1996 Yukon Vortec 5.7 issues starting

[Etheridege]

I will try to keep this brief and concise.

1996 Yukon Vortec 5.7 was having issues starting after periods of heavy rain. Just couldn't get it to start, but after sitting for a day or two to dry it started with some hesitance and an occasional backfire. Thought it may be a cracked distributor cap so I replaced it along with the plugs and also new plug wires. It seemed okay for a bit but eventually the starter gave way so I replaced the starter. Backfire caused that new starter to break nose cone so I replaced. Everything ran fine for a couple of weeks until I let it set for a few days without cranking. I started to get the starter/flywheel grind when turning ignition. I eventually started it once so I doubt I broke starter nose again. It failed to start after shutting off engine. I will check starter and see.

After some research I came across the Sunlitcomet post regarding a tsb listed below.

I connected my Actron CP9175 but it shows no codes. Is it possible it won't throw a code? I guess I will try replacing the crankshaft position sensor. I thought it was located just above and to the front of the starter, but it looks nothing like the sensor listed as the replacement. The one I found does not have the three prongs, it only has one pin. Any help locating it on this engine would be great, along with any other suggestions.



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.

 

[Etheridege]

***Update***

So I pulled the starter and the nose cone was not broken so I took it down to the auto parts place and it failed the bench test, even though it was only a month old. Glad it was covered by warranty.

I also pulled the crankshaft position sensor. It was pretty gunked up. I replaced it as well and the engine initially had a bit of flywheel grind, but stopped after the first couple of bumps to the starter and the engine fired. I started it about a half dozen times then to continued success. I did notice some liquid around the area of the CPS but couldn't tell if it was a leak from the water pump or the gasket. At least it is running now.

Thanks to Sunlitcomet for the TSB concerning the crankshaft position sensor.

This '96 still runs great but I expect it to have more problems going forward considering its age and the fact that it has 275,000 miles on it.

Thanks to all who viewed the previous post.

 

[SunlitComet]

The code will not always happen but it is a giveaway when seen with those symptoms. Hope all goes well.