series for the testing

Turbine Doc was too far away from home to walk, so EFI prudence was in order.

TDG - Also noticed something else - 'hot-chipped' PCMs seem to run with increased CT values.
CR's, TD's, mine - all running between 1.92 - 1.97ms after upgrading, all with over 80mm3 fuel rate programming.
Mine drops down into 1.70's at higher rpm while accelerating rapidly, which is normal, but runs 1.92 - 1.95 at 65-70mph.
All three with 5521(?) Inj Pump

GMCTD The ringing is normal, I see it all the time. I am still working on a harness. What did you order for a break out harness?

I get any needed parts from any of the local boneyards, here.

I was expecting ringing - it is an inductor drive signal - but the extra wire lengths has to be increasing the level and period - musta been a 10ft total harness length.

I'll get mine set up to take measurements with FSD on the IP for reference, comparison to extended harness lengths.

Test extensions will be about 3", open-ended probe wiring about 1 - 2', soldered to ftb pcb with probe hook loops.

TDG - Also noticed something else - 'hot-chipped' PCMs seem to run with increased CT values. CR's, TD's, mine - all running between 1.92 - 1.97ms after upgrading, all with over 80mm3 fuel rate programming.
Mine drops down into 1.70's at higher rpm while accelerating rapidly, which is normal, but runs 1.92 - 1.95 at 65-70mph.My explantion for this is yes, the Injection pump, specifically, the FSOL of course. Running higher fuel rates (75+) @ high RPMs, the FSOL has less time to open fully between injections than the pump was designed for. Now I'm not saying you can't do it, but you probably should have the poppet valve spring replaced with a new one, and shims trimmed just a hair to give slightly faster CTimes. Also, I've noticed that new poppet valve springs do a lot to help make more consistent CTimes across the RPM/load range. I've got a theory that this also has to do with the runaways like CR has mentioned, poppet valve does not fully open intime, due to weak spring, slightly more than desired fuel is injected and PCM has difficulty adjusting to it. Just a theory for now, on a side note, I hooked the scanner on to mine this morning and got a shock, CTime: 1.89, WHOA! So, pulled the pump, pulled the head out, replaced the Poppet valve spring, reset poppet lift, CTime now 1.55ms ;) I think this has cured my surging problem as well. Have to wait till warmer months to know for sure.

JD harness length is 8' with Heath & JK combined, no pulse count on MT2500 tool so looks like T2 only way to look at close rate.

TDG I sure wish I knew how to take a injection pump apart and work on it.

JD
Made trip back okay, MT2500 does have a closure rate; 1.95ms at 80++mph ):h need GPS top know how much ++ buried speedo past 100. L65 reflash working fine no hicuups in drive back from Houston pullin MAF one less air restriction as we surmised, I was limited to 3000 rpm with MAF installed on drive over & L56 reflash. Coming home with MAF removed and running L65 I ran out of safe road to stay fast for long; too many folks on the road I got to 3200rpm and still increasing speed 650 post turbo EGT so I still had some more room, also was peaking 15 + psi more easily than before. I think though bottom end launch is different I have more top end power seems to get some added kick at about 2800 rpm, will have to hook up to a load to know for sure.

Can I buy the optical sensors for the IP from a diesel repair shop or parts house?

I would imagine.
http://dieselplace.com/forum/attachment.php?attachmentid=602&stc=1
something like this might cost~ $300 plus the install. I have a pump requiring this to be installed and I was going to take these parts and my pump to a diesel shop and see what it would take to install it dollar wise.

JD
L65 reflash working fine no hicuups in drive back from Houston pullin MAF one less air restriction as we surmised, I was limited to 3000 rpm with MAF installed on drive over & L56 reflash. Coming home with MAF removed and running L65 OK Can someone explain about this MAF? just so I can keep understanding what he talking bout

MAF= mass airflow sensor. It's an alternative system to the MAP only L65.

Ah Thats what I thought it was but didn't know 6.5 had them. thought they were gasser only stuff. So all L65 have them or just OBD II ?

