Slow Acceleration / Reduced Top Speed - 1981 DD 8V71

[chessie4905]

Had that happen on our 4104. Couple large chunks of solder would come up and partially block fuel flow.  Solder probably came from a previous tank  repair in it's life. Acted like fuel filters were plugging up. Randomly. Last time, it did it again shortly after changing them. While I had tank out, I noticed the crud build up on bottom of tank from years of accumulation. Thoroughly cleaned tank while I was at it. After installed, I put fuel back in in 5 gallon at a time to record when reached movement on gauge, then when It read 1/4 tank. Never had the problem again.

[chessie4905]

Had that happen on our 4104. Couple large chunks of solder would come up and partially block fuel flow.  Solder probably came from a previous tank  repair in it's life. Acted like fuel filters were plugging up. Randomly. Last time, it did it again shortly after changing them. While I had tank out, I noticed the crud build up on bottom of tank from years of accumulation. Thoroughly cleaned tank while I was at it. After installed, I put fuel back in in 5 gallon at a time to record when reached movement on gauge, then when It read 1/4 tank. Never had the problem again.

[HenryTX]

You already have a diesel/water fuel separater-- your primary fuel filter.  Sorry, but maybe you need an honest to God Detroit Diesel mechanic to get you through this.

PROBLEM SOLVED.

In the end, I took it to one of the few Detroit Diesel mechanics here in the city.
There was nothing wrong with the fuel pressure.
His diagnosis was a malfunctioning fuel valve inside the governor.

Upon taking apart the governor housing, they found a buildup of gunk preventing an emergency air valve from pushing completely open the fuel line into the left side injector panel.
The issue was inconsistent, however, with the fuel line opening more or less depending on the day.
After cleaning out the gunk and clearing the motion inside the governor, acceleration and performance were back to normal, actually with a mild increase in horsepower.

The mechanic was very complimentary of the condition of the engine, saying it sounds GREAT
We took her out driving on a camping trip the past four days, and, apart from strong head winds, it was a beautiful trip and the bus behaved admirably.


Thanks to everyone who participated in helping me get this fixed!

[Geoff]

Translated, your air shut down cylinder was sticking, not allowing full rack travel for full power.  I would be worried about the gunk inside your governor-- that is usually from water/antifreeze leaking into the oil.

I would have a lab analysis of your oil done.

Geoff

[kingfa39]

so I guess all the water I find in my aircraft fuel tanks don't come out of the air?? I guess if you don't live in Florida or SE Texas you wouldn't know. condensation in the fuel tanks have killed thousands of people in airplanes, and what is it in the mornings when I go out to my bus and it is wet?? is that something else??
   In high humidity there is condensation , and guess what, not a lie

[chessie4905]

Don't leave the fuel filler cap off, allowing moisture in. Sounds like those planes need a better fuel mangement system.

[richard5933]

A couple of good reads about condensation in fuel tanks:

http://www.mycleandiesel.com/pages/SolutionWater.aspx

https://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm