Highway cruise fluctuations 85 300TDT

[shear2001]

I've been noticing a uneveness when cruising at 55-60mph. It seems like I have a faulty filter. I changed both fuel filters 3k ago. Does anyone have any experience with the tank filter on a 85300td. Could that be clogged? Also could it be my fuel pump or maybe the injector pump? Is there any test? Just don't want to suddenly die on the road. Approaching 400k miles probably by summer so I have some concerns. Any input appreciated. Thanks

[Ken300D]

Also take the fuel primer pump into consideration if you have an original. Check to see that the pump handle is screwed down tight as a minimum. Look for diesel weepage in that area.

Look for air bubbles entering the plastic fuel pre-filter - that indicates a leaking supply line between it and the tank, possibly the one right there at the pre-filter. Also look for foreign matter like specs of algae/fungus. Your spin-on filter is probably not clogged with tank scum unless the pre-filter is getting clogged too.

I did die on the road once so far and it was the fuel primer pump leaking air into the system - the handle had come loose running down the road.

Ken300D

[shear2001]

I'll take a look at the pre filter. As far as the primer pump, that was changed along with the folter 3k ago. Thanks, I'll also look for algae.

[Palangi]

When mine had cruise fluctuations, I found that the shaft on top of the valve cover where the linkage from the cruise actuator pivots was loose and wobling in it's bracket. Fixed with JB weld.