Won't start when engine hot - 1994 Volvo 850

You could have a faulty engine coolant sensor or intake air temperature sensor. Fuel injectors clogged or dirty flooding engine.
Clean fuel injectors, replace fuel filter and air filter, and see if the problem persists.
If it does ECT sensor is bad. If CMP sensor was bad, the vehicle won\'t start whether cold or hot. CKP senso and CMP sensor work together if either one fails, the vehicle won\'t start. Have the vehicle code scanned.

Someone will need to figure out if you are dealing with a no spark or no fuel pressure issue to proceed.
Could be a long list of things including relays and electrical components.

sometimes when the starter gets hot it won't allow the Bendix to engage properly.

My first guess would be a relay or the ignition module.
Do you have spark at the plugs when it won't start ?

probably needs a new battery

What kind of car/truck,what engine?????????

ENGINE FLOODING REPLACE AIR FILTER AND CLEAN FUEL INJECTORS DIRTY LEAKING FUEL INJECTORS WILL LEAK CAUSE ENGINE TO FLOOD OUT.

Maybe needs a new radiator, thermostat, how is the water pump?I had this engine for 400.000km.

Make sure you don't have an OVERHEATING problem. Engine damage is sure to occur if it's running too hot. don-ohio

Check your fuel tank, fuel pipe and hoses might have a leaky somewhere.. else your injection pump has a leaky internal high presure pump.