7.3 liter hard start in am

I recently bought a '98 E-350 with a 7.3 liter diesel engine. I looked at it a couple times before buying it and it started right up both times. Now when I go to start it in the morning it takes several attempts. It doesn't seem to matter if it's warm outside or not. If I run it at all during the day it will start right up again easily. When I leave it over night it's hard to start again.

I have checked all the glow plugs and have 1 ohm at each. I have changed oil, and fuel filter. I learned there was an open recall for the crank sensor, so I had Ford replace that. The hard start problem persists. They suggested I might try changing the glow plug relay before paying for a diagnosis. They also noticed a slight fuel smell from under the hood. I may have not gotten the fuel filter cap on quite tight enough.

When the truck is running it runs nice. Lots of power. but when you are coasting at low speed, 30 MPH or so, it almost sounds like the engine stops running sometimes, it doesn't though because it jumps right up when you touch the pedal. (normal?)

Does any one have any ideas where I might look for a cause?

Thanks