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Old 02-13-2020, 04:41 PM   #1 (permalink)
Tr00b
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Injector testing, rebuilding and pop pressure adjustment

I am CHEFFING up a big old injector salad. I have roughly 60 plus injectors and at my disposal to try to rebuild one set for my truck. Paleyjim and I pooled resources to buy a pop tester and put as many injectors in one place as possible to choose from (because I'm poor).

I have an S code EGR truck. Its been long deleted and MPG has been for a long time. But its also been starting hard and smoky for years even with basically new glow plugs which were extensively tested. Clatter that has been called injector knock until super warm by trained ears. So I downed the truck to fix them. The trucks performance is pretty strong for a 6.5.

Most of the injectors that have been removed from parts engines are testing bad-ish with a rougher spray pattern between 1900 and 2100 psi, no chatter. A few bad as 1000 psi. Kind of disappointing.

I half of my injectors out. Mind you, there's no record of these ever being replaced or worked on. They are testing at right on 1800 psi with nice chatter and the best pattern I've seen yet, but only done the passenger side bank so far.

I do not want to buy new nozzles unless absolutely necessary.

Questions:

Did the S code turbo trucks come with 1800 psi injectors? This thread didn't include injector specs for S-Code engines.

https://www.dieselplace.com/forum/2429991-post2.html

If you leave an injector out of use for awhile, stored reasonably (but uncapped), will it reduce it's spray pattern or create deposits that reduce injector performance, requiring cleaning? IE... like storing a carb with gas in it?

Can injector pins/nozzles be lapped successfully? This thread seems to indicate you can (near the end)

https://www.dieselplace.com/forum/63...d-today-2.html

Will higher pressure injectors increase performance? Worth it to shim mine out or try to build ones with 2200 psi spec? Or just try to get as balanced as possible? I'd sort of call this thread inconclusive on that.

https://www.dieselplace.com/forum/63...ml#post2429991

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1996 GMC K1500xcab 6.5 3.73 4L80E rear bags Bought at 99k 12/13 now 138k 9/17
Repairs:
BWD OPS 1/14 Heath PMD kit 3/14 Airtex boost solenoid 6/14 Lube Specialist cooler lines and cooler, rad support mounts, Pro Comp ES9000 Shocks, rear brakes 7/14 Interstate Batts, Cooper AT3 tires, Hummer H3 rims, stepper motor 4x4, coolant flush 11/14 Stabilizer bar links, soot trap gasket 9/15 Dorman tank, sending unit/sock delete, filler neck, filler neck, hose, Leroy's Tank Barbs, SAE30R9 lines, WIX filter head and prefilter with brackets by paleyjim, intake manifold gaskets 3/16 Used transmission, dipstick tube, fluid flush, drain plug pan by paleyjim, power steering fluid flush, transfer case seals and fluid 9/16 Duraterms 11/16 Ball Joints and wheel bearing drivers side. Powerstop pads, lubed sliders 4/17 AD244, Leroy's Flight Systems PMD 9/17
Performance:
Ashland Muffler 2.5 X-over 12/13 FTB FFM by paleyjim, ported upper egr delete S-code, lower F-code, ported IP fitting, FASS DRP-02 lift pump 3/16 Transgo Shift Kit by paleyjim, Energy Susp. engine+trans mounts 9/16 Ported GM8, Diamond Eye, Quadstar tune 11/16 K47 Box, Glowshift 3-1 1/17 Leroy's Billet Crank pulley, Fluidampr. 9/17

Last edited by Tr00b; 02-13-2020 at 04:43 PM. Reason: fix link
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Old 02-13-2020, 08:25 PM   #2 (permalink)
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[QUOTE=Tr00b;9878978]
>>>Did the S code turbo trucks come with 1800 psi injectors?

No

>>>If you leave an injector out of use for awhile, stored reasonably will it reduce i injector performance?

A varnish can develope and require disassembly and cleaning.

>>>Can injector nozzles be lapped successfully?
Not really, Good cleaning in carb cleaner or acetone better/ Lapping to much or to coarse of a compound can ruin a injector. Light 1,000 grit

>>>Will higher pressure injectors increase performance?

No. Set it around 2,100-2,150 PSI and be happy. Sometimes setting a good old injector higher can make them not chatter.

