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Old 11-07-2012, 10:14 AM   #11
hatzie
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Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,931
Re: 6.2 starting issues

Diesels need 2 things. Fuel & Compression. These 6.x Detroits also need glow plugs to really get enough fire when they're cold.

Your tests show you have two of the three. Fuel and probably Glow.

Have you checked the compression on all 8 cylinders?
Numbers should be in the 350-500psi range. Each cylinder should be within 75% of the other 7. If #4 is 410 then no cylinder should be less than 305. 300psi is a minimum for ignition but it will be hard starting and smoky at 300.

The compression gauge has an adapter to screw into the glow plug hole. I usually remove all the glow plugs to make it crank easier.

Unplug the FSS and HPCA before you crank it because it's possible to fire a cylinder and blow up the gauge.

Do not ever add oil to the cylinders. It could fire that cylinder and blow up the gauge.

Wear eye and face protection and don't look directly at the glow holes as the compression blows chunks of carbon and rust around.

A Diesel compression gauge on Amazon. http://www.amazon.com/Compression-Adapters-Lincoln... http://www.amazon.com/Compression-Adapters-Lincoln...
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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