shamrock246

I just bought this truck about 3 weeks ago the previous owner thought it had a bad engine so i took a chance on it, i ran across the tech note about the cranck sensor going bad and throwing the engine out of time and doing damage to fly etc. i changed the sensor and the truck fired right up and ran great,i changed out the flexplate and after that it worked fine i decided to degrease the engine and trans so i could get an idea if hads caused any leaks after doing that it started doing the same thing dried out the connector on the crank sensor and still did it went and bought a new cranck sensor and it fired right up,so i decided to seal the connector going to the crank sensor with some sealant to make sure that if i went thru a puddle water wouldn't get in and wreck the sensor it strarted right up after that,i sat for about 3 days and it rained today and when i went to go start it,it sounded like the crank sensor went bad again and the engine actually stalls the starter motor, i didn't drive it in the rain and it had stopped about 3 hours before i was goingt to leave,

1-the sensors are from autozone pn# SU1207 and come with a 2 year warrenty should i buy from napa or maybe OEM

2-does the crankshaft variation test have to done right away or will it just give false misfire codes until i get it done

3-i'm going to be using this vehical to tow my boat so reliability is top on my list


any help would be great
Sean

RacerX

are the contacts in the wire harness to the crank sensor moving? This could be your bad connection. One of the wires comes loose and you get a bad signal.

shamrock246

thanks racerx thats one of the things i'm looking into replacing the circuit looks simple and goes strait back to the computer i would like to do all right the second time before i tear up a flywheel i just put in

RacerX

what code do you get? Intermittent crank signal or something like that?

shamrock246

theres no code,the tech bulliton said it won't throw a code,yesterday it started mulliple times without a problem and i hadn't touched a thing i took the cap of the distribitur and checked the base timing i gave it a little adjustment in the direction of rotation (retarded it)it might not been enouph to even matter,when the problem was happening i would watch it on an timing light it would give me 2 blinks @ tdc the it try to start and the mark would go in the advanced driection and the starter would stall from my research the computer controls the ignition timing thru the crank sensor i have a new connector on order thru napa and will install it and check as much of the harness as possilbe



Sean

RacerX

pull back on some of the looms and see if the wires are pinched or broken also.

j-wilco5

racerx-shamrock246 hey im new to the site just looking seen post of crank senser-tring to fix 97 z71-think might be senser-this tech note could you possibly help direct me to find it-sorry for just postin out of blue

shamrock246

j-wilco-what is yours doing no start,trying to start?i pasted the bulletin,if i unplug the sensor i get no spark


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.

Important : Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal.

Parts Information

Parts are currently available from GMSPO.