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Old 02-13-2020, 09:52 PM   #3 (permalink)
56pan
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For whatever this is worth: I replaced all of my injectors about 6 weeks ago. '93 C2500, 506 block mil. surplus engine. DB2 mech. inj. pump. The old ones and the engine had about 80,000 m. on them, but I was hearing what I believed was injector knock. Had a pop tester and every one of the old injectors sprayed at_exactly_1800 psi. Not a dime's worth of difference between them. Some were streaming a little instead of a good spray pattern. The new ones all sprayed at_exactly_2200 psi and no difference at all in that pressure on all of them. Spray pattern looked the same to me as the old ones with a little streaming. These were new Bosch injectors. Truck starts quicker and I'm getting noticeably better mileage. Injector knock is still there, but found out that my HPCA is stuck in full advance. Engine's running with full advance all the time, and it's not the solenoid stuck. That'll be a post I make here looking for advice when I've looked into it some more when I've got time. Probably need a new/rebuilt inj. pump.
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'93 C2500 280,000 m.
60k on new AMG mil. surplus engine
Turbo with name that starts with A.
Straight pipe exh. (but it ain't that loud).
Peninsular intercooler
Boost, EGT, Glowshift intercooler in/out temp. 3 guage pod.
Rebuilt complete susp. with polyurethane bushings. (Bad idea).
20k on GM 4L80E rebuilt trans.
Dual thermostat/Duramax fan/high flow water pump.
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Old 02-13-2020, 10:04 PM   #4 (permalink)
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Pop test with gauge closed. Sharp, short blast on the handle is how you test them.

Long full stroke on the handle is not how you test them. This will make the injector check bad.
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Old 02-14-2020, 12:40 AM   #5 (permalink)
56pan
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That is how I checked them. Some of the old and the new still had partial stream, not all spray. Didn't worry about it.
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'93 C2500 280,000 m.
60k on new AMG mil. surplus engine
Turbo with name that starts with A.
Straight pipe exh. (but it ain't that loud).
Peninsular intercooler
Boost, EGT, Glowshift intercooler in/out temp. 3 guage pod.
Rebuilt complete susp. with polyurethane bushings. (Bad idea).
20k on GM 4L80E rebuilt trans.
Dual thermostat/Duramax fan/high flow water pump.
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Old 02-14-2020, 12:33 PM   #6 (permalink)
Tr00b
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That's how I'm testing mine too. Usually takes 5 or so bumps to get the air out of the injector body, then testing can commence.

I'm going to try chrome polish to lap/clean the pins, way finer than 1000 grit. Start with the most fubar ones... Haven't started tearing them apart yet.

If I build a set out of my original injectors, and 2 or 3 chatter but the rest do not, does it matter? How significant is the chatter vs pattern vs pressure balance?
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1996 GMC K1500xcab 6.5 3.73 4L80E rear bags Bought at 99k 12/13 now 138k 9/17
Repairs:
BWD OPS 1/14 Heath PMD kit 3/14 Airtex boost solenoid 6/14 Lube Specialist cooler lines and cooler, rad support mounts, Pro Comp ES9000 Shocks, rear brakes 7/14 Interstate Batts, Cooper AT3 tires, Hummer H3 rims, stepper motor 4x4, coolant flush 11/14 Stabilizer bar links, soot trap gasket 9/15 Dorman tank, sending unit/sock delete, filler neck, filler neck, hose, Leroy's Tank Barbs, SAE30R9 lines, WIX filter head and prefilter with brackets by paleyjim, intake manifold gaskets 3/16 Used transmission, dipstick tube, fluid flush, drain plug pan by paleyjim, power steering fluid flush, transfer case seals and fluid 9/16 Duraterms 11/16 Ball Joints and wheel bearing drivers side. Powerstop pads, lubed sliders 4/17 AD244, Leroy's Flight Systems PMD 9/17
Performance:
Ashland Muffler 2.5 X-over 12/13 FTB FFM by paleyjim, ported upper egr delete S-code, lower F-code, ported IP fitting, FASS DRP-02 lift pump 3/16 Transgo Shift Kit by paleyjim, Energy Susp. engine+trans mounts 9/16 Ported GM8, Diamond Eye, Quadstar tune 11/16 K47 Box, Glowshift 3-1 1/17 Leroy's Billet Crank pulley, Fluidampr. 9/17
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Old 02-14-2020, 08:29 PM   #7 (permalink)
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Got to chatter to work right

Try disassembly and cleaning first.... Polish the bad ones then
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Last edited by DieselPro; 02-14-2020 at 08:31 PM.
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Old Yesterday, 09:51 PM   #8 (permalink)
Tr00b
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Thanks for the replies dieselpro and 56pan.

