Starting problem
 

My 2003 Duramax LB7 is one of those that has the starting problem when it is hot. Starts fine when cold. Won't start when hot. Runs great, smooth, no smoke, when it starts. Dealer says injectors test ok.
I have done the following:
Put an Air Dog lift pump on and removed the stock fuel filter head and replaced the fuel hoses.
Shimmed the fuel pressure regulator valve.

I have found a way to start it when it is hot which will sound bizarre but it works every time. Put a bag of ice cubes on top of the engine where the thermostat head is and wait 15 minutes and it will start. Not kidding. It works.

My question is what might be located in the general are of the thermostat cover that would keep the engine from starting when it is hot and be effected by cold water enough that it would then allow the engine to start when it is cold.

Any ideas out there.

The only thing I can think of is the Fuel Pressure Regulator.

Thank you for any help.

if the dealer didn't check the return rates then there is no way they can tell you the injectors are fine. most will jest scan for the balance rates and make judgments from that.

hot start issues are typically from high return rates. hotter fuel in the lines is thinner and more will leak by the injectors. it has also been from cracked injectors. are you making oil?

as to your ice trick, that is new to me. the only sensor that i know of in that area is the ECT sensor. in the programming, the colder the temp the more the ECM injects fuel. the only way i can see it working is if the increase is done by increasing fuel pressure. there is a table in the programming that will do that so it may be it.

the pressure regulator is a little further back and deeper in the valley of the engine. hard to see your ice cooling this off.

looks like it is time to check injector return rates.

No fuel in the oil. Guess I am going to have to bit the bullet and replace the injectors.

Try to diagnose your problem before throwing parts at it!!

Get the injector RETURN rates checked first:hellox: