Truck Repair: Ford Power Stroke Diesel 7.3, power stroke diesel, fuel tank cap

Question
Truck started one morning and check engine light came on and the truck seemed to lose power.  Took truck back home and drove other truck to work. After work came home, drove truck and it ran fine, no light.  Changed fuel filter and added a can of Sea foam.  Next day same thing, but I continued driving for about 20 miles with light on.  At lunch I took it to a Ford Dealer, of course, it ran fine all the way there.  They hook up the computer and found no code.  Could not find any problems.  Drove the truck for two more day with no engine light.  The truck did want to surge a little.  After two days it stopped and I had to have it towed to another Ford Dealer.  After towing the service writer restarted the truck. So they checked it out.  They replace some type of fuel requlator and the cam positioning sensor.  Truck ran fine for about a week and stopped again. This time at home.  The Ford dealer's mechanic as been here twice.  He brought the computer and really hasn't found any code.  He thought that it might be a broken wire. Now he thinks it's the processor.  He disconnected the glow plug circuit and told me that i could drive it like that. I've tried to crank it a couple of times with no success.  On a hot day it will crank, but the engine surges and finally shuts off.  My opinion, this mechanic doesn't know what he doing.  I think the problems in the fuel system.  I've worked on cars (gas engines) all my life, but know nothing about diesels.  I'm about $600.00 in the whole and still have a broke truck.  

Thanks for help,
Danny

Answer
Hello Danny,
Make sure you are using the correct motor oil. That truck uses a high pressure oil pump, separate from the engine oil pump, but using the engine oil to operate the injectors. Any oil that can foam can cause a problem in the injection process.

Make sure the fuel tank cap is correct one, so a vacuum doesn't form in the fuel tank.

Make sure there are no leaks in the fuel supply line from the tank to the lift pump, or the lift pump itself. Any small leak will allow it to suck air, which is very hard for a diesel to get rid of.

And the glow plugs are pretty much needed, even in summer.

Van