Took the worst injector I could find (one of Jim's) 1000 psi with a bad pattern. Cleaned it and put it back together. Went from 1000 to 1800 psi with a decent pattern and somewhat of a chatter. Lapped just the conical tip area with chrome polish and got a better pattern but with less chatter, lots of vapor floating around the shop. I didn't find a spacer in the injector body. Going to try to lap it some more. Didn't improve the pop pressure really.

Where are the spacers usually located?

What causes "chatter" and how do you improve it?
__________________
1996 GMC K1500xcab 6.5 3.73 4L80E rear bags Bought at 99k 12/13 now 138k 9/17
Repairs:
BWD OPS 1/14 Heath PMD kit 3/14 Airtex boost solenoid 6/14 Lube Specialist cooler lines and cooler, rad support mounts, Pro Comp ES9000 Shocks, rear brakes 7/14 Interstate Batts, Cooper AT3 tires, Hummer H3 rims, stepper motor 4x4, coolant flush 11/14 Stabilizer bar links, soot trap gasket 9/15 Dorman tank, sending unit/sock delete, filler neck, filler neck, hose, Leroy's Tank Barbs, SAE30R9 lines, WIX filter head and prefilter with brackets by paleyjim, intake manifold gaskets 3/16 Used transmission, dipstick tube, fluid flush, drain plug pan by paleyjim, power steering fluid flush, transfer case seals and fluid 9/16 Duraterms 11/16 Ball Joints and wheel bearing drivers side. Powerstop pads, lubed sliders 4/17 AD244, Leroy's Flight Systems PMD 9/17
Performance:
Ashland Muffler 2.5 X-over 12/13 FTB FFM by paleyjim, ported upper egr delete S-code, lower F-code, ported IP fitting, FASS DRP-02 lift pump 3/16 Transgo Shift Kit by paleyjim, Energy Susp. engine+trans mounts 9/16 Ported GM8, Diamond Eye, Quadstar tune 11/16 K47 Box, Glowshift 3-1 1/17 Leroy's Billet Crank pulley, Fluidampr. 9/17
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Old Yesterday, 10:02 PM   #9 (permalink)
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Shims located in top of injector. Place thick shims against spring. Think .003" equals 100 psi.

Chatter does not improve with lapping, it usually gets worse. If it doesn't chatter discard it.

Vapor is flammable so use in a well ventilated area.
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Old Yesterday, 11:20 PM   #10 (permalink)
Tr00b
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Do the injectors always have a spacer? Or only ones more than 1800psi? Did not find one in this particular one.

Discard the pin/nozzle or the whole injector? Is when switching nozzles/putting in new nozzles when you need to lap the parts inside of the injector body?

Do you use the heat shield in the tip?

Does it matter if the lower injector body is really pitted from rust?

__________________
1996 GMC K1500xcab 6.5 3.73 4L80E rear bags Bought at 99k 12/13 now 138k 9/17
Repairs:
BWD OPS 1/14 Heath PMD kit 3/14 Airtex boost solenoid 6/14 Lube Specialist cooler lines and cooler, rad support mounts, Pro Comp ES9000 Shocks, rear brakes 7/14 Interstate Batts, Cooper AT3 tires, Hummer H3 rims, stepper motor 4x4, coolant flush 11/14 Stabilizer bar links, soot trap gasket 9/15 Dorman tank, sending unit/sock delete, filler neck, filler neck, hose, Leroy's Tank Barbs, SAE30R9 lines, WIX filter head and prefilter with brackets by paleyjim, intake manifold gaskets 3/16 Used transmission, dipstick tube, fluid flush, drain plug pan by paleyjim, power steering fluid flush, transfer case seals and fluid 9/16 Duraterms 11/16 Ball Joints and wheel bearing drivers side. Powerstop pads, lubed sliders 4/17 AD244, Leroy's Flight Systems PMD 9/17
Performance:
Ashland Muffler 2.5 X-over 12/13 FTB FFM by paleyjim, ported upper egr delete S-code, lower F-code, ported IP fitting, FASS DRP-02 lift pump 3/16 Transgo Shift Kit by paleyjim, Energy Susp. engine+trans mounts 9/16 Ported GM8, Diamond Eye, Quadstar tune 11/16 K47 Box, Glowshift 3-1 1/17 Leroy's Billet Crank pulley, Fluidampr. 9/17
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