The diesel is running great. I have been doing the back and forth to work thing with it and have noticed when getting out on open road sometimes it runs right up to 65 mph and sometimes it just won't go. Feels like it runs out of throttle. I will have the pedel on the floor and it is like I have leveled it out at 55... I know the explination is not very good but this is all I have...

I am wondering if the Spedo is right. The truck has 31 10.50's on it and I bet the orignal spedo gear. I bet I am running faster than I think. Seems in the 55 zones I am keeping up at about 45...

I had the same problem of losing power. The problem was the check valve in the return fuel line . This little known item is located on the front of the injector pump where the return fuel line comes out. It has a spring and ball conifuration that sometimes sticks closed. You take it out with a 9/16 wrench and clean it with carb cleaner and use a paper clip to free it up. It could also be your lift fuel pump. I put in a new check valve and mine worked fine after it was changed.tks Chuck

Will the engine rev up to the point of the governor shutting off the fuel if held in a lower gear at WOT? :eek: When is the last time you changed the fuel filter? Can you get any black smoke out of the exhaust under full throttle?

What year model is the truck? If its a later model 6.2 it will have an adjustable guide stud giving you the option to raise governor cutoff a little.

It is an 83

I never get black smoke out the back. A little white on imeadiate start up, but goes away quickly.

I have not tried anything. Course I don't know anything to try.

The PO said they changed the filter at the beginning of winter.

'83 won't have the adjustable guide stud, also, governor cutoff should be >4000 RPM.
I suspect you have an injection pump problem, check your supply pump first though, but I think you will find its working fine.

Find the advance lever on the passenger side of the injection pump, with engine idleing, depress lever(it pushes in on a button on the bottom of the pump) engine should stumble and run rough when you do this. Watch button to see if it returns to where it was when you first depressed it. This button is the advance piston and sometimes it gets stuck in the bore. Next I would replace the fuel filter, if you have an 83, just replace the secondary filter(little spin on) you should have 2 filters, primary and secondary. Primary is mainly a water separator, but the secondary is the one that will plug up and starve the engine for fuel. It has a very small micron rating, about 5 if I remember right. Some times people just change the primary filter because it is the one that you see and they don't do the secondary. It is the important one for fuel flow. Mark the filter with a permanent marker with date and mileage so you will know when to change it again. good luck:grd:

Where is the secondary? The primary is o the firewall right?

1982-1983 trucks had the secondary filter bolted directly on the back of the intake manifold. take the air cleaner off and look on the back of it, between the manifold and the firewall. you cant miss it.

and yes, the primary filter is on the firewall