No L65 have them, only l56 with egr 95-98?

Oh OK only 95-98 L56's with EGR's. Good one less thing for me to worry about.

MAF= mass airflow sensor. It's an alternative system to the MAP only L65.MAP & MAF aren't same device MAP is a pressure sensitive device used on both L56 & L65 MAP is actually the BOOST sensor for both but on all L56, on L65 & 56 some earlyOBDI there is a firewall sensor that GM will give you if you ask for a MAP and not a boost sensor.

MAF is a flow device used only in L56 engines calibrated wires and honecomb that tells PCM how much air is flowing to the turbo from filter, it's restrictive aftermarket hi flow ones are available for gassers none for Diesels at this point so I eliminated mine, L56 PCM looks for it hence my swap to L65 so I don't get codes. I'm also fairly certain MAF is OBD-II L56 device

hrjack - try Wickliff Diesel Service, for the Optical Sensor and other stuff.
They have a website.

Your Correct I was just trying to understand your post and mods and the fact that I don't have either to worry bout, which is the good part.

Keeping the Boost up keeps the EGT's down, as your run has proven once again, Tim.

Was a kinda nagging worry about the 'scope probe killing the engine during testing, but coulda been the pf cap in the probe discharging into opposite signal level.

Don't know if it's the 5521 IP calibration, or the upgraded software causing the 1.95ms pw, but at 1.5 low to 2.5ms hi spec, 2.0 is right in the middle.
1.95ms may be jus' rite for late OBD_II, '98 up.

Don't know if it's the 5521 IP calibration, or the upgraded software causing the 1.95ms pw, but at 1.5 low to 2.5ms hi spec, 2.0 is right in the middle. 1.95ms may be jus' rite for late OBD_II, '98 up.
I don't know where your getting 2.5ms as high end of spec, I've heard 98+ PCMs allow up to 2.1ms without tripping codes, but I"m not 100% on that. I do know that Stanadyne's test plan for ALL DS pumps specs CT at 1.5-1.9 in Test As Recieved and Test Following Service. Long CTimes mean your FSOL armature or the poppet valve are dragging and/or the spring is weak and/or the Solenoid/Armature/Cap are worn.

Another thing that really erks me, and your post just reminded me of this, is that most scanners refer to Closure Time as Pulse Width and its not. The two are completely different things, Pulse Width is Duration, how long the FSOL stays energized, Closure Time is how long it takes to close.

I don't know what the big deal is, I punched out early (3:30) pulled the pump, did what I had to do to it, recalibrated it and was headed home before 5:30 ;)

DTC 35 sets below 1.5ms, DTC 36 sets above 2.5ms, meaning 2.0ms is not a problem.

CR and TD have the 5521 IP in their '98 and '00 OBD-II trucks, both showing ~1.95ms.

I installed a new 5521 IP in my OBD-I, and get the same 1.95ms reading, where it was 1.88 with the 5288 IP now residing in QM's truck.
I removed the FSD from the 5288 and installed it on the 5521, which should then give the same reading - NOT..........

All three trucks - CR, TD, gmctd - have upgraded PCM with ~80mm3 fuel rate.

That pulse width or c.t. display is rather unclear, particularly since it should be measured in micro-seconds, if it is closure time.
Well - 1.9ms is 1900 microseconds

I've noticed many ambiguosities between OBD-I and OBD-II, lot of stuff hidden\disguised in OBD-II - makes it seem as tho no performance gain is achieved by advancing base timing above +3.5deg.

Tech-II - with mfg date FEB 2004 - signs + and - for TDCO figures on my '95 OBD-I, yet gives an un-signed 1.67 number where TD's Snap-On MT2500 just read -2.0 on his '98 OBD-II.

Ain't no way his TDCO is at +1.67deg, nor is there any such thing as 1.67.
It's either retarded (-) after TDC, zero (0) TDC, or advanced (+) before TDC.

Still trying to figger it all out..............

