My 2000 Ram 1500 5.9 truck runs great when it runs. Some days it will fire right up like it should. Some days it acts as if it has lost the fuel prime. If I crank and crank and crank on it it will eventually start. Most times I will have drained the battery and had to put the charger on it. After I get it to start the first time it will run perfect for the rest of the day. Between this problem and the fuel gauge being off, I figured a new pump would correct my problems. Installed the new pump last Sunday, ran great, the truck sat from last Sunday until today (Wednesday). Went to use it today and back to the same thing. What else would cause a loss in prime?

 

Do you hear the fuel pump prime when you first turn the key on?

If it doesn't wanna start, don't crank the motor, just cycle the key on/off, and prime the pump a couple times, if it still doesn't wanna fire after that, then you either got a bad pump, (not airtex by any chance was it?) or something else is going awry.

 

Yes, I do hear the pump. I have tried cycling it on repeatedly as you suggested but that dosent seem to work. I'm not sure of the brand of pump. Ive already thrown the box away, I'll have to check my records and get back to you. Thanks for the suggestions.

 

Autozone has the fuel pressure guage loaner tool for $115, get your money back when the tool is returned. Would be nice to see what the line pressure is.

 

You have all the signs of a failing fuel pump. I agree with beeker, check fuel pressure.