I have a 1994 Dodge Diesel...that has ran/started fine up to 2 weeks ago. One morning (85 degrees) it wouldnt start......not even fire. I checked the fuel solenoid and it worked fine. Next, a friend suggested I pressurize the fuel tank. I did and the truck started and ran fine. The next morning (after setting all night) it wouldnt start again. This leads me to believe the check valve in the X-fer pump isnt working. Can anyone tell me if my thinking is correct or offer another idea......THANKS?

 

Just replaced mine 225,000 miles. You probably need a new lift pump. doug

 

Most likely your return fuel line is leaking air. It can allow air in without leaking fuel out. Less than 2 feet of 5/16" diesel rated hose will fix it right up. Definitely try this before replacing the pump, I know of several lift pumps that have gone over 500k.
In red below.

 

It could be the fuel return line that runs behind the fuel filter real close to the block. The rubber breaks down from being so close to the engine heat. Do a search on here and you'll find what you're looking for.

 

Dang! infidel beat me to it! hehe. Thats what you need to know right there in his post.

 

Mine did the same thing 2 weeks ago, running fine.. then would'nt start, turned out to be the 1/2" 90*hose between pre filter and lift pump.

 

I just did my return line near the block last week on my 95 ,also I did not like what I saw when I looked at all the lines,they all appear to be on there way out,so you may whant to think about that also.....