[QUOTE=gmctd]
That pulse width or c.t. display is rather unclear, particularly since it should be measured in micro-seconds, if it is closure time.
Well - 1.9ms is 1900 microseconds

So are you saying the c.t. should be 2.0 microseconds or milliseconds?

Manuals state microseconds, which is 'us'.
Manuals then state actual figures in milliseconds, which is 'ms'.

Tech-II calls out FS pulse width in ms, which is ms.

I observed ~2milliseconds, which is ms, between Closure Signal on E and Injection Signal on A, which compared to FS Drive on B.

I'm fairly certain that, even at 0.005" travel, the FS armature and poppet is gonna take more than 1.5 microseconds to get started moving, much less make the transition in that time.

We need to make some additional readings and comparisons OBD-I and -II, where moving the probe point-to-point does not kill the engine.
I know why that happens, but it's scary with the DS4\FSD history.
Guess I'll set up some 1.5 - 10kohm c\l resistors in the test harness - shouldn't effect the 1\10megohm scope probe and input impedance.
Test harness will be ~3" - male\female connector length - with test points brought out via 24" wiring extension.
This to maintain original control path wire lengths to get pristine PCM signals.

I'll try to test with a loaner 4-channel scope, so all FSD probes will be in place.

Also want to check CPS, OS Hi and Lo res, along with FSD signals.

Stepper advance will be visual vs OSED and CPS to check for electronic 'bump' at -0.5deg TDCO vs -1.94deg TDCO.

To answer your question - I got more questions than answers after this first testing.
Any input helps.

FYI, including some studied conjecture.....

PM at the engine plant physically sets the IP to +3.5deg base timing.
He does this with a microwave setup while the engine is running in a test stand.
When engine is installed in a truck, new OBD-II PCM 'learns' TDC Offset.
TDCOL in majority of installations has resulted in numbers between -0.3 to -0.7deg - this number has been published in OEM Shop Manuals as being correct for +3.5deg base timing.

Everyone rattles off these numbers as law, because that is what they've been taught, and that is ONLY what is published - I have all the Shop Manuals, Training Manuals and CD's, as proof. (and my test scores certify me as Mr. Goodwrench-compatible, as long as I don't question Time Set\TDC Offset!):cool:
(maybe freethinking employee offenders are sent to work in the GEO Metro plant..........);)

All OEM Manuals state 'no performance gains will result from advanced base timing - timing must be set to +3.5deg'.

All OEM Manuals state 'TDC Offset allows PCM to correct back to top dead center'.
Most people flatly argue that it is to make up for mechanical slack resulting from machining tolerances, timing chain\sprockets, IP drive\driven gears, IP tolerances, etc.

Which is a crock, based on the factory blurb.........

Time Set performs this routine admirably, by physically retarding the OS to a known, repeatable position, then measuring that distance in degrees to the Optical Encoder Disk TDC, compared to the Crank Position Sensor TDC.
This gives the precise positional advance of the IP body\distributor to Optical Encoder Disk TDC.
This also gives the offset, due to mechanical slack, between the Encoder Disk TDC and CPS TDC.
Which also determines the precise position of the rotor, as referenced to the distributor, OPS, and CPS.

These timing and offset numbers are stored in PCM memory and referenced for compensation due to normal chain\sprockets wear over the lifetime of the Inj Pump.

If, as stated, TDC Offset performed this offset function, the -0.5 'learned' figure would NOT vary to a more negative number - more retarded - for increase in base timing advance.

AND - TDC Offset would automatically vary to a more negative number - retarded - over any period of time as mechanical slack increased due to timing chain\sprockets deterioration.

Physically retard the IP - TDC Offset number does become more positive.
As IP shaft and rotor timing retards via loose chain set - TDC Offset should become more negative.

Physically advance the IP - TDC Offset number does become more negative.
Re-advance rotor timing by replacing worn timing set - TDC Offset should become less negative.

It don't EVEN work that way, folks.

