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93 Dodge Ram 150 318

After changing the water pump and small hose going into water pump, my truck will start when cold but will not start after it is warmed up. It will turn over but won’t start. I am not sure I did something wrong or is it a new problem.

Check all your vacuum hoses…twice.

Might have accidentally disconnected an engine coolant temperature sensor in the process so the computer thinks the engine is cold all the time and when its actually warm the mixture is too rich and it won’t start. If there’s air remaining in the cooling system that could confuse the sensor readings too, if the sensor is located in an air pocket.

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Does the truck stall after it warms up or does it run fine until you shut it off and then not restart?

The truck runs until turned off. Then it will not start again - after being warmed up.

Thanks for information, will look into that.

ECM codes can be accessed by switching the key to the ON position, then back to OFF three times then leaving the key in the ON position and watching the ENGINE light. When 55 is pulsed there are no more codes and 12 is not a problem code. Post results.

If this turns out to be a coincidence, nothing to do with the cooling system work, then my guess is an ignition system problem. If this engine uses a crank position sensor, start with that as they are known to suffer hot-soak problems. Check the ignition module and coil after that.

No codes came up. Also this is a 5 speed standard transmission.

Have you attempted to start the warm engine with the accelerator pressed down?

Yes- pull the codes, if no codes come up, see it the throttle body housing is dirty inside, can be cleaned up with carb cleaner, an old toothbrush and some rags.