chevy 99 2500 vortec 5.7

[Vrat]

Few weeks ago, my truck out of the blue had some starting issues, where it would crank pause, crank pause, even with a full charge.

Few hours later it cranked right up. The next day, same issues, however this time it burnt my stock starter up. I assumed then that my starter may have just been going bad. I went and purchased a new one, installed it, and the first crank was instant, the following day however, the truck did the same starting sequence, but now with bad grinding noises. I attempted to shim, and un shim the starter to no success. In a final attempt to try and get the truck to start, it kicked back and slung my starter complete of its bolts.

I managed to get the broken bolts out an reinstalled the starter, however instead of pushing it, I decided to research a bit. Found this..

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Engine - No/Hard/Slow Start/Backfire/Kickback

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 00-06-04-014

Date: April, 2000

TECHNICAL

Subject:
No, Hard, or Slow Start, Backfire or "Kickback" During
Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338
(Replace Crankshaft Position Sensor)

Models:
1999-2000 Cadillac Escalade
1995-2000 Chevrolet and GMC SIT Models
1996-2000 Chevrolet and GMC C/K, M/L, G, P Models
1996-2000 Oldsmobile Bravada
with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine
(VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29)

Condition:
Some customers may comment on one or more of the following conditions:

^ Backfire during crank/start
^ "Kickback" during crank/start
^ "No" start
^ "Slow" or "hard" start/crank
^ "Grinding" or unusual noises during crank/start
^ Cracked or broken engine block at the starter boss
^ Broken starter drive housing
^ Broken starter ring gear on flywheel
^ Any combination of the above

Cause:
A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss.

Correction:
Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear).

Notice : When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel.
-----------------------------------

Ok so I checked the old sensor, and sure enough it was broken, or atleast when i took it off, it showed spliting, and pealed right off, leaving some in the motor, which i was able to get out, and inside looked oily and basically looked bad..

Anyway I purchased, and installed a new one, however the symptoms have not gone, to the point i'm now on starter #3--- At start of starting it sounds fine, by 2-3 rotations its like the motor locks up...then wait a few an same results.

I pulled all of the plugs at one point, turned it over, and it cranks like a champ, no grinding noises, and smooth...

I know or have read about relearning, which is fine, but how would I get it to relearn if not running? will a tech 2 fix the problem? anyone had similar experience that can shed some light on it, before I waste more $$...

[j cAT]

replacing the starter should be easy but many times its not.

I use USA starters because they are not too expensive and I have yet to shim one.

shiming requires engaging the solenoid and measuring the gap . I like about .125 in which is a bit too much. BUT this is the starting point. if the gap is too tight things get broken.

the flywheel needs to be marked and rotated completely for damage.

JUST BECAUSE ITS NEW OR SHOULD I SAY NEWLY REBUILT DON'T MEAN MUCH IN TODAYS WORLD.

IF THE CRANKSENSOR IS BROKEN IT SHOULD NOT RUN. NO SIGNAL !

IF THE TIMING IS THAT FAR OFF THEN ITS TIMING CHAIN JUMPING OR A WORN OUT DISTRIBUTOR.

[j cAT]

forgot about hydrolock. coolant flooding the cylinder will also do it .

[Vrat]

Originally Posted by j cAT

forgot about hydrolock. coolant flooding the cylinder will also do it .

Yea I covered that at the bottom of my post, pulled all the plugs, the rotations are smooth, and sounds like it did before all this mess while in cranking motion. Am able to turn it with ratchet at the crank pully with ease--

I know it didn't "hyperlock" while driveing (done that a couple of times to know the symtoms) but even if possible over night hyperlocking, removing the plugs and clearing it, replacing them would atleast get it to crank it seems (as ive done that before too)

Ive reserched this inside and out, and ofcourse to no success, other than people claiming to need a tech 2 scan after changing a faulty crank sensor---But they also say they are able to drive it to get it done mine wont even crank---

BTW mentioned that the sensor was broken--

[jamesslcx]

Vrat, could the computer be advancing the timing too far during cranking? Sounds like you've covered everything else and it turning over easy by hand and cranking with the plugs out got me to thinking. Very weird problem though, good luck.

[Vrat]

50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss.

Yea in that GM deal I posted it mentions that it does advance it... and as said, causes starter issues.. Problem i am having, is getting it running long enough to go get it tech 2 done. I live in farm country, so its not like a GM dealer easily gotten to for me at them moment, and the tow bill would be insane. But for most part really hoping someone experienced this issue before, and is positive a tech 2 work done on it is all that it needs.

I have the plugs out now, gonna let it sit over night, and give it a try again to re-test the hydrolock theory, or just to see if maybe some water is sitting in there. I do live in wet climates.. And since the truck is out of commission at the moment I may just go ahead an change the upper intake gasket, since ive read these vortecs are very prone to blwo em.

But if their is away to adjust I could adjust somthing to get the thing started (the advance) I would appriciate it, I'd much rather drop it at a shop and get it all done. But mobile mechenics here would bust my bawz just in travel expenses.

[j cAT]

Originally Posted by jamesslcx

Vrat, could the computer be advancing the timing too far during cranking? Sounds like you've covered everything else and it turning over easy by hand and cranking with the plugs out got me to thinking. Very weird problem though, good luck.

the distributor controls timing. if you have arcing there the wrong cylinder gets a spark. this then could cause the starter to get damaged.

not a common problem but still it happens.

[j cAT]

unplug/disable the distributor see if it cranks good. if so then look for distributor failure. these vehicles have distributor issues at this age/mileage.