TDC Offset adjusts the Timing Stepper motor to the amount of dialed-in Inj Pump advance - more retarded for more IP advance.
At ~11deg total Stepper advance, which translates to ~22deg crank advance, more than enough travel is available for the +5deg IP advance from oem +3.5deg BTDC to performance +8.5deg BTDC.

TDC Offset is -0.5deg @ +3.5deg base timing, 'Learns' to -1.5deg @ +8.5deg base, and is manipulatable to -1.94deg (and beyond), for further power increase.

And, folks - timing does not retard BELOW base timing setting - you only get advance from base, and fall back to base, even under heavy demand.

+17deg at cruise, drops back toward +8.5deg loaded up a hill - has never retarded below +8.5deg.

So, something else is going on here, aside from simple TS motor positioning.
Ongoing continued observation on this point for further info.


The Stanadyne DS4 Inj Pump is highly precision machined and adjusted, such that any pump placed in any vehicle will run to same performance as any other pump in that vehicle.........

providing the 'new' IP is located to the precise position the previous IP was bolted down to, as determined by the imprint on the timing cover.

If this is precisely accomplished, one instructor has stated that only TDC Offset Learn is required - if timing chain-set has not also been replaced.
IP can be 'tweaked in' to correct -0.5deg value by observing TDC Offset and performing 'Learn' routine.

If timing chain-set AND Inj Pump is replaced, Time Set is required, along with TDC Offset Learn.

This indicates - to me - that Time Set does all timing and mechanical offset measurements.
Period.

Where TDC Offset Learn compensates for Inj Pump distributor advance, and minor positional variances upon replacement, PCM would have all mech offset values up to point of replacement stored in memory, values which would be correct to compensate for mechanical wear at that time, and which would not require new Time Set routine.

Any one care to debate this, from a GM\Stanadyne technical background point of view?

Trying to get to the bottom of this, folks - any\all input helps.

If this is precisely accomplished, one instructor has stated that only TDC Offset Learn is required - if timing set has not also been replaced.

If timing set AND Inj Pump is replaced, Time Set is required, along with TDC Offset Learn.

This indicates - to me - that Time Set does all timing and mechanical offset measurements.
Period.

Where TDC Offset Learn compensates for Inj Pump distributor advance, and minor positional variances upon replacement, PCM would have all mech offset values up to point of replacement stored in memory, values which would be correct to compensate for mechanical wear at that time, and which would not require new Time Set routine.


Time set requires a reprogrammer?

Time Set is a commanded function of Tech-I and -II - establishes mechanical timing relationships.
Requires bi-directional communication between scanner and PCM.

TDC Offset Learn must be commanded in OBD-I, is an automatic function in OBD-II, based on routine described in Manuals, and by Turbine Doc, in FAQ's area.

DTC 35 sets below 1.5ms, DTC 36 sets above 2.5ms, meaning 2.0ms is not a problem. CR and TD have the 5521 IP in their '98 and '00 OBD-II trucks, both showing ~1.95ms. I installed a new 5521 IP in my OBD-I, and get the same 1.95ms reading.
I still don't know where your getting 2.5ms from? But I can show you on a test stand how long CTIMEs (1.9+) will lose fuel quantity at higher RPMs. I also don't think that GM's increased tolerance (1.9 max in pre-98) is a good enough reason to accept 1.9+ CTIMEs as acceptable. I could tell a difference bringing mine down from 1.89 to 1.55. Not huge, but the slight stumble was gone and top end power was improved.

Tex, the question that comes to my mind is what would your ctime run if you swapped in a heath 2.0 prom? It seemed like gmctd thought the pcm change made the ctime longer. If that's right and it came up to 1.90ms with a chip would you shim the plunger spring further to get it back down to 1.5ms?

I agree, it might have, but not directly. Closure time is a measure of FSOL performance, PCM can't slow down the FSOL, instead, it keeps it energized longer than it was designed to stay and the result is less recoil time for the FSOL and longer CTIMEs.

