Hello all Happy Holidays,
My 99 had the lift pump replaced last month, new fuel filter w/112,000 miles on it. Since then the turbo (I think) has not been running. I had been losing MPG, did fuel test, methanol, a lot of it in cheaper fuels. Switched to higher grade fuel plus fuel additive, cleaned out and recharged the K&N filter, still getting 6.7 mpg!! NO SMOKE, not much loss in power just lousy mileage. Is the waste gate on the turbo vacuum controlled or sensor controlled? I am relatively attuned to listening to the truck and there has been no roaring from turbo bearings going down. HELP!! I know diesel is pretty cheap right now but this is ridiculous.
Oh,BTW not all fuels are created equally, there's some bad sh@#t out there. Any info. would be great! Houston TX

 

Inspect the Charge Air Cooler hoses and clamps for proper installation. Inspect all connections and clamps for looseness. Verify that no leaks are present when the engine is under boost conditions. Pay close attention to the exhaust connections.
Inspect the fuel tank rollover valve for restrictions. While performing the following road test, verify that the turbo boost pressure is 16 psi (33 in. of Hg.) during wide open throttle (WOT) acceleration.

 

What do you mean by this?
I've noticed people at the pumps filling up with #1 in the summer, they think because it's more expensive it's higher grade.
It isn't, in fact it contains less btus thus less power and mpgs.

 

How are you calculating your fuel mileage? By hand or by the display? You stated that you haven't lost power, and no smoke. If in fact the turbo wasn't working, you'd have a noticeable power loss, and lots of smoke. For a quick wastegate check, clamp off the hose and run the truck, look for a change in performance. Also, you stated you changed the fuel filter/lift pump, have you noticed any leaks? Another check, check your oil level. It seems unrelated, but one of the injector tubes may have sprung a leak, dumping fuel into the crankcase. It is unlikely, but odd things do happen.
One other thing, scan for codes. A VP44 on it's way out can cause a noticeable mileage loss. I consider this unlikely as well, given that you haven't mentioned a CEL, or any other symptoms, but thought it should be included, just to cover all the bases.

 

Thanks all, sorry I posted in the wrong section. I am writing all these checks down to test. Last night ran the truck on open road (no traffic) there is some loss of power. Fuels I have been having trouble with here in Texas, Valero and Phillips. Mechanics have been running Chevron and Shell with no problems. Fuel mileage readout (overhead) reads 6.6, did calibrate with exactly 10 gallons of fuel and ran 82 miles on that. I have been alittle concerned that it may be the VP44 on its way out,ouch. Will check as you all recommend, no CEL or error codes...yet. BD diesel wastegate kits? Looks like vacuum pressure controls wastegate? Thanks again DTR

 

No, boost pressure controls the wastegate. Stock your wastegate should open at about 20 psi.