dodge ram 318 cranks really fast but doesnt start

Have you done a compression check yet?

No i havent tried a compression check. But the truck runs fine after it starts. If it had to do with compression it would bog out wouldnt it?

An engine that is cranking over unevenly or abnormally fast, is a key indicator of an engine mechanical failure. A compression check should be performed to detect a mechanical failure. If the engine is in proper mechanical order, the ignition system should be inspected for spark while the engine is cranked. If there is no spark, the ignition control module, distributor pick-up or crankshaft sensor should be tested. A visual inspection of the distributor cap and rotor (if so equipped) should be performed. If spark and proper engine compression are present, a diagnosis of the fuel system will be necessary. Fuel pressure and injector pulse should be tested. You will need to determine if the electric fuel pump is operating, the injectors are firing and there is adequate fuel pressure. If compression is too low it will be very hard to start but may run, but with less power than normal.

Thanks ill check what you have said.

I have a1976 Dodge van/RV with a 318 with a carter thermaquad carb on it. If I let it sit for more than 2 or 3 days, the only way I can get it to start is to pull the air cleaner cover and spray starter fluid several times. Once it starts, I have to continue to spray for 4-5 seconds , and then it runs fine. The engine only has 18000 miles on it, but it has set for extended periods of time in the past . Is it possible it is losing the carburetor prime somehow? Any help is greatly appreciated . Jim F

Fuel rail and injectors.. Take it apart and clean it well