The stated 1.5\2.5ms figures are noted in GM Factory Service and Training Manuals, as low\high criteria for setting Fuel Solenoid DTC 35 or 36 in OBD-I and the equivalent code for OBD-II, TDG.

They undoubtedly do exceed the figures you stated, which I would assume are Stanadyne specs intended for calibration on a flow bench.
Specs which would keep the IP functioning well within real-world operation - somebody's truck - in summer as well as winter, with all qualities of fuel.

I'm trying to get to the bottom of the mechanics involved - PCM\FSD\DS4 - and your input has helped, considerably.

Further, I do intend to determine the difference in similarities between C.T. and FS Pulse Width in ms - may be which part of the signal is being measured.

Very strange that three different hot-rodded DS4-5521's, from different parts of the country, all indicate ~1.95ms pw.
Been very cold up there, very warm down here.......

Anyway, your last statement above is what I was thinking about the 80mm3 fuel rate increase programming - it seems to have resulted in increased FS pulse width, which may or may not be the closure time you refer to.

I am sure it is all intended to be ambiguous.

Thats cool, I was just wondering where you got that figure from ;) Same here, learning curve never ends on the mysterious 6.5/DS.

Very strange that three different hot-rodded DS4-5521's, from different parts of the country, all indicate ~1.95ms pw.
I understand what you mean, but you have to trust me, we do repair Stanadynes warranty pumps still you know, and the Long CT is THE problem they have, I believe I did discuss this with you in a PM before too. Outside of 'New' DS pumps, long/short/erratic CT is top of the list of ALL DS4 complaints in general. Its a critical component to pump performance, I don't let the go to the shelf unless they're between 1.55 and 1.70, because long CT is the biggest problem with them.

GMCTD next time I'm over that way we will plug in the stock PCM I still have, why we did not think of that while I was there is beyond me, maybe we need a written test plan so we don't miss the obvious.

Is a good idea, Tim.

TDG- the three 5521's in question all appear to be about 2000 vintage - do you recollect any significant or excessive return for 'Long C.T.' failures for IP's of that particular chronology?

Mine runs ~1.95 max, decreases to ~1.70's at ~3000rpm, which would seem to indicate no mechanical FS problem, such as dragging, or off-spec spring.
It is a new IP, which I've had in storage, installing it in June of this year.

And, again, I'm talking FS pulse width, as displayed by Tech-II

Now that you mention it, I do remember seeing several with '00 on the date tag, and a couple of '02s and one '04, but none from years before that. The fix for all of them has been replacing the shims under the poppet valve to get them in the 36-41 thou range which is Stanadyne's spec, ALL pumps of the '00 up range with long CT complaint had too tall of shims.

What is your take on pump-spill, fill-pump-spill, and spill-pump-spill, with regards to varying the fill-pump-spill injection cycle over various rpm and engine loading?

I am familiar with fill-pump-spill injection cycle, and have noted the accumulator in the spill chamber, which can absorb and store fuel pressure.

DB2/4, DM2/4 all employ the fill-pump, variable start, fixed end of injection. The Metering Valve controls how much fuel fills the plungers, which determines when they hit the cam lobe and the end of injection is at the peak of the ramp.

DE2s (Late model John Deere Electronic) use the spill-pump-spill, variable start, variable end method with basically the same FSOL setup as the DS pumps. Loooong cam lobes allow these dead cam pumps to spill until desired advance is reached, then FSOL energizes until desired fuel quantity is reached and de-energize to spill the excess.

DS4 Pumps employ the fixed start of injection, variable end of injection, and pump-spill method to control fuel quantities. FSOL is energized at the same point relative to the cam ring (LO Res), before the ramp starts and ends when desired fuel quantity is delivered (HI Res).

There are 2 accumulators in DS4 heads, The first is on a medium spring its role is to absorb and smooth the Transfer Pressure changes inside the pump, the second is a heavier spring that buffers the spilled fuel to keep the high pressure changes from causing damage/erosion inside the head.