6.5 won't start after it warms up

[lnvphoto]

I have a 93 6.5L K2500 4WD 5-speed. Starts great when its cold but after it warmsup and runs from 30min on, it wont start or it will after I turn the crank for 10 to 15 seconds. Any suggestions?

[More Power]

A hard to start hot problem can usually be attributable to a couple difference causes. 1- Slow cranking speed. 2- Worn fuel injection pump.

Injectors well past their prime can also be a contributor, because they may not properly atomize fuel at cranking speeds (something less than 200-rpm). Those engines that start better warm/hot with a glow cycle usually have worn out injectors. Glow plugs help ignite the poorly atomized fuel.

The winterized diesel fuel we have access to here in the north is pretty thin. With the engine at operating temperature, it's even thinner. Really thin fuel makes it hard for a worn out fuel injection pump to generate high enough pressures to pop the injectors at cranking speeds - with the engine close to operating temperature.

Changing a fuel injection pump is a big step. To be sure whether it is the pump, try raising the fuel's viscocity. Do this by adding straight 30 weight motor oil to the fuel to produce a 10% oil / 90% fuel mixture. Mix the oil/fuel in a separate container before pouring it into the tank. Obviously, this is much easier if the fuel tank is nearly empty.

If the problem disappears with the thicker fuel, you've just discovered the source of the problem - a worn out fuel injection pump.

Jim

[JeepSJ]

Another quick test is to pour cold water over the injection pump. When my pump started failing, I always carried a bottle of water with me. When it wouldn't start, I dumped water on the pump and it would start right up.

[racer55]

Room temp water is good enough-actual cold water might shock a hot IP too much and make it seize.