P0251-shop thinks its timing chain stretch? - Page 2 - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
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6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum

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Old 04-29-2019, 05:00 PM   #11 (permalink)
JMJNet
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Add fuel filter to that list and make sure there is no leak between the filter and IP.

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Old 04-29-2019, 09:42 PM   #12 (permalink)
DieselPro
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Quote:
Originally Posted by vstech View Post
150K timing chain? Really? Wow.
...
Quote the whole thing >>>And your timing chain should be replaced around 150K for best performance. <<<

You will notice I said best performance. While the chain will work fine for years and years it does get slack in it over time. From dirty oil, wear, or whatever. The real problem is the injection pump is tied into this system.

The injection pump does not like to "chatter". Basically vibrating back and forth with pulsations. The fuel output can do weird things when this slop appears. I have seen it on a test stand do all kinds of things when the drive coupling is loose. Most test stands built today have 50 lb. flywheels in them to eliminate this chatter. So like I said 150K for best performance. Just might restore the like new truck performance in an old truck.

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Old 04-29-2019, 10:19 PM   #13 (permalink)
dauber
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Quote:
Originally Posted by JMJNet View Post
Add fuel filter to that list and make sure there is no leak between the filter and IP.

Filter replaced less than 200 miles ago, no leaks found.
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Old 04-29-2019, 10:34 PM   #14 (permalink)
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So I picked up my suburban today and drove it home. Talked to mechanic, he stated he cleared codes and spent less than 15 minutes on it. He re-learned everything with the cpu, checked TDC and it is at -.92, TDC was at -.58 back in December so he believes this is due to chain slack. I asked about optical sensor and he said I am welcome to remove the pump and bring it in so they can test it, but he strongly feels its the chain.



Can someone who has more knowledge than me tell me if the chain slack is the only reason for the timing to change? could a bad optical sensor or worn harmonic balancer cause this ?



Suburban ran perfect home, but I know the P0251 code is soon to show up.
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Old 04-29-2019, 11:00 PM   #15 (permalink)
jnlperformance
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Tdco is reset every 50 starts by the ecm...
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I'll get back to this later...
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Old 04-29-2019, 11:12 PM   #16 (permalink)
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Originally Posted by jnlperformance View Post
Tdco is reset every 50 starts by the ecm...

Thank you. So I will stick to my previous plan and start trouble shooting and repairing this coming weekend.
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Old 04-30-2019, 01:30 PM   #17 (permalink)
JMJNet
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How is the truck running now?
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Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator
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Old 04-30-2019, 05:47 PM   #18 (permalink)
dauber
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Truck ran great on the way home. About 30 minutes from shop to home, no codes or issues. I have it parked for now until I return home on Saturday to change out HB and pulley as well as pmd and look closer to see if there may be a optical filter present.
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1998 TDI Jetta-sold
1996 TDI Passat-sold
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Old 05-01-2019, 02:47 PM   #19 (permalink)
JMJNet
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I know it is a Preventative Maintenance but if there nothing wrong with the HB and Pulley, just leave it alone.
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1995 GMC Suburban:
PMD in Bumper
Leroy Diesel Flight System PMD
Leroy Diesel Oil Cooler Line
4" Warpspeed Exhaust
Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator
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Old 05-01-2019, 09:54 PM   #20 (permalink)
dauber
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Even if it’s never been changed? So you are saying it’s not likely causing my problem.

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1998 TDI Jetta-sold
1996 TDI Passat-sold
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