Fallfork

98.5 24-Valve with an automatic. 355,000 miles and on its second long block (about 100,000 miles on the new engine.) After sitting over the winter, my truck produces low power when trying to reach or maintain highway speeds. I have already replaced the fuel filter, APPS, and lift pump - with no improvement. The truck runs fine when driving around town, but it struggles to get up to 65 mph. It does not miss or hesitate, it's just a slow poke. With my trailer (empty) hooked up, it will only maintain 55 mph on flat ground - anything more arduous and the transmission downshifts and the engine just won't make any appreciable power. There is no increased response from about 1/2 throttle to WOT. Furthermore, my exhaust no longer produces that typical light cloud of black smoke under WOT. The engine and the turbo "sound" fine. Only code in the computer is a P0720, but I cleared that and it hasn't come back yet. It just seems like the engine is not getting the full amount of fueling when you try to get it to work hard. Is this typical of a VP-44 starting to die? What else should I check? Thanks in advance for your thoughts.

nickg

have the codes pulled with a scanner, some places do it for free, you might not have gotten all the info out of the computer, depending on what type of scanner you used.

you can never use how a truck/turbo sounds when diagnosing faults, you would need to know what your fuel pressure is (install a gauge) as even a NEW stock LP can and will fail as fast as you can instal them.
If your making more than 20psi boost the ECM/PCM will defuel the truck and it will act like a gutless wonder, without a gauge, hard to troubleshoot, if over boosting you should see a code set, if under boosting, say a tear in an intercooler boot or having some intercooler piping pop off, will produce an under achieving power house, again a boost gauge would be an asset,

you could pick up a gauge or two from a local hardware/surplus shop and plumb them in for testing purposes, I'm sure a couple cheap gauges and some hose would only cost a couple dollars, actually an old mechanical oil pressure gauge would work for testing fuel pressure (something reading from 0-20psi) your fuel pressure should be no less than 10psi in any operating situation, likely if a stock LP it will be lower than 10psi

nickg

here is a link to help trouble shoot a VP

http://www.bluechipdiesel.com/vp44diagnostichelp.html

Fallfork

Thanks for the help. I am ordering a fuel pressure gauge kit. On the subject of boost, where do you measure intake manifold pressure - is there an easy place to tap into the system with a gauge?

nickg

anywhere you can find a place tap a hole between the turbo and intake manifold

here is a link to a boost bolt, basically a hollow bolt that replaces an intake manifold bolt

http://www.vulcanperformance.com/Boo...c-p/bstblt.htm

Fallfork

Got the boost bolt - and what do you know, there is no boost!! That certainly explains the lack of get-up-and-go. Now my efforts to troubleshoot the lack of boost are kicking my butt. Started another post on that subject. Thanks again.

nickg

you can make a "homemade boost checker" basically a couple rubber caps and a tire valve stem, pressure up the intake system and if there are leaks it will show up.
a seach should show you how to make one

Fallfork

Did the search. Off to home depot. Thanks again!